Patent Publication Number: US-2020282200-A1

Title: Externally programable magnetic valve assembly and controller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15/675,497 filed on Aug. 11, 2017, and titled “EXTERNALLY PROGRAMMABLE MAGNETIC VALVE ASSEMBLY AND CONTROLLER,” which claims the benefit under 35 U.S.C. § 119(e) and PCT Article 8 of U.S. Provisional Application No. 62/374,046 [expired] filed on Aug. 12, 2016, and titled “EXTERNALLY PROGRAMMABLE MAGNETIC VALVE ASSEMBLY AND CONTROLLER,” which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Hydrocephalus is a condition associated with ventricular enlargement caused by net accumulation of fluid in the ventricles of the brain. Non-communicating hydrocephalus is hydrocephalus associated with an obstruction in the ventricular system and is generally characterized by increased cerebrospinal fluid (CSF) pressure. In contrast, communicating hydrocephalus is hydrocephalus associated with obstructive lesions within the subarachnoid space. Normal Pressure Hydrocephalus (NPH), a form of communicating hydrocephalus, primarily occurs in persons over 60 years of age and is characterized by CSF at nominally normal pressure. Classic symptoms of NPH include gait disturbance, incontinence and dementia. In summary, NPH presents as an enlargement of the ventricles with a virtually normal CSF pressure. 
     The objective in the treatment of hydrocephalus is to reduce the ventricular pressure so that ventricular size returns to a normal level. Hydrocephalus is often treated by implanting into the brain a shunt that drains excess CSF from the ventricles or from the lumbar thecal space (in communicating hydrocephalus). Such shunts are termed ventriculoatrial (VA) when they divert fluid from the ventricle to the atrium, or ventriculoperitoneal (VP) when fluid is diverted from the ventricle to the peritoneum, or lumboperitoneal (LP) when CSF is diverted from the lumbar region to the peritoneum. These shunts are generally comprised of a cerebral catheter (for ventricular shunts) inserted through the brain into the ventricle or a lumbar catheter (for lumbar shunts) inserted through a needle into the lumbar thecal space and a one-way valve system that drains fluid from the ventricle into a reservoir of the body, such as the jugular vein (ventricular shunts) or the peritoneal cavity (ventricular or lumbar shunts). 
     U.S. Pat. No. 4,595,390 describes a shunt that has a spherical sapphire ball biased against a conical valve seat by stainless steel spring. The pressure of the CSF pushes against the sapphire ball and spring in the direction tending to raise the ball from the seat. When the pressure difference across the valve exceeds a so-called “popping” or opening pressure, the ball rises from the seat to allow CSF to flow through the valve and thereby vent CSF. U.S. Pat. No. 4,595,390 further describes an externally programmable shunt valve that allows the pressure setting of the valve to be varied by applying a transmitter that emits a magnetic signal over the head of the patient over the location of the implanted shunt. Use of an external programmer with a magnetic transmitter allows the pressure setting of the valve to be adjusted non-invasively according to the size of the ventricles, the CSF pressure and the treatment objectives. 
     U.S. Pat. No. 4,615,691 describes examples of a magnetic stepping motor that can be used with the shunt valve of U.S. Pat. No. 4,595,390, for example. 
     Although magnetically adjustable shunts allow the pressure of an implanted shunt to be adjusted externally, these existing shunts have some limitations. For example, when a patient with an implanted magnetically adjustable shunt valve is within proximity of a strong magnet or strong magnetic field, such as a magnetic resonance imaging (MRI) device, the pressure setting of the valve can change. In addition, verification of the pressure setting of existing magnetic valves can require use of a radiopaque marker on the valve that is detected using an X-ray taken of the location where the valve is implanted. Also, some programmers utilized to adjust the pressure setting of an implanted valve are relatively large and heavy and require a connection to a wall outlet. 
     It would therefore be desirable to design improved ventricular and lumbar shunts, as well as an improved programmer to adjust the shunts. 
     SUMMARY OF THE INVENTION 
     Aspects and embodiments are directed to an externally programmable valve assembly comprising a magnetic motor that is configured to increase or decrease the pressure setting of the valve either continuously or in finite increments. The valve assembly may be adapted for implantation into a patient to drain fluid from an organ or body cavity of the patient. In these embodiments, the valve assembly includes an inlet port adapted for fluid connection (either during manufacture or by the surgeon during surgery) to one end of a catheter. The second end of the catheter is inserted into the organ or body cavity to be drained of fluid. The valve assembly further includes an outlet port adapted for fluid connection to an end of a drainage catheter. The other end of the drainage catheter can be inserted into a suitable body cavity, such as a vein or the peritoneal cavity, or into a drainage reservoir external to the body, such as a bag. Examples of organs and body cavities that can be drained using the valve assembly of the invention include without limitation the eye, cerebral ventricle, peritoneal cavity, pericardial sac, uterus (in pregnancy), and pleural cavity. In particular, the valve assembly may be adapted for implantation into a patient suffering from hydrocephalus. In such embodiments, the inlet port is adapted for fluid connection to a first end of an inflow catheter (i.e. an intracerebral or intrathecal catheter) and the outlet port is adapted for fluid connection to a first end of a drainage catheter. When implanted in the patient, the second end of the intracerebral catheter is inserted in a ventricle or lumbar intrathecal space of the patient and the second end of the drainage catheter is inserted into a suitable body reservoir of the patient, such as the jugular vein or the peritoneal cavity. Thus, when implanted in the patient, this device provides fluid communication between the ventricle or lumbar region of the patient and the body reservoir of the subject, allowing cerebrospinal fluid to flow from the ventricle or lumbar region through the valve casing to the body reservoir when the intraventricular or CSF pressure exceeds the opening pressure of the valve assembly. The patient may suffer from hydrocephalus with increased intracranial pressure, or may suffer from normal pressure hydrocephalus. The removal of CSF from the ventricle or lumbar space reduces the intraventricular pressure. 
     Further aspects and embodiments are directed to methods of determining the pressure setting of an implanted valve assembly, and adjusting the pressure setting of the valve assembly following implantation into a patient. As discussed in more detail below, according to certain embodiments, adjustment of the pressure setting of the valve may be accomplished via displacement of a magnetically actuated rotor in the valve assembly, resulting in a change in the tension of a spring providing a biasing force against the valve element. The rotor will rotate within the rotor casing responsive to an applied external magnetic field. 
     As discussed in more detail below, certain aspects and embodiments are directed to a magnetically operable motor that is suitable for incorporation into an implantable valve assembly. The magnetic motor assembly includes a stator having a plurality of stator lobes, and a rotor that includes a plurality of magnetic poles and which is configured to rotate about the stator. An externally applied magnetic field (from outside the body into which the valve assembly is implanted) is used to magnetize the stator so as to cause rotation of the rotor, as discussed further below. The magnetically operable motor has the advantage of allowing mechanical movement within the implantable valve assembly to alter the pressure setting of the valve, avoiding the need for physical connection to the valve assembly from outside the body or the use of implanted batteries. Additionally, as discussed further below, embodiments of the magnetic motor assembly are configured to be highly resistant to any influence from external strong magnetic fields that are not specifically associated with desired control of the motor, such as fields generated by MRI or nuclear magnetic resonance (NMR) devices. Further, certain embodiments of the magnetic motor include a mechanism by which an individual, for example, a doctor, can view the current pressure setting of the valve in which the magnetic motor is used, without requiring the use of an X-ray or other imaging technique. 
     Certain aspects also include a method of decreasing ventricular size in a patient in need thereof, including surgically implanting the valve assembly into the patient, and setting the opening pressure of the valve to a pressure that is less than the ventricular pressure prior to implantation of the valve. Alternatively, the opening pressure of the implanted valve assembly may be set to a pressure that is higher than the ventricular pressure, such that the ventricular size may be increased in a patient in need thereof. 
     According to one embodiment a surgically-implantable shunt valve assembly comprises a housing, an exterior of the housing being formed of a physiologically-compatible material, and a magnetically operable motor disposed within the housing, the magnetically operable motor including a stator and a rotor configured to rotate relative to the stator responsive to a changing magnetic polarity of the stator induced by an external magnetic field, the rotor including a rotor casing and a plurality of rotor permanent magnet elements disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, rotation of the rotor relative to the stator producing a selected pressure setting of the shunt valve assembly. The shunt valve assembly further comprises an inlet port positioned between the rotor casing and an exterior of the housing, the inlet port terminating at its rotor casing end in a valve seat, a spring, a valve element biased against the valve seat by the spring, the valve element and the valve seat together forming an aperture, and an outlet port positioned between the rotor casing and the exterior of the housing, the shunt valve assembly configured such that the aperture opens when a pressure of the fluid in the inlet port exceeds the selected pressure setting of the shunt valve assembly so as to vent fluid through the aperture into the outlet port. 
     Another embodiment is directed to a system comprising an externally programmable surgically-implantable shunt valve assembly, a non-implantable transmitter head, and a control device coupled to the transmitter head. The surgically-implantable shunt valve assembly may include a housing having an exterior formed of a physiologically compatible material, a magnetically operable motor disposed within the housing, the magnetically operable motor including a stator and a rotor configured to rotate relative to the stator responsive to a changing magnetic polarity of the stator induced by an external magnetic field, the rotor including a rotor casing and a plurality of rotor permanent magnet elements disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, a number of the rotor permanent magnet elements being such that radially opposing ones of the plurality of rotor permanent magnet elements have the same magnetic polarity, rotation of the rotor relative to the stator producing a selected pressure setting of the shunt valve assembly, an inlet port positioned between the rotor casing and an exterior of the housing, the inlet port terminating at its rotor casing end in a valve seat, a spring, a valve element biased against the valve seat by the spring, the valve element and the valve seat together forming an aperture, and an outlet port positioned between the rotor casing and the exterior of the housing, the shunt valve assembly configured such that the aperture opens when a pressure of the fluid in the inlet port exceeds the selected pressure setting of the shunt valve assembly so as to vent fluid through the aperture into the outlet port. The non-implantable transmitter head may include a magnet assembly configured to produce the external magnetic field to induce the rotation of the rotor relative to the stator. The control device may be configured to provide a signal to the transmitter head to control the transmitter head to produce the external magnetic field so as to set the pressure setting of the shunt valve assembly to the selected pressure setting. 
     Another embodiment is directed to a surgically-implantable valve including a magnetic motor for adjusting a pressure setting of the valve, the magnetic motor being physically isolated from electrical power sources and powered by an external magnetic field applied from outside the valve. The magnetic motor may comprise a rotor including a circular rotor casing and a plurality of permanent rotor magnets disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, the rotor casing configured to rotate about a central axis of rotation, and a stator composed of a magnetically soft and permeable material shaped as opposing circular stator discs and positioned with respect to each of four quadrants underneath the rotor magnets so that when magnetized under the influence of the external field the stator strengthens and orients a local magnetic field in its vicinity so as to cause incremental movement of the rotor about the central axis of rotation. The number of the permanent rotor magnets may be such that radially opposing ones of the plurality of permanent rotor magnets have either the same or opposite magnetic polarity. 
     According to another embodiment a surgically-implantable shunt valve assembly comprises a spring, a valve element biased against a valve seat by the spring, the valve element and the valve seat together forming an aperture through which fluid is shunted by the valve, and a magnetic motor for adjusting a pressure setting of the valve, the magnetic motor being physically isolated from electrical power sources and powered by an external magnetic field applied from outside the valve assembly. The magnetic motor may include a rotor having a rotor casing, a plurality of permanent rotor magnets disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, and a cam that engages the spring, the rotor being configured to rotate about a central axis of rotation, and a stator composed of a magnetically soft and permeable material and positioned below the rotor so that when magnetized under the influence of the external field the stator strengthens and orients a local magnetic field in its vicinity so as to cause rotation of the rotor about the central axis of rotation, the rotation of the rotor causing rotation of the cam that adjust a tension of the spring against the valve element and thereby adjusts the pressure setting of the shunt valve assembly. 
     According to another embodiment a surgically-implantable shunt valve assembly comprises a spring, a valve element biased against a valve seat by the spring, the valve element and the valve seat together forming an aperture through which fluid is shunted by the valve, and a magnetic motor for adjusting a pressure setting of the valve, the magnetic motor being physically isolated from electrical power sources and powered by an external magnetic field applied from outside the valve assembly. The magnetic motor may include a rotor having a rotor casing, a plurality of permanent rotor magnets disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, and a cam that engages the spring, the rotor being configured to rotate about a central axis of rotation, a stator composed of a magnetically soft and permeable material and positioned below the rotor so that when magnetized under the influence of the external field the stator strengthens and orients a local magnetic field in its vicinity so as to cause rotation of the rotor about the central axis of rotation, the rotation of the rotor causing rotation of the cam that adjust a tension of the spring against the valve element and thereby adjusts the pressure setting of the shunt valve assembly, and a mechanical brake magnetically operable between a locked position and an unlocked position and configured, in the locked position, to prevent rotation of the rotor. 
     Another embodiment is directed to a surgically-implantable valve including a magnetic motor for adjusting a pressure setting of the valve, the magnetic motor being isolated physically from electrical power sources and powered by the influence of an external magnetic field applied from outside the valve, the magnetic motor comprising a rotor including a circular rotor casing and a plurality of permanent rotor magnets disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, the rotor casing configured to rotate about a central axis of rotation, and an X-shaped stator composed of a magnetically soft and permeable material shaped and positioned with respect to the rotor such that when magnetized under the influence of the external field, the stator strengthens and orients a local magnetic field in its vicinity so as to cause incremental movement of the rotor about the central axis of rotation. The number of the permanent rotor magnets may be such that radially opposing ones of the plurality of permanent rotor magnets have either the same or opposite magnetic polarity. 
     According to another aspect, a method of adjusting a working (operating) pressure of a shunt valve assembly implanted in a patient in need thereof, comprises applying an external magnetic field in proximity to the implanted shunt valve assembly and exterior to the patient. 
     According to one embodiment, a method of decreasing ventricular size in a patient in need thereof comprises implanting in the patient a shunt valve assembly, and setting the selected pressure of the valve assembly to a pressure that is less than a ventricular pressure of the patient prior to implantation of the valve. 
     According to another embodiment, a method of treating a patient suffering from hydrocephalus comprises implanting in the patient a shunt valve assembly, and setting the selected pressure of the shunt valve assembly to a pressure that is less than a ventricular pressure of the patient. 
     In another embodiment, a method of increasing ventricular size in a patient in need thereof comprises implanting in the patient a shunt valve assembly, and setting the selected pressure of the shunt valve assembly to a pressure that is greater than a ventricular pressure of the patient. 
     During the course of treatment, it is anticipated that increasing or decreasing the selected operating pressure of the valve will be required to be performed by the clinician to effectively manage the patient&#39;s condition. However, during use, the valve will be exposed to environmental magnetic fields that may potentially change the operating pressure of the valve. Aspects and embodiments provide a valve mechanism design that facilitates adjusting the valve mechanism using a magnetic field produced by the programmer while resisting adjustment by extraneous environmental magnetic fields. 
     Further aspects and embodiments are directed to a kit for setting a pressure in a surgically-implantable shunt valve. In some embodiments, the kit comprises a surgically-implantable shunt valve assembly having a magnetically operable motor configured to provide a selected pressure setting of the shunt valve assembly; a pressure reader configured to provide a pressure reading of the surgically-implantable shunt valve assembly; and a programmer having at least one programmer magnet, the at least one programmer magnet being selectively movable and configured to actuate the magnetically operable motor to allow a user to adjust the pressure setting of the surgically-implantable shunt valve assembly to match a pressure setpoint of the programmer. 
     In some embodiments, the pressure reader further comprises an arrow on an upper surface of the pressure reader. 
     In some embodiments, the pressure reader further comprises a concave surface defined on a lower surface of the pressure reader. 
     In some embodiments, the programmer further comprises a user interface. 
     In some embodiments, the programmer further comprises a first button to increase the pressure setpoint and a second button to decrease the pressure setpoint. 
     In some embodiments, the programmer further comprises a wheel being rotatable in a first direction to increase the pressure setpoint, and the wheel being rotatable in a second direction to decrease the pressure setpoint. 
     In some embodiments, the programmer further comprises a cavity on a lower surface of the programmer. 
     In some embodiments, the pressure reader includes one of a magnet and a Hall sensor. 
     In some embodiments, the surgically-implantable shunt valve assembly comprises a housing, an exterior of the housing being formed of a physiologically-compatible material; the magnetically operable motor disposed within the housing, the magnetically operable motor including a stator and a rotor configured to rotate relative to the stator responsive to a changing magnetic polarity of the stator induced by an external magnetic field, the rotor including a rotor casing and a plurality of rotor permanent magnet elements disposed in a ring within the rotor casing and arranged with alternating magnetic polarities, rotation of the rotor relative to the stator producing the selected pressure setting of the shunt valve assembly; an inlet port positioned between the rotor casing and an exterior of the housing, the inlet port terminating at its rotor casing end in a valve seat; a spring; a valve element biased against the valve seat by the spring, the valve element and the valve seat together forming an aperture; and an outlet port positioned between the rotor casing and the exterior of the housing, the shunt valve assembly configured such that the aperture opens when a pressure of the fluid in the inlet port exceeds the selected pressure setting of the shunt valve assembly so as to vent fluid through the aperture into the outlet port. 
     In some embodiments, the surgically-implantable shunt valve assembly includes a rotor marker attached to the rotor such that the rotor marker rotates with the rotor and a housing marker fixedly attached to the housing, wherein a position of the rotor marker relative to the housing marker is indicative of the pressure setting of the surgically-implantable shunt valve assembly. 
     In some embodiments, the rotor marker comprises tantalum and the housing marker comprises tantalum. 
     In some embodiments, the magnetically operable motor is a stepper motor having a rotatable rotor, and wherein the surgically-implantable shunt valve assembly further comprises a mechanical brake mechanism magnetically operable between a locked position and an unlocked position and configured, in the locked position, to prevent rotation of the rotor; and an indicator magnet assembly configured to allow an external sensor to magnetically determine a position of the rotor and thereby to determine the pressure setting. 
     Another embodiment is directed to a surgically-implantable shunt valve assembly comprising a housing. An exterior of the housing is formed of a physiologically-compatible material. The valve assembly further comprises a magnetically operable motor disposed within the housing. The magnetically operable motor includes a stator and a rotor configured to rotate relative to the stator responsive to a changing magnetic polarity of the stator induced by an external magnetic field. The rotor includes a rotor casing and a plurality of rotor permanent magnet elements disposed in a ring within the rotor casing and arranged with alternating magnetic polarities. Rotation of the rotor relative to the stator produces a selected pressure setting of the shunt valve assembly, the rotor casing having a plurality of motor teeth. The valve assembly further comprises an inlet port positioned between the rotor casing and an exterior of the housing, with the inlet port terminating at its rotor casing end in a valve seat. The valve assembly further comprises a spring, a valve element biased against the valve seat by the spring, the valve element and the valve seat together forming an aperture, and an outlet port positioned between the rotor casing and the exterior of the housing. The valve assembly is configured such that the aperture opens when a pressure of the fluid in the inlet port exceeds the selected pressure setting of the shunt valve assembly so as to vent fluid through the aperture into the outlet port. The valve assembly further comprises a magnetically operated mechanical brake assembly including an indicator having an indicator housing a magnet disposed within the indicator housing, and a brake coupled to the indicator and movable in response to movement of the indicator between a locked position in which the brake is positioned between teeth of the plurality of motor teeth to prevent rotation of the rotor and an unlocked position in which the brake disengages the teeth of the plurality of rotor teeth, with the indicator being movable in response to being exposed to the external magnetic field. 
     Embodiments of the valve assembly further may include configuring the rotor casing includes a cam that engages the spring such that rotation of the rotor changes a biasing tension of the spring against the cam thereby adjusting a tension of the spring against the valve element to produce the selected pressure setting of the shunt valve assembly. The cam may be formed to achieve a shape of an Archimedean spiral or combinations of Archimedean spirals. The spring may be a cantilever spring. The cantilever spring may include a cantilevered arm that rests against the valve element and a second arm that rests against the cam. The rotor casing further may include a rotor stop that prevents 360 degree rotation of the rotation of the rotor. The stator may be plus (+)-shaped. The valve assembly further may include a cam which engages the spring and is integrated with the rotor casing, such that the rotation of the rotor causes rotation of the cam and adjusts a tension of the spring against the valve element. The spring may be a cantilever spring including a fulcrum, a first arm attached to the fulcrum and configured to engage the cam, and a cantilevered arm extending from the fulcrum and having a free end configured to rest against the valve element. The fulcrum, the first arm, and the cantilevered arm may be configured to provide a lever effect such that a first force applied by the cam to the first arm is translated by the cantilever spring into a second force applied against the valve element, the second force being less than the first force. The spring may be a cantilever spring. The magnetically operable motor further may include first and second positioning magnets that orient an indicator magnet which allows an external sensor to magnetically determine a position of the rotor. The valve assembly further may include a rotor marker attached to the rotor such that the rotor marker rotates with the rotor and a housing marker fixedly attached to the housing. A position of the rotor marker relative to the housing marker may be indicative of the pressure setting of the surgically-implantable shunt valve assembly. The rotor marker may include tantalum and the housing marker comprises tantalum. 
     Another embodiment is directed to a kit for setting a pressure in a surgically-implantable shunt valve. In one embodiment, the kit comprises a surgically-implantable shunt valve assembly having a magnetically operable motor configured to provide a selected pressure setting of the shunt valve assembly, a monitor device configured to detect a pressure setting of the surgically-implantable shunt valve assembly, and programmer device having at least one programmer magnet. The at least one programmer magnet is selectively movable and configured to actuate the magnetically operable motor to allow a user to adjust the pressure setting of the surgically-implantable shunt valve assembly to match a pressure setpoint of the programmer. The surgically-implantable shunt valve assembly includes a magnetically operated mechanical brake assembly including an indicator having an indicator housing and a magnet disposed within the indicator housing and a brake coupled to the indicator and movable in response to movement of the indicator between a locked position in which the brake is positioned between teeth of a plurality of motor teeth to prevent rotation of a rotor of the motor and an unlocked position in which the brake disengages the teeth of the plurality of rotor teeth, the indicator being movable in response to being exposed to an external magnetic field applied by the programmer device. 
     Embodiments of the kit further may include configuring the programmer device to have a user interface. The programmer device further may include at least one button to turn ON and OFF the programmer device. The user interface of the programmer device may include a first button to increase the pressure setpoint and a second button to decrease the pressure setpoint. The programmer device may include at least one start button to initiate the programming sequence. The user interface further may include a liquid crystal display (LCD) configured to display a pressure reading. The programmer device may include a housing, a motor coupled to the housing, and a magnet assembly coupled to the motor and configured to rotate with respect to the housing. The magnet assembly may include at least one permanent magnet to apply the external magnetic field on the surgically-implantable shunt valve assembly. The motor may include a shaft having a driver gear. The magnet assembly further may include a magnet support having a bearing, a driven gear coupled to the driver gear, a magnetic bridging plate coupled to the magnet support, and the at least one permanent magnet being coupled to the magnetic bridging plate. The motor may be DC motor. The programmer device may include software to control the movement of the at least one permanent magnet to achieve the proper programming sequence. The monitor device may include a user interface. The user interface may include a button to turn ON and OFF the monitor device. The user interface further may include a liquid crystal display (LCD) configured to display a pressure setting reading. The monitor device may include a housing and a monitor assembly supported by the housing. The monitor assembly may include a monitor sensor configured to center the monitor assembly and to detect a position of the magnetically operable motor of the surgically-implantable shunt valve assembly. The at least one monitor sensor may include a first sensor to center the monitor assembly and a second sensor to detect a position of the magnetically operable motor of the surgically-implantable shunt valve assembly. The valve assembly further may include a housing. An exterior of the housing may be formed of a physiologically-compatible material. The magnetically operable motor may be disposed within the housing. The magnetically operable motor may include a stator and the rotor configured to rotate relative to the stator responsive to a changing magnetic polarity of the stator induced by the external magnetic field. The rotor may include a rotor casing and a plurality of rotor permanent magnet elements disposed in a ring within the rotor casing and arranged with alternating magnetic polarities. Rotation of the rotor relative to the stator may produce the selected pressure setting of the shunt valve assembly. The rotor casing may have the plurality of motor teeth. The valve assembly further may include an inlet port positioned between the rotor casing and an exterior of the housing, with the inlet port terminating at its rotor casing end in a valve seat. The valve assembly further may include a spring, a valve element biased against the valve seat by the spring, the valve element and the valve seat together forming an aperture, and an outlet port positioned between the rotor casing and the exterior of the housing. The valve assembly may be configured such that the aperture opens when a pressure of the fluid in the inlet port exceeds the selected pressure setting of the shunt valve assembly so as to vent fluid through the aperture into the outlet port. The valve assembly may include a rotor marker attached to the rotor such that the rotor marker rotates with the rotor and a housing marker fixedly attached to the housing. A position of the rotor marker relative to the housing marker may be indicative of the pressure setting of the surgically-implantable shunt valve assembly. The rotor marker may include tantalum and the housing marker comprises tantalum. The kit further may include a positioning disk that is used to position the monitor device and optionally the programming device on the surgically-implantable shunt valve assembly. 
     Another embodiment is directed to a kit for setting a pressure in a surgically-implantable shunt valve. In one embodiment, the kit comprises a surgically-implantable shunt valve assembly having a magnetically operable motor configured to provide a selected pressure setting of the shunt valve assembly, a monitor device configured to detect a pressure setting reading of the surgically-implantable shunt valve assembly, and programmer device having at least one programmer magnet. The at least one programmer magnet is selectively movable and configured to actuate the magnetically operable motor to allow a user to adjust the pressure setting of the surgically-implantable shunt valve assembly to match a pressure setpoint of the programmer. The programmer device includes a housing, a motor coupled to the housing, and a magnet assembly coupled to the motor and configured to rotate with respect to the housing, the magnet assembly including at least one permanent magnet to apply the external magnetic field on the surgically-implantable shunt valve assembly. 
     Embodiments of the kit further may include configuring the programmer device to have a user interface. The programmer device further may include at least one button to turn ON and OFF the programmer device. The user interface of the programmer device may include a first button to increase the pressure setpoint and a second button to decrease the pressure setpoint. The programmer device may include at least one start button to initiate the programming sequence. The motor may include a shaft having a driver gear. The magnet assembly further may include a magnet support having a bearing, a driven gear coupled to the driver gear, a magnetic bridging plate coupled to the magnet support, and the at least one permanent magnet being coupled to the magnetic bridging plate. The motor may be a DC motor. The kit further may include a positioning disk that is used to position the monitor device and optionally the programming device on the surgically-implantable shunt valve assembly. The programmer device may be configured to rotate the rotor of the valve device in a first direction to a lowest pressure setting prior to initiating a rotation of the rotor in a second, opposite direction to the selected pressure setting. 
     Another embodiment is directed to a kit for setting a pressure in a surgically-implantable shunt valve. In one embodiment, the kit comprises a surgically-implantable shunt valve assembly having a magnetically operable motor configured to provide a selected pressure setting of the shunt valve assembly, a monitor device configured to detect a pressure setting reading of the surgically-implantable shunt valve assembly, and programmer device having at least one programmer magnet. The at least one programmer magnet is selectively movable and configured to actuate the magnetically operable motor to allow a user to adjust the pressure setting of the surgically-implantable shunt valve assembly to match a pressure setpoint of the programmer. The monitor includes a housing and a monitor assembly supported by the housing. The monitor assembly includes at least one monitor sensor configured to center the monitor assembly and to detect a position of the magnetically operable motor of the surgically-implantable shunt valve assembly. 
     Embodiments of the kit further may include configuring the monitor device to have a user interface. The user interface may include a button to turn ON and OFF the programmer device. The user interface further may include a liquid crystal display (LCD) configured to display a pressure setting reading. The kit further may include a positioning disk that is used to position the monitor device and optionally the programming device on the surgically-implantable shunt valve assembly. The monitor further may include a pressure recall button configured to recall a previous pressure reading. The at least one monitor sensor may include a first sensor to center the monitor assembly and a second sensor to detect a position of the magnetically operable motor of the surgically-implantable shunt valve assembly. 
     Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. Embodiments disclosed herein may be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein, and references to “an embodiment,” “some embodiments,” “an alternate embodiment,” “various embodiments,” “one embodiment” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings in which like reference characters refer to the same parts throughout the different views. For purposes of clarity, not every component may be labeled in every drawing. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. The drawings are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the invention. In the drawings: 
         FIG. 1A  is a plan view of one example of an implantable valve assembly, showing a top view, according to aspects of the invention; 
         FIG. 1B  is a cross-sectional view of the valve assembly of  FIG. 1A ; 
         FIG. 2  is a three-dimensional drawing of one example of an implantable valve according to aspects of the present invention; 
         FIG. 3A  is a diagram showing a plan view of one example of an implantable valve, corresponding to the example shown in  FIG. 2 , according to aspects of the invention; 
         FIG. 3B  is a side view of the example of the implantable valve shown in  FIG. 3A ; 
         FIG. 4A  is a cross-sectional view of one example of the valve of  FIGS. 2 and 3A -B taken along line A-A in  FIG. 3A ; 
         FIG. 4B  is a cross-sectional view of the example of the valve of  FIGS. 2 and 3A -B taken along line B-B in  FIG. 3A ; 
         FIG. 4C  is a cross-sectional view of the example of the valve of  FIGS. 2 and 3A -B taken along line C-C in  FIG. 3A ; 
         FIG. 5  is a three-dimensional cross-sectional view of an example of the valve of  FIGS. 2 and 3A -B, according to aspects of the invention; 
         FIG. 6A  is a diagram showing an enlarged view of a portion of the valve of  FIG. 5 , with the cam shown in a position of minimum tension against the biasing spring, according to aspects of the invention; 
         FIG. 6B  is a diagram showing another view of a portion of the valve of  FIG. 5 , with the cam shown in a position of minimum tension against the biasing spring, according to aspects of the invention; 
         FIG. 6C  is a diagram showing an enlarged view of a portion of the valve of  FIG. 5 , with the cam shown in a position of maximum tension against the biasing spring, according to aspects of the invention; 
         FIG. 6D  is a diagram showing an enlarged view of a portion of the valve of  FIG. 5 , showing an example of the spring biased against the valve element and the cam, according to aspects of the invention; 
         FIG. 7A  is a diagram showing an example of a flat spring according to aspects of the present invention; 
         FIG. 7B  is a partial perspective view showing an example of the flat spring of  FIG. 7A  installed in a valve according to aspects of the present invention; 
         FIG. 8A  is a diagram showing an example of a u-shaped spring according to aspects of the present invention; 
         FIG. 8B  is a diagram showing the u-shaped spring of  FIG. 8A  installed in a programmable valve, according to aspects of the present invention; 
         FIG. 8C  is a diagram showing a portion of the programmable valve of  FIG. 8B  when the programmable valve is set at the lowest pressure setting; 
         FIG. 8D  is a diagram showing a portion of the programmable valve of  FIG. 8B  when the programmable valve is set at the highest pressure setting; 
         FIG. 9A  is a diagram illustrating another example of a spring according to aspects of the present invention; 
         FIG. 9B  is a diagram showing the spring of  FIG. 9A  engaging a valve element, according to aspects of the present invention; 
         FIG. 10A  is a schematic diagram of one example of a rotor for use in embodiments of a magnetically-operable implantable valve according to aspects of the present invention, showing the rotor positioned for a minimum pressure setting of the valve; 
         FIG. 10B  is a schematic diagram of the rotor of  FIG. 10A  showing the rotor positioned for a maximum pressure setting of the valve; 
         FIG. 11A  is a diagram of an implanted valve and an example of an external valve programmer with a control and display, according to aspects of the invention; 
         FIG. 11B  is a diagram of an implanted device and another example of an external programmer according to aspects of the invention. 
         FIG. 11C  is a diagram of an implanted valve and an example of a pressure reading device for reading the pressure setting of the valve, according to aspects of the invention; 
         FIG. 12  is a block diagram of one example of an external control device that can be used in combination with an implantable programmable valve according to aspects of the invention; 
         FIG. 13  is a diagram showing operation of one example of a magnetic motor including twelve rotor magnet elements and controlled by a controller including a plurality of electromagnets according to aspects of the invention; 
         FIG. 14  is a three-dimensional partial cross-sectional view of one example of a magnetic motor according to aspects of the invention; 
         FIG. 15  is a table showing an example of a sequence of energizing the electromagnets of the controller of  FIG. 13  to effect clockwise rotation of the magnetic rotor, according to aspects of the invention; 
         FIGS. 16A-H  are diagrams showing the magnetic polarity of the stator and movement of the rotor responsive to the energizing sequence of  FIG. 15 ; 
         FIG. 17  is a table showing an example of a sequence of energizing the electromagnets of the controller of  FIG. 13  to effect counter-clockwise rotation of the magnetic rotor, according to aspects of the invention; 
         FIGS. 18A-H  are diagrams showing the magnetic polarity of the stator and movement of the rotor responsive to the energizing sequence of  FIG. 17 ; 
         FIG. 19  is a block diagram of another example of an external valve programmer that can be used with embodiments of the implantable valve assembly according to aspects of the invention; 
         FIG. 20A  is a diagram of one example of a permanent magnet assembly for the external valve programmer of  FIG. 19 , according to aspects of the invention; 
         FIG. 20B  is a diagram of another example of a permanent magnet assembly for the external valve programmer of  FIG. 19 , according to aspects of the invention; 
         FIGS. 21A-E  are diagrams illustrating an example of the changing magnetic polarity of the stator and movement of the rotor under control of an example of an external valve programmer incorporating the permanent magnet assembly of  FIG. 20A , according to aspects of the invention; 
         FIG. 22  is a flow diagram illustrating an example of the changing polarity of the stator and movement of the rotor as exemplified in  FIGS. 21A-E  representative of one full rotation of an external permanent magnet valve programmer, according to aspects of the invention; 
         FIG. 23A  is a diagram showing a top plan view of one example of a valve programmer according to aspects of the present invention; 
         FIG. 23B  is a diagram showing a bottom plan view of the valve programmer of  FIG. 23A ; 
         FIG. 23C  is a diagram showing an end view of the valve programmer of  FIGS. 23A-B ; 
         FIG. 23D  is a diagram showing a perspective view of the valve programmer of  FIGS. 23A-C ; 
         FIG. 23E  is a diagram showing a top plan view of another example of a valve programmer according to aspects of the present invention; 
         FIG. 24  is a flow diagram for one example of a method of operating the valve programmer of  FIGS. 23A-D  to program the pressure setting of an implantable valve according to aspects of the present invention; 
         FIGS. 25A-C  are diagrams showing examples of different configurations of stators in combination with a twelve-magnet rotor, according to aspects of the invention; 
         FIGS. 26A-C  are diagrams showing further examples of stators in combination with a twelve-magnet rotor, according to aspects of the invention; 
         FIG. 27  is a diagram of one example of a rotor including reference magnet elements according to aspects of the invention; 
         FIGS. 28A-C  are diagrams showing further examples of a motor assembly including reference magnet elements according to aspects of the present invention; 
         FIG. 29  is a block diagram of one example of an external valve programmer including a magnet sensor to detect the reference magnet elements, according to aspects of the invention; 
         FIG. 30A  is a perspective view of one example of a pressure reader according to aspects of the present invention; 
         FIG. 30B  is a top plan view of the pressure reader of  FIG. 30A ; 
         FIG. 31  is a flow diagram of one example of a method of operating a pressure reader to read the pressure setting of an implanted valve according to aspects of the present invention; 
         FIG. 32  is a diagram showing a cross-sectional view of another example of a motor including reference or position-indicating magnet elements according to aspects of the invention; 
         FIG. 33  is a partial cross-sectional three-dimensional view of one example of a programmable valve including a brake mechanism according to aspects of the invention; 
         FIG. 34  is a schematic diagram showing certain aspects of an example of the brake mechanism according to aspects of the invention; 
         FIG. 35  is a diagram illustrating another example of a permanent magnet assembly for the external valve programmer of  FIG. 19  incorporating a magnetic brake controller mechanism, according to aspects of the invention; 
         FIG. 36  is a flow diagram of one example of a method of programming an implanted programmable valve according to aspects of the invention; 
         FIG. 37A  is a cross-sectional view of one example of the programmable valve of  FIG. 33  according to aspects of the invention showing the brake in the locked position; 
         FIG. 37B  is a corresponding cross-sectional view showing the brake in the unlocked position; 
         FIG. 38  is a diagram illustrating another example of a permanent magnet assembly for the external valve programmer of  FIG. 19 , according to aspects of the invention; 
         FIG. 39  is a flow diagram of another example of a method of programming an implanted programmable valve according to aspects of the invention; 
         FIG. 40  is diagram showing another example of the programmable valve including a brake mechanism according to aspects of the invention; 
         FIG. 41  is a partial cross-sectional perspective view of another example of programmable valve including a magnetic motor incorporating a brake mechanism according to aspects of the invention; 
         FIG. 42  is a plan view of the example of the valve shown in  FIG. 41 ; 
         FIG. 43  is a plan view of another example of a motor assembly of a valve similar to that shown in  FIG. 41 , according to aspects of the invention; 
         FIG. 44A  is a cross-sectional view of the example of the valve shown in  FIG. 42  taken along line A-A in  FIG. 42 ; 
         FIG. 44B  is a cross-sectional view of the example of the valve shown in  FIG. 42  taken along line B-B in  FIG. 42 ; 
         FIG. 45  is a diagram showing another example of a brake spring according to aspects of the invention; 
         FIG. 46A  is a schematic cross-sectional view of the example of the valve shown in  FIG. 42 , showing the brake in the locked position; 
         FIG. 46B  is a corresponding schematic cross-sectional view of the example of the valve shown in  FIG. 42 , showing the brake in the unlocked position; 
         FIG. 47A  is a plan view of another example of a programmable valve according to aspects of the invention; 
         FIG. 47B  is a cross-sectional view of the programmable valve shown in  FIG. 47A  taken along line A-A in  FIG. 47A ; 
         FIG. 48  shows another example of a programmable valve incorporating a brake mechanism according to aspects of the present invention. 
         FIG. 49  is a perspective view of an implantable valve assembly of another embodiment of the present disclosure; 
         FIG. 50  is a perspective view of a programmable valve of the implantable valve assembly according to aspects of the present disclosure; 
         FIG. 51  is an exploded perspective view of the programmable valve; 
         FIG. 52  is a perspective view of the programmable valve with outer packaging removed to reveal components housed within the programmable valve; 
         FIG. 53  is another perspective view of the programmable valve; 
         FIG. 54  is a perspective cross-sectional view of the programmable valve; 
         FIG. 55  is a cross-sectional view of the programmable valve; 
         FIG. 56A  is a top perspective view of a programmer device, with the magnetic shield cover attached, for the valve device of an embodiment of the present disclosure; 
         FIG. 56B  is a side view of the programmer device shown in  FIG. 56A ; 
         FIG. 56C  is a perspective view of the magnetic shield separated from the programmer device; 
         FIG. 56D  is a bottom view of the magnetic shield attached to the programmer device; 
         FIG. 57  is a bottom perspective view of the programmer device, without the magnetic shield cover; 
         FIG. 58  is a top plan view of the programmer device; 
         FIG. 59  is an exploded perspective view of the programmer device; 
         FIG. 60A  is a top perspective view of a monitor device for the valve device of an embodiment of the present disclosure; 
         FIG. 60B  is a bottom perspective view of the monitor device; 
         FIG. 61  is a top plan view of monitor device; 
         FIG. 62  is an exploded perspective view of the monitor device; 
         FIG. 63  is a cross-sectional view of the monitor device; 
         FIG. 64  is a top perspective view of a circuit board of the monitor device; 
         FIG. 65  is a bottom perspective view of the circuit board of the monitor device; 
         FIG. 66  is a perspective view of a positioning disk that is used to position the monitor device and the programmer device on the valve device; 
         FIG. 67  is a top plan view of the positioning disk; and 
         FIG. 68  is a perspective view of a programmer device having a magnetic shield, a monitor device connected to a power cord, and a positioning disk disposed under the monitor device of embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Aspects and embodiments are directed to a valve assembly that incorporates a magnetic motor configured to increase or decrease the working pressure of the valve either continuously or in finite increments. As discussed in more detail below, by magnetically repositioning a rotor within a casing of the valve assembly, the opening pressure of the valve element may be adjusted, thereby increasing or decreasing the flow of fluid through the valve assembly. Certain embodiments of the valve assembly are adapted for implantation into a patient suffering from hydrocephalus, and may be used to drain CSF. 
     In particular, certain aspects and embodiments provide an externally and magnetically programmable valve incorporating a magnetic motor and external controller having the following features. The valve is configured such that an operator, for example, a doctor, is able to adjust the valve either continuously or in small pressure increments (e.g., increments of approximately 10 mm H 2 O) up to a pressure of about 200 mm H 2 O, and the valve has a “closed” setting of approximately 300-400 mm H 2 O. The valve is highly resistant to non-programming external magnetic fields in the environment, such as the magnetic field of a 3 Tesla MRI, for example, such that the pressure setting of the valve does not change appreciably when the patient is in the proximity of an MRI machine or other instrument (other than the valve controller) that generates a magnetic field. In certain embodiments, the valve is configured such that the operator (e.g., the doctor) is able to verify the pressure setting of the valve with a method other than X-Rays. Furthermore, according to certain embodiments the valve controller is small, very portable, and battery-operated. These and other features and configurations of the valve according to various embodiments are discussed in more detail below. 
     Referring to  FIGS. 1A and 1B , there is illustrated one example of an implantable shunt valve assembly  100  including two valves  200  and  300  separated by a pumping chamber  110 . In one example, a ventricular catheter  120  can be connected to an inlet  130  of the valve assembly  100 , and a drainage catheter can be attached to a connector  140  and connected to an outlet  150  of the valve assembly. Depression of the pumping chamber  110  pumps fluid through the valve  300  toward the outlet  150  and the drainage catheter. Releasing the pumping chamber after it has been depressed pumps fluid through the valve  200 . The valve  200  is an externally programmable valve including a magnetic motor, as discussed in more detail below. The second valve  300  can be a check valve, for example. In this case, after passing through the programmable valve  200 , fluid flows through the check valve  300  before exiting into the drainage catheter. In one example the programmable valve  200  operates to keep the valve assembly  100  closed until the fluid pressure rises to a predetermined pressure setting of the valve. Generally, the check valve  300  may be set at a low pressure, allowing the pressure setting of the programmable valve  200  including the magnetic motor to control the flow of fluid through the valve assembly  100 . In other examples, the second valve  300  can be a gravity-activated valve that allows the valve assembly  100  to automatically adjust in response to changes in CSF hydrostatic pressure that occur when the patient&#39;s posture changes (i.e., moving abruptly from a horizontal (recumbent) to a vertical (erect) position). In particular, to avoid the valve opening responsive to these pressure changes, which could cause over-drainage of CSF, the valve assembly  100  can include a gravity activated valve connected in series with and on the outlet side of the programmable valve  200 , as shown in  FIGS. 1A and 1B , the gravity activated valve being configured to open at higher pressures when the patient is substantially vertical. 
     Those skilled in the art will appreciate, given the benefit of this disclosure, that the length, size, and shape of various embodiments of the valve assembly  100  can be adjusted. Certain embodiments of the valve assembly  100  may further comprise a reservoir or pre-chamber or antechamber for sampling the fluid and/or injecting pharmaceutical agents or dyes, power on/off devices, anti-siphon or other flow compensating devices, and/or additional catheters. When included, the pre-chamber (not shown in  FIGS. 1A and 1B ) would be connected between the inlet  130  and the programmable valve  200 . According to certain embodiments, the valve assembly  100  may include a combination of the pumping chamber  110 , a pre-chamber, the second valve  300  (which can be a check valve or gravity-activated valve, for example), and optionally an anti-siphon device (not shown). In other embodiments, one or more of these components may be omitted. For example, the valve assembly  100  may include the pumping chamber  110  and second valve  300 , without a pre-chamber, as shown in  FIGS. 1A and 1B . The pumping chamber  110  may also or alternatively be omitted. In such embodiments, after the fluid passes through the programmable valve  200 , it flows through the second valve  300 . Alternatively, the valve assembly  100  may include a pre-chamber, with or without the pumping chamber  110  or the second valve  300 . The valve assembly  100  can be surgically implanted into a patient using well-known procedures. 
       FIG. 2  illustrates a three-dimensional view of one example of an implantable magnetically programmable valve  200  according to certain aspects.  FIGS. 3A and 3B  illustrate external views of the implantable magnetically programmable valve  200  of  FIG. 2 , according to certain embodiments.  FIG. 3A  is a plan view and  FIG. 3B  is an end view. The valve  200  includes a valve body  202  (also referred to as a housing) that houses the components of the valve. The valve  200  includes an inlet port  204  and an outlet port  206 . The inlet port  204  may be connected to a proximal (or inflow) catheter, and the outlet port  206  may be connected to a distal or outflow catheter. In the case of a valve assembly that shunts CSF fluid, the proximal catheter may be the ventricular catheter  120  or a lumbar catheter. In this case, the CSF fluid from the ventricle enters the ventricular catheter or lumbar catheter and enters the inlet port  204  of the valve assembly  100 . The distal catheter acts as the drainage catheter connected to the connector  140  to direct fluid to a remote location of the body (such as the right atrium (VA shunting) of the heart or the peritoneal cavity (VP or LP shunting) for drainage. 
     The valve body  202  may include a top cap  202   a  and a bottom cap  202   b  that mates with the top cap  202   a  to form a sealed enclosure that is suitable for implantation into the human body. The “top” of the valve  200  is the side of the device oriented to face up toward the patient&#39;s scalp when implanted. The valve body  202  may be made from any physiologically compatible material. Non-limiting examples of physiologically compatible materials include polyethersulfone and silicone. As will be appreciated by those skilled in the art, the valve body  202  may have a variety of shapes and sizes, at least partially dependent on the size, shape, and arrangement of components within the valve  200 . 
     Various aspects and features, and operation, of the valve  200 , including operation of the magnetic motor, are discussed below with reference to  FIGS. 2, 3A -B and  4 A-D.  FIG. 4A  is a cross-sectional view of one example of the valve  200  taken along line A-A in  FIG. 3A  and showing certain components of the magnetic motor.  FIG. 4B  is a three-dimensional cross-sectional view of the example of the valve  200  of  FIGS. 2 and 3A -B, taken along line B-B in  FIG. 3A  and showing certain components of the magnetic motor.  FIG. 4C  is another cross-sectional view of the example of the valve  200  of  FIGS. 2 and 3A -B, taken along line C-C in  FIG. 3B  and showing certain components of the magnetic motor.  FIG. 5  is another cross-sectional view of the example of the valve  200  of  FIGS. 2 and 3A -B, taken along line A-A in  FIG. 3A . 
     Referring to  FIGS. 2, 3A -B, and  4 A-C, according to certain embodiments, the valve  200  includes a valve element  208  biased against a valve seat  210  by a spring  400 . The spring  400  may comprise, for example, an extension spring, a compression spring, a helical or coiled spring, a torsional spring, a flat spring, a leaf spring, or a cantilever spring. Certain embodiments of the spring  400  are discussed in more detail below. 
     Fluid enters the valve  200  via the ventricular catheter, for example, and flows through the inlet port  204 , which terminates at its casing end at the valve seat  210 . The pressure of the fluid (e.g. CSF) pushes against the valve element  208  and the spring  400  in the direction tending to raise the valve element  208  from the valve seat  210 . Surfaces of the valve element  208  and valve seat  210  together define an aperture, and the size or diameter of the aperture determines the rate and amount of fluid flow through the valve  200 . The valve element  208  preferably has a diameter greater than the valve seat  210  such that when the valve element  208  rests against the valve seat  210 , the aperture is substantially closed. The valve element  208  is placed on the inlet side of the aperture and is biased against the circular periphery of the aperture, keeping it closed until the CSF pressure in the inlet chamber exceeds a preselected popping pressure. The term “popping pressure” refers to the opening pressure of the valve and is generally, a slightly higher pressure than the working pressure and is required to overcome inertia when the ball has settled in to the seat. The term “working pressure” can also be referred to as the “operating pressure” and is the pressure of the valve while fluid flows through the valve  200 . The closing pressure is the pressure of the valve at which the flow of fluid through the valve stops. 
     The valve element  208  can be a sphere, a cone, a cylinder, or other suitable shape. In the example illustrated in  FIGS. 4C and 5 , the valve element  208  is a spherical ball. The spherical ball and/or the valve seat  210  can be made from any appropriate material including, for example, synthetic ruby or sapphire. The valve seat  210  provides a complementary surface, such as a frustoconical surface for a spherical valve element such that, in a closed position of the valve  200 , seating of the valve element  208  within the valve seat  210 , results in a fluid tight seal. The pressure setting, for example, the opening pressure, of such valves is adjusted by altering the biasing force of the valve element  208  against the valve seat  210 . In one example the valve element  208  and valve seat  210  may be press-fit into the housing  202 , and, once the initial pressure setting is reached, held in place by the friction. In one example of this configuration, the valve element  208  includes a ruby ball, and the valve seat  210  is also made of ruby. 
     According to one embodiment, biasing of the spring  400  against the valve element  208  is achieved using a magnetic motor that increases or decreases the working pressure of the valve  200  either continuously or in finite increments. According to certain embodiments, the magnetic motor includes a stator  528  and a rotor  510  that rotates relative to the stator  528  responsive to an external magnetic control field. In one example, the rotor  510  rotates about a central axis of rotation  214 . Configuration and operation of embodiments of the magnetic motor are discussed in more detail below. 
     Referring to  FIGS. 2, 4A -C, and  5 , according to certain embodiments, the rotor  510  includes a plurality of rotor magnet elements  512  arranged in a rotor casing  514 .  FIGS. 4C and 5  show the plurality of rotor magnet elements  512  arranged in a circle and disposed within the rotor casing  514 . Thus, the rotor casing  514  includes an approximately circular channel  522  in which the rotor magnet elements  512  are contained. In one example, the rotor magnet elements  512  are permanent magnets, each having a south pole and a north pole. The rotor magnet elements  512  are arranged approximately in a circle, as shown in  FIG. 4C , with alternating polarity, such that, whether viewed from the top (as in  FIG. 4C ) or bottom, the south and north poles alternate between every rotor magnet element. Thus, at any one angular position, the pole exposed on the top surface of the element is opposite that of the one exposed on the bottom surface. The rotor magnet elements  512  can be fixedly mounted to the rotor casing  514 , which can act as a magnet guide to contain and direct rotation of the rotor magnet elements  512 . In  FIGS. 2, 4C, and 5 , the rotor magnet elements  512  are shown as circular disks; however it is to be appreciated that the rotor magnet elements  512  need not be disk-shaped, and can have any shape, such as, but not limited to, oblong, square, rectangular, hexagonal, free-form, and the like. It is preferable that all the rotor magnet elements  512  are either of approximately the same size or approximately the same magnetic strength even if their size varies to ensure smooth rotation of the rotor  510 . According to one embodiment, the rotor  510  includes twelve rotor magnet elements  512  arranged in a circle, as shown in  FIG. 4C . According to another embodiment, the rotor  510  includes ten rotor magnet elements  512  arranged in a circle, as discussed further below. In other examples the rotor  510  may include other numbers of rotor magnet elements  512 , and embodiments of the programmable valve disclosed herein are not limited to including ten or twelve rotor magnet elements. 
     According to certain embodiments, in addition to the rotor magnet elements  512 , the rotor  510  can further include one or more additional reference magnet elements (also referred to as positioning magnets)  524 , as shown in  FIGS. 4A and 5 . The reference magnet elements  524  can be read by a pressure reader as described herein, or the reference magnet elements  524  can be used as positioning magnets to orient an indicator magnet, such as the indicator magnet  552  discussed below with reference to  FIG. 32 . The reference magnet element(s)  524  can be placed on top of one or more rotor magnet elements  512 , and can be used to allow a doctor, for example, to determine a pressure setting of the valve  200  using an external magnetic sensor, such as a Hall sensor, for example, without requiring X-rays or other imaging techniques, as discussed further below. 
     The rotor  510  is configured to rotate about the rotor axis  214  responsive to an applied external magnetic field that acts upon the stator  528 . The rotor  510  thus can further include bearing rings  516  arranged adjacent an inner circumference of the rotor casing  514 , as shown in  FIGS. 4A and 4B , to allow rotation of the rotor casing  514 . The bearing rings  516  may be made of synthetic ruby, for example. In certain examples the magnetic motor includes two bearing rings  516 , namely an upper bearing ring and a lower bearing ring, as shown in  FIGS. 4A and 4B . However, in other examples the upper bearing ring may be omitted. In this case, the rotor  510  may tilt on the lower bearing ring  516  as it rotates. In certain examples, this tilting may be advantageous in increasing resistance of the magnetic motor to adjustment by extraneous environmental magnetic fields. In other examples, the lower bearing ring  516  may be made sufficiently wide to avoid any tilting of the rotor  510  as it rotates on the bearing ring. 
     According to one embodiment, magnetic pulses from an external magnetic field are used to selectively magnetize the stator  528 , which acts upon the magnetic rotor and thereby controls movement of the rotor  510 . The external magnetic field may be produced, for example, by a magnetic coil or permanent magnet that is placed in proximity to the valve assembly, as discussed in more detail below. The stator  528  can be made of a soft magnetic material that can be selectively magnetized, and the magnetic polarity of which can be selectively controlled, by the application of the external magnetic field. For example, the stator  528  can be made of a Nickel-Iron alloy, for example, having approximately 72-83% Nickel. By controlling the magnetization and magnetic polarity of the stator  528 , the rotor  510  can be made to rotate in a controlled manner as the rotor magnet elements  512  respond to the changing magnetization and magnetic polarity of the stator  528 , as discussed further below. 
     The valve  200  is configured such that rotation of the rotor  510  controls the spring  400  to adjust the biasing of the valve element  208  against the valve seat  210 , thereby adjusting the size of the aperture and controlling the flow of fluid through the valve  200 . In one embodiment, the valve  200  includes a cam  212 , which engages the spring  400 , as shown in  FIGS. 2, 4C, and 5 . In the illustrated example, the cam  212  is integrated with the rotor casing  514 , thereby avoiding the need for a separate cam element. In other embodiments; however, the cam can be coupled to the rotor  510  and positioned in contact with the spring  400  such that rotation of the rotor  510  causes movement of the cam  212  which, in turn, adjusts the tension of the spring  400  against the valve element  208 . For example, the cam  212  could be attached to the rotor casing  514  via a central shaft  520 , such that the rotor casing  514  and the cam  212  can rotate together about the central axis  214 . As used herein the term “cam” refers either to a separate cam element that can be attached to the rotor or to the rotor casing  514  acting as a cam, as in the illustrated examples in which the cam is integrated with the rotor casing. 
     For certain applications of the valve assembly  100 , such as the treatment of hydrocephalus, for example, the pressure range of the valve may be approximately 0-200 mm H 2 O or 0-400 mm H 2 O, for example, which are very low pressure ranges. Furthermore, it may be desirable to make small pressure changes within the range. However, it may not be practicable (due to manufacturing constraints, etc.) to produce a valve assembly in which the cam  212  is capable of making very minute movements, for example, on the order of a few micrometers. Therefore, in order to accommodate the low-pressure range and small incremental changes in pressure, a very soft spring may be required. Conventionally, in order to obtain a sufficiently soft spring, the spring  400  would be very long. However, accommodating a very long, soft spring inside an implantable housing may pose challenges. Accordingly, aspects and embodiments are directed to spring configurations that produce a lever or “gear reduction” effect, such that reasonable (i.e., within standard manufacturing capabilities) movements of the cam  212  may be translated into very small adjustments in low-pressure settings. In particular, certain embodiments include a cantilever spring configuration, as shown in  FIG. 6A , for example. 
       FIGS. 6A, 6B, 6C, and 6D  illustrate views of the portions of the programmable valve  200 , showing the cam  212  and the spring  400  biased against the valve element  208 .  FIGS. 6A and 6B  show the cam  212  in the position of minimum tension against the biasing spring  400 , and  FIG. 6C  shows the cam  212  in the position of maximum tension against the biasing spring  400 .  FIG. 6D  shows an enlarged view of one example of the spring  400 . In  FIG. 6D  the spring  400  is shown with the valve element  208  seated in the valve seat  210 . In this example the spring  400  is a cantilever spring and includes a first spring arm  410  that is in direct or indirect contact with the cam  212 , and a cantilevered arm  420  that is biased against the valve element  208 . Both the first spring arm  410  and the cantilevered arm  420  extend in the same direction from a fulcrum  430  (or fixed attachment point of the spring  400 ). Thus, the cantilevered arm  420  has a fixed end at the fulcrum  430  and a free end  422  that rests against the valve element  208 , as shown in  FIGS. 6A and 6C . Similarly, the first spring arm  410  has a fixed end at the fulcrum  430  and a free end that engages the cam  212 . In certain examples the cantilevered arm  420  may be longer than the spring arm  410 . In the illustrated example the spring arm  410  is “bent”, including an inflection point  412 . This configuration allows for a reduction in the overall size of the spring  400  relative to examples in which the first spring arm is straight. Rotation of the cam  212  causes pressure against the spring arm  410  in contact with the cam, changing the tension in the spring  400 . That pressure is spread and reduced through the spring structure, such that resulting pressure applied against the valve element  208  by the cantilevered arm  420  can be very low, and in particular, can be within a desired range (e.g., 0-200 mm H 2 O, as mentioned above), without placing difficult or impracticable constraints on the rotational movement of the cam  212 . By appropriately selecting the relative lengths of the two arms  410  and  420 , and the widths of each arm, the equivalent of a lever or gear reduction mechanism may be achieved. Thus, a sufficiently soft spring to provide the low pressures (e.g., 0-200 mm H 2 O) needed for certain applications may be achieved using a short, two-armed spring  400 , rather than a conventional long spring. 
     The spring  400  can have a variety of different shapes and configurations, not limited to the example shown in  FIGS. 6A-D . For example,  FIG. 7A  and  FIG. 7B  show a flat spring  460 .  FIG. 7A  shows the flat spring alone, and  FIG. 7B  shows the spring installed in a valve and biased against the valve element  208 . The flat spring  460  includes a first spring arm  462  that is in direct or indirect contact with the cam  212  and a cantilevered arm  464  that is biased against the valve element  208 . In this example, the cantilevered arm  464  includes a rounded end portion  464   a  that rests against the valve element  208 . Both the first spring arm  462  and the cantilevered arm  464  are flat and extend from a fulcrum  430 . The cam  212  is not shown in  FIG. 7B . 
       FIGS. 8A and 8B  show an example of a u-shaped cantilevered spring  480 .  FIG. 8A  shows the u-shaped spring  480  alone.  FIG. 8B  is a sectional view of a portion of an example of the programmable valve  200  showing the u-shaped spring  480  installed in the valve  200 . The u-shaped spring  480  includes a first spring arm  482  that is in direct or indirect contact with the cam  212  and a cantilevered arm  484  that is biased against the valve element  208 . The cantilevered arm  484  has a free end  486  that rests against the valve element  208 . The first spring arm  482  and the cantilevered arm  484  are connected by a u-shaped portion  483  that is supported by a post  488 . In some embodiments, the u-shaped portion  483  is spring biased around the post  488  so the u-shaped portion  483  frictionally engages the post  488 . 
     Similar to  FIGS. 6B and 6C  discussed above,  FIGS. 8C and 8D  show examples of the u-shaped spring  480  positioned corresponding to different pressure settings of the programmable valve  200 .  FIG. 8C  shows the u-shaped spring  480  when the cam  212  is oriented such that the programmable valve  200  is set at the lowest pressure setting.  FIG. 8D  shows the u-shaped spring  480  when the cam  212  is oriented such that the programmable valve  200  is set at the highest pressure setting. 
       FIG. 9A  shows another example of a cantilevered spring  490  having a first spring arm  492  that is configured to be in direct or indirect contact with the cam  212  and a cantilevered spring arm  494  that is biased against the valve element  208 . The cantilevered spring arm  494  has a free end  496  that rests against the valve element  208 . In this example, the first spring arm  492  and the cantilevered spring arm  494  are secured to a post  498 , for example, by welding.  FIG. 9B  shows an example of the spring  490  of  FIG. 9A  in a programmable valve  200 . The post  498  is configured to rotate on two ruby bearings  491  and  493 . One ruby bearing  491  is positioned at an upper portion of the post  498  and the second ruby bearing  493  is positioned at a lower portion of the post  498 . The ruby bearings  491 ,  493  allow the post  498  to pivot with respect to the valve body  202 . 
     As will be appreciated by those skilled in the art, given the benefit of this disclosure, the spring  400  may have other configurations in addition to those described above and shown in the drawings. 
     In certain examples as the cam  212  rotates, the force exerted against the spring  400  is adjusted in fine increments or continuously over a range from minimum force to maximum force. As shown in  FIG. 6C , when the cam  212  is in the position in which the maximum pressure is exerted by the cam  212  against the spring  400 , the cantilevered arm  420  is moved toward the valve element  208 . Thus, the pressure setting of the valve  200  is highest for this position of the cam  212 . In one example, pressure exerted by the cam  212  against the spring  400 , and therefore the tension in the spring  400 , increases with clockwise rotation of the cam  212 , as indicated by arrow  216 . However, those skilled in the art will appreciate, given the benefit of this disclosure, that the rotor  510 , cam  212 , and spring  400  may alternatively be configured such that counter-clockwise rotation of the rotor  510  increases the tension in the spring  400 . 
     As described above, the valve element  208  and valve seat  210  form an aperture through which the fluid flows. The inlet port  204  can be oriented such that fluid enters the aperture (or, in other words, pushes against the valve element) in a direction perpendicular to a central axis of the rotor  510 . The inlet port  204  can also be oriented such that fluid enters the aperture (or pushes against the valve element) in a direction that is perpendicular to the central axis  214  of the rotor  510 . In certain aspects, when the inlet port  204  is oriented such that fluid enters the aperture in a direction perpendicular to the central axis  214  of the rotor  510 , the cam  212  directly or indirectly produces horizontal displacement of the spring  400 , as shown in  FIGS. 6A and 6B , for example. 
     The cam  212  in embodiments of the valve assembly  100  disclosed herein, in any configuration, can have a constant or linear slope, a piecewise linear slope, a non-linear slope and combinations of such slopes in the surface(s) that engage the spring  400 . If the cam  212  has a linear slope, rotation of the cam  212  increases or decreases the pressure setting in a linear way. If the cam  212  has a non-linear slope, the pressure, for example, can increase more towards the end of the rotation. This allows the possibility of having minute increments of pressure initially, for example, between 0 and 200 mm H 2 O, and larger increments of pressure thereafter. For example, the cam  212  illustrated in  FIGS. 6A and 6B  includes a surface with a non-linear slope that engages the first arm  410  of the spring  400 . Specifically, the cam  212  includes a projection  218 , which alters the rate of increase in the pressure exerted by the cam  212  on the spring  400  as the cam  212  rotates. Thus, in certain examples the force exerted by the cam  212  on the spring  400  increases in a substantially linear manner over the majority of the rotational cycle of the cam  212 ; however, toward the end of the cycle, the force increases more dramatically due to the influence of the projection  218 . 
     In certain applications, for example, in the treatment of hydrocephalus in children, it may be desirable to be able to determine whether or not the patient is still in need of the valve after some time of use or whether hydrocephalus has become arrested and is no longer in need of shunting. For example, depending on the cause of hydrocephalus, after several years of using an implanted shunt valve assembly  100 , the patient may no longer need the valve. One method of testing to determine whether or not the valve is still needed in the patient is to significantly increase the pressure of the spring  400  against the valve element  208 , thereby almost completely closing the valve  200 , and observe the patient&#39;s condition thereafter. Accordingly, the above-described configuration in which the step pressure increase is significantly larger at or close to the maximum pressure position of the spring  400  and cam  212  may advantageously allow this testing to be performed. If the patient&#39;s condition deteriorates after the pressure setting of the valve  200  is significantly increased, the pressure setting may simply be decreased again, by rotating the cam  212 . Thus, this configuration provides a safe quasi-OFF setting for the valve  200 , without having the valve  200  completely closed or removed. 
     According to certain examples the magnetic motor may include a rotor stop or cam stop  220  that prevents 360 degree rotation of the cam  212 , and thereby prevents the valve from being able to transition immediately from fully open to fully closed, or vice versa, in one step. The cam  212  can rotate either clockwise or anticlockwise up to the position set by the cam stop  220 , and then must rotate in the opposite direction. Thus, a full rotation of the cam  212  is required to transition the valve from fully open to fully closed, or vice versa, rather than only a small step or incremental rotation. 
     In certain examples, after the valve assembly  100  is manufactured, a calibration device is typically needed to adjust the pressure settings. For example, in certain embodiments the spring  400  may be constructed such that it is linear with respect to each step, that is, with each step of rotation of the cam  212 , the spring  400  is tensioned so that the pressure of the valve  200  goes up by X amount, and this is true for each additional step of rotation. Accordingly, it may be necessary to calibrate the device to set the cam  212  at a given position and pre-tension the spring  400  to an appropriate pressure for that position. Therefore, after the valve  200  is assembled and during the calibration, there may be a flow of nitrogen (or some other fluid) through the valve assembly. 
       FIGS. 10A and 10B  schematically illustrate an example of the magnetic rotor  510  including ten rotor magnet elements  512  arranged in a circle, as discussed above, and configured such that clockwise rotation increases the pressure setting of the programmable valve  200 .  FIG. 10A  shows the rotor  510  and the spring  400  in the position of minimum tension on the spring, corresponding to a lowest pressure setting of the valve  200 .  FIG. 10B  shows the rotor  510  and the spring  400  after clockwise rotation from position shown in  FIG. 10A  into the position of maximum tension on the spring, corresponding to a highest pressure setting of the valve  200 . As discussed above, the rotor  510  may rotate through a plurality of incremental steps, indicated at  518 , each step corresponding to a defined change in the pressure setting of the valve  200 . As also discussed above, the rotor  510  may include the cam stop  220  which may prevent 360 degree rotation of the cam  212 , and thereby prevents the valve from being able to transition immediately from fully open to fully closed, or vice versa, in one step. In one example, schematically illustrated in  FIGS. 10A and 10B , at the maximum and minimum pressure settings of the valve  200 , the cam stop  220  abuts a housing stop  222 . The cam stop  220  and housing stop  222  are sized and arranged such that the cam stop cannot pass the housing stop, thereby preventing further rotation of the cam in the same direction. Accordingly, when the rotor  510  is in the position of the minimum pressure setting of the valve  200  ( FIG. 10A ), the rotor must rotate clockwise, thereby gradually increasing the pressure setting of the valve. Counter-clockwise rotation, which would transition the valve  200  from the minimum pressure setting to the maximum pressure setting in one step is prevented by the cam stop  220  and housing stop  222 . Similarly, when the rotor  510  reaches the position corresponding to the maximum pressure setting of the valve  200  ( FIG. 10B ), further clockwise rotation of the cam is prevented by cam stop  220  and the housing stop  222 , such that the rotor must rotate counter-clockwise, thereby gradually decreasing the pressure setting of the valve. 
     As also shown schematically in  FIGS. 10A and 10B , in certain examples the valve  200  may include a pair of radiopaque markers, namely a rotor marker  224  and a housing marker  226 , that can be seen in an X-ray and indicate the position of the rotor  510 , and therefore the pressure setting of the valve  200 . In one example the pair of radiopaque markers  224  and  226  are localized in such a way that at the lowest pressure setting of the valve, the two markers are aligned with the center of the cam, as shown in  FIG. 10A . The housing marker  226  is fixed in the housing of the valve  200  and does not rotate with the rotor  510 , whereas the rotor marker  224  rotates with the cam/rotor. 
     In some embodiments, the radiopaque markers  224 ,  226  include tantalum. In some embodiments, the radiopaque markers  224 ,  226  include tantalum spheres and/or tantalum beads. 
     As discussed above, because embodiments of the valve assembly  100  comprise a magnetically actuated rotor  510 , the pressure setting of the implanted programmable valve  200  can be adjusted by positioning an external adjustment device (also referred to herein as a valve programmer) in proximity to the implanted valve  200  but external to the body. The valve programmer includes a magnetic field generator, along with various control and input/output (I/O) components to allow a user (e.g., a doctor) to control the valve programmer to set and optionally read the pressure setting of the implanted programmable valve  200 . In certain embodiments, the magnetic field generator can include an arrangement of electromagnets, as discussed below with reference to  FIGS. 11A, 13, 15, 16A -H,  17 , and  18 A-H. In other embodiments, the magnetic field generator can include one or more permanent magnets, and the valve programmer can be battery operated, as discussed further below with reference to  FIGS. 11B, 11C, 19-22, 23A -E, and  24 . 
       FIG. 11A  illustrates a valve programmer  600  including a transmitter head  610  which may be placed over the patient&#39;s head at a location over an implanted magnetically-programmable valve  200 . The transmitter head  610  includes a magnetic field generator, as discussed further below, that applies magnetic pulses to selectively magnetize the stator  528  and thereby cause rotation of the rotor  510 . Fluid flows from the ventricle, through a ventricular catheter  120 , through the implanted valve, into the distal catheter connected to the connector  140 , which then drains the fluid at a remote location of the body (such as the right atrium of the heart or to the peritoneal cavity). The valve programmer  600  may send a magnetic signal through the transmitter head  610  to effect rotation of the rotor  510 . A control device  620  may be used to control the transmitter head  610  to produce the magnetic pulses, as discussed further below, and may be coupled to the transmitter head  610  via a communications link  630 , such as a cable or wireless link, for example. 
     Referring to  FIG. 12 , according to certain embodiments, the control device  620  can include a variety of components or modules to enable a user to control the adjustment device to alter the pressure setting of the implantable valve  200 , and to determine the current pressure setting of the valve. The control device  620  can include a user interface  622  that allows a user to interact with the control device. The user interface can include one or more displays or input devices, such as input keys, touch screens, etc., to allow a user to view and adjust the pressure settings of the valve  200 . In certain embodiments the control device  620  can further include drive circuitry  624  in communication with the transmitter head  610 . A controller  632  may be used to provide instruction to the drive circuitry  624  to drive the magnetic field generator in the transmitter head  610  with a predetermined current, duration, cycle, etc., based on instructions received via the user interface  622 , for example. The controller  632  may further receive inputs from a setting detector  626 , and control the user interface  622  to display the valve pressure setting responsive to information received from the setting detector. The controller  632  may be preprogrammed, for example, by computer instructions stored on a computer readable medium or device, such as a hard disk drive, an optical disk readable by an optical disk reader, a flash memory device, and the like. The control device  620  may be operated to allow a user to adjust the valve  200  through the programmable controller  632  and to determine a setting of the valve  200 . In some embodiments, the control device  620  may further include a communication interface  628 , which can be used to connect the control device  620  to another device, such as an application server of a networked computer for similarly controlling or otherwise operating the valve  200 . 
       FIG. 11B  illustrates another embodiment of an external adjustment device  640  that includes a single integrated device, rather than a separate transmitter head  610  and control device  620  as in the example of  FIG. 11A . According to one example, the external adjustment device  640  includes permanent north and south magnets that generate a magnetic field, which when rotated, selectively magnetizes the stator  528  and thereby causes rotation of the rotor  510 . 
       FIG. 11C  illustrates an example of an external valve reading device that includes a valve reading device (pressure reader)  660  for detecting the positional aspect of the rotor  510  in determining the pressure setting of the valve  200 . In the illustrated example the pressure reader  660  includes a mechanical compass; however, in other examples the mechanism can be electronic, including a magnetic positional sensor, for example. Embodiments of the pressure reader are discussed in more detail below. In certain examples the pressure reader can be incorporated into embodiments of the valve programmer  600  of  FIG. 11A , and configured to determine the positional aspect of the rotor  510 , or otherwise read the pressure setting of the valve  200 , when the magnetic field generator in the transmitter head  610  is off. 
     According to certain embodiments, valve pressure adjustments can be made by applying a pulsed magnetic field to the vicinity of the programmable shunt valve as shown diagrammatically in  FIGS. 13, 14, 15, 16A -H,  17 , and  18 A-H. The transmitter head  610  is placed in proximity to the implanted valve  200 . In one embodiment, the transmitter head  610  contains four electromagnets, illustrated schematically in  FIG. 13  as coils 1, 2, 3, and 4, which are separately controlled by the external control device  620  (for example, via drive circuitry  624  as discussed above). In the example shown in  FIGS. 13 and 14  and as discussed above, the magnetically operable motor of the implanted valve  200  includes the rotor  510 , having twelve rotor magnet elements  512  arranged with alternating polarity in channel  522  of the rotor casing  514 ), as discussed above. The motor further includes the stator  528  positioned below the rotor  510 . In the illustrated example, the stator  528  has an X shape. Thus, in this example, the four electromagnets (also referred to as coils) in the transmitter head  610  are positioned such that coils 1 and 3 and coils 2 and 4 are closer to one another than are coils 1 and 4 and coils 2 and 3, as shown in  FIG. 13 . The four electromagnets can further be positioned equidistant from a central axis  530 . When the transmitter head  610  is positioned properly over the implanted valve  200 , the central axis  530  of the electromagnets is coincident with the axis of rotation  214  of the rotor  510 , and each electromagnet is aligned at the same angular position as one arm of the stator  528 , as shown in  FIG. 13 . It is not, however, necessary that this alignment be exact. Embodiments are tolerant of alignment errors, which may be unavoidable owing to the inability of the user to see the rotor  510  or the stator  528  and to the small size of those elements relative to the size of the external electromagnets. 
     Each of electromagnets 1, 2, 3, and 4 can be energized to have either the north or south polarity facing the stator  528 , or each can remain off altogether. Movement of rotor  510 , in the desired direction and through the desired angle, is achieved by energizing the electromagnets in the sequences shown in the tables in  FIG. 15  (clockwise rotation) or  FIG. 17  (counter-clockwise rotation), which in turn magnetizes the stator  528 , which then attracts or repels the rotor magnet elements  512  (depending on polarity), causing rotation of the rotor  510 . 
     For example, referring to  FIGS. 15 and 16A -H, clockwise motion is achieved by first energizing both electromagnets 1 and 2 to south polarity, and leaving electromagnets 3 and 4 off (step 1). In the next step (step 2) electromagnets 1 and 2 are left off, and electromagnets 3 and 4 are both energized to south polarity. In step 3, electromagnets 1 and 2 are both energized to north polarity, while electromagnets 3 and 4 remain off, and in step 4, electromagnets 1 and 2 are left off while electromagnets 3 and 4 are energized to north polarity. The sequence repeats itself after the fourth step. 
     The rotor  510  is shown in  FIG. 16B  in the position reached after the first step (the polarities of the rotor magnet elements  512  are those corresponding to the bottom surface). As shown in  FIGS. 16A and 16B , energizing the electromagnets 1 and 2 such that the south poles are towards the stator  528 , and face towards each other, causes the stator  528  to become magnetized with a north polarity. Accordingly, the now north-magnetized stator  528  pulls those rotor magnet elements  512  having south polarity towards itself, while repelling those rotor magnet elements  512  having north polarity. The result is clockwise rotation of the rotor  510 , as indicated by arrow  532 . Rotation of the rotor  510  may further be seen through  FIGS. 16A-H  by observing the changing position of reference marker  526 . Similarly, in step 2 when electromagnets 3 and 4 are energized such that the south poles are towards the stator  528 , and face towards each other, the stator  528  is again magnetized with a north polarity, and acts on the rotor magnet elements  512  to induce further clockwise rotation of the rotor  510 , as shown in  FIGS. 16C and 16D .  FIGS. 16E-H  demonstrate the operation corresponding to steps 3 and 4 of  FIG. 15 . In particular, energizing the electromagnets 1 and 2 such that the north poles are towards the stator  528 , and face towards each other (step 3), causes the stator  528  to become magnetized with a south polarity, as shown in  FIG. 16E . Accordingly, the now south-magnetized stator  528  pulls those rotor magnet elements  512  having north polarity towards itself, while repelling those rotor magnet elements  512  having south polarity. The result is further clockwise rotation of the rotor  510 , as indicated by arrow  532  and shown in  FIG. 16F . Similarly, in step 4 when electromagnets 3 and 4 are energized such that the north poles are towards the stator  528 , and face towards each other, the stator  528  is again magnetized with a south polarity, and acts on the rotor magnet elements  512  to induce further clockwise rotation of the rotor  510 , as shown in  FIGS. 16G and 16H . 
     Movement of rotor  510  is influenced predominantly by the stator  528  positioned beneath the rotor  510  and close to the rotor magnet elements  512  of the rotor  510 . Thus, the applied external magnetic field from the electromagnets 1, 2, 3, and 4 does not directly cause movement of the rotor  510 , but instead controls magnetization and polarity of the stator  528 , which then acts upon the rotor magnet elements  512  to induce rotation of the rotor  510 . The number of rotor magnet elements  512  and the shape of the stator  528  are selected such that two conditions are met. First, when one pair of radially opposite stator arms is aligned with one pair of radially opposite rotor magnet elements  512  (e.g., referring to  FIG. 16C , stator arms  534   a  and  534   b  are aligned with rotor magnet elements  512   a  and  512   b , respectively) the other two stator arms are each staggered halfway between two of the rotor magnet elements  512 , as shown in  FIG. 16C , for example. Second, each pair of radially opposite rotor magnet elements (e.g.,  512   a  and  512   b  in  FIG. 16C ) has the same magnetic polarity. In operation, control device  620  energizes the electromagnets closest to the pair of stator arms staggered between two rotor magnet elements  512 , thereby causing the rotor  510  to move through an angle corresponding to one half the width of one rotor magnet element  512 . As discussed above, in one example there are twelve magnetic rotor elements  512  and thus  24  angular increments in one full revolution of the rotor  510 . Furthermore, this configuration, in which radially opposite rotor magnet elements  512  have the same magnetic polarity and radially opposite electromagnets are also energized to have the same magnetic polarity facing the stator  528  (e.g., south in  FIG. 16A ) advantageously results in the magnetically programmable valve being highly resistant to other (non-programming) magnetic fields. Randomly applied magnetic fields resulting from natural phenomena or external devices unrelated to the control device  620  (e.g., MRI machines) are highly unlikely to have two same poles (e.g., both poles being either north or south) applied at opposite ends of the stator  528 . To the contrary, an external, non-programming field is far more likely to have side-by-side north and south poles, which will fail to uniformly magnetize the stator  528 , as is required for controlled operation (as shown in  FIGS. 16A-H ) and therefore will fail to cause unwanted or accidental rotation of the rotor  510 . In contrast, a conventional magnetic rotor, such as that disclosed in U.S. Pat. No. 4,615,691, for example, the rotor includes radially opposite permanent magnets having opposite magnetic polarities (as shown in FIG. 9 of U.S. Pat. No. 4,615,691), along with a cross-shaped stator that is magnetized with one half having one polarity and the other half having the opposite polarity, unlike the stator  528  disclosed herein, which is uniformly magnetized with a single magnetic polarity responsive to the external programming field, as discussed above. Consequently, the conventional device is far more susceptible to unwanted rotation, and therefore unwanted adjustment of the pressure settings of the valve, due to external non-programming magnetic fields. 
     As discussed above, in one example the rotor  510  includes twelve rotor magnetic elements  512 ; however, in other examples the rotor  510  can be sized and designed to include a different number of rotor magnet elements  512  (e.g., eight), provided that radially opposite elements have the same magnetic polarity. Further, in other examples in which the rotor  510  is configured to be operated by a differently configured valve programmer, as discussed in more detail below, the rotor may be sized and designed to accommodate a number of rotor magnet elements  512  such (e.g., ten) that radially opposite rotor magnet elements have opposite polarity. 
     Similar operation can be initiated to induce counter-clockwise rotation of the rotor  510 . For example,  FIG. 17  is a table, similar to that illustrated in  FIG. 15 , showing an example of an energizing sequence of the electromagnets of the device of  FIG. 13  to effect counter-clockwise rotation of the rotor  510 .  FIGS. 18A-H  illustrate the magnetic polarities of the electromagnets and stator  528 , and resulting movement of the rotor  510 , corresponding to the sequence shown in  FIG. 17 . 
     Thus, referring to  FIGS. 17 and 18A -H, counter-clockwise motion is achieved by first energizing both electromagnets 1 and 2 to north polarity, and leaving electromagnets 3 and 4 off (step 1). In the next step (step 2) electromagnets 1 and 2 are left off, and electromagnets 3 and 4 are both energized to south polarity.  FIGS. 18A-D  correspond to steps 1 and 2, with  FIG. 18B  showing the rotor  510  in the position reached after step 1, and  FIG. 18D  showing the rotor  510  in the position reached after step 2. As shown in  FIGS. 18A-B , energizing the electromagnets 1 and 2 to north polarity causes the stator  528  to become magnetized to south polarity, and induces counter-clockwise rotation of the rotor  510 , indicated by arrow  536 , by acting on the rotor magnet elements  512  as discussed above. Similarly, as shown in  FIGS. 18C-D , energizing the electromagnets 3 and 4 to south polarity causes the stator  528  to become magnetized to north polarity, and induces further counter-clockwise rotation of the rotor  510 , indicated by arrow  536 . In step 3, electromagnets 1 and 2 are both energized to south polarity, while electromagnets 3 and 4 remain off, and in step 4, electromagnets 1 and 2 are left off while electromagnets 3 and 4 are energized to north polarity.  FIGS. 18E-H  demonstrate the operation corresponding to steps 3 and 4 of  FIG. 17 . In particular, energizing the electromagnets 1 and 2 such that the south poles are towards the stator  528 , and face towards each other (step 3), causes the stator  528  to become magnetized with a north polarity, as shown in  FIG. 18E . Accordingly, the now south-magnetized stator  528  pulls those rotor magnet elements  512  having north polarity towards itself, while repelling those rotor magnet elements  512  having south polarity. The result is further counter-clockwise rotation of the rotor  510 , as indicated by arrow  536  and shown in  FIG. 18F . Similarly, in step 4 when electromagnets 2 and 3 are energized such that the north poles are towards the stator  528 , and face towards each other, the stator  528  is magnetized with a south polarity, and acts on the rotor magnet elements  512  to induce further counter-clockwise rotation of the rotor  510 , as shown in  FIGS. 18G and 18H . The sequence repeats itself after the fourth step. Each step results in an increment of angular movement of the rotor  510  corresponding to one half the width of one rotor magnet element  512 , as discussed above. 
     Although operation of the magnetic motor and transmitter head  610  is discussed above with reference to a rotor including twelve rotor magnet elements  512 , given the benefit of this disclosure, those skilled in the art will appreciate that operation of the transmitter head  610  and its electromagnets can be adjusted for a rotor having a different number of rotor magnet elements, such as ten rotor magnet elements, for example. 
     Thus, using an implanted valve  200  having the magnetic motor discussed above, along with an external controller that includes a control device  620  and transmitter head  610  having the four electromagnets 1, 2, 3, and 4, the pressure setting of the implantable valve can be non-invasively controlled in small increments. The configuration of the cam  212  and the tension in the spring  400  can be designed and calibrated such that each angular increment of the rotor  510  produces a well-defined selected change in the pressure setting of the valve (e.g., 10 mm H 2 O). In one example, the control device  620  can be configured to allow the user to enter a desired pressure setting for the valve, and then automatically activate the transmitter head  610 , using one of the sequences shown in  FIG. 15 or 17 , for example, to achieve the selected pressure setting. 
     In one example, to ensure an accurate pressure setting of the valve  200 , the control device  620  can be configured to first activate the counter-clockwise rotation sequence of  FIG. 17  to set the valve  200  to its fully open position, and then activate the clockwise rotation sequence of  FIG. 15  to set the valve  200  to the selected pressure setting entered by the user. According to certain examples, when the counter-clockwise rotation sequence is activated, the valve programmer is configured to actuate the rotor  510  to rotate through a sufficient number of counter-clockwise steps such that the rotor will be positioned such that the valve  200  has its lowest pressure setting. As discussed above, the presence of the cam stop  220  and housing stop  222  prevent the rotor from continuing to rotate past the minimum pressure setting position. After the programmer stops the counter-clockwise rotation sequence, it may start the clockwise sequence from a known position (the position corresponding to the minimum pressure setting and with the cam stop  220  abutting the housing stop  222 ). The valve programmer  700  may actuate the rotor  510  to rotate through a selected number of clockwise steps so as to program the valve  200  to the pressure setting selected by the user. 
     Although the example discussed above uses clockwise rotation of the rotor  510  to program the pressure setting of the valve  200  (and counter-clockwise rotation to set the rotor to a known position from which to begin the programming sequence), those skilled in the art will appreciate, given the benefit of this disclosure, that the system (valve and programmer) can instead be configured for the opposite arrangement, namely to use counter-clockwise rotation of the rotor to program the pressure setting of the valve (and clockwise rotation to set the rotor to a known position from which to begin the programming sequence). 
     In some instances it may be preferable that the external valve programmer can be battery operated. Transmitter heads such as transmitter head  610  that include electromagnets may require too much power (to energize the electromagnets) to be battery-powered. Accordingly, further aspects and embodiments are directed to a valve programmer, such as the example valve programmers illustrated in  FIG. 11B , that incorporates permanent magnets along with a small DC motor, such as a stepper motor, for example, to provide a very low power controller that can be used with the implanted valve  200  and that can be battery-powered. 
     Referring to  FIG. 19  there is illustrated a block diagram of one example of a valve programmer  700  incorporating permanent magnets rather than electromagnets. The valve programmer  700  includes a controller  702 , a user interface  704 , a battery  706 , a stepper motor  708 , and a permanent magnet assembly  710 . These components can be packed together in a single housing that can be held near the implanted valve  200  to control and adjust the pressure setting of the valve  200 , as illustrated in  FIG. 11B , for example. Alternatively, certain components, such as the permanent magnet assembly  710 , stepper motor  708  and battery  706  can be packaged together, optionally including a controller that may perform all or some of the functionality of the controller  702 , and user interface  704  (optionally with a controller that may perform all or some of the functionality of the controller  702 ) can be packaged separately to allow the user to more conveniently view the user interface  704  while operating the valve programmer  700 . For example, the user interface  704  can be implemented as an application running on a mobile computing device, such as a smart-phone or table computer, for example, that allows the user to view the pressure setting of the valve  200  and enter commands (such as to select a desired pressure setting of the valve  200 ). The user interface  704  can receive pressure setting information from the controller  702 , for example, and transmit the user commands to the other, optionally separately packaged components of the valve programmer  700 , for example to the controller  702  or to the stepper motor  708  to actuate the permanent magnet assembly  710  to adjust the pressure setting of the valve  200 . 
       FIG. 20A  is an illustration of one example of a permanent magnet assembly  710   a  that can be used in the valve programmer  700  according to certain embodiments. The permanent magnet assembly  710   a  includes a housing  712  and a rotatable magnet guide  714  disposed within the housing  712  and configured to rotate about a central axis of rotation  716 . In one example, the stepper motor  708  drives rotation of the magnet guide  714  under control of the controller  702 . The rotation of the magnet guide  714  can be continuous or a series of discrete steps. A plurality of permanent magnets are mounted to or within the magnet guide  714  such that the permanent magnets rotate with the magnet guide  714 . In the example illustrated in  FIG. 20A  there are four permanent magnets  722 ,  724 ,  726 , and  728 . The two radially opposite permanent magnets have the same magnetic polarity. For example, as illustrated in  FIG. 20A , permanent magnets  722  and  724  have north polarity while permanent magnets  726  and  728  have south polarity. This configuration is appropriate for controlling the rotor  510  having twelve rotor magnet elements  512 , for example. 
     Those skilled in the art will appreciate that a wide variety of modifications to the permanent magnet assembly  710  can be made. For example, although the four permanent magnets  722 ,  724 ,  726 , and  728  are illustrated in  FIG. 20A  as being round, they may have other shape, such as, but not limited to, rectangular, oval, bar-shaped, rod-shaped, and the like. Additionally, there may be more than or fewer than four permanent magnets. For example,  FIG. 20B  illustrates a configuration in which the permanent magnet assembly  710   b  includes a pair of permanent magnets  732  and  734  of opposite magnetic polarity. This configuration may be appropriate for controlling the rotor  510  having ten rotor magnet elements  512 , instead of twelve, for example. In another example, the permanent magnet assembly  710   b  can include a single diametrically magnetized permanent magnet, rather than two separate magnets of opposite polarity. It is further to be appreciated that any of the permanent magnets  722 ,  724 ,  726 ,  728 ,  732 , or  734  can be comprised of a cluster of multiple permanent magnets of the same magnetic polarity, rather than being single permanent magnets. Actuated by the stepper motor  708 , the magnet guide  714 , and therefore the plurality of permanent magnets  722 ,  724 ,  726 , and  728 , or  732  and  734 , rotate about the axis of rotation  716 . When the valve programmer  700  is placed over the implanted valve  200 , the permanent magnet assembly  710  magnetizes the stator  528 . Rotation of the magnet guide  714  changes the magnetization of the stator  528 , and thereby induces movement of the rotor  510 , similarly as discussed above with respect to the transmitter head  610 . 
       FIGS. 21A-E  diagrammatically illustrate an example of the changing magnetic polarity of the stator  528 , and resulting rotation of the rotor  510 , responsive to rotation of the magnet guide  714  for the example of the valve programmer  700  including the permanent magnet assembly  710   a  of  FIG. 20A . In  FIGS. 21A-E , the permanent magnet assembly  710   a  is diagrammatically represented by ring  718 . As shown in  FIG. 21A , for example, the ring  718  has four magnetic quadrants, two of each magnetic polarity ( 730   a  and  730   c  are north, and  730   b  and  730   d  are south) and with radially opposite quadrants having the same magnetic polarity, corresponding to the four permanent magnets  722 ,  724 ,  726 , and  728  shown in  FIG. 20A . The ring  718  includes a controller reference marker  736  which is intended to illustrate rotation of the magnet guide  714  through  FIGS. 21A-E  and which does not necessarily correspond to a physical structure. Similarly, a rotor reference marker  538  is illustrated on one of the rotor magnet elements  512  to illustrate rotation of the rotor  510  through  FIGS. 21A-E . 
     Referring to  FIG. 21A , in a first position, the two oppositely positioned permanent magnets having south polarity (permanent magnets  726  and  728  in  FIG. 20A ) corresponding to quadrants  730   b  and  730   d  of ring  718  cause the opposing stator arms  534   c  and  534   d  to which they are closest or aligned to be magnetized to north. Similarly, the other two oppositely positioned permanent magnets having north polarity (permanent magnets  722  and  724  in  FIG. 20A ) corresponding to quadrants  730   a  and  730   c  of ring  718  cause the other two opposing stator arms  534   a  and  534   b  to which they are closest or aligned to be magnetized to south. The stator arms  534   a  and  534   b  now magnetized to south are staggered between two rotor magnet elements of opposite magnetic polarity, and therefore pull the north-polarized rotor magnet elements  512   a  and  512   b  while repelling the south-polarized rotor magnet elements  512   c  and  512   d , resulting in rotation of the rotor  510  to the position shown in  FIG. 21B . The rotor  510  rotates through an angle corresponding to one half the width of one rotor magnet element  512 , as illustrated by the relative displacement of the rotor reference marker  538  from  FIG. 21A  to  FIG. 21B . The degree of rotation of the rotor  510  corresponds to a 45 degree rotation of the ring  718 , as illustrated by the relative displacement of the controller reference marker  736  from  FIG. 21A  to  FIG. 21B . 
     In  FIG. 21A , the four permanent magnets  722 ,  724 ,  726 , and  728 , represented by quadrants  730   a - d  of the ring  718 , are each aligned with one of the stator arms  534   a - d , respectively. Referring to  FIG. 21B , in this second position, which is achieved by 45 degrees of rotation of the ring  718  (i.e., as indicated by the reference marker  736  of the permanent magnet assembly  710   a ) from the first position ( FIG. 21A ), each of the four permanent magnets  722 ,  724 ,  726 , and  728 , represented by quadrants  730   a - d  of the ring  718 , is now staggered across two stator arms. As a result, each of the stator arms  534   a - d  has a split magnetic polarization, with a portion of each arm being magnetized to north and another portion being magnetized to south, as shown in  FIG. 21B . 
     Referring to  FIG. 21C , a further 45 degree rotation of the magnet guide  714  as indicated by the reference marker  736  re-aligns the four permanent magnets  722 ,  724 ,  726 , and  728  of the permanent magnet assembly  710   a  with the stator arms  534   a - d . As shown, opposing stator arms  534   a  and  534   b  are now magnetized to north, and opposing stator arms  534   c  and  534   d  are now magnetized to south. The stator arms  534   a  and  534   b  now magnetized to north are again staggered between two rotor magnet elements  512  of opposite magnetic polarity, and therefore repel the north-polarized rotor magnet elements  512   a  and  512   b  and pull the south-polarized rotor magnet elements  512   c  and  512   d , resulting in another angular increment (corresponding to one half the width of one rotor magnet element  512 ) of rotation of the rotor  510  to the position shown in  FIG. 21D . 
     Referring to  FIG. 21D , a further 45 degree rotation of the magnet guide  714 , represented by ring  718  and indicated by the reference marker  736 , again results in the arms of the stator  528  each having split magnetic polarity. Another 45 degree rotation of the magnet guide  714  returns the stator  528  to the magnetic polarity configuration of  FIG. 21A  and causes rotor  510  to rotate by another angular increment, as shown in  FIG. 22 . The cycle continues to repeat with further rotation as shown in  FIG. 21E  of the magnet guide  714  for the external permanent magnets  722 ,  724 , 726 , and  728  of  FIG. 20A . 
     Thus, for the implementation of the rotor  510  shown in  FIG. 4C , for example (circular arrangement of twelve rotor magnets  512 ) and the valve controller including the permanent magnet arrangement shown in  FIG. 20A , 180 degrees of rotation of the magnet guide  714  (as can be seen by comparing the positions of the controller reference marker  736  in  FIGS. 21A and 21E ) results in four angular increments of rotation of the rotor  510  (corresponding to movement equivalent to two times the width of one rotor magnet element  512 ), as may be seen by comparing the positions of the rotor reference marker  538  in  FIGS. 21A and 21E . Thus, three complete revolutions of the magnet guide  714  results in one complete revolution of the rotor  510 . This “gear reduction” effect achieved through the indirect action of the valve programmer  700  on the rotor  510  (via the stator  528 ) advantageously allows for very small incremental movements of the rotor  510  without requiring correspondingly small movements in the valve programmer  700 . This can improve ease of use of the valve programmer  700  by a user, or simplification of manufacture of the valve programmer  700  because the magnet guide  714  is not required to be as small as the rotor  510  of the implantable valve  200 . 
     Adjustments in the gear ratio between the valve programmer  700  and the rotor  510  can be achieved by altering the configuration (e.g., number of magnets) of the permanent magnet assembly or the rotor  510 . For example, using a similar rotor arrangement as shown in  FIG. 4C , but with ten rotor magnets instead of twelve rotor magnets, and the permanent magnet assembly with two permanent magnets  732  and  734  of  FIG. 20B  instead of that of  FIG. 20A , results in five complete revolutions of the magnet guide  714  causing one complete revolution of the rotor  510 . As will be appreciated by those skilled in the art, given the benefit of this disclosure, various other combinations of external permanent magnets and rotor magnets can be implemented, and are considered as part of this disclosure and intended to be within the scope of the present invention. 
       FIG. 22  is a flow diagram showing rotation of the valve programmer and corresponding changing magnetization of the stator and rotation of the rotor, in accord with the operation discussed above with reference to  FIGS. 21A-E . Arrows  119 A show rotation of the rotor at each step in the flow diagram. 
     In certain examples the valve programmer  700  can be packaged in a hand-held housing  762  such that it is comfortable and easy for a user to use.  FIGS. 23A-23D  illustrate an example  760  of the valve programmer  700 . In this example, the valve programmer  760  has a shape that is similar to a computer mouse. As shown, in some embodiments, the valve programmer  760  has rounded corners on its outer surfaces, and may have an overall rounded shape, which may be easy and/or comfortable for a user to hold. In some embodiments, the valve programmer  760  can be easily held by a user in one hand. 
       FIG. 23A  shows a top view of the valve programmer  760 .  FIG. 23B  shows an underside view of the valve programmer  760 .  FIG. 23C  shows an end view of the valve programmer  760 , and  FIG. 23D  shows a perspective view of the valve programmer  760 . 
     As discussed above, the valve programmer  760  can be battery operated. Accordingly, in some embodiments, the housing  762  can house one or more batteries, along with the magnet assembly  710  (not shown in  FIGS. 23A-D ). As discussed above, in some embodiments, the valve  200  includes a ten magnet stepper motor, and the magnet assembly  710  of the valve programmer  760  two oppositely magnetized magnets for rotating the stepper motor of the valve  200 . The two oppositely magnetized magnets have opposite fields oriented downwardly within the valve programmer  760 . In some embodiments, the programmer magnets have a surface field strength of 6000 gauss. 
     As shown in  FIGS. 23A and 23D , the valve programmer  760  may include a user interface  764  that shows information such as the pressure setting, the battery status  770 , and optionally other information. For example, the center of the user interface  764  screen may show the pressure that was selected (in a digital read-out). The border of the screen may include an indication of what an X-ray would show, or the position of the valve rotor that may be indicated by a pressure reader, as discussed further below. 
     The valve programmer  760  includes an interface mechanism to allow a user to select the pressure setpoint of the valve programmer  760 , and thereby to set the pressure of the valve  200 . In some embodiments, as shown in  FIG. 23A , the valve programmer  760  includes a first button  761   a  to increase the pressure setpoint and a second button  761   b  to decrease the pressure setpoint. Alternatively, the valve programmer  760  may include a wheel (such as the wheel shown in the embodiment of  FIG. 23E ) that is rotatable in a first direction to increase the pressure setpoint, and rotatable in a second direction to decrease the pressure setpoint. In some embodiments, the valve programmer  760  can include the first button  761   a , the second button  761   b , and the wheel. In some embodiments, the valve programmer  760  can set the valve  200  to one of 20 pressure settings, as discussed above. In some embodiments, the highest pressure setting does not completely close the valve  200 . This can be useful for testing whether the patient still needs the valve  200  without completely closing the valve  200  and thereby avoiding potential injury to the patient. 
     The valve programmer  760  may further include a programming button  769  that when pressed causes the valve programmer  760  to actuate the magnet assembly  710  to program the valve  200 . In some examples the programming button  769  can be located on the front edge of the housing  762 , as shown in  FIG. 23A . 
     The valve programmer  760  may also include an on/off button  772 , as shown in  FIGS. 23A and 23C . 
     Referring to  FIGS. 23B and 23C , the housing  762  of the valve programmer  760  can be shaped to facilitate correctly orienting the valve programmer  760  over an implanted valve  200  to program the pressure setting of the valve  200 . In certain examples, the housing  762  includes a molded cavity  763  defined by sidewalls  765  on the bottom of the valve programmer  760 . The cavity  763  is shaped and sized to correspond at least approximately to the shape and size of the implanted valve  200 . The cavity  763  includes a pair of channels  767  defined in the sidewalls  765 . As discussed above, the inlet port of the programmable valve  200  can be connected to an inflow catheter, and the outlet port of the programmable valve  200  can be connected to a drainage catheter. The channels  767  can be sized and arranged such that, when the valve programmer  760  is placed over the implanted valve  200  on the patient&#39;s head, the channels  767  align with the inflow catheter and the drainage catheter, thereby assisting to correctly align the valve programmer  760  with the implanted valve  200 . 
     After the user sets the desired pressure setpoint on the programmer  760 , the user places the programmer  760  on top of the valve  200 . Next, the user presses the programming button  769  on the front edge of the programmer  760  to start the programming. 
       FIG. 23E  shows a top view of a valve programmer  777 . The valve programmer  777  has a housing  762  that can be held in a user&#39;s hand. The valve programmer  777  includes a user interface  764  that shows information such as the pressure setting, the battery status  770 , and optionally other information. The valve programmer  777  includes a wheel  787  that is rotatable in a first direction to increase the pressure setpoint, and rotatable in a second direction to decrease the pressure setpoint. In  FIG. 23E , the wheel partially extends horizontally beyond a side of the housing  762  so that it can be rotated by a user&#39;s finger. 
       FIG. 24  is a flow diagram illustrating an example of a method  1100  of operating a valve programmer  700 , such as the valve programmer  760  of  FIGS. 23A-D  or the valve programmer  777  of  FIG. 23E . In step  1102 , the user turns on the valve programmer  760  by pressing the on/off button  772  on the programmer. In some embodiments, the valve programmer  760  turns on when the user presses and holds the on/off button  772  for two seconds. After being turned on, the valve programmer  760  proceeds to the initial mode at step  1104 . In the initial mode, the valve programmer  760  performs a self-test in which the motor turns counterclockwise and counts the steps for one turn, and compares the number of steps to the number of steps that should be needed for one turn. In some embodiments, the motor self-test is always active when the motor is turning. In some embodiments, the valve programmer display (user interface screen)  764  shows all icons for three seconds in step  1104 . If the charge on the valve programmer battery is too low, the valve programmer  760  proceeds to step  1106 , in which a battery status indicator  770  or indicator flashes on the user interface screen  764  and the valve programmer  760  turns off. In some examples, if the battery charge of the valve programmer  760  is low, the battery status indicator  770  flashes slowly on the programmer display  764 , and if the battery charge is extremely low, the battery status indicator  770  flashes quickly on the programmer display  764 . 
     If the battery charge is sufficient, the valve programmer  760  proceeds to step  1108 , which is edit mode. The battery status may be displayed on the user interface screen  764 , as discussed above. In the edit mode of step  1108 , an icon showing that the edit mode is enabled appears on the programmer display  764 . In the edit mode, a user can press the increase button  761   a  or the decrease button  761   b  to increase or decrease the valve programmer&#39;s pressure setpoint for the implanted valve  200 . In other examples in which the valve programmer  760  includes a wheel  787  for pressure setpoint adjustment rather than the buttons  761   a ,  761   b , the user can rotate the wheel in step  1108  to select a desired pressure setting. 
     Once the pressure setpoint has been selected, the valve programmer  760  is ready to be used to program an implanted valve  200 . Accordingly, the user can place the valve programmer  760  on a patient&#39;s head over the implanted valve  200 , using the shape of the housing  762  to correctly align the valve programmer  760  with the implanted valve  200 , as discussed above. To begin programming the valve  200 , the user presses the programming button  769  on the valve programmer  760 , and the programming mode at step  1110  is entered. In the programming mode, the programmer display  764  may show the selected pressure setpoint value along with a lock symbol, as shown in  FIG. 23A , for example. 
     In one example, to ensure an accurate pressure setting of the valve  200 , the valve programmer  700  can be configured to first actuate rotation of the magnet guide  714  in one direction (e.g., counter-clockwise) to set the valve  200  to its fully closed position, and then begin a sequence of rotations in the opposite direction (e.g., clockwise) to set the valve  200  to the selected pressure setting entered by the user. Accordingly, in certain embodiments after predetermined time period, for example, one second, the valve programmer  760  proceeds to step  1112 , in which the programmer magnets turn counterclockwise to initialize the valve  200 . For example, the programmer magnets of a permanent magnet assembly  710   a ,  710   b  can first be rotated counterclockwise for approximately six turns so that the cam of the programmable valve  200  is at its lowest position. After the initial position is reached, the valve programmer  760  proceeds to step  1114 , in which the programmer magnets start to turn clockwise. While the programmer magnets are turning the valve programmer  760  displays the current and final positions for the valve  200 . When the final position of the programmer magnets is reached, the valve programmer  760  proceeds to step  1116 , in which an alert, such as an audible alert, indicates that the selected pressure setpoint has been reached. After a predetermined time period, for example, three seconds, the valve programmer  760  returns to the edit mode of step  1108 . At this stage, a user can turn the valve programmer  760  off by pressing an on/off button  772 . In some embodiments, after a certain time period, e.g., 60 seconds, of no user interaction with the valve programmer  760 , the valve programmer  760  turns off automatically. 
     Returning to  FIGS. 14, 16A -H,  18 A-H,  21 A-E, and  22 , in the above-discussed examples, the stator  528  has an X shape, as shown in  FIG. 14 , for example, and is a “solid” or unitary structure. The shape of the stator  528  may vary between a + shape, with a 90° angle between the stator arms to a very narrow X shape, for example. In addition, according to certain embodiments, the stator  528  can be implemented using a plurality of discrete stator elements, rather than a single solid or unitary structure.  FIGS. 25A-C  illustrate three schematic examples of stators with different shapes, in combination with a twelve-magnet rotor.  FIG. 25A  shows an example of a +-shaped unitary stator  540 .  FIG. 25B  shows an example of a stator including four stator elements  542  placed beneath the rotor magnet elements  512  at positions roughly corresponding to the tips of the four stator arms in the example shown in  FIG. 25A . In the example illustrated in  FIG. 25B , the four stator elements  542  are configured as four circular dots; however, the stator elements may have any of variety of other shapes. For example,  FIG. 25C  illustrates another example of the stator including four stator elements  544  configured as “double circular dots” or extended ovals. In other examples, the stator elements  542  or  544  may be squares or rectangles, or have other geometric or non-geometric shapes. 
     In each of the examples shown in  FIGS. 25A-C , the angle  546  between the stator “arms” is approximately 90°; however, as discussed above, the angle  546  may vary. As will be appreciated by those skilled in the art, given the benefit of this disclosure, the angle  546  may have any value between 90° and a non-zero smallest value (an angular value of zero or very close to zero results in a two-arm stator, instead of a four-arm stator, which would change the operation of the magnetic motor) that may be dependent on the size of the stator  528  and the configuration of the rotor  510 , for example.  FIGS. 26A-C  illustrate further examples of stators in which the angle  546  is approximately 75°. In particular,  FIG. 26A  shows an example of an X-shaped unitary stator  540   a  in which the angle between the closer two stator arms is 75° and therefore the complimentary angle between the further apart stator arms is 105°.  FIGS. 26B and 26C  show examples stators including four discrete stator elements  542  and  544 , respectively, in which the angle  546  is 75°. In certain examples, the value of the angle  546  may be selected based at least in part on achieving resistance to external non-programming magnetic fields (e.g., from an MRI or other magnetic field generator not associated with the valve programmer) and desired movement of the rotor  510  (e.g., specific incremental movements of the rotor that correspond to particular incremental pressure settings of the valve). In certain examples, it may be desirable to configure the stator  528  such that the motor has a relatively high cogging torque. Cogging torque corresponds to the force required to keep the rotor  510  in a particular position. A high cogging torque may increase the motor&#39;s resistance or immunity to external non-programming magnetic fields, and can also prevent the rotor  510  from being moved by the counterforce of the spring  400 . 
     The use of discrete stator elements  542  or  544 , rather than a solid stator, reduces the amount of magnetic material as compared to the examples of the stator  540 ,  540   a  as exemplified in  FIGS. 25A and 26A . The magnetization of the stator elements  542  or  544  from an external magnetic field acts to rotate the rotor  510  in a similar manner as described above with reference to  FIGS. 16A-H ,  18 A-H,  21 A-E, and  22 . The rotation of the rotor  510  may be accomplished with either external electro-magnets, such as discussed above and shown in  FIG. 13 , for example, or with external permanent magnets, such as discussed above and shown in  FIGS. 20A and 20B , for example. In certain examples, the stator elements  542  may each be slightly larger (e.g., larger diameter if circular) than the rotor magnet elements  512 . For example, if the rotor magnet elements  512  have a diameter of 1.3 mm, the circular stator elements  542  shown in  FIG. 25B or 26B  may have a diameter of 1.4 mm. 
     As discussed above, according to certain embodiments the programmable valve  200  can include a magnetic indicator mechanism by which to allow a doctor, for example, to determine a pressure setting of the valve  200  using an external magnetic sensor, such as a Hall sensor for example, without requiring X-rays or other imaging techniques. In particular, in certain examples the magnetic motor can include one or more reference or indicator magnets that indicate a position of the rotor  510 . As discussed above, the rotor position is directly correlated to the pressure setting of the programmable valve  200 . Accordingly, in some examples the external valve programmer  700  can include a magnetic sensor configured to read or detect the pressure setting of the implanted valve  200  based on the indicator magnet(s). In other examples, a separate pressure reader can be provided, as discussed further below. 
     According to certain embodiments, the indicator mechanism can be incorporated into the rotor  510 . For example, as discussed above, the rotor  510  can include reference or positioning magnet elements  524  positioned on top of certain ones of the rotor magnet elements  512 , as illustrated in  FIGS. 4A, 5, 6A, and 14 .  FIG. 27  illustrates a schematic example of the rotor  510  including three reference magnet elements  524   a ,  524   b , and  524   c  positioned above certain ones of the rotor magnet elements  512 . In the illustrated example, reference magnet element  524   a  has north magnetic polarity, and reference magnet elements  524   b  and  524   c  are positioned approximately radially across from reference magnet element  524   a  (on either side of the rotor magnet element  512  that is directly radially opposite the reference magnet element  524   a ) and both have south magnetic polarity. As discussed above, the rotor magnet elements  512  are arranged with alternating magnetic polarity and such that each two rotor magnet elements  512  that are directly radially opposite one another have the same magnetic polarity. Accordingly, in order to provide a reference magnet that has both a north pole and a south pole and that spans the rotor  510 , an arrangement of three reference magnet elements  524  such as that shown in  FIG. 27  can be used. As discussed above, in other embodiments, the rotor  510  may include a number of rotor magnet elements  512  other than twelve. For example, the rotor  510  may include ten magnet elements. In such an example, only two reference magnet elements  524  may be used because the opposing rotor magnet elements in a ten-magnet rotor have opposite polarities, unlike the twelve-magnet rotor. In another example in which the rotor  510  includes ten magnet elements, four reference magnets (two opposingly-arranged pairs) can be used. Thus, as will be appreciated by those skilled in the art, given the benefit of this disclosure, various numbers and arrangements of reference magnet elements  524  can be used, at least partially based on the configuration of the rotor  510 . Additionally, in certain embodiments, rather than including separate reference magnet elements  524 , the rotor magnet elements  512  corresponding to the desired positions of the reference magnet elements can simply be made “taller” than the other rotor magnet elements, and thereby act as both rotor magnet elements that effect rotation of the rotor  510  and position-indicating magnets. 
     In other examples, instead of positioning the reference magnet elements  524  above the rotor magnet elements  512 , as shown in  FIGS. 4A, 5, 6A, 14, and 27 , the reference or positioning magnet elements can be positioned to the side(s) of the rotor  510 .  FIGS. 28A-28C  show examples of motor configurations in which vertically oriented (relative to the horizontally oriented rotor magnet elements  512 ) side positioning magnet elements  553  are positioned radially outward of the rotor magnet elements  512 . As discussed further below with reference to  FIG. 32 , the positioning magnets orient an indicator magnet (not shown in  FIGS. 28A-C ) that can be read by the pressure reader  660 , for example, to indicate a position of the rotor  510  and therefore the pressure setting of the valve  200 . Referring to  FIG. 28A , in there is illustrated an example in which two side positioning magnet elements  553  are provided. In this example, the polarity of the respective inner face  555  (i.e., face closer to the rotor magnet elements) of each side positioning magnet element  553  is opposite to the polarity of the top face of the adjacent rotor magnet element  512 . In some embodiments, each side positioning magnet  553  has, for example, a 1.0 millimeter diameter and a height of 0.3 millimeters.  FIG. 28B  shows another example in which four side positioning magnet elements  557  are provided. In this example, the polarity of the respective inner face  555  of each side positioning magnet element  557  is the same as the polarity of the top face of the adjacent rotor magnet element  512 . In some embodiments, each side positioning magnet  557  has, for example, a diameter of 0.85 millimeters and a height of 0.25 millimeters.  FIG. 28C  shows another example in which two side positioning magnet elements  559  are provided. In contrast to the example shown in  FIG. 28A , in which the two side positioning magnet elements  553  are placed diametrically opposite one another across the rotor  510 , in the example shown in  FIG. 28C  the two side positioning magnet elements are positioned in a same hemisphere of the rotor  510 . The polarity of the respective inner side  555  of each side positioning magnet  559  is the same as the polarity of the top face of the adjacent rotor magnet. In some embodiments, each side positioning magnet  559  has, for example, a diameter of 1.0 millimeter and a height of 0.3 millimeters. 
     Referring to  FIG. 29  there is illustrated a block diagram of an example of an external valve programming assembly  800  that incorporates a magnetic sensor  812  configured to detect a magnetic signal from the reference magnet elements  524  or indicator magnet (positioned by the positioning magnet elements  553 ,  557 , or  559 , for example) and derive therefrom a position of the rotor  510  and corresponding pressure setting of the valve  200 . As shown in  FIG. 29 , the valve programming assembly  800  can include a transmitter head  810  including a magnet assembly  814  (such as either the permanent magnet assembly  710  or a collection of electromagnets such as described above with reference to transmitter head  610 ) for adjusting the pressure setting of the valve  200  and communications/control circuitry  816  (such as an electronic communications port, motor, actuator, drive circuitry, and the like) as may be needed to control and operate the magnet assembly  814 . The valve programming assembly  800  further includes a control device  820  that includes a user interface  822  to allow the user to view information, such as the current pressure setting of the valve  200 , for example, and provide control commands, such as a desired pressure setting of the valve  200 , for example, along with communications/control circuitry  824  as may be needed to operate the control device  820  or communicate with the transmitter head  810 . In certain examples, the transmitter head  810  and control device  820  are separate and communicate via a wired or wireless communication link  804 . In other examples, the transmitter head  810  and control device  820  can be packaged together, as indicated by dashed line  802 , such as in the valve programmer  760 . The magnetic sensor  812  can be in communication with either the communications/control circuitry  816  in the transmitter head  810  or the control device  820 . In certain examples in which the magnet assembly  814  includes electromagnets that can be turned off, the magnetic sensor  812  may be packaged in the transmitter head  810 . In other examples, it can be a packaged as a separate unit. 
     In one embodiment including the magnetic sensor  812  in the transmitter head  810  allows the pressure setting of the implanted valve  200  to be detected and communicated to the control device  820 . In one example, the magnetic sensor  812  detects the position of the rotor  510  inside the valve  200  and translates the detected position into a pressure setting reading. Such correlations between rotational position and pressure settings can be determined for each valve according to a calibration process. The correlation can provide a look-up capability in which a rotational position can be translated into the pressure setting, and vice versa. A resolution of such pressure adjustment can be accomplished according to the techniques employed herein (e.g., based on a known size of the rotor magnet elements  512 ). Alternatively, or in addition, a selection of the spring type and/or spring constant in combination with a shape of the cam can be used to control pressure variations per rotational step. The magnetic sensor  812  can be a Hall sensor or compass, for example. 
     According to certain embodiments, a valve programming assembly, such as the valve programming assembly  800 , can include a valve programmer, such as the valve programmer  760  discussed above, and a separate pressure reader. The pressure reader can be used to read the pressure setting of an implanted programmable valve  200 , and the valve programmer  760  can be used to program the pressure setting of the implanted valve  200 , as discussed above. The pressure reader can be a compass that includes a magnet configured to provide a pressure reading based on an orientation of the magnet. The compass can be a mechanical compass or an electronic compass. 
     In some embodiments, the pressure reader can be hand-held. In some embodiments, the pressure reader is electronic. In certain examples the pressure reader can have a physical appearance that is very similar to that of the valve programmer  760 , for example. 
       FIGS. 30A and 30B  illustrate an example of a pressure reader  660  according to certain embodiments.  FIG. 30A  is a perspective view of the pressure reader  660  and  FIG. 30B  is a top view. A magnet of the pressure reader  660  is oriented with respect to the valve  200  by placing the pressure reader  660  over an implanted valve  200  such that the arrow  662  on the upper surface of the pressure reader  660  is aligned with the direction of the flow of fluid through the valve  200 . The pressure reader  660  can be shaped and sized to facilitate its alignment with an implanted valve  200 . For example, the pressure reader  660  can include a recess or cavity on its lower surface that corresponds to the size and shape of the implanted valve  200 , similar to as discussed above with respect to the valve programmer  760 . As shown in  FIGS. 30A and 30B , the pressure reader  660  can have a circular shape, and may include a display having a range of pressure settings arranged around its circumference. The display can be mechanical or electronic. When the pressure reader  660  is placed over and aligned with the implanted valve  200 , a pressure indicator  664  points to a pressure setting on the pressure reader  660  (as shown in  FIG. 30B ) that corresponds to a pressure setting of the valve  200 , based on the reference magnet elements as discussed above. 
       FIG. 31  shows an example of a method  1000  of operating a pressure reader such as the pressure reader  660  of  FIGS. 30A-B . In step  1002 , a user turns on the pressure reader  660 . In some embodiments, the pressure reader  660  turns on when the user holds down an on/off button on the pressure reader for a predetermined time period, such as two seconds, for example. After being turned on, the pressure reader  660  proceeds to its initial operation mode in step  1004 . In the initial mode of step  1004 , the pressure reader sensor is calibrated to remove or compensate for the effects of the earth&#39;s magnetic field, for example. During the calibration, devices that may generate magnetic fields, such as the valve programmer  760 , should be kept away from the pressure reader  660 . In certain embodiments in which the pressure reader  660  includes an electronic display, the display can include a battery status indicator, similar to as described above with reference to the valve programmer  760 . According to certain embodiments, if the battery charge of the pressure reader  660  is too low, the battery status indicator may flash, and then the pressure reader proceeds to step  1006 , in which the pressure reader turns itself off. During operation of the pressure reader  660 , if the battery charge becomes too low, the battery status indicator may flash to indicate to the user that the batteries of the pressure reader need to be replaced. If the battery charge becomes extremely low, the battery status indicator may begin to flash more quickly, and eventually the pressure reader  660  may turn itself off. 
     If the battery charge of the pressure reader  660  is sufficient, the pressure reader  660  performs the magnetic sensor calibration in step  1004 , and then the pressure reader  660  proceeds to step  1008 ; searching mode. During the searching mode, the user may position the pressure reader  660  on a patient&#39;s head over an implanted valve  200 . In the searching mode of step  1008 , a search icon, such as a magnifying glass icon, may appear on an electronic display of the pressure reader  660  to show the user that the strength of the detected magnetic field is too low. This prompts the user to reposition the pressure reader  660  so that the detected magnetic field is stronger. If the detected magnetic field strength cannot be improved, this may indicate to the user that the pressure reader  660  magnetic field indication is not reliable. 
     When the pressure reader  660  detects a magnetic field with sufficient strength, the display of the pressure reader  660  shows the direction of the magnetic field of the valve at step  1010 , which corresponds to the pressure setting of the valve. For example, as shown in  FIG. 30A , the pressure indicator  664  can indicate the pressure setting of the valve  200 . In examples in which the pressure reader  660  includes an electronic display, at step  1012 , the pressure setting of the valve can be displayed and updated at periodic intervals, e.g., every two seconds. At either of step  1010  and step  1012 , if the strength of the magnetic field is too low, the pressure reader  660  returns to step  1008 , where the display can indicate that the pressure reader is searching for a sufficiently strong magnetic field. 
     A user can turn the pressure reader  660  on and off by pressing the on/off button on the pressure reader  660 . In certain examples, after a predetermined time period, e.g., 360 seconds, the pressure reader  660  automatically turns off. 
     According to certain aspects, a kit for setting a pressure in a surgically-implantable shunt valve  200  can include the pressure reader  660  and the valve programmer  760 . In other examples, a valve assembly  100  can include an integrated valve programmer  760  and pressure reader  660 . In certain examples the pressure reader  660  and the valve programmer  760  can be provided to a user together as part of a kit, or they can be provided separately from each other. In some examples, the kit can further include a surgically-implantable programmable shunt valve or valve assembly, such as a surgically-implantable shunt valve  200  or valve assembly  100 , or another surgically-implantable programmable shunt valve or valve assembly. 
     In certain circumstances where the indicator mechanism rotates with the rotor  510  (e.g., where the indicator mechanism includes reference magnet elements  524  or certain ones of the rotor magnet elements, as discussed above), external, non-programming magnetic fields, such as the field from an MRI, for example, can act upon the indicator/reference magnets and undesirably induce a torque on the rotor  510 . Accordingly, referring to  FIG. 32  there is illustrated an example of the programmable valve showing an alternate example of an indicator mechanism that can avoid this occurrence. In the illustrated example, the indicator mechanism includes a positioning magnet  550  that is attached to the rotor  510 , very close to the center of the rotor. The positioning magnet  550  can be used to orient an indicator magnet  552 . Thus, the indicator mechanism further includes the indicator magnet  552  that is not attached to the rotor  510  and pivots freely on its own ruby bearing. In this example, both the positioning magnet  550  and the indicator magnet  552  have the shape of a ring and are diametrically magnetized. When the rotor  510  moves, the positioning magnet  550  rotates with the rotor  510  and magnetically attracts the indicator magnet  552  to make it rotate in the same amount. In one embodiment, the positioning magnet  550  has a very small magnetic force, and therefore the influence of an MRI or other non-programming magnetic field on the positioning magnet  550  will be insufficient to overcome the cogging torque of the motor and cause the rotor  510  to rotate. The magnetic force of the positioning magnet  550  is enough to attract the indicator magnet  552  to make it rotate in the same amount, as discussed above. The side positioning magnets  553 ,  557 , and  559  discussed above may operate in a similar manner. In certain examples the indicator magnet  552  has a strong magnetic field, which can be read by a compass, Hall Sensor, or other magnet sensor  812  located outside of the patient&#39;s body (e.g., at a distance of 10 mm or more from the second indicator magnet). For example, the indicator magnet can be a single diametrically magnetized (i.e., having one north pole and one opposing south pole) magnet. The indicator magnet  552  may be influenced by a non-programming magnetic field, such as the field from an MRI; however, because the indicator magnet  552  can rotate freely on its own bearing, its movement does not cause the rotor  510  to rotate. When the non-programming magnetic field is removed (e.g., after the MRI scan is finished), the positioning magnet  550  will automatically re-orient the indicator magnet  552 . By splitting the magnetic indicator mechanism into two separate magnets  550 ,  552 , the valve  200  can have a magnet strong enough to be read from the outside and at the same time, a strong non-programming magnetic field, such as the one produced by an MRI, will not change the pressure setting of the valve  200  because the strong indicator magnet ( 552 ) is decoupled from the rotor  510 . 
     In another embodiment, the positioning magnet  550  may be configured as two small disk magnets with the north and south polarities axially magnetized, rather than as a diametrically magnetized single ring magnet. In this case, for one of the two small disk magnets, the north is facing up towards the indicator magnet  552  and south is pointing away from the indicator magnet  552 . For the other of the two small disk magnets, south is facing up towards the indicator magnet  552  and north faces away from the indicator magnet  552 . The principle of operation of such a configuration is the same as discussed above with respect to creating a local magnetic field for identifying the position of the indicator magnet  552 . The use of two very small disk magnets to implement the positioning magnet  550  may be preferred over a ring magnet in certain applications because this configuration may produce fewer artifacts in an image of the patient&#39;s body (as may be taken using an MRI or CT scan, for example). 
     The positioning magnet  550  can have a variety of other configurations as well. For example, as discussed above with reference to  FIGS. 28A-C , in other embodiments the positioning magnet  550  can be replaced with any of the arrangements of positioning magnets  553 ,  557 , or  559 , or similar arrangements. 
     As discussed above, one limitation of conventional magnetically adjustable valves is that verifying a pressure setting can entail the use of an X-ray to detect a radiopaque marker on the implanted device. According to certain embodiments, an initial orientation of the rotor  510  can be determined with respect to a reference, such as the housing and/or casing, using an indication mechanism as discussed above. The pressure setting of the implanted valve  200  may be verified by placing a compass over the patient&#39;s head in the vicinity of the implanted valve  200 . The needle of the compass will align itself with the direction of the indicator magnet  552 , as illustrated in  FIG. 32 , or the reference magnet elements  524   a - c , as illustrated in  FIG. 27 , thus indicating the position of the rotor  510 . The physician is then able to determine the pressure setting of the valve  200  by considering the position of the rotor  510  relative to the housing  202 . 
     Accordingly, the position of the rotor  510  may be precisely determined, and thereby a precise setting of the valve&#39;s threshold opening pressure may also be determined. In at least some embodiments, the rotor  510  is free to rotate in at least one direction, beyond one full revolution, with the pressure settings repeating for each revolution. In this manner, a position of the rotor  510  can uniquely identify a popping pressure. 
     As discussed above, in certain embodiments the magnetic motor is intrinsically immune or highly resistant to external non-programming magnetic fields, including even strong magnetic fields associated with an MRI. However, in certain instances, further immunity (for example, very high or complete assurance that no movement of the rotor  510  will occur) to very strong magnetic fields, such as those associated with an MRI, may be desired. Accordingly, in certain embodiments the programmable valve  200  may include a mechanical brake that prevents movement of the rotor  510  when the brake is applied. 
     Referring to  FIG. 33 , there is illustrated a partial cross-sectional view of one example of a magnetic motor including an example of a mechanical brake according to one embodiment. In this example the mechanical brake includes a brake spring  554  and a brake cylinder  556  that can rotate about a central pivot  558 . In one example the brake cylinder is made of a thermoplastic, such as Polyoxymethylene, for example. The brake spring  554  may be made of metal, for example, stainless steel. In the example illustrated in  FIG. 33 , the brake spring  544  is a disk with a shaped cut-out; however, the brake spring can have a variety of different shapes, some examples of which are discussed further below. The brake cylinder  556  includes a plurality of brake cylinder teeth  560  that are configured to engage with a corresponding plurality of motor teeth  562 . When the brake is in the locked position, the brake cylinder teeth  560  engage with the motor teeth  562  to prevent rotation of the rotor. When the brake is unlocked, the brake cylinder teeth  560  disengage with the motor teeth  562 , allowing the rotor to rotate freely responsive to the applied programming magnetic field, as discussed above. 
     According to certain embodiments, locking and unlocking of the brake is achieved using the second indicator magnet  552 . As discussed above, in certain examples the indicator magnet  552  is a single magnet that is diametrically magnetized. Accordingly, although small, the second indicator magnet can have a relatively strong magnetic field that can be used to release the brake. As discussed above, the second indicator magnet  552  is a freely rotating magnet, not tied to rotation of the rotor  510 . If an external magnet is placed close to the second indicator magnet  552 , the second indicator magnet will rotate to position itself according to the magnetic field of the external magnet. In examples in which the second indicator magnet  552  is a diametrically magnetized magnet, if the external magnet is axially magnetized, it will not pull the second indicator magnet towards itself, because one pole of the second indicator magnet will be attracted to the external magnet, while the other is repelled, and the two opposing forces balance one another. In contrast, if the external magnet is also diametrically magnetized, when it is placed close to the valve, the second indicator magnet  552  will rotate to position itself according to the magnetic field of the external magnet, and then will be attracted to the external magnet. Thus, the second indicator magnet  552  will be pulled upwards towards the external magnet. This upward movement can be used to disengage the brake, allowing rotation of the rotor  510  to program a pressure setting of the valve  200 . When the external magnetic field is not applied, the brake spring  554  presses the brake cylinder down, keeping the brake cylinder teeth  560  engaged with the motor teeth  562 . Referring to  FIG. 34 , in one example in which the central pivot  558  is circular, the brake cylinder  556  includes one or flat sections  563  on its interior wall surrounding the central pivot such that the brake cylinder can only move up and down and will not rotate. In other examples, other features or shapes can be employed to prevent rotation of the brake cylinder  556 .  FIG. 34  shows a schematic example of the motor  510  with the brake released. 
     Accordingly, in certain embodiments, the permanent magnet assembly  710  of the valve programmer  700  includes a diametrically magnetized brake controller magnet that is used to disengage the brake when the valve programmer is placed in proximity to the valve  200  to program the pressure setting of the valve.  FIG. 35  illustrates an example of a permanent magnet assembly  710   c  of the valve programmer  700  including a brake controller magnet  740 . The example shown in  FIG. 35  is similar to the permanent magnet assembly shown in  FIG. 20A , and can be used to program a valve including a twelve-magnet rotor  510 , as discussed above. 
     An example of operation of the motor and mechanical brake using an example of the valve programmer  700  including the magnet assembly  710   c  shown in  FIG. 35  is discussed below with reference to  FIGS. 36, 37A, and 37B .  FIG. 36  is a flow diagram of one example of a method of programming the valve  200 .  FIG. 37A  illustrates a cross-sectional view of one example of the valve  200  showing aspects of the magnetic motor and mechanical brake with the brake in the locked position, and  FIG. 37B  is a corresponding view showing the brake in the unlocked position. 
     Referring to  FIG. 36 , in a first step  902  of programming a pressure setting of the valve  200 , a physician or other user selects the new pressure setting for the valve  200  directly on the valve programmer  700 . In one example this can be achieved using a round display, such as illustrated in  FIG. 11B , for example using a capacitive touch. In step  904 , the physician/user places the valve programmer  700  one or near the patient&#39;s head in proximity to the implanted valve. As the start of the process, the brake is in the locked position, as shown for example in  FIG. 37A . In some instances, it may be easier or more convenient for the physician/user to first select the desired pressure setting of the valve (step  902 ) and the place the valve programmer  700  in proximity to the patient&#39;s head (step  904 ); however, those skilled in the art will appreciate that steps  902  and  904  may be performed in the reverse order. In step  906  the brake in the valve  200  is released so that the valve programmer  700  can act on the magnetic motor to program the selected pressure setting. In one embodiment of the valve programmer  700  including the permanent magnet assembly  710   c , the central diametrically magnetized brake controller magnet  740  is in a higher position than the other four magnets  722 ,  724 ,  726  and  728 . For example, the brake controller magnet  740  can be held in this position by a spring pushing up. The physician/user can press down on the brake controller magnet  740  until it touches the skin on top of the implanted valve  200 , for example. When the brake controller magnet  740  is touching the skin, it unlocks the brake by attracting the second indicator magnet  552 , as discussed above and as shown in  FIG. 37B , for example. In step  908  the valve programmer  700  is used to program the selected pressure setting of the valve  200  by magnetizing the stator  528  to cause rotation of the rotor  510  to the position corresponding to the selected pressure setting, as discussed above. In one example the valve programmer  700  can include a programming “on” switch that can be activated after the brake is released to allow programming to begin. The “on” switch can be built into permanent magnet assembly  710 , and in particular, into the brake release mechanism. For example, the physician/user can push down slightly harder on the brake controller magnet  740  to trigger the switch to start the programming. In one example the switch must remain pressed while the programming is taking place. After the programming has been completed, an indication of completion can be provided to the physician/user, for example, an acoustic feedback can be heard. At this indication, the brake controller magnet  740  is released by the physician/user, and pushed back up into its inactive position by the spring. Upon removal of the magnetic field from the brake controller magnet  740 , and the second indicator magnet  552  is no longer attracted upwards, and returns to its neutral position, and as a result, the brake cylinder  556  moves downward (pressed down by the brake spring  554 ), causing the brake cylinder teeth  560  to re-engage with the motor teeth  562  and lock the rotor  510  in the programmed position (step  910 ). The valve programmer  700  can then be removed from the patient&#39;s head (step  912 ). 
       FIG. 38  illustrates another example of a magnet assembly  710   d  that can be used in the valve programmer  700  to program a valve including a ten-magnet rotor  510 , for example. In this example, the two permanent magnets  732 ,  734  of the example permanent magnet assembly  710   b  shown in  FIG. 20B  have been replaced with a single diametrically magnetized controller magnet  742  which is used to both release the brake and program the pressure setting of the valve  200  as discussed above. 
       FIG. 39  is a flow diagram of one example of a method of programming the valve  200  having a ten-magnet rotor  510  and using a valve programmer  200  that includes an example of the magnet assembly  710   d  shown in  FIG. 38 . As in the example discussed above, in a first step  902  of the programming sequence, the physician/user selects the new pressure setting for the valve  200  directly on the valve programmer  700 . The physician/user can then place the valve programmer  700  in proximity to the implanted valve (step  914 ), which automatically releases the brake due to the presence of the diametrically magnetized controller magnet  742 . In step  916  the physician/user actuates the programming sequence. This can be achieved by pressing a “start” button on the valve programmer  200 , for example. In step  918  the valve programmer  700  is used to program the selected pressure setting of the valve  200  by magnetizing the stator  528  to cause rotation of the rotor  510  to the position corresponding to the selected pressure setting, as discussed above. When the programming sequence is complete, and the selected pressure setting has been reached, the programmer may signal completion of the programming sequence (step  920 ) using, for example, an acoustic or visual indicator (e.g., a beep, displaying a light or flashing light of a particular color, etc.). After the programming has been completed and the signal is heard/seen, the physician/user can remove the valve programmer from proximity to the patient&#39;s head, thereby automatically engaging the brake (step  922 ). 
     As shown in  FIGS. 37A and 37B , in one embodiment the motor includes a pair of ruby bearings  564  that allow the second indicator magnet  552  to rotate with respect to the brake cylinder  556  for the purpose of indicating the position of the rotor  510  and the corresponding pressure setting of the valve  200 , as discussed above. In one example the second indicator magnet  552  is contained in a casing that rotates on the ruby bearings  564 . 
     As will be appreciated by those skilled in the art, given the benefit of this disclosure, the brake mechanism and its components can have a variety of different structural forms and be implemented in combination with any of various embodiments of the magnetic motor and its components. In the example shown in  FIGS. 37A and 37B , the magnetic indicator mechanism includes the first indicator magnet(s)  550  that cooperate with the second indicator magnet  552 . However, the brake mechanism can also be implemented with valve configurations in which one or more slightly “taller” rotor magnet elements  512 , as discussed above, are used in combination with the second indicator magnet  552  for position sensing instead of the first indicator magnet(s)  550 . In the example shown in  FIG. 33 , the brake cylinder teeth  560  and the motor teeth  562  are shown close to the central pivot  558 , to the “inside” of and “below” the second indicator magnet  552 . However, a wide variety of the other configurations can be implemented. For example, referring to  FIG. 40  there is illustrated another embodiment in which the brake cylinder  556  spans the second indicator magnet  552  and the brake cylinder teeth  560  and corresponding motor teeth  562  are positioned to the “outside” of the second indicator magnet  552 . 
     In the examples shown in  FIGS. 33, 34, 37A -B, and  40 , the brake cylinder  556  includes brake cylinder teeth  560  that engage the motor teeth  562  to lock the rotor  510  in position, as discussed above. According to another embodiment, the brake spring  554  can include features that engage with the motor teeth  562 , thereby removing the need for the brake cylinder teeth  560 . For example, referring to  FIG. 41  there is illustrated a partial cross-sectional perspective view of another embodiment of the programmable valve  200  in which the brake spring  554  includes a pair of arms  566  each having a projection  566   a  configured to engage with the motor teeth  562  to lock the rotor  510 . In this example the motor teeth  562  are positioned around a circumference of the rotor casing  514 .  FIG. 42  is a plan view of one example of the embodiment shown in  FIG. 41  in which the rotor  510  includes twelve rotor magnet elements  512 .  FIG. 43  is a plan view of another example of a similar embodiment to that shown in  FIG. 41  in which the rotor  510  includes ten rotor magnet elements.  FIG. 44A  is a cross-sectional view taken along line A-A in  FIG. 42 , and  FIG. 44B  is another cross-sectional view taken along line B-B in  FIG. 42 . In one example, in which the rotor includes twelve rotor magnet elements  512 , the plurality of motor teeth  562  includes 24 motor teeth, such that the rotor can be locked into each position corresponding to rotation step of one half-width of a rotor magnet element. However, different configurations can include different numbers of motor teeth  562 . 
     In the examples shown in  FIGS. 41 and 42 , the brake spring  554  includes two arms  566 , and each arm includes a projection  566   a  at its tip, the projection being thinner/narrower than the body of the arm  566  and configured to fit between a pair of adjacent motor teeth  562  when the brake is in the locked position. However, as will be appreciated by those skilled in the art, given the benefit of this disclosure, a variety of different configurations can be implemented, provided only that the brake spring  554  includes one or more features that are configured to engage with the motor teeth  562  to prevent rotation of the rotor  510 . For example, the brake spring  554  shown in  FIG. 43  includes arms  566  that are more uniform in width, lacking the defined projection  566   a . Referring to  FIG. 45 , in another embodiment the brake spring  554  includes four arms  566 , rather than two, positioned around a central ring portion  568 , and the arms are more uniform in width, similar to the example shown in  FIG. 43 , rather than having the narrower end projections  566   a  illustrated in  FIG. 40 . In the examples shown in  FIGS. 43 and 45 , the width of the arms  566  and spacing between adjacent motor teeth  562  can be selected such that the arms can fit between adjacent motor teeth to lock to rotor  510  in position and prevent its rotation. 
     Referring to  FIGS. 46A and 46B , embodiments of the magnetic motor that incorporate a brake mechanism using the brake spring  554  to engage the motor teeth  562  can be operated in the same manner as discussed above using a brake controller magnet  740  or  742  to unlock or release the brake. In one example, the motor teeth  562  are positioned on the top circumference of the rotor casing  514 , as shown in  FIG. 46A , and in the locked position, the spring  554  rests such that the arms  566  are located between adjacent motor teeth such that rotation of the rotor  510  is thereby prevented. The brake spring  554  can be supported by the top cover  202   a  of the valve. As discussed above, and as shown in  FIG. 46B , when the diametrically magnetized brake controller magnet  740  or  742  is placed above the valve  200 , it will attract the second indicator magnet  552  and push up the brake spring  554 , thereby unlocking the rotor  510  so that it is free to rotate. As shown in  FIGS. 46A and 46B , in one example the second indicator magnet  552  is located in a casing  570  that includes a casing projection  572 . When the second indicator magnet  552  is pulled upwards by the brake controller magnet  740  or  742 , the casing projection  572  presses against the spring arms  566 , lifting the arms above the motor teeth  562  so that the rotor  510  can rotate. When the brake controller magnet  740  or  742  is removed, the brake spring  554  drops back down such that the arms  566  again rest between adjacent motor teeth  562 , as shown in  FIG. 46A . 
       FIGS. 47A and 47B  show another example of a programmable valve  200  including a ten-magnet rotor  510 , also showing an example of the brake mechanism.  FIG. 47A  is a plan view of the programmable valve  200 , and  FIG. 47B  is a cross-sectional view taken along line A-A in  FIG. 47A . 
       FIG. 48  shows another example of a programmable valve  200   a  including a stepper motor, a brake mechanism, and an indicator magnet assembly according to certain embodiments. In this example the cam  212  has an inclined surface  213  and the spring  409  includes a central arm  409   j  flanked by two parallel arms  409   k . The central arm  409   j  is a cantilevered arm with a free end  409   h  resting against the valve element  208 , and the two parallel arms  409   k  are fixed to the underside of a pivot point  407 . The relationship between the position of the cam  212  and the tension of the spring  409  is dependent on the location of the pivot point  407 , the point of the contact between the spring  409  and the cam  212 , and the point of contact between the cantilevered arm  409   g  and the valve element  208 . Depending on these relationships, when the cam  212  is at its highest position, the cantilevered arm  409   g  can be pushed toward the valve element  208 , or alternatively, the cantilevered arm  409   g  can be pushed away from the valve element  208 . In the configuration depicted in  FIG. 48 , when the cam  212  is at its highest position (or its highest level of incline) against the spring  409 , the tension of the spring  409  is the greatest and tends to push the cantilevered arm  409   g  in the direction toward the valve element  208 . The valve  200   a  of  FIG. 48  incorporates brake teeth  562  that engage a brake spring  554 , as discussed above, to prevent unwanted changes to the pressure setting of the valve  200   a  when exposed to a magnetic field (other than a programming field). 
     Embodiments of the valve assembly  100  may be implanted in a patient using well-described surgical procedures. The pressure setting of the valve  200  can be adjusted to a desired pressure setting prior to surgical implantation. In one aspect, the working pressure can be set to be approximately equal to the patient&#39;s ventricular CSF pressure such that no pressure change occurs after the surgery. After the patient recovers from surgery, the pressure setting can be adjusted as desired. For example, in a patient suffering from NPH, the pressure setting can be decreased in order to initiate a reduction in the size of the ventricles. Additional adjustments in the pressure setting can additionally be made. For example, once the size of the ventricles had been reduced sufficiently, the pressure setting of the valve can be increased. As will be appreciated, use of the implanted valve  200  permits the pressure setting of the valve  200  to be externally adjusted as needed over the course of treating the patient. 
     In certain embodiments, a method of treating hydrocephalus includes implanting an embodiment of the valve assembly  100  having a ventricular catheter  120  within a ventricular cavity of the patient&#39;s brain and distal catheter connected to the connector  140  installed at a remote location in the patient&#39;s body where the fluid is to drain. Remote locations of the body where CSF drains include, for example, the right atrium of the heart and the peritoneum. 
     In addition to hydrocephalus, there are several other conditions associated with the accumulation of excess fluid and that can be treated by draining the fluid using a suitably-designed inflow catheter into another part of the body. Such conditions include, for example, chronic pericardial effusions, chronic pulmonary effusion, pulmonary edema, ascites, and glaucoma in the eye. It is contemplated that embodiments of the programmable valve  200  may be used in the treatment of these conditions. 
     The pressure settings of the valves described herein can be adjusted in many discrete steps or increments, or continuously over a predetermined range, as discussed above. Embodiments of the valves described herein may vary in pressure from a low pressure, for example, 10 mm H 2 O, to a high pressure, for example 400 mm H 2 O. Most conventional valves only have pressures as high as 200 mm H 2 O and can only be adjusted in relatively high increments between each pressure setting. 
     Improved Valve 
     Referring to  FIG. 49 , another example of an implantable shunt valve assembly, generally indicated at  4900 , including two valves  4902  and  4904  separated by a pumping chamber  4906 . In one example, a ventricular catheter can be connected to a connector  4908  at an inlet  4910  of the valve assembly  4900 , and a drainage catheter can be attached to a connector  4912  and connected to an outlet  4914  of the valve assembly. Depression of the pumping chamber  4906  pumps fluid through the valve  4904  toward the outlet  4914  and the drainage catheter. Releasing the pumping chamber  4906  after it has been depressed pumps fluid through the valve  4902 . The valve  4902  is an externally programmable valve including a magnetic motor, as discussed in more detail below. The second valve  4904  can be a check valve, for example. In this case, after passing through the programmable valve  4902 , fluid flows through the check valve  4904  before exiting into the drainage catheter. In one example the programmable valve  4902  operates to keep the valve assembly  4900  closed until the fluid pressure rises to a predetermined pressure setting of the valve. Generally, the check valve  4904  may be set at a low pressure, allowing the pressure setting of the programmable valve  4902  including the magnetic motor to control the flow of fluid through the valve assembly  4900 . In other examples, the second valve  4904  can be a gravity-activated valve that allows the valve assembly to automatically adjust in response to changes in CSF hydrostatic pressure that occur when the patient&#39;s posture changes (i.e., moving from a horizontal (recumbent) to a vertical (erect) position). 
     As with valve assembly  100 , those skilled in the art will appreciate, given the benefit of this disclosure, that the length, size, and shape of various embodiments of the valve assembly  4900  can be adjusted. 
     Referring to  FIGS. 50 and 51 , an implantable magnetically programmable valve device of an embodiment of the present disclosure is generally indicated at  5000 . The valve device  5000  includes a base  5002  (also referred to as a body or a housing) that houses the components of the valve device. The base  5002  of the valve device  5000  includes a bottom wall  5004  and a peripheral wall  5006  that extends upwardly from the bottom wall to define a cavity  5008 . The peripheral wall  5006  of the base  5002  includes an inlet port  5010  and an outlet port  5012 . The inlet port  5010  may be connected to a proximal (or inflow) catheter  4908  of the valve assembly  4900 , and the outlet port  5012  may be connected to a distal or outflow catheter. In the case of a valve assembly that shunts CSF fluid, the proximal catheter  4908  may be the ventricular catheter or a lumbar catheter. In this case, the CSF fluid from the ventricle enters the ventricular catheter or lumbar catheter and enters the inlet port  5010  of the valve device  5000 . The distal catheter acts as the drainage catheter connected to the connector to direct fluid to a remote location of the body (such as the right atrium (VA shunting) of the heart or the peritoneal cavity (VP or LP shunting) for drainage. 
     The valve device  5000  further includes a top cap or lid  5014  that mates with the base  5002  of the valve device to form a sealed enclosure that is suitable for implantation into the human body. The top cap  5014  of the valve device  5000  is the side of the device oriented to face up toward the patient&#39;s scalp when implanted. The base  5002  and the top cap  5014  of the valve device  5000  may be made from any physiologically compatible material. Non-limiting examples of physiologically compatible materials include polyethersulfone, polysulfone and silicone. As will be appreciated by those skilled in the art, the base  5002  and the top cap  5014  of the valve device  5000  may have a variety of shapes and sizes, at least partially dependent on the size, shape, and arrangement of components within the valve device. 
     According to certain embodiments, the valve device  5000  includes a valve element  5016  biased against a valve seat  5018  by a spring, which is generally indicated at  5020 . The spring  5020  may comprise, for example, a cantilever spring. Certain embodiments of the spring  5020  are discussed in more detail below. In one embodiment, the valve seat  5018  is press fit within the inlet port  5010  to secure the valve seat in place. 
     Fluid enters the valve device  5000  via the ventricular catheter  4908 , for example, and flows through the inlet port  5010 , which terminates at its casing end at the valve seat  5018 . The pressure of the fluid (e.g., CSF) pushes against the valve element  5016  and the spring  5020  in the direction tending to raise the valve element from the valve seat. Surfaces of the valve element  5016  and valve seat  5018  together define an aperture, and the size or diameter of the aperture determines the rate and amount of fluid flow through the valve device  5000 . The valve element  5016  preferably has a diameter greater than the valve seat  5018  such that when the valve element rests against the valve seat, the aperture is substantially closed. The valve element  5016  is placed on the inlet side of the aperture and is biased against the circular periphery of the aperture defined by the valve seat  5018 , keeping it closed until the CSF pressure in the inlet chamber exceeds a preselected popping pressure. 
     The valve element  5016  can be a sphere, a cone, a cylinder, or other suitable shape, and in the shown embodiment the valve element is a spherical ball. The spherical ball and/or the valve seat  5018  can be made from any appropriate material including, for example, synthetic ruby or sapphire. The valve seat  5018  provides a complementary surface, such as a frustoconical surface for a spherical valve element such that, in a closed position of the valve device, seating of the valve element within the valve seat, results in a fluid tight seal. The pressure setting, for example, the opening pressure, of such valves is adjusted by altering the biasing force of the valve element  5016  against the valve seat  5018 . In one example, as described above, the valve element  5016  and valve seat  5018  may be press-fit into the inlet port  5010  of the base  5002 , and, once the initial pressure setting is reached, held in place by the friction. In one embodiment, the valve element  5016  includes a ruby ball, and the valve seat  5018  is also made of ruby. 
     According to one embodiment, biasing of the spring  5020  against the valve element  5016  is achieved using a magnetic motor, generally indicated at  5022 , that increases or decreases the working pressure of the valve device  5000  either continuously or in finite increments. According to certain embodiments, the magnetic motor  5022  includes a stator  5024  and a rotor, generally indicated at  5026 , that rotates relative to the stator responsive to an external magnetic control field. In one example, the rotor  5026  rotates about a central axis of rotation about a post  5028  that extends upward from the bottom wall  5004  of the base  5002 . Configuration and operation of embodiments of the magnetic motor  5022  are discussed in more detail below. 
     Referring additionally to  FIGS. 52-54 , according to certain embodiments, the rotor  5026  includes a rotor casing  5030  and a plurality of rotor magnet elements, each indicated at  5032 , arranged within the rotor casing. In one embodiment, the rotor casing  5030  includes a cylindrical body  5034  having a circumferential wall with steps, each indicated at  5036 , formed on a top surface of the circumferential wall. In the shown embodiment, there are 20 steps  5036 , thus enabling rotation of the rotor 18-degrees between each step. The rotor casing  5030  further includes a bottom having a channel  5038  formed therein. The plurality of rotor magnet elements  5032  is arranged in a circle and disposed within the channel  5038 . As shown, there are ten rotor magnet elements  5032 . In one example, the rotor magnet elements  5032  are permanent magnets, each having a south pole and a north pole. The rotor magnet elements  5032  are arranged approximately in a circle, with alternating polarity, such that, whether viewed from the top or bottom, the south and north poles alternate between every rotor magnet element. Thus, at any one angular position, the pole exposed on the top surface of the rotor magnet element  5032  is opposite that of the one exposed on the bottom surface. The rotor magnet elements  5032  can be fixedly mounted to the rotor casing  5030  within the channel  5038 , which can act as a magnet guide to contain and direct rotation of the rotor magnet elements. The rotor magnet elements  5032  are shown as circular disks; however, it is to be appreciated that the rotor magnet elements need not be disk-shaped, and can have any shape, such as, but not limited to, oblong, square, rectangular, hexagonal, free-form, and the like. It is preferable that all the rotor magnet elements  5032  are either of approximately the same size or approximately the same magnetic strength even if their size varies to ensure smooth rotation of the rotor. According to one embodiment, the ten rotor magnet elements  5032  are glued to the rotor casing  5030  within the channel  5038 . 
     According to certain embodiments, in addition to the rotor magnet elements  5032 , the rotor  5026  can further include X-ray markers, indicated at  5040 ,  5044 , and positioning magnets, each indicated at  5042 . In one embodiment, the X-ray markers  5040 ,  5044  are tantalum spheres, which are radiopaque and capable of being detected by X-ray equipment. The X-ray marker  5040  is secured to the base by adhesive, e.g., glue, and remains static during operation of the rotor  5026 . The X-ray marker  5044  is secured to the rotor  5026  by adhesive, e.g., glue, and rotates with the rotor. The pressure setting of the valve device  5000  corresponds to a specific angular rotation of the rotor  5026 , therefore allowing a physician to read the current pressure setting of the valve by means of taking an X-ray and comparing the angular deflection between the X-ray marker  5040  and the X-ray marker  5044 . Additionally, the X-ray marker  5040  indicates the righthand side of the valve device  5000 , so the physician knows how to properly orient the X-ray to read the pressure setting of the valve device. 
     Referring additionally to  FIG. 55 , the rotor  5026  is configured to rotate about the rotor axis of the post  5028  responsive to an applied external magnetic field that acts upon the stator  5024 . The rotor  5026  thus can further include one or more bearing rings arranged adjacent an inner circumference of the rotor casing  5030  to allow rotation of the rotor casing. For example, the rotor casing  5030  includes a single bearing ring  5046 , which may be made of synthetic ruby, for example, to enable relative rotation of the rotor casing about the post  5028 . 
     According to one embodiment, magnetic pulses from an external magnetic field are used to selectively magnetize the stator  5024 , which acts upon the magnetic rotor  5026  and thereby controls movement of the rotor. In one embodiment, the stator  5024  is secured to the bottom wall  5004  of the base  5002  within a recess contoured to receive the plus (+)-shaped stator. The external magnetic field may be produced, for example, by a magnetic coil or permanent magnet that is placed in proximity to the valve device  5000 , as discussed in more detail below. The stator  5024  can be made of a soft magnetic material that can be selectively magnetized, and the magnetic polarity of which can be selectively controlled, by the application of the external magnetic field. For example, the stator  5024  can be made of a Nickel-Iron alloy, for example, having approximately 72-83% Nickel. By controlling the magnetization and magnetic polarity of the stator  5024 , the rotor  5026  can be made to rotate in a controlled manner as the rotor magnet elements  5032  respond to the changing magnetization and magnetic polarity of the stator, as discussed further below. 
     The valve device  5000  is configured such that rotation of the rotor  5026  controls the spring  5020  to adjust the biasing of the valve element  5016  against the valve seat  5018 , thereby adjusting the size of the aperture and controlling the flow of fluid through the valve device. In one embodiment, the valve device  5000  includes a cam  5048 , which engages the spring  5020 . In the illustrated example, the cam  5048  is integrated with the rotor casing  5030  at the bottom of the rotor casing outboard of the cylindrical body  5034 , and in one embodiment, is formed to achieve a shape of one or more Archimedean spirals. 
     For certain applications of the valve device  5000 , such as the treatment of hydrocephalus, for example, the pressure range of the valve may be approximately 0-300 mm H 2 O, for example, which are very low pressure ranges. Furthermore, it may be desirable to make small pressure changes within the range. However, it may not be practicable (due to manufacturing constraints, etc.) to produce a valve device in which a cam is capable of making very minute movements, for example, on the order of a few micrometers. Therefore, in order to accommodate the low-pressure range and small incremental changes in pressure, a very soft spring may be required. Conventionally, in order to obtain a sufficiently soft spring, the spring would be very long. However, accommodating a very long, soft spring inside an implantable housing may pose challenges. Accordingly, aspects and embodiments are directed to spring configurations that produce a lever or “gear reduction” effect, such that reasonable (i.e., within standard manufacturing capabilities) movements of the cam may be translated into very small adjustments in low-pressure settings. In particular, certain embodiments include the cantilever spring  5020  shown and described herein. 
     As best shown in  FIGS. 52 and 53 , the cam  5048  and the spring  5020  are biased against the valve element  5016 , with the cam in the position of minimum tension against the biasing spring. In the shown embodiment, the spring  5020  is a cantilever spring and includes a first spring arm  5050  that is biased against the valve element  5016  and a second, cantilevered arm  5052  that is in direct or indirect contact with the cam  5048 . Both the first spring arm  5050  and the cantilevered arm  5052  extend in the same direction from a fulcrum  5054  (or fixed attachment point of the spring). Thus, the first spring arm  5050  has a fixed end at the fulcrum  5054  and a free end that rests against the valve element  5016 . Similarly, the cantilevered arm  5052  has a fixed end at the fulcrum  5054  and a free end that engages the cam  5048 . In one embodiment, the fulcrum  5054  of the spring  5020  is secured to the base  5002  by a lower spring support  5056  and an upper spring support  5058 , which are inserted within a dedicated cavity formed in the base  5002 . 
     In certain examples the first spring arm  5050  may be longer than the second, cantilevered spring arm  5052 . In the illustrated example the cantilevered spring arm  5052  is “bent,” including an inflection point. Rotation of the cam  5048  causes pressure against the cantilevered spring arm  5052  in contact with the cam, changing the tension in the spring  5020 . That pressure is spread and reduced through the spring structure, such that resulting pressure applied against the valve element  5016  by the first spring arm  5050  can be very low, and in particular, can be within a desired range (e.g., 0-200 mm H 2 O, as mentioned above), without placing difficult or impracticable constraints on the rotational movement of the cam  5048 . By appropriately selecting the relative lengths of the two arms  5050 ,  5052 , and the widths of each arm, the equivalent of a lever or gear reduction mechanism may be achieved. Thus, a sufficiently soft spring to provide the low pressures (e.g., 0-200 mm H 2 O) needed for certain applications may be achieved using a short, two-armed spring, rather than a conventional long spring. 
     In one embodiment, the fulcrum  5054 , the first spring arm  5050 , and the cantilevered arm  5052  are configured to provide a lever effect such that a first force applied by the cam  5048  to the first arm is translated by the cantilever spring into a second force applied against the valve element, with the second force being less than the first force. 
     As shown, as the cam  5048  rotates, the force exerted against the spring  5020  is adjusted in fine increments or continuously over a range from minimum force to maximum force. When the cam  5048  is in the position in which the maximum pressure is exerted by the cam against the spring  5020 , the first spring arm  5050  is moved toward the valve element  5016 . Thus, the pressure setting of the valve device  5000  is highest for this position of the cam  5048 . In one example, pressure exerted by the cam  5048  against the spring  5020 , and therefore the tension in the spring, increases with clockwise rotation of the cam. However, those skilled in the art will appreciate, given the benefit of this disclosure, that the rotor  5026 , cam  5048 , and spring  5020  may alternatively be configured such that counter-clockwise rotation of the rotor increases the tension in the spring. 
     As described above, the valve element  5016  and valve seat  5018  form an aperture through which the fluid flows. The inlet port  5010  can be oriented such that fluid enters the aperture (or, in other words, pushes against the valve element  5016 ) in a direction perpendicular to a central axis of the rotor  5026 . In certain aspects, when the inlet port  5010  is oriented such that fluid enters the aperture in a direction perpendicular to the central axis of the rotor  5026 , the cam  5048  directly or indirectly produces horizontal displacement of the spring  5020 . 
     The cam  5048  in embodiments of the valve device  5000  disclosed herein is shaped to mimic an Archimedean spiral; however, the cam can have a constant or linear slope, a piecewise linear slope, a non-linear slope and combinations of such slopes in the surface(s) that engage the spring  5020 . 
     According to certain examples the magnetic motor  5022  may include a rotor stop or rotor stop  5060  that prevents 360 degree rotation of the cam  5048 , and thereby prevents the valve device  5000  from being able to transition immediately from fully open to fully closed, or vice versa, in one step. As shown, the rotor stop  5060  is provided on the rotor casing  5030  of the rotor  5026  to prevent the rotor from rotating past a minimum rotor pressure position. As shown, the spring  5020  is configured to engage the rotor stop  5060  to prevent the rotation of the rotor  5026 . A second stop (not shown) can be formed in the top cap  5014  of the valve device  5000  to prevent the rotor  5026  from rotating past a maximum rotor pressure position. The cam  5048  can rotate either clockwise or anticlockwise up to the position set by the rotor stop  5060 , and then must rotate in the opposite direction. Thus, a full rotation of the cam  5048  is required to transition the valve device  5000  from fully open to fully closed, or vice versa, rather than only a small step or incremental rotation. 
     In certain examples, after the valve device  5000  is manufactured, a calibration device is typically needed to adjust the pressure settings. For example, in certain embodiments the spring  5020  may be constructed such that it is linear with respect to each step, that is, with each step of rotation of the cam  5048 , the spring is tensioned so that the pressure of the valve device  5000  goes up by X amount, and this is true for each additional step of rotation. Accordingly, it may be necessary to calibrate the valve device  5000  to set the cam  5048  at a given position and pre-tension the spring  5020  to an appropriate pressure for that position. Therefore, after the valve device  5000  is assembled and during the calibration, there may be a flow of nitrogen (or some other fluid) through the valve device. 
     As described above, in one embodiment, the magnetic motor  5022  including ten rotor magnet elements  5032  arranged in a circle and configured such that clockwise rotation increases the pressure setting of the programmable valve device  5000 . As discussed above, the rotor  5026  may rotate through a plurality of incremental steps, each step corresponding to a defined change in the pressure setting of the valve device  5000 . As also discussed above, the rotor  5026  may include the rotor stop  5060  which may prevent 360 degree rotation of the cam  5048 , and thereby prevents the valve device  5000  from being able to transition immediately from fully open to fully closed, or vice versa, in one step. Accordingly, when the rotor  5026  is in the position of the minimum pressure setting of the valve device  5000 , the rotor must rotate clockwise, thereby gradually increasing the pressure setting of the valve device. Counter-clockwise rotation, which would transition the valve device  5000  from the minimum pressure setting to the maximum pressure setting in one step is prevented by the rotor stop  5060 . Similarly, when the rotor  5026  reaches the position corresponding to the maximum pressure setting of the valve device  5000 , further clockwise rotation of the cam  5048  is prevented by rotor stop  5060 , such that the rotor must rotate counter-clockwise, thereby gradually decreasing the pressure setting of the valve device. 
     As described above, the valve device  5000  includes the X-ray markers  5040  and  5044 , which can be seen in an X-ray and indicate the position of the rotor  5026 , and therefore the pressure setting of the valve device. In one example, the X-ray markers  5040 ,  5044  are localized in such a way that at the lowest pressure setting of the valve device  5000 , the X-ray markers  5040 ,  5044  are aligned with the center of the cam  5048 . The X-ray marker  5040  is fixed in the base  5002  of the valve device  5000  and does not rotate with the rotor  5026 , whereas the X-ray marker  5044  rotates with the rotor. 
     In some embodiments, the X-ray markers  5040 ,  5044  include tantalum. In some embodiments, the X-ray markers  5040 ,  5044  include tantalum spheres and/or tantalum beads. 
     The implanted programmable valve device  5000  further includes a brake assembly to lock the rotor  5026  in place and to selectively release the rotor for programming. In one embodiment, the implanted programmable device  5000  further includes an indicator, generally indicated at  5064 , which is positioned within the rotor casing  5030  over the post  5028 . The indicator  5064  includes an indicator housing  5066  and a diametrically magnetized annular indicator magnet  5068 , which is positioned within the indicator housing and secured to the indicator housing, e.g., by adhesive or glue. The arrangement is such that the indicator  5064  is capable of rotating with respect to the rotor  5026  when exposed to an external magnetic force. The implanted programmable valve device  5000  further includes a brake or stabilizer, generally indicated at  5070 , which is provided to lock the rotor  5026  in place once a desired pressure is achieved. Specifically, the brake  5070  includes a circular body  5072  and a pair of diametrically opposite arms  5074 ,  5076  that extend beyond the body and when placed over the rotor casing  5030  of the rotor  5026  are received between steps  5036  of the rotor casing. The body  5072  of the brake  5070  includes a shaped opening  5078  designed to fit over a shaped end of the post  5028  to prevent the brake from rotating with respect to the post. The arrangement is such that the brake  5070  is prevented from rotating with respect to the post  5028  but the pair of arms  5074 ,  5076  are capable of being displaced axially. 
     The positioning magnets  5042  orient or position the indicator  5064 , which contains the diametrically magnetized magnet  5068 . The indicator  5064  has two purposes. One purpose is to release the brake  5074  from the steps  5036  when the programmer is positioned on top of the valve device to allow the rotor  5026  of the magnetic motor  5022 . Another purpose is that whenever the programmer is not in proximity to the valve, that is, at all times except when the valve is being programmed, the indicator  5064  is magnetically oriented by the two positioning magnets  5042 . The monitor reads the angular or circumferential orientation of the indicator  5064  and not of the positioning magnets  5042 . The magnetic field produced by the two relatively small positioning magnets  5042  is not powerful enough to be read by the external monitor. The indicator  5064  acts as a magnetic amplifier mimicking the orientation of the two small positioning magnets  5042 , which has a magnetic field strong enough to be read by the external monitor, yet the indicator must be able to rotate freely when exposed to a powerful external magnetic field, such as the one produced by an MRI machine, and not change the pressure setting of the valve device  5000 . When a patient with an implanted valve is introduced into an MRI machine, the indicator  5064  will align itself according to the orientation of the magnetic field of the MRI machine, but it will not be pulled up from the rotor  5026 . This allows the rotor  5026  to remain static, with the brake engaged. Once the patient leaves the MRI machine, the two positioning magnets  5042  re-align the indicator  5064 , which can then be read by the monitor. 
     When an external magnetic force is applied to the valve device, e.g., by a programmer, the indicator  5064  is attracted to the external magnetic force raising the brake arms  5074 ,  5076  from the rotor  5026 , thereby enabling the rotor to rotate to allow change of pressure of the valve device. Specifically, the indicator  5064  moves axially along the post  5028  toward the magnetic force, thus, in this specific configuration, the outer edge of the indicator  5064  axially displaces the brake arms  5074 ,  5076 . The arms  5074 ,  5076  of the brake  5070  are removed from the spaces between the steps  5036  of the rotor casing  5030  to enable the rotor  5026  to rotate. Simultaneously, the stator  5024  is magnetized to attract the rotor magnet elements  5032  thereby preventing the rotor  5026  from moving axially. 
     Once a desired pressure is achieved, the external magnetic force can be removed to enable the brake arms  5074 ,  5076  to move back to the position in which the arms  5074 ,  5076  of the brake are positioned between steps  5036  of the rotor casing  5030 . Specifically, once the external magnetic force is removed the indicator  5064  moves back toward the rotor  5026  taking along the brake arms  5074 ,  5076 , which are positioned to lock the rotor in place. 
     Programmer Device 
     As discussed above, because embodiments of the valve device  5000  comprise a magnetically actuated rotor  5026 , the pressure setting of the implanted programmable valve device can be adjusted by positioning a programmer, which is placed in proximity to the implanted valve device but external to the body. The programmer includes a magnetic field generator, along with various control and input/output (I/O) components to allow a user (e.g., a doctor) to control the programmer to set and optionally read the pressure setting of the implanted programmable valve device  5000 . In certain embodiments, the magnetic field generator can include an arrangement of electromagnets. In other embodiments, the magnetic field generator can include one or more permanent magnets, and the programmer can be battery operated. 
     In one embodiment, the programmer is configured to be placed over the patient&#39;s head at a location over an implanted magnetically-programmable valve device. The programmer includes a magnetic field generator, as discussed further below, that applies magnetic pulses to selectively magnetize the stator  5024  and thereby cause rotation of the rotor  5026 . Fluid flows from the ventricle, through a ventricular catheter, into the inlet connector  4908 , through the implanted valve device  5000 , into the distal catheter connected to the connector  4912 , which then drains the fluid at a remote location of the body (such as the right atrium of the heart or to the peritoneal cavity). The programmer may send a magnetic signal to effect rotation of the rotor  5026 . The programmer may be used to produce the magnetic pulses, as discussed further below, and may be coupled to a communications link, such as a cable or wireless link, for example. 
     Referring to  FIGS. 56A-59 , a programmer device of an embodiment of the present disclosure is generally indicated at  5600 . As shown, the programmer device  5600  includes a casing  5602  having a top  5604  ( FIGS. 56A and 58 ), a bottom  5606  ( FIG. 57 ) and a contiguous side wall  5608  that connects the top and bottom of the casing. The casing  5602  of the programmer device  5600  is sized to fit within a hand of a doctor or professional using the programmer device. The top of the programmer device  5600  includes a user interface  5610  including a liquid crystal display (LCD)  5612 , which will be described in greater detail below, to enable a doctor to program the valve device  5000 . The side wall  5608  of the programmer device  5600  includes two programming start buttons  5614 ,  5616  to start the programming sequence of the programmer and control the operation of the valve device  5000 . The casing  5602  is configured to support the components of the programmer device  5000 . Optionally, a USB port  5670  can be provided to charge rechargeable batteries and/or to modify or update the software of the programmer device  5600 . 
     Referring particularly to  FIG. 59 , the casing  5602  of the programmer device  5600  includes a lower casing  5618  and an upper casing  5620 . The lower casing  5618  includes a battery housing  5622  configured to receive batteries, e.g., four AAA batteries, and a battery cover  5624  configured to close the battery housing. The programmer device  5600  further includes a motor  5626  coupled to the battery housing  5622  and a gear  5628  mounted on a shaft of the motor. In one embodiment, the casing  5602  includes a support  5630  that is configured to support the motor  5626  when the programmer device  5600  is assembled. The batteries provided in the battery housing  5622  provide power to the motor  5626  to drive the rotation of the gear  5628 . 
     The programmer device  5600  further includes a magnet support  5632  having a central hub configured to support a magnet gear  5634 , a ball bearing  5636 , a magnetic bridging plate  5638  and two permanent magnets, each indicated at  5640 . The arrangement is such that the gear  5628  is configured to engage the magnet gear  5634  to drive the rotation of the two permanent magnets  5640  that are held by the magnet support  5632 . In the shown embodiment, the magnets  5640  are formed from two pieces each having north and south sides, both attached to the magnetic bridging plate  5638 . The magnets  5640  are configured to drive the rotation of the rotor magnet elements  5032  to program the valve device  5000 . The programmer device  5600  further includes a first programmer electronic board  5642  and a second programmer electronic board  5644 , which together control the operation of the programmer device. 
     In one embodiment, for every rotation of the permanent magnets  5640  of the programmer device  5600 , the rotor  5026  of the valve device  5000  rotates ⅕ of a single rotation. Thus, the programmer device  5600  is configured to provide incremental movement of the rotor  5026  of the valve device  5000  to finely position the rotor at a desired pressure. Additionally, in one embodiment, for every rotation of the permanent magnets  5640  of the programmer device  5600 , the indicator  5064  of the valve device  5000  rotates 1 revolution (1/1). 
     In certain examples the casing  5602  of the programmer device  5600  is packaged such that it is comfortable and easy for a user to use. In this example, the programmer device  5600  has a shape that is similar to a computer mouse. As shown, in some embodiments, the programmer device  5600  has rounded corners on its outer surfaces, and may have an overall rounded shape, which may be easy and/or comfortable for a user to hold. In some embodiments, the programmer device  5600  can be easily held by a user in one hand. 
     As discussed above, the programmer device  5600  can be battery operated. Accordingly, in some embodiments, the battery housing  5622  of the casing  5602  can house one or more batteries. As discussed above, in some embodiments, the motor  5626  of the programmer device  5600  is a DC motor and the magnets  5640  of the programmer device include two oppositely magnetized magnets to rotate the rotor  5026  of the valve device  5000 . The two oppositely magnetized magnets  5640  have opposite fields oriented downwardly within the programmer device  5600 . In some embodiments, the magnets  5640  of the programmer device  5600  have a surface field strength of 6000 gauss. 
     The programmer device  5600  further includes a keyboard foil designed to create the user interface  5610  and the aforementioned LCD  5612 , which is provided at the top  5604  of the casing  5602  having the user interface to enable the doctor to operate the programmer device and view relevant information, e.g., pressure setting information in mm H 2 O. The programmer device  5600  further includes a worm hole housing  5646 . The top  5604  of the casing  5602  of the programmer device  5600  is designed to enable the doctor to view the positioning of the valve device  5000  relative to the programmer device  5600 . Specifically, the user interface  5610  can be configured to show information such as the pressure setting, the battery status, and optionally other information. For example, the center of the user interface screen  5610  may show the pressure that was selected (in a digital read-out). The border of the screen may include an indication of what an X-ray would show, or the position of the rotor  5026  of the valve device  5000  that may be indicated by the pressure device  5000 , as discussed further below. 
     The user interface  5610  of the programmer device  5600  is configured to allow a user to select the pressure setpoint of the programmer device, and thereby to set the pressure of the valve device  5000 . In some embodiments, the button  5652  of the programmer device  5600  can be configured to turn ON and turn OFF the programmer device. The user interface  5610  can be configured to include plus (+) and minus (−) buttons  5648 ,  5650  to increase the pressure setpoint and to decrease the pressure setpoint, respectively. The user interface  5610  further can be configured to include two programming start buttons  5614 ,  5616  and optionally a light button to provide illumination during use. 
     The casing  5602  of the programmer device  5600  can be shaped to facilitate correctly orienting the programmer device over an implanted valve device  5000  to program the pressure setting of the valve device. In certain examples, the casing  5602  includes a molded cavity  5654  formed on the bottom  5606  of the programmer device  5600 . The cavity  5654  is shaped and sized to correspond at least approximately to the shape and size of the implanted valve device  5000 . The cavity  5654  includes a pair of channels defined in the bottom  5606  of the casing  5602 . As discussed above, the inlet port  5010  of the programmable valve device  5000  can be connected to an inflow catheter, and the outlet port  5012  of the programmable valve device can be connected to a drainage catheter. The channels can be sized and arranged such that, when the programmer device  5600  is placed over the implanted valve device  5000  on the patient&#39;s head, the channels align with the inflow catheter and the drainage catheter, thereby assisting to correctly align the programmer device with the implanted valve device. After the user sets the desired pressure setpoint on the programmer device  5600 , the user places the programmer device on top of the valve device  5000 , which automatically releases the brake. Next, the user presses either of the two programming start buttons  5614 ,  5616  on the side wall  5608  to start the programming. 
     Referring back to  FIGS. 56A-56D , in one embodiment, the programmer device  5600  can optionally include a magnetic shield  5660  to shield the very strong magnetic force produced by the permanent magnets  5640  of the programmer device when not in use. In one embodiment, the magnetic shield  5660  has a molded plastic outer body, which encapsulates an internal steel plate. When attached to the bottom of the programmer device  5600 , the magnetic field generated by the internal magnets  5640 , closes a magnetic “circuit” through the steel shield, thereby isolating the environment outside the programmer device from the strong magnetic field. The magnetic shield  5660  is removed before operating the programmer device  5600  as described above. In one embodiment, the programmer device  5600  is incapable of operating as a safety feature until the magnetic shield  5660  is removed. 
     Monitor Device 
     Referring to  FIGS. 60A and 60B , a monitor device of embodiments of the present disclosure is generally indicated at  6000 . The monitor device  6000  can be used to monitor the pressure setting of the valve device  5000 . It can be used in conjunction with the programmer device  5600  to verify the pressure setting of the valve device  5000  before and/or after the programming device  5600  has programmed the valve device  5000 . As shown, the monitor device  6000  includes a disk-shaped casing  6002  having a top  6004 , a bottom  6006  and a side wall  6008  that connects the top and bottom of the casing. 
     Referring additionally to  FIG. 61 , the top  6004  of the casing  6002  of the monitor device  6000  includes an LCD  6010  and a central opening  6012  through which the user can view the placement and operation of the monitor device during use. The LCD  6010  of the monitor device  6000  is used by the doctor to measure the pressure setting of the valve device  5000 . The top  6004  of the casing  6002  further includes a keyboard foil to provide a user interface  6014  to operate the monitor device  6000 . For example, a dial  6016  showing the position of the rotor  5026  of the valve device  5000  is provided on the top  6004  of the casing  6002  of the monitor device  6000 . An ON/OFF button  6018  configured to operate, i.e., turn ON and turn OFF, the monitor device  6000  is provided, as well as a pressure recall button  6020  to access the previously read pressure setting. Optionally, a USB port  6070  can be provided to charge rechargeable batteries and/or to modify or update the software of the monitor device  6000 . 
     Referring to  FIGS. 62 and 63 , the casing  6002  of the monitor device  6000  includes a lower casing  6022  and an upper casing  6024 . The lower casing  6022  of the monitor device  6000  includes a battery housing  6026  configured to contain one or more batteries to power the operation of the monitor device  6000 . Battery covers, together indicated at  6028 , are provided to cover the battery housing  6026 . 
     The monitor device  6000  further includes a monitor electronic board  6034  and a monitor sensor board  6036 , which is provided to locate and detect the angular or circumferential orientation of indicator  5064  of the valve device  5000  to determine the pressure setting of the valve device. The monitor device  6000  further includes a compass bridge  6038  provided on top of the monitor assembly  6034 . In one embodiment, the compass bridge  6038  is a plastic cover that is part of the casing  6002 . One purpose of the compass bridge  6038  is to protect sensors. 
     Referring to  FIGS. 64 and 65 , the monitor sensor board  6036  includes a first (top) surface  6040  ( FIG. 64 ) and a second (bottom) surface  6042  ( FIG. 65 ). The monitor sensor board  6036  includes a circular central body  6044  having a first arm  6046  that terminates to a first tab and a second arm  6048  that terminates to a second tab. Referring particularly to  FIG. 65 , the central body  6044  includes four sensors, each indicated at  6050 , that are configured to detect the diametrically magnetized magnet  5068  of the indicator  5064  of the valve device  5000  and to center the monitor device  6000  on the valve device when placing the monitor device over the valve device. Thus, the monitor device  6000  is configured to self-center on the valve device  5000  during a procedure in which the valve device is programmed by using the monitor device and the programmer device  5600  in the manner described below. In one embodiment, the monitor device  6000  includes a circular array of lights which indicate the user in which direction the monitor has to be moved to achieve its accurate centering over the valve device  5000 . 
     The monitor sensor further includes a fifth sensor indicated at  6052 , which is centrally positioned with respect to the four sensors  6050 . This sensor  6052  is configured to measure the angular or circumferential orientation of the indicator  5064 , of the valve device  5000  to determine the pressure setting of the valve device. The angular or circumferential orientation of the indicator  5064  is in direct correlation to the angular or circumferential orientation of the rotor  5026 , which is in direct correlation with the pressure setting of the valve device  5000 . In one embodiment, every 18 degrees of rotation correspond to a particular pressure of the valve device  5000 . A pair of light emitting diodes (LEDs), each indicated at  6054 , is provided to shed light on the patient when using the monitor device  6000 . The first tab of the first arm  6046  includes a first magnetic sensor  6056  that measures the Earth&#39;s magnetic field and/or any other magnetic field present. Similarly, the second tab of the second arm  6048  includes a second magnetic sensor  6058  that also measures Earth magnetic field and/or any other magnetic field present. Prior to placing the monitor  6000  in close proximity to the valve device  5000 , magnetic sensor  6048  and magnetic sensor  6056  read the external magnetic fields to later subtract them from the reading of sensor  6052 . This enables sensor  6052  to accurately read the angular or circumferential orientation of indicator  5064 , disregarding other external magnetic fields. 
     As with the programmer device  5600 , the monitor device  6000  includes a molded cavity  6060  ( FIG. 60B ) formed on the bottom  6006  of the monitor device. The cavity  6060  is shaped and sized to correspond at least approximately to the shape and size of the implanted valve device  5000 . The cavity  6060  includes a pair of channels defined in the bottom  6006  of the casing  6002 . The channels can be sized and arranged such that, when the monitor device  6000  is placed over the implanted valve device  5000  on the patient&#39;s head, the channels align with the inflow catheter and the drainage catheter, thereby assisting to correctly align the monitor device with the implanted valve device. 
     Positioning Disk 
     Referring to  FIGS. 66 and 67 , a positioning disk of an embodiment of the present disclosure is generally indicated  6600 . In the shown embodiment, the positioning disk  6600  includes a thin body  6602  having a cutout  6604  that is configured to receive a bulge produced by the implanted valve device  5000  to guide the positioning disk during use. The positioning disk is placed over the valve device  5000  such that the arrows  6610  on the positioning disk indicate direction of the flow of fluid within the valve device  5000 . The body  6602  of the positioning disk  6600  further includes a recessed portion  6606  with a positioning feature  6608  configured to seat the monitor device  6000  on the positioning disk. During use, the cutout  6604  of the positioning disk  6600  is positioned over the valve device  5000  to roughly position the positioning disk on the patient. Once roughly positioned, the monitor device  6000  is positioned within the recessed portion  6606  with the positioning feature  6608  being received within a mating feature provided on the monitor device. At this point, the monitor device  6000  is operated to center the monitor device on the valve device  5000 . As shown, the monitor device  6000  can move together with the positioning disk  6600 , towards the direction indicated by the monitor, to center both the positioning disk and the monitoring device with respect to the valve device  5000 . 
     Once centered, the monitor device  6000  can be removed from the positioning disk  6600 , leaving the positioning disk in place and the programmer device  5600  can now be positioned on the positioning disk to program the valve device  5000 . As with the monitor device  6000 , the programmer device  5600  is positioned within the recessed portion  6606  with the positioning feature  6608  being received within a mating feature provided on the programmer device. 
     Operation of Improved Valve, Programmer Device and Monitor Device 
       FIG. 68  illustrates the programmer device  5600  having the magnetic shield  5660 , the monitor device  6000  connected to a power cord  6620  via the USB port  6070 , and the positioning disk  6600  disposed under the monitor device. 
     In certain embodiments, the valve device  5000  requires periodic monitoring to ensure a proper pressure is being achieved. In other embodiments, the valve device  5000  requires periodic reprogramming to increase or decrease the pressure. When monitoring pressure, the positioning disk  6600  is placed over the valve device  5000  as referenced above so that the opening of the positioning disk receives the contour of the implanted valve device therein, and the monitor device  6000  is placed on the positioning disk. The monitor device  6000  is operated to center the monitor device and the positioning disk  6600  on the valve device  5000 . Once centered, the monitor device  6000  will detect the existing pressure of the valve device  5000 , which is displayed on the LCD  6010 . The position of the rotor  5026  of the valve device  5000  can also be detected on the user interface  6014  of the monitor device  6000  on the dial  6016 . If the detected pressure is acceptable as determined by the doctor, the monitor device  6000  is turned OFF by the ON/OFF button  6018 , and the monitor device and the positioning disk  6600  is removed from the patient. 
     If the detected pressure is not acceptable as determined by the doctor, or if the valve device  5000  was scheduled to be reprogrammed, the monitor device  6000  is removed from the positioning disk  6600  and is turned OFF by the ON/OFF button  6018 . Once the monitor is removed from the positioning disk  6600 , the programmer device  5600  is turned ON by the ON/OFF button  5652 . Once activated, the doctor selects a pressure on the programmer device  5600 , e.g., 100 mm H 2 O, by manipulating the plus (+) and minus (−) buttons  5648 ,  5650  as described above. In some embodiments, the programmer device  5600  can be programmed to a preset pressure, e.g., 70 mm H 2 O. Once the pressure is selected, the programmer device  5600  is placed on the positioning disk  6600 , and either start button  5614  or start button  5616  are pressed to initiate the programming sequence. The programmer device performs a reset operation as described above, and then sets the pressure of the valve device  5000  to the selected or preset pressure. Specifically, the magnets  5640  of the programmer device  5600  are magnetized to lift the indicator  5064  and lift brake arm  5074  and brake arm  5076  to release the rotor  5026  of the magnetic motor  5022 . The rotor magnet elements  5032  of the valve device  5000  are manipulated by the stator  5024 , which is sequentially magnetized by the magnets  5640  of the programmer device  5600  in a manner similar to valve device  200  to rotate the rotor  5026  to a selected position and pressure. Once the rotor  5026  is moved to the proper position, the programmer is lifted away from the implanted valve device  5000 , allowing the indicator  5064  to go back to its resting position in which the brake  5070  is positioned between steps  5036  of the rotor  5026  to lock the rotor in place. The programmer device  5600  is removed from the patient and turned OFF by the ON/OFF button  5652 . The doctor can repeat the cycle with the monitor to verify that the valve device  5000  programmed correctly. Once the pressure has been verified, the doctor can remove the monitor device  6000  and the positioning disk  6600  from the patient. 
     According to certain embodiments, valve pressure adjustments can be made by applying a pulsed magnetic field to the vicinity of the programmable implanted valve device  5000 . Once the positioning disk  5600  is centered by the monitor device  6000 , the programmer device  5600  is placed in proximity to the implanted valve device  5000  by using the positioning disk  6600 . In the shown embodiment, the magnets  5640  of the programmer device  5600  are configured to operate the rotor  5026  of the valve device  5000 . The magnetically operable motor  5022  of the implanted valve device  5000  includes the rotor  5026 , having ten rotor magnet elements  5032  arranged with alternating polarity in the channel of the rotor casing  5030 . The magnetic motor  5022  further includes the stator  5024  positioned below the rotor  5026 , which is magnetized by the programmer device  5600 . 
     The operation of the valve device  5000  is similar to the operation of valve device  200 . For example, the magnets  5640  of the programmer device  5600  can either be permanent magnets or be energized to have either the north or south polarity facing the stator  5024 , or each can remain off altogether. Movement of rotor  5026  of the valve device  5000 , in the desired direction and through the desired angle, is achieved by either movement of the permanent magnets or the energizing of the magnets  5640  in prescribed sequences, which in turn magnetizes the stator  5024 , which then attracts or repels the rotor magnet elements  5032  (depending on polarity), causing rotation of the rotor  5026 . 
     Thus, using an implanted valve device  5000  having the magnetic motor  5022  discussed above, along with an external controller that includes the programmer device  5600  and the monitor device  6000 , the pressure setting of the implantable valve device can be non-invasively controlled and measured in small increments. The configuration of the cam  5048  and the tension in the spring  5020  can be designed and calibrated such that each angular increment of the rotor  5026  produces a well-defined selected change in the pressure setting of the valve device  5000  (e.g., 10 mm H 2 O). In one example, the programmer device  5600  can be configured to allow the user to enter a desired pressure setting for the valve device  5000 . In one embodiment, the programmer device  5600  can be configured to set the pressure of the valve device from 0 to 300 mm H 2 O, with 10 mm increments from 0 to 180 mm H 2 O and 40 mm increments from 180 to 300 mm H 2 O. In one embodiment, a default or preset pressure is 70 H 2 O. 
     In one example, to ensure an accurate pressure setting of the valve device  5000 , the programmer device  5600  can be configured to first activate the counter-clockwise rotation sequence to set the valve device to its fully open position, and then activate the clockwise rotation sequence to set the valve device to the selected pressure setting entered by the user. According to certain examples, when the counter-clockwise rotation sequence is activated, the programmer device  5600  is configured to actuate the rotor  5026  to rotate through a sufficient number of counter-clockwise steps such that the rotor will be positioned such that the valve device  5000  has its lowest pressure setting. As discussed above, the presence of the rotor stop  5060  prevents the rotor  5026  from continuing to rotate past the minimum pressure setting position. After the programmer device  5600  stops the counter-clockwise rotation sequence, it may start the clockwise sequence from a known position (the position corresponding to the minimum pressure setting and with the rotor stop  5060 ). The programmer device  5600  may actuate the rotor  5026  to rotate through a selected number of clockwise steps so as to program the valve device  5000  to the pressure setting selected by the user. 
     Although the example discussed above uses clockwise rotation of the rotor  5026  to program the pressure setting of the valve device  5000  (and counter-clockwise rotation to set the rotor  5026  to a known position from which to begin the programming sequence), those skilled in the art will appreciate, given the benefit of this disclosure, that the system (valve device  5000 , programmer device  5600 , monitor device  6000 , and positioning disk  6600 ) can instead be configured for the opposite arrangement, namely to use counter-clockwise rotation of the rotor  5026  to program the pressure setting of the valve device  5000  (and clockwise rotation to set the rotor to a known position from which to begin the programming sequence). 
     Embodiments of the valve assembly  4900  may be implanted in a patient using well-described surgical procedures. The pressure setting of the valve device  5000  can be adjusted to a desired pressure setting prior to surgical implantation. In one aspect, the working pressure can be set to be approximately equal to the patient&#39;s ventricular CSF pressure such that no pressure change occurs after the surgery. After the patient recovers from surgery, the pressure setting can be adjusted as desired. For example, in a patient suffering from NPH, the pressure setting can be decreased in order to initiate a reduction in the size of the ventricles. Additional adjustments in the pressure setting can additionally be made. For example, once the size of the ventricles had been reduced sufficiently, the pressure setting of the valve can be increased. As will be appreciated, use of the implanted valve device permits the pressure setting of the valve device to be externally adjusted as needed over the course of treating the patient. 
     In certain embodiments, a method of treating hydrocephalus includes implanting an embodiment of the valve assembly  4900  having a ventricular catheter within a ventricular cavity of the patient&#39;s brain and distal catheter connected to the connector installed at a remote location in the patient&#39;s body where the fluid is to drain. Remote locations of the body where CSF drains include, for example, the right atrium of the heart and the peritoneum. 
     In addition to hydrocephalus, there are several other conditions associated with the accumulation of excess fluid and that can be treated by draining the fluid using a suitably-designed inflow catheter into another part of the body. Such conditions include, for example, chronic pericardial effusions, chronic pulmonary effusion, pulmonary edema, ascites, and glaucoma in the eye. It is contemplated that embodiments of the programmable valve device may be used in the treatment of these conditions. 
     The pressure settings of the valves described herein, including valve device  5000 , can be adjusted in many discrete steps or increments, or continuously over a predetermined range, as discussed above. Embodiments of the valves described herein may vary in pressure from a low pressure, for example, 0 mm H 2 O, to a high pressure, for example 300 mm H 2 O. Most conventional valves only have pressures as high as 200 mm H 2 O and can only be adjusted in relatively large increments between each pressure setting. 
     Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention should be determined from proper construction of the appended claims, and their equivalents.