Abstract:
Implantable physiological shunt systems and related fluid flow control devices and accessories for use therewith. Devices, systems and methods relating to implantable medical fluid flow control devices, rotors and magnets with increased resistance to inadvertent setting changes. Devices, systems and methods relating implantable medical fluid flow control devices, rotors and magnets which provide improved magnetic coupling to fluid flow control device accessories such as adjustment tools.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 13/804,875, filed Mar. 14, 2013, and entitled “Fluid Flow Control Devices, Rotors and Magnets with Increased Resistance to Inadvertent Setting Change and Improved Accessory Tool Coupling” that claims the benefit of U.S. Provisional Application No. 61/662,664, filed on Jun. 21, 2012, the entire teachings of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates generally to implantable physiological shunt systems and related fluid flow control devices as well as accessories for use therewith. More specifically, the present disclosure provides devices, systems and methods relating to implantable medical fluid flow control devices, rotors and magnets with increased resistance to inadvertent setting changes. The present disclosure also provides devices, systems and methods relating implantable medical fluid flow control devices, rotors and magnets which provide improved magnetic coupling to fluid flow control device accessories such as adjustment tools. 
         [0003]    Generally, a fluid flow control device includes a one-way control valve for controlling the flow of cerebrospinal (CSF) fluid out of a brain ventricle and preventing backflow of fluid into the brain ventricle. One example of a fluid flow control device is disclosed, for example, in U.S. Pat. No. 5,637,083 entitled, “Implantable Adjustable Fluid Flow Control Valve”, incorporated by reference herein in its entirety. Hydrocephalus, a neurological condition which may affect infants, children and adults, results from an undesirable accumulation of fluids, such as CSF, within the ventricles, or cavities, of the brain and which accumulation may exert extreme pressure with brain and in infants, skull deforming forces. Treatment of hydrocephalus often involves draining CSF away from the brain ventricles utilizing a drainage or shunt system including one or more catheters and a shunt valve which may generally be described as a fluid flow control device. The shunt valve, or fluid flow control device, may have a variety of configurations and may be adjustable in that the valve mechanism of the device may be set to a threshold pressure level at which fluid may be allowed to begin to flow through the valve and drain away from the brain. Fluid flow control devices may be subcutaneously implantable and percutaneously adjustable. Flow control devices may have a number of pressure settings and may be adjustable to the various pressure settings via external magnetic adjustment tools. Some fluid flow control devices are magnetic in that the devices include a magnetic rotor or rotor assembly which interacts with a valve mechanism and an adjustment mechanism to selectively adjust a valve opening pressure. The magnetic rotor or rotor assembly may magnetically couple with an external magnetic adjustment tool or tools. Magnetized rotors often include a single magnet or dual magnets arranged or configured to have aligned horizontal polarity. The magnetic adjustment tools are designed to externally (i.e., external to a patient) couple to a rotor magnet of a fluid flow control device implanted in a patient such that upon coupling, the rotor may be deliberately rotated to thereby adjust the pressure setting of the device non-invasively. Adjustment tools can include magnets which may be placed in line with the rotor magnet or magnets in order to couple to and drive the rotor externally, or through the tissue, after the valve is implanted. Typically, an adjustment tool is placed externally, for example, on the patient&#39;s head and in proximity to the implanted device. In this manner, it is possible to set the valve rotor into a desired position in a non-invasive manner. 
         [0004]    A rotor or rotor assembly having a single magnet or dual magnets with aligned horizontal polarity may cause the magnetic rotor to be susceptible to movement or inadvertent setting adjustment by a strong nearby magnetic field since the internal magnetic elements arranged in this manner may tend to align with the external field. A magnetic rotor might thus be unintentionally adjusted when in the presence of a strong external magnetic field such as encountered in a magnetic resonance imaging (MRI) procedure, for example an MM field of up to 3.0 Tesla. Unintentional adjustment can result in the rotor moving to a position whereby the pressure setting of the fluid flow control device is other than optimal for the particular patient. Depending upon how a valve or device (and thereby the magnetic rotor) enters the MM, the magnetic field of the MRI equipment may work to turn (i.e., rotate) the rotor to a new setting, or, if the valve enters the MRI equipment at a 90 degree angle to the MRI magnetic field, the MRI field may work to flip (tilt) the rotor. Potential unintended adjustment may therefore require checking and/or re-adjustment via the external accessories and/or adjustment tools each time a patient is or has been in the presence of a strong external magnetic field. Therefore, the need exists for a fluid flow control device, rotor, and/or magnet which provides increased resistance to inadvertent setting changes. 
         [0005]    Intentional adjustment, verification and indication of fluid flow control device or valve pressure settings may be accomplished via external tools and/or accessories including, for example, locator, indicator and/or adjustment tools. As described above, an adjustment tool may include a magnet or magnets for coupling to and rotating an implanted rotor assembly thereby setting a device or valve pressure threshold. However, since during use the adjustment tool is located at a distance from the implanted valve and is external to the patient, device components and/or tissue between the adjustment tool magnets and valve magnet or magnets may interfere with the magnetic coupling of the two. This interference can result in a decreased magnetic field strength making intentional adjustment of pressure settings more challenging. Therefore it may be desirable to improve or increase the magnetic coupling or magnetic field strength between an implanted fluid flow control device and related external magnetically coupleable accessories. 
         [0006]    U.S. Pat. No. 5,643,194 to Negre describes a subcutaneous valve and device for externally setting it. Negre describes two micromagnets mounted in a rotor and locking means for locking the rotor in predetermined positions. The locking means described require internal device parts to move linearly to engage mechanical stops for locking the rotor in place. It may be desirable to avoid this type of mechanism since moving mechanical parts tend to decrease life of a product and increase mechanical wear. In addition, it is often desirable to design components which utilize or take up as little space as possible in implantable medical devices such as fluid flow control devices. The locking mechanism described by Negre may undesirably or unnecessarily utilize space for several reasons not the least of which may include by virtue of requiring the particular moving parts disclosed. Another disadvantage of this design is that biological debris is more likely to undesirably interfere with or jam the movable parts. 
         [0007]    U.S. Patent Application Publication No. 2012/0046595 to Wilson et. al. describes an implantable adjustable valve. Wilson et. al. describe a rotor for a valve unit where rotor magnets may have axes of magnetization arranged to lie at an angle relative to an axis of rotation of the rotor purportedly to achieve improved interaction with an indicator or adjustment tool. Wilson et. al. describes the angled axes of magnetization are achieved by physically tilting the magnets within the valve assembly such that the magnets themselves lie in a plane angled with respect to a flat or horizontal planar surface of the valve. Physically tilting or angling the magnets in the manner described by Wilson et. al. may also undesirably utilize space within a device. 
       SUMMARY 
       [0008]    In some embodiments the present disclosure provides a rotor assembly for an adjustable fluid flow control device comprising a base and two magnets mounted in the base where each of the two magnets are polarized in a substantially vertical orientation and are oppositely oriented with respect to one another. In some embodiments the rotor assembly may include a base comprising a central aperture and a single magnet or a plurality of magnets may be embedded in the base. An embodiment according to the disclosure may further include a cartridge assembly comprising a cartridge housing and a rotor assembly at least partially received therein. The cartridge housing may include a central rotor pivot or axle configured to engage a central aperture of a rotor assembly and about which a rotor assembly is configured to rotate. The central rotor pivot may comprise at least one spline and the rotor central aperture may comprise at least one groove which at least one groove is configured to engage the at least one spline such that rotation of the rotor assembly about the rotor pivot is inhibited upon engagement of the at least one groove with the at least one spline. In some embodiments an at least one spline comprises a plurality of splines and in some embodiments at least one groove comprises a plurality of grooves. 
         [0009]    In some embodiments an at least one spline or each spline of a plurality of splines comprises a spline height which is less than a height of a rotor pivot and the rotor assembly is configured to lift vertically upwardly along the rotor pivot such that the at least one groove is configured to disengage an at least one spline when the rotor assembly is lifted vertically upwardly a sufficient distance or such that a lower end of the at least one groove is in spaced relation and is above an upper end of the at least one spline. The rotor assembly may be configured to rotate about the rotor pivot upon disengagement of the at least one groove with the at least one spline. 
         [0010]    Still further embodiments according to the disclosure provide a cartridge assembly including a rotor or rotor assembly comprising a base comprising at least one notch along an outer perimeter of the base, a magnet or magnets embedded in the base, and a cartridge housing configured to at least partially receive the rotor assembly therein, where the rotor assembly is configured to rotate within the cartridge housing and wherein the rotor assembly is configured to lift vertically upwardly with respect to a bottom surface of the cartridge housing. The cartridge housing may comprise a rotor pivot about which the rotor or rotor assembly is configured to rotate. In some embodiments, the cartridge housing comprises an inner wall comprising at least one tab configured to engage the at least one notch such that rotation of the rotor assembly within the cartridge housing is inhibited upon engagement of the at least one notch with the at least one tab In some embodiments, an at least one tab comprises a height less than a height of the inner wall and the at least one tab is configured to disengage with the at least one notch when the rotor assembly is lifted such that a lower end of the at least one notch is in spaced relation and is above an upper end of the at least one tab. The rotor may be configured to rotate within the cartridge housing upon disengagement of the at least one notch with the at least one tab. In some embodiments the at least one notch comprises a plurality of notches and in some embodiments the at least one tab comprises a plurality of tabs. In some embodiments where the cartridge housing includes a rotor pivot and a plurality of notches, the rotor pivot further includes at least one spline and the rotor assembly includes at least one groove. 
         [0011]    In some embodiments, a cartridge assembly may comprise a rotor assembly, as disclosed in any of several embodiments, where the rotor assembly is magnetically coupleable to an adjustment tool and is further configured to lift vertically upwardly upon magnetically coupling with the adjustment tool. 
         [0012]    Some embodiments according to the disclosure provide a rotor assembly for an adjustable fluid flow control device comprising a base comprising a central vertical axis, two magnets mounted in the base, where each magnet comprises a planar surface and wherein each of the two magnets are embedded in the base such that the planar surface of each magnet lies in a plane substantially perpendicular to the central vertical axis; and wherein each magnet comprises an angle of polarization from 0 degrees to less than 90 degrees relative to the central vertical axis. Each magnet may comprise a horizontal planar surface and a horizontal magnet axis and the angle of polarization of each magnet may comprise an angle greater than 0 degrees and equal to or less than 90 degrees relative to the horizontal magnet axis. In some embodiments, the rotor assembly having magnets with angled magnetization or polarization may comprise two angularly polarized magnets coupled together to form a single rotor magnet. 
         [0013]    Systems according to the disclosure include an implantable fluid flow control device comprising an inlet and an outlet spaced from the inlet, a valve mechanism for controlling the flow of fluid from the inlet to the outlet where the valve mechanism comprises a ball and spring configured to interact with a rotor assembly and a fixed dual concentric stair-step array. The rotor assembly may be configured to rotate relative to the stair-step array in response to an externally applied magnetic field wherein such rotation raises or lowers the rotor assembly with respect to the stair-step array and wherein the rotor assembly comprises a base comprising a two magnets mounted in the base where each of the two magnets may be polarized in a substantially vertical or vertical orientation oppositely oriented with respect to one another or may be polarized at an angle with respect to a horizontal magnet axis. 
         [0014]    Systems according to the disclosure include an implantable fluid flow control device comprising an inlet and an outlet spaced from the inlet, a valve mechanism for controlling the flow of fluid from the inlet to the outlet where the valve mechanism comprises a ball and spring configured to interact with a rotor assembly and a fixed dual concentric stair-step array. The rotor assembly may be configured to rotate relative to the stair-step array in response to an externally applied magnetic field wherein such rotation raises or lowers the rotor assembly with respect to the stair-step array and wherein the rotor assembly comprises a base comprising a magnet mounted in the base and a mechanical stop configured to inhibit unintentional rotation of the rotor assembly when the device is in the presence of a strong magnetic field and further configured to allow intentional rotation of the rotor assembly to adjust a pressure setting of the device. 
         [0015]    Methods according to the disclosure may comprise methods of manufacturing or producing magnets with angled polarization or magnetization whereby magnets comprising angled magnetization may be manufactured or produced by machining magnetic material along a material grain which comprises an angle equal to the desired angle of polarization of the magnet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a subcutaneously implantable and percutaneously adjustable fluid flow control device useful with the present disclosure. 
           [0017]      FIG. 2  is a side cross-sectional view of the fluid flow control device of  FIG. 1 . 
           [0018]      FIG. 3  is an exploded view of the device of  FIG. 1 . 
           [0019]      FIG. 4  is a three-dimensional cross-section of a portion of the device of  FIG. 2 . 
           [0020]      FIG. 5  is a cross-sectional top view of rotor assembly and magnet useful with the present disclosure. 
           [0021]      FIG. 6  is a cross-sectional top view of a rotor assembly for a fluid flow control device according to an embodiment. 
           [0022]      FIG. 6A  is a cross-sectional side view of the rotor assembly of  FIG. 6 . 
           [0023]      FIG. 7  is a three-dimensional view of the rotor assembly of  FIGS. 6 and 6A  showing two rotor magnets in phantom, according to an embodiment. 
           [0024]      FIG. 8  is a three-dimensional view of a rotor magnet according to an embodiment. 
           [0025]      FIG. 9A  is a three-dimensional view of a cartridge housing according to an embodiment. 
           [0026]      FIG. 9B  is a top view of the cartridge assembly of  FIG. 10 . 
           [0027]      FIG. 9C  is a side view of the cartridge assembly of  FIG. 9B  with portions of the rotor assembly and cartridge housing shown in phantom 
           [0028]      FIG. 10  is a three-dimensional view of a cartridge assembly according to an embodiment. 
           [0029]      FIG. 11  is a three-dimensional exploded view of a cartridge assembly according to an embodiment. 
           [0030]      FIGS. 12A-12E  depict a rotor assembly according to an embodiment. 
           [0031]      FIGS. 13A-13C  depict a cartridge housing according to an embodiment. 
           [0032]      FIGS. 14A-14E  depict a rotor assembly according to an embodiment. 
           [0033]      FIGS. 15A-15C  depict a cartridge housing according to an embodiment. 
           [0034]      FIGS. 16A-16E  depict a rotor assembly according to an embodiment. 
           [0035]      FIGS. 17A-17C  depict a cartridge housing according to an embodiment. 
           [0036]      FIG. 18  is an illustration of conventional magnet polarity for magnets useful with embodiments according to the disclosure. 
           [0037]      FIG. 19  is an illustration of angled magnet polarity for magnets useful with embodiments according to the disclosure. 
           [0038]      FIG. 20  is an illustration of angled magnet polarity for magnets useful with embodiments according to the disclosure. 
           [0039]      FIG. 21  is a plot illustrating attraction force between a fluid flow control device accessory tool and a rotor assembly of a fluid flow control device for rotor magnets magnetized at various magnetization angles according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]      FIG. 1  depicts a fluid flow control device  20  which may be useful with devices and assemblies according to the present disclosure. Fluid flow control device  20  may be subcutaneously implanted in a patient (not shown) and may be percutaneously adjustable. Fluid flow control device  20  comprises an inlet connector  22  and an outlet connector  24 , each for receiving one end of a piece of surgical tubing (not shown). Inlet  22  is configured to fluidly connect to a catheter (not shown) which may be inserted through a patient&#39;s skull into a brain ventricle containing cerebrospinal (CSF) under pressure. The outlet connector  24  is configured to fluidly connect to a distal catheter which serves to direct CSF to another location in the patient&#39;s body.  FIG. 2  depicts a cross-sectional view of the fluid flow control device of  FIG. 1  taken along section  2 - 2 . Fluid flow control device  20  includes a fluid reservoir  60 , a valve mechanism  38  and a rotor assembly  100  described in further detail with reference to  FIG. 4 . Also shown in  FIG. 2  is an external tool  140  described further herein below. 
         [0041]      FIG. 3  depicts an exploded view of the fluid flow control device  20  of  FIG. 1 . Fluid flow control device  20  comprises a cartridge assembly  40  including a cartridge housing  41 , for housing a rotor assembly  100  ( FIG. 2 ).  FIG. 4  depicts a three-dimensional partial view of the cross section of  FIG. 2 . Valve mechanism  38  provides means for controlling fluid flow “F from the inlet connector  22  to the outlet connector  24 . More particularly, the valve mechanism  38  controls fluid flow “F” from a flushing reservoir  60  to a cartridge outlet fluid passageway  50 . The valve mechanism  38  includes a ball  94  which seats against a valve seat  92  to control the flow of fluid through a fluid passageway  90 . A pressure spring  96  is disposed below and in contact with the ball  94  to bias the ball  94  against the valve seat  92  to keep passageway  90  closed until a fluid pressure differential between the inlet  22  and outlet  24  exceeds a selected or desired valve opening pressure. Pressure spring  96  is supported at an end opposite the ball  94  by an first upper surface  98  of rotor assembly  100 . Rotor assembly  100  includes a magnet  120  or may include any of the magnets described herein below. Magnet  120  is provided within a base  122  which defines upper and lower surfaces  98  and  104 . The magnet or magnets  120  may be embedded or encapsulated in base  122 .  FIG. 5  shows a top plan view of rotor assembly  100  including a base  122  with a single rotor magnet  120  embedded therein. 
         [0042]    Returning to  FIG. 4 , the lower surface  104  of rotor assembly  100  may include a single or multiple projections protruding from the lower surface  104 . For example, the lower surface  104  may include a single or multiple legs, tabs or feet.  FIG. 4  depicts inner and outer legs  134  and  136  depicted in  FIG. 4 , other configurations of a projection or projections are described below. Regardless, the projection or projections are configured to bear against either a single stair step array  602  ( FIG. 13A ) or a selected one of a plurality of inner and outer steps  108  and  110  of a fixed dual concentric stair-step array  102 . Rotor assembly  100  is configured to rotate in response to an applied magnetic field as described below. 
         [0043]    The single  602  ( FIG. 13A ) or dual concentric stair-step array  102  allows adjustment of the amount of bias applied to the ball  94  in order to vary the selected valve mechanism  38  opening pressure. Lower surface  104  of the rotor assembly  100  is supported by the stair-step array  102 ,  602  which interacts with the projection or projections (i.e., legs  134 ,  136  in  FIG. 4 ) projecting from surface  104  to vary the relative height of the rotor assembly  100  with respect to the valve mechanism  38 . The dual concentric stair-step array  102  shown, for example in  FIG. 4, 9A , comprises a plurality of inner steps  108  surrounding the rotor pivot  106  and a corresponding plurality of outer steps  110  extending peripherally about the inner steps  108 . The inner and outer steps  108  and  110  are constructed so that those steps opposite to one another with respect to a central rotor axis A, subtend the same arch and are located at the same level. 
         [0044]    The rotor assembly  100  includes a rotor magnet  120  which may include a single magnet (as shown) or dual magnets with horizontally aligned polarity or may comprise any of the magnets described herein below. An external magnetic tool or accessory  140  ( FIG. 2 ) may be used to adjust, locate or verify position of the rotor assembly  100 . Inner and outer legs  134 ,  136  are illustrated in  FIGS. 2 and 4  as comprising nubs however, legs  134  and  136  may comprise other configurations such as projections having various shapes or may include other projections as described above. 
         [0045]    It is to be understood that any of the fluid flow control device elements disclosed or described herein and/or depicted in the various embodiments herein including rotor assemblies, cartridges, cartridge housings, bases, magnets, and/or other housings or assemblies useful therewith, may be useful with fluid flow control device  20  or with any of the elements described herein. As but one example, rotor assembly  655  and cartridge housing  610  ( FIGS. 12A, 13A ) may be used in lieu of or in place of rotor assembly  100  and cartridge housing  41  of fluid flow control device  20 . As another example, magnets  315  and  325  ( FIG. 11 ) could be used in lieu of or in place of magnet  120  or in place of magnets  300  and  310  (e.g.,  FIG. 8 ) and so on. Likewise, any of the fluid flow control device elements disclosed herein may be useful in a variety of other fluid flow control devices (not depicted). 
         [0046]      FIG. 6  depicts a cross-sectional top plan view of a rotor assembly  200  according to an embodiment. Rotor assembly  200  includes a housing or base  222  and two magnets, a first magnet  300  and a second magnet  310 , embedded in the base  222 . An outer ring  228  defines a lip around the circumference of the base  222 . Outer ring  228  is more clearly depicted in  FIG. 6A  which is a cross-sectional side view of the rotor assembly  200  of  FIG. 6 . Ring  228  may include a lock-step tab  266  which may interact with a portion of a fluid flow control device to function as a stop to limit rotation of the rotor assembly  200  relative to the stair-step array e.g.,  402  ( FIG. 9A ) to less than 360°. However, ring  228  may be provided without a lock-step tab  266  in some embodiments. Inner legs  234  and outer legs  236  illustrated in the form of nubs, depend from a lower surface  270  of the base  222  and are configured to interact with a portion of a fluid flow control device  20  such as with a dual concentric stair step array e.g.,  402  ( FIG. 9A ). 
         [0047]      FIG. 7  is a three-dimensional view of rotor assembly  200  in which lock-step tab  266  can be seen projecting from outer ring  228 . Inner and outer legs  234 ,  236  are depicted partially in phantom. Magnets  300 ,  310  are also shown in phantom in base  222 . Magnets  300 ,  310  may be mounted in or embedded in base  222  such that magnets  300 ,  310  are positioned at various distances relative to one another within base  222 . Magnets  300 ,  310  may be positioned in very close proximity such that magnets  300 ,  310  are nearly in contact or are in contact with one another. Likewise, magnets  300 ,  310  may be positioned with space (as shown) between magnets  300 ,  310 . 
         [0048]    First and second magnets  300 ,  310  are each shown as comprising a five-sided polygonal shape (in a top plane or top cross-sectional view) with approximately straight edges or sides. However, magnets  300 ,  310  may comprise any shape or combination of shapes including circular, semi-circular, spherical, hemispherical, elliptical, or polygonal, as but several examples. First magnet  300  and second magnet  310  may comprise substantially similarly shaped configurations and sizes or may each comprise a different one of the several shapes described above. Regardless, both magnets  300  and  310  are polarized in a vertical or substantially vertical direction i.e., substantially parallel to a central vertical rotor axis A′ of rotor assembly  200  and polarity P 1 , P 2  of magnets  300  and  310 , respectively, is oppositely aligned. Thus, as depicted by arrows P 1  and P 2 , magnets  300  and  310  each comprise vertical polarity and comprise opposite or reverse polarity with respect to one another. 
         [0049]      FIG. 8  shows a three-dimensional view of one magnet  300  apart from rotor assembly  200  depicting vertical polarity as described above. Magnet  300  is polarized in a vertical or substantially vertical direction indicated by arrow P 1 . Polarity P 1  is vertical or substantially vertical with respect to a horizontal upper planar surface  320  of magnet  300 . 
         [0050]    A rotor assembly (e.g.,  200 ) comprising magnets  300 ,  310  which comprise vertical polarity P 1 , P 2  in the manner disclosed may tend to resist aligning with a strong or nearby external magnetic field, such as during a magnetic resonance imaging (Mill) procedure since opposite alignment of the polarity P 1 , P 2  of the magnets  300  and  310  effectively cancels the net tendency of the magnets  300 ,  310  (and therefore the rotor or rotor assembly) to align with the external field. Thus, inadvertent pressure setting changes may be minimized or avoided while deliberate adjustment may still be carried out. Intentional or deliberate adjustment of the rotor assembly  200  to vary a valve opening pressure may be accomplished using an external adjustment tool (e.g.,  140 ,  FIG. 2 ) that simultaneously presents a tool magnet (not shown) comprising polarity configured in a complementary arrangement to the rotor assembly magnets  300 ,  310 . 
         [0051]    With reference between  FIGS. 9A and 10 , alternative embodiments of a rotor assembly and cartridge assembly will be described.  FIG. 9A  depicts a cartridge assembly  400  for receiving a rotor assembly  455 . As shown in  FIG. 9A , cartridge housing  410  includes a cavity  430  configured to receive at least a portion of rotor assembly  455  whereby the cartridge housing  410  and rotor assembly  455  form a cartridge assembly  400  as depicted in  FIG. 10 . Cartridge housing  410  includes a bottom surface  404  comprising a fixed dual concentric stair-step array  402  similar to stair-step array  102  described above. A central rotor pivot or axle  420  is configured to engage a central aperture  250  of rotor assembly  455  such that rotor assembly  455  may rotate about central rotor pivot  420  when rotor assembly  455  is positioned at various axial locations along central rotor pivot  420 . Inclusion of a central rotor pivot  420  may help to locate the rotor assembly  455  within cavity  430  and thus rotor pivot  420  aids in controlling the position of rotor assembly  455 . In addition, central rotor pivot  420  includes a central vertical pivot axis A″ and may comprise at least one spline  422 . Central rotor pivot  420  may comprise any number of splines  422  i.e., may comprise a plurality of splines, for example two or more splines  422  with two splines shown in  FIG. 9A . Splines  422  comprise a spline height “h s ”, a spline width, “w s ” and a spline depth, “d s ”. Spline height “h s ” may be less than a height “h p ” of central rotor pivot  420  and spline width “w s ” and depth “d s ” may be any width or depth and may advantageously be small relative to a diameter “d” of central pivot  420 . Notwithstanding the above, in some embodiments, spline width “w s ” and/or spline depth “d s ” may be equal to or larger than rotor pivot diameter “d”. 
         [0052]    Where central rotor pivot  420  comprises more than one spline  422 , the spline height “h s ” of each of the plurality of splines  422  may be the same or different. In other words, the height “h s ” of splines  422  may be varied. The spline or splines  422  are configured to engage an at least one groove  260  on rotor assembly  455  ( FIG. 10 ) when the central aperture  250  of rotor assembly  455  is slid over the central rotor pivot  420  such that rotor assembly  455  is positioned at least partially in cavity  430  of cartridge housing  410 . As indicated above, coupling of the rotor assembly  455  with cartridge housing  410  creates a cartridge assembly  400 . Cartridge assembly  400  is configured for use with a fluid flow control device such as fluid flow control device  20 . The cartridge assembly  400  may be positioned within a fluid flow control device such that the rotor assembly  455  interacts with a valve mechanism  38  ( FIG. 1 ) to control the flow of cerebrospinal fluid in a patient&#39;s brain. A cartridge fluid outlet  440  is therefore configured to allow passage of CSF beyond the valve mechanism  38  and out of the device. 
         [0053]    As depicted in  FIG. 10 , rotor assembly  455  includes magnets  315  and  325  where magnets  315  and  325  may comprise rounded or curved sides (not shown). In this embodiment, magnets  315  and  325  are positioned in spaced relation about central aperture  250  of rotor assembly  455  and thus are spaced about central rotor pivot  420  when rotor assembly  455  is positioned within cartridge housing  410  as shown. Magnets  315  and  325  may be similar to magnets  300  and  310  described above such that magnets  315  and  325  comprise substantially opposed vertical polarity. However, magnets  315  and  325  may comprise horizontal polarity (e.g., described with reference to  FIGS. 2, 18 ) or may comprise a single magnet or magnets comprising angled polarization as described more fully herein below with respect to  FIGS. 19-21 . Additionally, rotor assembly  455  may comprise a single magnet (not shown) with a magnet aperture (not shown) for coupling to the rotor pivot  420 . 
         [0054]    Rotor assembly  455  comprises at least one groove  260  in or along central aperture  250  and may comprise any number of grooves  260  i.e., may comprise a plurality of grooves, for example five grooves  260  as shown in  FIGS. 9A and 10 . Each groove  260  may have a size and shape which varies from one groove  260  to another, however, each groove  260  is configured to engage (e.g., via sliding over) each spline  422  of central rotor pivot  420 . The number of splines  422  and number of grooves  260  may differ, however, it may be desirable to include at least as many grooves  260  as splines  422 , i.e., there may or may not be more grooves  260  than splines  422 . 
         [0055]    The rotor assembly  455  is configured to be placed at least partially within cartridge housing  410  whereby the groove or grooves  260  are configured to engage the spline or splines  422  such that inner and outer leg or legs  334  and  336  depending from lower surface  470  ( FIGS. 9B and 9C ) of rotor assembly  455  are adjacent to, in close proximity, or in contact with the bottom surface  404  of cartridge housing  410 . As a point of reference, when legs  334 ,  336  are in contact with the bottom surface  404 , legs  334 ,  336  are in contact with the dual concentric stair step array  402 . Regardless of the proximity of surfaces  470  and  404 , as long as a groove  260  at least partially slides over or engages a spline  422 , rotor assembly  455  will be inhibited from rotating about central rotor pivot  420 . Thus, the at least one groove  260 , or plurality of grooves, is configured to engage the at least one spline  422 , or plurality of splines, such that rotation of the rotor assembly  455  about the central rotor pivot  420  is inhibited upon engagement. In this regard, the spline  422  and groove  260  configuration acts as a mechanical stop prohibiting inadvertent or undesired rotation of rotor assembly  455  about central rotor pivot  220 . This type of mechanical stop may be desired for example when, as described above, a fluid flow control device  20  (or rotor, rotor assembly or magnet of a device) is in the presence of an external magnetic field strong enough to cause alignment of the rotor assembly  455  with the external field but for the mechanical stop. 
         [0056]    If rotation of the rotor or rotor assembly is desired, i.e., deliberate adjustment is desired or required, the rotor assembly  455  is configured to lift vertically or upwardly along the rotor pivot  420 . When the rotor assembly  455  is lifted vertically (upward) such that a lower end  262  of the at least one groove  260  is in spaced relation and is above an upper end  423  of the at least one spline  422 , the at least one groove  260  disengages the at least one spline  422  whereby disengagement allows the rotor assembly  455  to freely rotate about the rotor pivot  420 . The freedom to rotate about the rotor pivot  420 , as described above, allows adjustment of the valve setting. 
         [0057]      FIG. 11  depicts an exploded view of another embodiment of a cartridge assembly, namely cartridge assembly  500 . Cartridge assembly  500  includes a cartridge housing  510  comprising a cartridge fluid outlet  540  similar to fluid outlet  440  described above. Likewise, housing  510  comprises a fixed, dual concentric stair-step array  502  similar to stair-step arrays  102  and  402  described above. Rotor assembly  555  may comprise any of the magnets described herein above and may for example comprise a single magnet or two magnets where the magnet or magnets may comprise vertical, substantially vertical or horizontal polarity and may comprise oppositely aligned vertical or angled polarity described with reference to  FIGS. 19-21 . Two outer legs  436  are shown in phantom and are similar to legs  236  and  336  described above. Cartridge housing  510  as depicted does not include a central rotor pivot as described above with reference to cartridge housing  410 , however, cartridge housing  510  may comprise a rotor pivot (not shown) similar to central rotor pivot  420  ( FIG. 10 ). Likewise, a central rotor pivot (not shown) may comprise at least one or a plurality of splines and/or grooves as described above with reference to  FIGS. 9A-10 . 
         [0058]    Housing  510  comprises at least one tab  424  on or adjacent an inner wall  428  of housing  510 . Housing  510  may comprise any number of tabs  424 , i.e., cartridge housing  510  may comprise a plurality of tabs  424 , for example two or more tabs  424 , with two tabs being shown in  FIG. 11 . Tabs  424  may comprise a variety of shapes, sizes and configurations, the rectangular tab shown in  FIG. 11  as but one exemplary embodiment. Tabs  424  comprise a tab height “h t ”, a tab width “w t ” and a tab depth “d t ” where “h t ” may be less than a height “h w ” of inner wall  428  and “w t ” and/or “d t ” may be relatively small compared to a width “w c ” of cartridge housing wall  411 . Maintaining a relatively small width and/or depth “w t ”, “d t ” of tabs  424  may advantageously require or consume the least or minimal amount of space in the cartridge assembly  510  which may be desirable for reasons described herein above. Accordingly, tabs may be considered low profile. Notwithstanding the above, alternatively, tab width “w t ” and or depth “d t ”, may be equal to or greater than cartridge wall width “w c ”. 
         [0059]    Where cartridge housing  510  comprises more than one tab  424 , the tab height “h t ” of each of the plurality of tabs  424  may be the same or different. In other words, the height “h t ” of tabs  424  may be varied. The tab or tabs  424  are configured to engage an at least one notch  224  on the perimeter of rotor assembly  555  when the rotor assembly  555  is positioned at least partially within cavity  430 ′ of housing  510 . The at least one notch  224  may comprise any number of notches  224 , i.e., may comprise a plurality of notches, for example nine notches  224  as shown (some in phantom) in  FIG. 14 . Each notch  224  may comprise a variety of size and shapes which may vary from one notch  224  to another, however, each notch  224  is configured to engage (e.g., via sliding over) each tab  424  of cartridge housing  510 . The number of tabs  424  and notches  224  may differ, however, it may be desirable to include at least as many notches  224  as tabs  424 , i.e., there may be more notches  224  than tabs  424 . Rotor assembly  555  is configured to be placed at least partially within cartridge housing  510  whereby the at least one notch  224  is configured to engage the at least one tab  424  such that a lower surface  570  (or inner and outer leg or legs  434 ,  436  depending from lower surface  570 ) of rotor assembly  555  is adjacent to, in close proximity to, or in contact with the bottom surface  504  of cartridge housing  510 . Regardless of the proximity of surfaces  570  (or legs,  434 ,  436 ) and  404 ′, as long as a notch  224  at least partially slides over or engages a tab  424 , rotor assembly  555  will be inhibited from rotating within cartridge housing  510 . Thus, the at least one notch  224  is configured to engage the at least one tab  424  such that rotation of the rotor assembly  555  is inhibited upon engagement. In this regard, the tab  424  and notch  224  configuration acts as a mechanical stop prohibiting inadvertent or undesired rotation of rotor assembly  555  within cartridge housing  510 . This type of mechanical stop may be desired for example when, as described above, a fluid flow control device  20  comprising rotor assembly  555  is in the presence of an external magnetic field strong enough to cause alignment of the rotor assembly  555  with the external field but for the mechanical stop. If rotation of the rotor or rotor assembly is desired, i.e., deliberate adjustment is desired or required, the rotor assembly  555  is configured to lift vertically or upwardly with respect to surface  404 ′. When the rotor assembly  555  is lifted vertically (upward) such that a lower end  225  of the at least one notch  224  is in spaced relation and is above an upper end  425  of the at least one tab  424 , the at least one notch  224  disengages the at least one tab  424  whereby the disengagement allows the rotor assembly  555  to freely rotate within cartridge housing  510 . 
         [0060]    As with cartridge assembly  400 , coupling of the rotor assembly  555  with cartridge housing  510  creates cartridge assembly  500 . Cartridge assembly  500 , like cartridge assembly  400 , is configured for use with a fluid flow control device such as fluid flow control device  20 . Cartridge assembly  500  may be positioned within a fluid flow control device such that the rotor assembly  555  interacts with a valve mechanism  38  ( FIG. 2 ) to control the flow of cerebrospinal fluid in a patient&#39;s brain. A cartridge fluid outlet  540  is therefore configured to allow passage of CSF beyond the valve mechanism  38  and out of the device  20 . 
         [0061]    With the above configurations of cartridge assemblies  400  and  500  in mind, rotation of a rotor assembly  455 ,  555 , and thus adjustment of pressure settings of a fluid flow control device (e.g.,  20 ) in which the cartridge assemblies  400 ,  500  may be placed, may be carried out deliberately via an external tool such as an adjustment tool  140 , described above. Adjustment tool  140  is configured to magnetically couple to a rotor magnet or magnets (e.g.,  120 ,  300 ,  315 ,  325 ,  615 ,  317 ,  327  etc.) embedded in rotor assembly  455 ,  555  to lift the rotor assembly  455 ,  555  in the manner described above i.e., whereby an at least one groove  260  or notch  224  is raised above and disengaged from an at least one spline  422  or tab  424  permitting rotation of the rotor assembly  455 ,  555  and therefore device pressure setting adjustment via adjustment of rotor assembly  455 ,  555 . Once the desired rotation and thus pressure setting is achieved, rotor assembly  455 ,  555  may be magnetically decoupled from the external tool  140  such that the at least one groove  260  or notch  224  is allowed to again or initially engage the at least one spline  422  or tab  424  and further rotation of rotor assembly  455 ,  555  about central rotor pivot  420  or rotor assembly  455 ,  555  within cartridge housing  410 ,  510  is prohibited until disengagement of the spline or splines  422  from the groove or grooves  260  (in the case of rotor assembly  455 ) or disengagement of the tab or tabs  424  from the notch or notches  224  (in the case of rotor assembly  555 ) is again achieved. 
         [0062]      FIGS. 12A-12E  depict a rotor assembly according to another embodiment. Rotor assembly  655  includes a housing or base  622  having a central aperture  650  for engaging a central rotor pivot or axle  620  of cartridge housing  610  ( FIGS. 13A-C ). Rotor assembly  655  includes a magnet  615  embedded in the base  622 . Magnet  615  comprises a single magnet having a groove  616  at one end and an arrow-shaped or pointed end  617  opposite the grooved end. This configuration of magnet  615  may aid in indicating a direction of fluid flow of a valve under using imaging techniques such as x-ray or fluoroscopy. The polarization of magnet  615  is indicated by the arrow P 5  which shows a horizontal polarization with respect to the lower surface  670  of rotor assembly  655 . Alternatively, magnet  615  may include other magnet configurations as described herein and for example may include one or more magnets polarized in a vertical, substantially vertical or angled direction. In this embodiment, magnet  615  includes a magnet central aperture  651  aligned with the rotor central aperture  650 . 
         [0063]    Rotor assembly  655  includes a protrusion  642  projecting downwardly from lower surface  670  of assembly  655 . Protrusion  642  comprises a stem portion  644  and a head portion  646 . However, protrusion  642  may include a variety of configurations and shapes, where the shape or configuration of the protrusion  642  is such that it is configured to engage with or fit within or between tabs or stops  632  of cartridge housing  610  ( FIG. 13A ). As indicated in  FIG. 12C , protrusion  642  has a lower or bottom surface  647 , a length “P L ”, a stem portion width “P w1 ” and head portion width “P w2 ” as well as a protrusion height, “P h ” ( FIG. 12E ). The widths, length and height may be selected to provide a protrusion  642  which is substantial enough to provide the requisite resistance to inadvertent setting changes (described further below), while being sized sufficiently small so as to minimize space taken up by the rotor assembly  655 . The head  646  of protrusion  642  may include rounded corners, as shown, or may include other geometries or shapes. 
         [0064]    As shown in  FIGS. 12A-12E , protrusion  642  is positioned radially along base  622  such that protrusion  642  is substantially perpendicular to the angle of polarization P 5  of magnet  615 . In other words, protrusion  642  is positioned radially about the perimeter of magnet  615  such that protrusion  642  is at a ninety degree angle to P 5 . Positioning protrusion  642  in this manner tends to minimize forces which would pull or lift the rotor out of a locked position. For example, when rotor assembly  655  is placed within cavity  630  of cartridge housing  610 , external forces acting on magnet  615  (e.g., if rotor  655  enters an Mill device at a substantially 90 degree angle to the magnetic field of the Mill equipment, as described above) may cause rotor assembly  655  to slightly rock back and forth along an axis perpendicular to P 5 . Since this “rocking” or tilting motion is not directly pulling up or acting on protrusion  642  (i.e. is not causing protrusion  642  to lift), despite the possible rocking or tilting motion described, the protrusion  642  tends to stay in a locked position between stops  632 . Even in light of the above, protrusion  642  may alternatively be positioned along base  622  at any radial location around the perimeter of magnet  615 . 
         [0065]      FIGS. 13A-13C  depict a cartridge housing in accordance with another embodiment and as described with reference to  FIGS. 12A-12E  above, may be particularly useful with rotor assembly  655 . Several features of cartridge housing  610  may be similar to other cartridge housings described herein. For example, cartridge housing  610  includes a cartridge fluid outlet  640  a central rotor pivot or axle  620 , and may include a generally similar outer housing profile. In addition, cartridge housing  610  includes a cavity  630  for receiving a rotor assembly such as  655 . When rotor assembly  655  is placed within cartridge housing  610 , the assembly may define a cartridge assembly (not shown) such as described with reference to cartridge assemblies  400  and  500 . However, one notable difference to other cartridge housings described herein is cartridge housing  610  includes a single stair-step array  602  as opposed to a dual concentric stair-step array (e.g.,  402 ). Since rotor assembly  655  includes only a single projection or protrusion  642 , only a single stair-step array  602  is provided. As with other stair-step arrays, stair-step array  602  includes five steps ( 603 ,  604 ,  605 ,  606 ,  607 ) corresponding to five settings of a fluid flow control device (e.g., valve  20 ). The single-protrusion rotor assembly, single, stair-step array cartridge housing combination results in a design which may be easier to manufacture, and avoids relatively small, potentially fragile features. 
         [0066]    As mentioned above, cartridge housing includes locks or stops  632  projecting inwardly from inner cartridge housing wall  637 . Each of locks  632  include an upper surface  631  where the upper surface  631  of each lock  632  lies in the same plane (e.g., as depicted in  FIG. 13B ). Locks  632  are positioned radially around inner wall  637  and five locks  632  are shown which correspond to the five stair steps of array  602 . Each individual lock  632  may include flattened edges  634  which angle inwardly as the lock  632  projects toward the rotor pivot  620 . This flat, angled configuration allows for stem  644  of protrusion  642  to have a line to line connection with the lock  632 , when the protrusion  642  is provided or located between two locks  632 . Additionally, upper edges  633  of lock  632  may be chamfered to provide a smooth transition of protrusion  642  along and over lock  632  when the protrusions  642  are deliberately lifted from a first position between two locks  632  to a second position between two other locks  632  such that protrusion  642  rests on a different stair step of the array  602  in each of the two positions. For example, protrusion  642  may rest on stair step  604  in a first position and may rest on stair step  605  in a second position, and so on. 
         [0067]      FIG. 13B  is a side cross-sectional view of cartridge housing  610  taken along line A-A. A portion of stair-step array  602  can be seen as well as several of locks  632 .  FIG. 13C  is a top view of cartridge housing  610  showing the arrangement of locks  632  around wall  637 . The rotor assembly  655  is configured to be placed within a cavity (e.g.,  630 ) of a cartridge housing, (e.g.  610 ). Central rotor pivot  620  is configured to engage central aperture  650  of rotor assembly  655  such that rotor assembly  655  may rotate about central rotor pivot  620  when rotor assembly  655  is positioned at various axial locations along central rotor pivot  620 . However, the protrusion  642  is configured to fit between stops  632  of the housing  610  when the rotor assembly  655  is lowered into cavity  630  such that the bottom surface  647  of rotor assembly  655  is positioned lower than the upper surface  631  of stops  632 . When protrusion  642  is positioned between two stops  632  in this manner, rotor assembly  655  may be in a first, locked position and will be inhibited from rotating about central rotor pivot  620 . In this regard, the protrusion  642  and lock  632  interaction acts as a mechanical stop prohibiting inadvertent or undesired rotation of rotor assembly  655  about central rotor pivot  620 . This type of mechanical stop may be desired for example when, as described above, a fluid flow control device  20  (or rotor, rotor assembly or magnet of a device) is in the presence of an external magnetic field strong enough to cause alignment of the rotor assembly  655  with the external field but for the mechanical stop. 
         [0068]    Conversely, if rotation of the rotor assembly  655  is desired, i.e., deliberate adjustment is desired or required, the rotor assembly  655  is configured to lift vertically or upwardly until the lower surface  647  of protrusion  642  is located above the upper surface of locks  632 . In this first, unlocked position, the rotor assembly  655  is free to rotate about the rotor pivot  620 . The freedom to rotate about the rotor pivot  620 , as described above, allows adjustment of the valve setting, for example, to a second, locked position (i.e., such that surface  647  or protrusion  642  rests on a step of the stair-step array  602  different from the step surface  647  rests on in a first, locked position). 
         [0069]      FIGS. 14A-14E and 15A-15C  depict a rotor assembly and cartridge housing according to further embodiments. Rotor assembly  755  is similar to rotor assembly  655  with the exception of an additional projection, leg  752 , extending from lower surface  770  of base  722 . Leg  752  may comprise various shapes, configurations and sizes as long as leg  752  is sized for interaction with an inner stair-step array  702 ″ (having steps  703 ′,  704 ′,  705 ′,  706 ′,  707 ′) of dual-concentric stair-step array  702  ( FIG. 15A ). Protrusion  742  is similar to protrusion  642  described above and is likewise located perpendicular to the polarization of magnet  715 . Leg  752  is located adjacent or proximate central aperture  750 . Leg  752  interacts with inner stair-step array  702 ″, such as described above with reference to feet  134 ,  234 ,  334  of  FIGS. 4-9 . As with the dual-concentric stair step array  102 , stair-step arrays  702 ′,  702 ″ are constructed so that those steps opposite to one another with respect to a central rotor axis  720 , subtend the same arch and are located at the same level. Thus, lower surface or edge  751  of leg  752  lies in the same plane as lower surface  747  of protrusion  742 . Leg  752  interacts with inner stair-step array  702 ″, such as described above with reference to inner legs  134 ,  234  etc. ( FIGS. 4-9 ). Protrusion  742  is configured to interact with outer stair-step array  702 ′ (having outer stair steps  703 ,  704 ,  705 ,  706 ,  707 ) and is configured to reside between stops  732  ( FIGS. 15A-C ) similar to protrusion  642  and stops  632  such that when lower surface  747  of protrusion  742  is lower than an upper surface  731  of stops  732 , rotation of rotor assembly  755  about central rotor pivot or axle  720  is essentially prohibited while raising rotor assembly  755  such that the lower surface  747  is above upper surface  731  allows rotor assembly  755  to rotate about axle  720  so as to adjust the setting as described above. 
         [0070]      FIGS. 16A-14E and 17A-15C  depict a rotor assembly and cartridge housing according to further embodiments. Rotor assembly  855  is similar to rotor assemblies  655  and  755 . Rotor assembly is similar to rotor assembly  655  in that two projections  844  and  846 , if coupled together, may resemble single projection  642  ( FIG. 12B ). Rotor assembly is similar to rotor assembly  755  in that the assembly includes two protrusion or projections, a tab  846 , and a stem  844 , extending from lower surface  870  of base  822 . Tab  846  may comprise various shapes, configurations and sizes as long as tab  852  is sized for interaction with an inner stair-step array  802 ″ (having steps  803 ′,  804 ′,  805 ′,  806 ′,  807 ′) of dual-concentric stair-step array  802  ( FIG. 17A ). A difference to rotor assembly  755  is tab  846  is spaced radially from (rather than adjacent to) central aperture  850 . Tab  846  interacts with inner stair-step array  802 ″, such as described above with reference to feet  134 ,  234 ,  334  and leg  752  of  FIGS. 4-9, 14B . 
         [0071]    Stem  844  is similar to protrusions or projections  642  and  742  described above in that stem  844  is likewise located perpendicular to the polarization of magnet  815 . Stem  844  is configured to interact with outer stair-step array  802 ′ (having outer stair steps  803 ,  804 ,  805 ,  806 ,  807 ) and is configured to reside between stops  832  ( FIGS. 17A-C ) similar to projections  642 ,  742  and stops  632 ,  732 . Lower surface or edge  848  of tab  846  lies in the same plane as lower surface  847  of stem  844 . Stair step array  802  is similar to array  702  although inner array  802 ′ may be radially wider than inner array  702 ′. Thus, when lower surface  847  of stem  844  is lower than an upper surface  831  of stops  832  of cartridge housing  810 , rotation of rotor assembly  855  about central rotor pivot or axle  820  is essentially prohibited, while raising rotor assembly  855  such that the lower surface  847  is above upper surface  831  allows rotor assembly  855  to rotate about axle  820  so as to adjust the setting as described above. 
         [0072]    The various rotor assemblies and cartridge housings described herein may comprise a variety of suitable materials such as suitable polymers. For example, rotor assemblies may comprise polysulfone and cartridge housings may comprise polysulfone, acetal, PEEK, polyphelylene, polyphenylsulfone, polyether sulfone, as but several non-limiting examples. Any suitable material may be used and may for example, include any material having a tensile strength high enough to prevent fracture of a central rotor pivot or axle (referenced generally). 
         [0073]      FIG. 18  shows two magnets  350 ,  360  useful with a rotor assembly e.g.,  100 ,  200 ,  455 ,  555 . The magnets  350  and  360  depict conventional horizontal polarization indicated at arrows P 3  and P 4 . That is, each magnet  350 ,  360  is magnetized in a plane horizontal to an upper planar surface  351 ,  361  of the magnet. Stated another way, magnets are magnetized in a direction substantially perpendicular to a central horizontal magnet axis A 1  or A 2 .  FIG. 19  depicts two magnets  317  and  327  according to an embodiment. Magnets  317  and  327  comprise horizontal upper planar surfaces  520  and  521  which may be substantially flat. Magnets  317  and  327  also comprise horizontal magnet axes H 1  and H 2 , respectively. In contrast to the horizontal polarity P 3 , P 4  of conventional magnets  350  and  360 , magnets  317  and  327  comprise angled magnetization indicated at arrows P 1 ′ and P 2 ′, where the angle of polarization with respect to the horizontal magnet axes H 1  or H 2  may be any angle greater than 0 and less than 90 degrees. For example, the angle of polarization may be approximately greater than 0 and less than or equal to 20 degrees relative to horizontal magnet axes H 1  or H 2 . 
         [0074]    In the embodiment of magnet  327  shown, an angle of magnetization of 15 degrees is depicted. It is to be understood, however, that magnets  317 ,  327  may comprise any angle of magnetization. Magnets  315  and  325  may be used in any of the rotor assemblies (e.g.,  10 ,  200 ,  455 ,  555 ) described herein above or any other rotor assembly or fluid flow control device (e.g.,  20 ). Magnets  317  and  327  may be positioned or embedded in a rotor assembly  100 ,  200 ,  455 ,  555 , cartridge housing  410 ,  510  or fluid flow control device  20  such that horizontal planar surfaces  520 ,  521  lie in a plane substantially perpendicular to a central vertical rotor axis or central vertical pivot axis A, A′ or A″ ( FIGS. 2, 7 and 10 ) of a rotor assembly  100 ,  200 ,  455  or cartridge housing  410 ,  510  while magnetization or polarization of magnets  315 ,  325  remains at an angle ‘with respect to the horizontal magnet axes A, A′ or A″. In other words, magnets  315 ,  327  themselves are not substantially or significantly tilted with respect to a base (e.g.,  122 ,  222 ,  522 ) or cartridge housing (e.g.,  41 ,  410 ,  510 ), rather, the magnetization or polarization of magnets  315 ,  325  is “tilted” or angled by virtue of processing and/or manufacturing methods used in producing the magnets  317 ,  327  which will be further described below.  FIG. 20  describes an alternative embodiment where magnets  317  and  327  are similar to magnets  315  and  327  with the exception that the magnets are joined or coupled together and may thus form a single magnet. 
         [0075]    Tilting or angling the magnetization or polarization P 1 ′, P 2 ′ of magnets  317 ,  327  may allow for or result in stronger magnetic forces between an external device tool  140  and a rotor magnet or magnets e.g.,  300 ,  315 , 310 ,  325  etc. when deliberate adjustment, location or indication of a pressure setting of a fluid flow control device, or shunt valve is desired. Tissues located between the site of implant of a fluid flow control device  20  and the area external to the patient in proximity to the implanted device may interfere with magnetic coupling or adequate coupling between a tool  140  and rotor assembly  100 ,  200 ,  455 . It has been found that angling the magnetization or polarization P 1 ′, P 2 ′ may advantageously produce higher magnetic forces between an external tool  140  and rotor magnets e.g.,  317 ,  327 , may provide better resistance to demagnetization, and when used with an axle or rotor pivot such as central rotor pivot  420  ( FIG. 9A ), may create additional friction in an MRI environment which may aid in resisting alignment with the MM field. The higher forces between an external tool and rotor magnets is illustrated in the graph of  FIG. 21 .  FIG. 21  is a computer simulated plot of Force (in Newtons) versus a Magnetization angle (in degrees) from a horizontal magnet axis such as described above with reference to  FIG. 19 . As illustrated in the plot, Force may be greatest where magnets comprise a magnetization angle between approximately 0 and 20 degrees. 
         [0076]    In order to produce or manufacture magnets with angled polarization as disclosed above, the magnets  315 ,  317 ,  325 ,  327  may be machined at an angle. Magnets in general and some magnets useful with fluid flow control devices are typically or conventionally machined with the grain of the magnetic material parallel to the magnet dimensions, such as illustrated by magnets  350  and  360  described above. If instead, and according to the disclosure, magnetic material is machined so that the grain of the material matches the desired polarization angle e.g., P 1 ′, P 2 ′, then the magnet or magnets (e.g.,  317 ,  327 ) may be positioned in a rotor assembly (e.g.,  200 ,  455 ,  555 ) in a substantially physically flat (or horizontal as described above) configuration while maintaining angled polarity P 1 ′, P 2 ′ with the advantage of increased coupling strength, as described above, and a space saving design. 
         [0077]    Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.