Patent Description:
Lower back injuries and chronic joint pain are major health problems resulting not only in debilitating conditions for the patient, but also in the consumption of a large proportion of funds allocated for health care, social assistance and disability programs. In the lower back, disc abnormalities and pain may result from trauma, repetitive use in the workplace, metabolic disorders, inherited proclivity, and/or aging. The existence of adjacent nerve structures and innervation of the disc are very important issues in respect to patient treatment for back pain. In joints, osteoarthritis is the most common form of arthritis pain and occurs when the protective cartilage on the ends of bones wears down over time.

A minimally invasive technique of delivering high-frequency electrical current has been shown to relieve localized pain in many patients. Generally, the high-frequency current used for such procedures is in the radiofrequency (RF) range, i.e. between <NUM> and <NUM> and more specifically between <NUM>-<NUM>. The RF electrical current is typically delivered from a generator via connected electrodes that are placed in a patient's body, in a region of tissue that contains a neural structure suspected of transmitting pain signals to the brain. The electrodes generally include an insulated shaft with an exposed conductive tip to deliver the radiofrequency electrical current. Tissue resistance to the current causes heating of tissue adjacent resulting in the coagulation of cells (at a temperature of approximately <NUM> for small unmyelinated nerve structures) and the formation of a lesion that effectively denervates the neural structure in question. Denervation refers to a procedure whereby the ability of a neural structure to transmit signals is affected in some way and usually results in the complete inability of a neural structure to transmit signals, thus removing the pain sensations. This procedure may be done in a monopolar mode where a second dispersive electrode with a large surface area is placed on the surface of a patient's body to complete the circuit, or in a bipolar mode where a second radiofrequency electrode is placed at the treatment site. In a bipolar procedure, the current is preferentially concentrated between the two electrodes.

To extend the size of a lesion, radiofrequency treatment may be applied in conjunction with a cooling mechanism, whereby a cooling means is used to reduce the temperature of the electrode-tissue interface, allowing a higher power to be applied without causing an unwanted increase in local tissue temperature that can result in tissue desiccation, charring, or steam formation. The application of a higher power allows regions of tissue further away from the energy delivery device to reach a temperature at which a lesion can form, thus increasing the size/volume of the lesion. The cooling means can include internal circulation of a cooling fluid fluid within a probe comprising the electrode, where the cooling fluid never contacts the patient, or through external irrigation, in which a physiologic solution is used to continuously irrigate and cool the electrode-tissue interface or treatment site. Regardless of the cooling approach, accurate control of the cooling fluid flow rate is critical in creating an effective lesion. However, known cooled radiofrequency treatment systems vary the speed of a pump that pumps the cooling fluid through the system to control the flow rate. Such an open loop approach is technically challenging and expensive to implement, particularly in configurations requiring high accuracy such irrigated cooling. Due to the inability in typical systems to directly measure the cooling fluid flow rate, open loop control must rely on high tolerance of the pump head and tubing, as well as consistent set up of the system to achieve repeatable speed based flow rate control.

The treatment of pain using high-frequency electrical current has been applied successfully to various regions of patients' bodies suspected of contributing to chronic pain sensations. For example, with respect to back pain, which affects millions of individuals every year, high-frequency electrical treatment has been applied to several tissues, including intervertebral discs, facet joints, sacroiliac joints as well as the vertebrae themselves (in a process known as intraosseous denervation). In addition to creating lesions in neural structures, application of radiofrequency energy has also been used to treat tumors throughout the body. Further, with respect to knee pain, which also affects millions of individuals every year, high-frequency electrical treatment has been applied to several tissues, including, for example, the ligaments, muscles, tendons, and menisci.

Thus, the art is continuously seeking new and improved systems and methods for treating chronic pain using cooled RF ablation techniques. For example, improved systems utilizing direct measure of a flow rate of a cooling fluid delivered to a distal end of a medical probe assembly would be useful. More particularly, systems having a flow sensor integrated in a tubing that provides cooling fluid to the medical probe assembly to directly measure the cooling fluid flow rate would be advantageous. Methods for controlling the cooling fluid flow rate using the closed-loop feedback control system enabled by the flow sensor also would be desirable.

<CIT> discloses a system for regulating, maintaining and/or controlling the temperature of fluids and tissues during therapeutic or ablative tissue treatment applications.

Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

According to a first aspect of the present invention, there is provided a cooling system for a medical probe assembly according to claim <NUM>. It should also be understood that the cooling system may further include any of the additional features as described herein.

According to a second aspect of the present invention, there is provided a method for controlling a flow rate of a cooling fluid through a cooling circuit of a medical probe assembly according to claim <NUM>. It should also be appreciated that the method may further include any of the additional features as described herein.

According to a third aspect of the present invention, there is provided a system according to claim <NUM>. It should also be understood that the system may further include any of the additional features as described herein.

These and other features, aspects and advantages of the present subject matter will become better understood with reference to the following description and appended claims.

A full and enabling disclosure of the present subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:.

Reference will now be made in detail to one or more embodiments of the invention, examples of the invention, examples of which are illustrated in the drawings. Each example and embodiment is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment. It is intended that the invention include these and other modifications and variations as coming within the scope of the invention.

For the purposes of the present subject matter, a lesion refers to the region of tissue that has been irreversibly damaged as a result of the application of thermal energy, and the present subject matter is not intended to be limited in this regard. Further, for the purposes of this description, proximal generally indicates that portion of a device or system next to or nearer to a user (when the device is in use), while the term distal generally indicates a portion further away from the user (when the device is in use).

Generally, the present subject matter provides pump systems, pump assemblies, and pump heads for pumping fluid to one or more systems or assemblies. More particularly, the present subject matter provides a pump system comprising a plurality of pump assemblies, and each pump assembly of the plurality of pump assemblies supplies a fluid to a cooling circuit. The cooling circuit may be used to supply cooling fluid to the distal end of a medical probe assembly for delivering energy to a patient's body, e.g., as part of a treatment procedure. The pump system further comprises a base for supporting the plurality of pump assemblies. Each pump assembly described herein comprises a pump head, a bezel surrounding an outer perimeter of the pump head, a motor, and tubing.

In general, the pump head comprises an occlusion bed, a rotor guide, a rotor assembly positioned between the occlusion bed and the rotor guide, and a pathway for tubing. The tubing supplies fluid to the cooling circuit. The pathway comprises an inlet portion, an outlet portion, and a connecting portion that connects the inlet portion to the outlet portion. The inlet portion of the pathway is defined between the occlusion bed and the rotor guide, the outlet portion of the pathway is defined between the occlusion bed and the rotor guide, and the connecting portion of the pathway is defined between the occlusion bed and the rotor assembly. Further, the occlusion bed is movable with respect to the rotor guide and the rotor assembly. As described herein, through such movement of the occlusion bed and other features, the pump head is configured to ease the task of inserting the tubing into the pump head such that correct insertion of the tubing is repeatable and safe. Once the tubing is inserted or loaded into the pump head, and the user is safely separated from the rotor assembly, e.g., by a rotor cover plate and pump head cover as described herein, the motor may be powered on to drive the rotor assembly and thereby begin pumping the fluid through the tubing.

Referring now to the drawings, <FIG> illustrates a schematic diagram of one embodiment of a system <NUM> of the present subject matter. As shown, the system <NUM> includes a generator <NUM>; a cable <NUM>; one or more probe assemblies <NUM> (only one probe assembly <NUM> is shown); one or more cooling devices <NUM>; a pump cable <NUM>; one or more proximal cooling supply tubes <NUM>; and one or more proximal cooling return tubes <NUM>. In an exemplary embodiment, the system <NUM> includes first, second, third, and fourth probe assemblies <NUM>. As shown in the illustrated embodiment, the generator <NUM> is a radiofrequency (RF) generator. Further, the generator <NUM> may include a display <NUM> (<FIG>) incorporated therein. The display <NUM> may be operable to display various aspects of a treatment procedure, including but not limited to any parameters that are relevant to a treatment procedure, such as temperature, impedance, etc. and errors or warnings related to a treatment procedure. If no display <NUM> is incorporated into the generator <NUM>, the generator <NUM> may include means of transmitting a signal to an external display. In one embodiment, the generator <NUM> is operable to communicate with one more devices, for example, with one or more of the probe assemblies <NUM> and the one or more cooling devices <NUM>. Such communication may be unidirectional or bidirectional depending on the devices used and the procedure performed.

In addition, as shown, a distal region <NUM> of the cable <NUM> may include a splitter <NUM> that divides the cable <NUM> into two or more distal ends <NUM> such that the probe assemblies <NUM> can be connected thereto. A proximal end <NUM> of the cable <NUM> is connected to the generator <NUM>. This connection can be permanent, whereby, for example, the proximal end <NUM> of the cable <NUM> is embedded within the generator <NUM>, or temporary, whereby, for example, the proximal end <NUM> of cable <NUM> is connected to generator <NUM> via an electrical connector. The two or more distal ends <NUM> of the cable <NUM> terminate in connectors <NUM> operable to couple to the probe assemblies <NUM> and establish an electrical connection between the probe assemblies <NUM> and the generator <NUM>. In alternate embodiments, the system <NUM> may include a separate cable for each probe assembly <NUM> being used to couple the probe assemblies <NUM> to the generator <NUM>. Alternatively, the splitter <NUM> may include more than two distal ends. Such a connector is useful in embodiments having more than two devices connected to the generator <NUM>, for example, if more than two probe assemblies are being used.

The cooling device(s) <NUM> may include any means of reducing a temperature of material located at and proximate to one or more of the probe assemblies <NUM>. For example, as shown in <FIG>, the cooling devices <NUM> may include a pump system <NUM> having one or more peristaltic pump assemblies <NUM> operable to circulate a fluid from the cooling devices <NUM> through one or more proximal cooling supply tubes <NUM>, the probe assemblies <NUM> (via internal lumens therein, as described in greater detail below), one or more proximal cooling return tubes <NUM> and back to the one or more cooling devices <NUM>. For example, as shown in the illustrated embodiment of <FIG> and <FIG>, the pump system <NUM> includes four peristaltic pump assemblies <NUM> coupled to a power supply <NUM>. In such embodiments, as shown in <FIG>, each of the plurality of pump assemblies <NUM> may be in separate fluid communication with one of the probe assemblies. The fluid may be water or any other suitable fluid or gas. In alternate embodiments, the pump system <NUM> may include only one peristaltic pump assembly <NUM> or greater than four pump assemblies <NUM>. In addition, as shown in <FIG>, each of the pump assemblies <NUM> may have an independent speed (i.e., RPM) controller <NUM> that is configured to independently adjust the speed of its respective pump assembly. The pump system <NUM> and pump assemblies <NUM> are described in greater detail below.

Referring to <FIG>, the system <NUM> includes a controller or control module <NUM> for facilitating communication between the cooling devices <NUM> and the generator <NUM>. In this way, feedback control is established between the cooling devices <NUM> and the generator <NUM>. The feedback control may include the generator <NUM>, the probe assemblies <NUM>, and the cooling devices <NUM>, although any feedback between any two devices is within the scope of the present subject matter. The feedback control may be implemented, for example, in a control module that may be a component of the generator <NUM>. In such embodiments, the generator <NUM> is operable to communicate bi-directionally with the probe assemblies <NUM> as well as with the cooling devices <NUM>. In the context of the present subject matter, bi-directional communication refers to the capability of a device to both receive a signal from and send a signal to another device.

As an example, the generator <NUM> may receive temperature measurements from one or both of the first and second probe assemblies <NUM>. Based on the temperature measurements, the generator <NUM> may perform some action, such as modulating the power that is sent to the probe assemblies <NUM>. Thus, both probe assemblies <NUM> may be individually controlled based on their respective temperature measurements. For example, power to each of the probe assemblies <NUM> can be increased when a temperature measurement is low or can be decreased when a measurement is high. This variation of power may be different for each probe assembly. In some cases, the generator <NUM> may terminate power to one or more probe assemblies <NUM>. Thus, the generator <NUM> may receive a signal (e.g., temperature measurement) from one or both of the first and second probe assemblies <NUM>, determine the appropriate action, and send a signal (e.g., decreased or increased power) back to one or both of the probe assemblies <NUM>. Alternatively, the generator <NUM> may send a signal to the cooling devices <NUM> to either increase or decrease the flow rate or degree of cooling being supplied to one or both of the first and second probe assemblies <NUM>.

More specifically, the pump assemblies <NUM> may communicate a fluid flow rate to the generator <NUM> and may receive communications from the generator <NUM> instructing the pumps <NUM> to modulate this flow rate. In some instances, the peristaltic pump assemblies <NUM> may respond to the generator <NUM> by changing the flow rate or turning off for a period of time. With the cooling devices <NUM> turned off, any temperature sensing elements associated with the probe assemblies <NUM> would not be affected by the cooling fluid, allowing a more precise determination of the surrounding tissue temperature to be made. In addition, when using more than one probe assembly <NUM>, the average temperature or a maximum temperature in the temperature sensing elements associated with the probe assemblies <NUM> may be used to modulate cooling.

In other embodiments, the cooling devices <NUM> may reduce the rate of cooling or disengage depending on the distance between the probe assemblies <NUM>. For example, when the distance is small enough such that a sufficient current density exists in the region to achieve a desired temperature, little or no cooling may be required. In such an embodiment, energy is preferentially concentrated between first and second energy delivery devices <NUM> through a region of tissue to be treated, thereby creating a strip lesion. A strip lesion is characterized by an oblong volume of heated tissue that is formed when an active electrode is in close proximity to a return electrode of similar dimensions. This occurs because at a given power, the current density is preferentially concentrated between the electrodes and a rise in temperature results from current density. Thus, as illustrated by these examples, the controller <NUM> may actively control energy delivered to the tissue by controlling an amount of energy delivered through the energy delivery device(s) <NUM> and by controlling a flow rate through the pump assembly(ies) <NUM>, e.g., the flow rate through tubing of a pump head <NUM> of a pump assembly <NUM>.

The cooling devices <NUM> may also communicate with the generator <NUM> to alert the generator <NUM> to one or more possible errors and/or anomalies associated with the cooling devices <NUM>. Such errors and/or anomalies may include whether cooling flow is impeded or if a lid of one or more of the cooling devices <NUM> is opened. The generator <NUM> may then act on the error signal by at least one of alerting a user, aborting the procedure, and modifying an action.

The controller <NUM>, as well as the other controllers or microcontrollers described herein, such as the microcontroller <NUM> and motor controller <NUM>, can include various components for performing various operations and functions. For example, the controller <NUM> can include one or more processor(s) and one or more memory device(s). The operation of the system <NUM>, including the generator <NUM> and cooling device(s) <NUM>, may be controlled by a processing device such as the controller <NUM>, which may include a microprocessor or other device that is in operative communication with components of the system <NUM>. In one embodiment, the processor executes programming instructions stored in memory and may be a general or special purpose processor or microprocessor operable to execute programming instructions, control code, or micro-control code. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, the controller <NUM> may be constructed without using a processor or microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. Components of the system <NUM> may be in communication with the controller <NUM> via one or more signal lines or shared communication busses.

Further, the one or more memory device(s) can store instructions that when executed by the one or more processor(s) cause the one or more processor(s) to perform the operations and functions, e.g., as those described herein for communicating a signal. In one embodiment, the generator <NUM> includes a control circuit having one or more processors and associated memory device(s) configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like disclosed herein). As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements.

Such memory device(s) may generally be configured to store suitable computer-readable instructions that, when implemented by the controller(s) or processor(s) <NUM>, configure the control circuit to perform various functions including, but not limited to, controlling an amount of energy delivered through the energy delivery device(s) <NUM>, controlling a flow rate through the pump assembly(ies) <NUM>, and/or other functions. More particularly, the instructions may configure the control circuit to perform functions such as receiving directly or indirectly signals from one or more sensors (e.g. voltage sensors, current sensors, and/or other sensors) indicative of various input conditions, and/or various other suitable computer-implemented functions, which enable the generator <NUM> or other components of system <NUM> to carry out the various functions described herein. An interface can include one or more circuits, terminals, pins, contacts, conductors, or other components for sending and receiving control signals. Moreover, the control circuit may include a sensor interface (e.g., one or more analog-to-digital converters) to permit signals transmitted from any sensors within the system to be converted into signals that can be understood and processed by the controller(s) or processor(s) <NUM>.

Still referring to <FIG>, the proximal cooling supply tubes <NUM> may include proximal supply tube connectors <NUM> at the distal ends of the one or more proximal cooling supply tubes <NUM>. Additionally, the proximal cooling return tubes <NUM> may include proximal return tube connectors <NUM> at the distal ends of the one or more proximal cooling return tubes <NUM>. In one embodiment, the proximal supply tube connectors <NUM> are female luer-lock type connectors and the proximal return tube connectors <NUM> are male luer-lock type connectors, although other connector types are intended to be within the scope of the present subject matter.

In addition, as shown in <FIG>, the probe assembly <NUM> may include a proximal region <NUM>, a handle <NUM>, a hollow elongate shaft <NUM>, and a distal tip region <NUM> that includes the one or more energy delivery devices <NUM>. The elongate shaft <NUM> and the distal tip region <NUM> together form a probe <NUM> that contact a patient's body to deliver energy thereto. The hollow elongate shaft <NUM> also may be described as an outer circumferential portion <NUM> of the probe <NUM>, and the energy delivery device <NUM> extends distally from the outer circumferential portion <NUM>. As further described herein, the elongate shaft <NUM> may be an electrically non-conductive outer circumferential portion <NUM>, e.g., the shaft <NUM> may be formed from an electrically non-conductive material or may be electrically insulated, and the energy delivery device(s) <NUM> may be electrically and thermally-conductive energy delivery device(s) <NUM>.

The proximal region <NUM> includes a distal cooling supply tube <NUM>, a distal supply tube connector <NUM>, a distal cooling return tube <NUM>, a distal return tube connector <NUM>, a probe assembly cable <NUM>, and a probe cable connector <NUM>. In such embodiments, the distal cooling supply tube <NUM> and distal cooling return tube <NUM> are flexible to allow for greater maneuverability of the probe assemblies <NUM> but alternate embodiments with rigid tubes are possible. Further, in several embodiments, the distal supply tube connector <NUM> may be a male luer-lock type connector and the distal return tube connector <NUM> may be a female luer-lock type connector. Thus, the proximal supply tube connector <NUM> may be operable to interlock with the distal supply tube connector <NUM> and the proximal return tube connector <NUM> may be operable to interlock with the distal return tube connector <NUM>.

The probe assembly <NUM> also may include a shaft supply tube <NUM> and a shaft return tube <NUM>, which are internal lumens for circulating cooling fluid to a distal end of the probe assembly <NUM>. The distal cooling supply tube <NUM> and the distal cooling return tube <NUM> may be connected to the shaft supply tube <NUM> and the shaft return tube <NUM>, respectively, within the handle <NUM> of the probe assembly <NUM>. In one embodiment, the shaft supply tube <NUM> and the shaft return tube <NUM> may be hypotubes made of a conductive material, such as stainless steel, that extend from the handle <NUM> through a lumen of the hollow elongate shaft <NUM> to distal tip region <NUM>. The number of hypotubes used for supplying cooling fluid and the number used for returning cooling fluid and the combination thereof may vary and all such combinations are intended to be within the scope of the present invention. For example, in some embodiments, the cooling fluid may pass through the shaft supply tube <NUM> out of the probe assembly <NUM> to the treatment site in the patient's body, externally cooling the distal end <NUM> through irrigation of the treatment site. Thus, in such embodiments, the cooling fluid may be a physiologic solution suitable for contacting the patient, and the tubes used for returning the fluid to the fluid source may be omitted or unused.

As illustrated in <FIG>, the cooling fluid flows in a cooling circuit <NUM> formed by the cooling device(s) <NUM>, the distal tip region <NUM> of the probe, and the various supply and return tubes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The arrows FF in <FIG> illustrate the direction of flow of the cooling fluid supplied by the cooling device(s) <NUM> through the cooling circuit <NUM>. More specifically, the cooling fluid flows from the cooling device(s) <NUM>, through proximal cooling supply tube <NUM> to distal cooling supply tube <NUM>, through distal cooling supply tube <NUM> to shaft supply tube <NUM>, through shaft supply tube <NUM> to the distal tip region <NUM>, from the distal tip region <NUM> to shaft return tube <NUM>, through shaft return tube <NUM> to distal return tube <NUM>, through distal return tube <NUM> to proximal return tube <NUM>, and through proximal return tube <NUM> to the cooling device(s) <NUM>.

Referring still to <FIG>, the probe cable connector <NUM> may be located at a proximal end of the probe assembly cable <NUM> and may be operable to reversibly couple to one of the connectors <NUM>, thus establishing an electrical connection between the generator <NUM> and the probe assembly <NUM>. The probe assembly cable <NUM> may include one or more conductors depending on the specific configuration of the probe assembly <NUM>. For example, in one embodiment, the probe assembly cable <NUM> may include five conductors allowing probe assembly cable <NUM> to transmit RF current from the generator <NUM> to the one or more energy delivery devices <NUM>, as well as to connect multiple temperature sensing elements to the generator <NUM>.

In addition, the handle <NUM> may be operable to easily and securely couple to an optional introducer tube, e.g., in an embodiment where an introducer tube would facilitate insertion of the one or more probe assemblies <NUM> into a patient's body. For instance, as shown, the handle <NUM> may taper at its distal end to accomplish this function, i.e., to enable the handle <NUM> to securely couple to an optional introducer tube. Generally, introducer tubes may include a proximal end, a distal end, and a longitudinal bore extending therebetween. Thus, the introducer tubes (when used) are operable to easily and securely couple with the probe assembly <NUM>. For example, the proximal end of the introducer tubes may be fitted with a connector able to mate reversibly with the handle <NUM> of a probe assembly <NUM>. An introducer tube may be used to gain access to a treatment site within a patient's body, and the hollow elongate shaft <NUM> of a probe assembly <NUM> may be introduced to the treatment site through the longitudinal bore of the introducer tube. Introducer tubes may further include one or more depth markers to enable a user to determine the depth of the distal end of the introducer tube within a patient's body. Additionally, introducer tubes may include one or more radiopaque markers to ensure the correct placement of the introducers when using fluoroscopic guidance.

The introducer tubes may be made of various materials, as is known in the art and, if the material is electrically conductive, the introducer tubes may be electrically insulated along all or part of their length, to prevent energy from being conducted to undesirable locations within a patient's body. In some embodiments, the elongate shaft <NUM> may be electrically conductive, and an introducer may function to insulate the shaft <NUM>, leaving the energy delivery device <NUM> exposed for treatment. Further, the introducer tubes may be operable to connect to a power source and, therefore, may form part of an electrical current impedance monitor (wherein at least a portion of the introducer tube is not electrically insulated). Different tissues may have different electrical impedance characteristics, and therefore, it is possible to determine tissue type based on impedance measurements, as has been described. Thus, it would be beneficial to have a means of measuring impedance to determine the type of tissue within which a device is located. In addition, the gauge of the introducer tubes may vary depending on the procedure being performed and/or the tissue being treated. In some embodiments, the introducer tubes should be sufficiently sized in the radial dimension so as to accept at least one probe assembly <NUM>. Moreover, in alternative embodiments, the elongate shaft <NUM> may be insulated so as not to conduct energy to portions of a patient's body that are not being treated.

The system <NUM> also may include one or more stylets. A stylet may have a beveled tip to facilitate insertion of the one or more introducer tubes into a patient's body. Various forms of stylets are well known in the art and the present subject matter is not limited to include only one specific form. Further, as described above with respect to the introducer tubes, the stylets may be operable to connect to a power source and may therefore form part of an electrical current impedance monitor. In other embodiments, one or more of the probe assemblies <NUM> may form part of an electrical current impedance monitor. Thus, the generator <NUM> may receive impedance measurements from one or more of the stylets, the introducer tubes, and/or the probe assemblies <NUM> and may perform an action, such as alerting a user to an incorrect placement of an energy delivery device <NUM>, based on the impedance measurements.

The energy delivery devices <NUM> may include any means of delivering energy to a region of tissue adjacent to the distal tip region <NUM>. For example, the energy delivery devices <NUM> may include an electrode, or any other energy delivery means. Similarly, energy delivered via the energy delivery devices <NUM> may take several forms, including but not limited to radiofrequency energy. For example, in one embodiment, the energy delivery devices <NUM> may include an electrode. The active region of the electrode <NUM> may be <NUM> to <NUM> millimeters (mm) in length and energy delivered by the electrode is electrical energy in the form of current in the RF range. The size of the active region of the electrode can be optimized for placement within, e.g., an intervertebral disc; however, different sizes of active regions, all of which are within the scope of the present subject matter, may be used depending on the specific procedure being performed. In some embodiments, feedback from the generator <NUM> may automatically adjust the exposed area of the energy delivery device <NUM> in response to a given measurement, such as impedance or temperature. For example, in one embodiment, the energy delivery devices <NUM> may maximize energy delivered to the tissue by implementing at least one additional feedback control, such as a rising impedance value. As previously described, each energy delivery device <NUM> may be electrically and thermally-conductive and may comprise a conductive outer circumferential surface to conduct electrical energy and heat from the distal tip region <NUM> of the probe <NUM> to a patient's body. Further, the distal tip region <NUM> includes one or more temperature sensing elements, which are operable to measure the temperature at and proximate to the one or more energy delivery devices <NUM>. The temperature sensing elements may include one or more thermocouples, thermometers, thermistors, optical fluorescent sensors or any other means of sensing temperature.

In one embodiment, the first and second probe assemblies <NUM> may be operated in a bipolar mode. For example, the distal tip region <NUM> of each of two probe assemblies may be located within an intervertebral disc. In such embodiments, electrical energy is delivered to the first and second probe assemblies <NUM>, and this energy is preferentially concentrated therebetween through a region of tissue to be treated (i.e., an area of the intervertebral disc). The region of tissue to be treated is thus heated by the energy concentrated between the first and second probe assemblies <NUM>. In other embodiments, the first and second probe assemblies <NUM> may be operated in a monopolar mode, in which case an additional grounding pad is required on the surface of a body of a patient, as is known in the art. Any combination of bipolar and monopolar procedures may also be used. It should also be understood that the system may include more than two probe assemblies <NUM>. For example, in some embodiments, three probe assemblies <NUM> may be used, and the probe assemblies <NUM> may be operated in a triphasic mode, whereby the phase of the current being supplied differs for each probe assembly <NUM>. In further embodiments, the system <NUM> may be configured to control one or more of the flow of current between electrically conductive components and the current density around a particular component. In such embodiments, the system <NUM> may be configured to alternate between monopolar configurations, bipolar configurations, or quasi-bipolar configurations during a treatment procedure.

As a particular example, to treat tissue of a patient's body according to an exemplary embodiment of the present subject matter, the energy delivery device <NUM> of each of two probe assemblies <NUM> may be inserted into the patient's body, e.g., using an introducer and stylet as described herein. Once a power source, such as the generator <NUM>, is connected to the probe assemblies <NUM>, a stimulating electrical signal may be emitted from either of the electrodes <NUM> to a dispersive electrode or to the other electrode <NUM>. This signal may be used to stimulate sensory nerves, where replication of symptomatic pain would verify that the tissue, such as an intervertebral disc, is pain-causing. Simultaneously, the cooling fluid may be circulated through the internal lumens <NUM>, <NUM> of the probe assemblies <NUM> via the pump assemblies <NUM> and energy may be delivered from the RF generator <NUM> to the tissue through the energy delivery devices <NUM>. In other words, radiofrequency energy is delivered to the electrodes <NUM> and the power is altered according to the temperature measured by the temperature sensing element in the tip of the electrodes <NUM> such that a desired temperature is reached between the distal tip regions <NUM> of the two probe assemblies <NUM>. During the procedure, a treatment protocol such as the cooling supplied to the probe assemblies <NUM> and/or the power transmitted to the probe assemblies <NUM> may be adjusted and/or controlled to maintain a desirable treatment area shape, size and uniformity. More specifically, actively controlling energy delivered to the tissue by controlling both an amount of energy delivered through the energy delivery devices <NUM> and individually controlling the flow rate of the pump assemblies <NUM>. In further embodiments, the generator <NUM> may control the energy delivered to the tissue based on the temperature measured by the temperature sensing element(s) in the distal tip region <NUM> of the probe assemblies <NUM> and/or based on impedance sensors.

Referring now to <FIG>, a schematic diagram is provided illustrating a cooling system <NUM> for the medical probe assembly <NUM>, according to an exemplary embodiment of the present subject matter. As shown in <FIG>, the cooling system <NUM> includes the cooling circuit <NUM> described in greater detail herein. More particularly, the cooling system <NUM> includes one or more pump assemblies <NUM>, and each pump assembly <NUM> supplies a cooling fluid to a probe assembly <NUM> via the cooling circuit <NUM>, which provides a pathway for the cooling fluid from a fluid source or reservoir <NUM> to the distal end <NUM> of the probe assembly <NUM>. In some embodiments, as described herein, the cooling circuit <NUM> includes a cooling device <NUM> and its associated cooling supply tube and connector <NUM>, <NUM> and cooling return tube and connector <NUM>, <NUM>, as well as the cooling supply tube and connector <NUM>, <NUM>, cooling return tube and connector <NUM>, <NUM>, and internal lumens (i.e., shaft supply and return tubes) <NUM>, <NUM> of the probe assembly <NUM>. In other embodiments, such as those embodiments in which the distal end <NUM> of the probe assembly <NUM> is cooled by external irrigation of the treatment site, the cooling return tube and connector <NUM>, <NUM>, cooling return tube and connector <NUM>, <NUM>, and lumen or return tube <NUM> may be omitted.

As illustrated in <FIG>, the pump assembly <NUM> comprises a control unit <NUM> having at least one controller, a motor <NUM>, and a pump head <NUM> driven by the motor <NUM>. The motor <NUM> is directly coupled to the pump head <NUM> to drive the fluid pumping mechanism, and the pump head <NUM> has a rotor assembly <NUM> that may rotate clockwise (as shown in <FIG>) or counterclockwise. The cooling system <NUM> further comprises a tubing <NUM> and a fluid reservoir <NUM>, which also are illustrated in <FIG> and are part of the cooling circuit <NUM>. In exemplary embodiments, the pump assembly <NUM> is a peristaltic pump assembly. As such, the tubing <NUM> extends through the pump head <NUM>, and the pump head <NUM>, driven by the motor <NUM>, compresses the tubing <NUM> to draw a cooling fluid from the fluid reservoir <NUM> and pump the cooling fluid into a lumen <NUM> that delivers the cooling fluid to the distal end <NUM> of the energy delivery device <NUM>, as previously described. Thus, the tubing <NUM> conveys the cooling fluid from the fluid reservoir <NUM> to the lumen <NUM> (also referred to herein as the shaft supply tube <NUM>). In some embodiments, the lumen <NUM> is disposed within the probe assembly <NUM> such that the cooling fluid circulates within the probe assembly <NUM>, e.g., within the shaft <NUM> at or near the distal end <NUM>. In other embodiments, the lumen <NUM> is disposed within the probe assembly <NUM> such that the cooling fluid exits the probe assembly <NUM> at the distal end <NUM>, e.g., to irrigate a treatment site of the probe assembly <NUM>.

In the exemplary embodiment depicted in <FIG>, the control unit <NUM> comprises two controllers, microcontroller <NUM> and motor controller <NUM>. It will be appreciated that, in some embodiments, the microcontroller <NUM> and motor controller <NUM> may be separate control or processor modules. Alternatively, the functions described with respect to the microcontroller <NUM> and the functions described with respect to the motor controller <NUM> may be performed by a single controller or module.

As shown in the figures, the cooling system <NUM> further comprises a flow sensor <NUM> for sensing a flow rate of the cooling fluid through the cooling system <NUM>. More particularly, the pump head <NUM> is disposed between the fluid reservoir <NUM> and the probe assembly <NUM> to pump the cooling fluid from the fluid reservoir <NUM> to the lumen <NUM> through the tubing <NUM>. The flow sensor <NUM> is disposed between the pump head <NUM> and the probe assembly <NUM>, in fluid communication with the flow of cooling fluid, to sense the flow rate of the cooling fluid. In some embodiments, the flow sensor <NUM> is positioned in the tubing <NUM> to detect the flow rate of the cooling fluid through the tubing <NUM> upstream of the probe assembly <NUM>, but in other embodiments, the flow sensor <NUM> is positioned in the lumen <NUM> to detect the flow rate of the cooling fluid through the lumen <NUM> upstream of the probe assembly distal end <NUM>.

In the exemplary embodiment depicted in <FIG>, the flow sensor <NUM> comprises an inlet port <NUM> for an ingress of the cooling fluid into the flow sensor <NUM> and an outlet port <NUM> for an egress of the cooling fluid from the flow sensor <NUM>. More specifically, the inlet port <NUM> and the outlet port <NUM> of the flow sensor <NUM> are connected inline to the tubing <NUM>, such that the cooling fluid flows through the flow sensor <NUM>. As such, the flow sensor <NUM> may include a wetted surface that is made from an inert, biocompatible material. The inline connection of the inlet and outlet ports <NUM>, <NUM> with the tubing <NUM> may be established during manufacturing of the tubing <NUM>, i.e., the flow sensor <NUM> may be installed in the tubing <NUM> during its manufacture. In some embodiments, the flow sensor <NUM> is sterilizable, such that it may be sterilized after use in a single procedure and then reused in another procedure, but in other embodiments, the flow sensor <NUM> is configured for single, one-time use and may be disposed of after use in a single procedure. Further, the flow sensor <NUM> may be a mass flow sensor and/or may be an ultrasonic flow sensor.

As will be described in greater detail with respect to <FIG>, the flow sensor <NUM> outputs a flow rate signal to the control unit <NUM>, which includes at least one controller <NUM>, <NUM>. As illustrated in <FIG>, a communication pathway <NUM>, such as a unidirectional communication pathway from the flow sensor <NUM> to the microcontroller <NUM>, may be maintained between the flow sensor <NUM> and the control unit <NUM>. The control unit <NUM> is configured to process the flow rate signal to obtain a processed flow rate signal. The control unit <NUM> outputs the processed flow rate signal to the generator <NUM>, which may be a radiofrequency generator or other power source for the energy delivery device <NUM> as described herein, for determining whether to adjust a speed of the motor <NUM>. That is, the generator <NUM> outputs parameters or data, including pumping speed, rotational direction, motor acceleration, and motor deceleration, to the control unit <NUM>, which maintains a bi-directional communication pathway <NUM> with the generator <NUM>. The control unit <NUM>, in turn, interprets the parameters or data from the generator <NUM> and, via the motor controller <NUM>, modulates the motor speed to thereby control the speed of the pump head <NUM>, e.g., by modulating the power supplied to the motor <NUM> to control the rotation of the motor <NUM>, which controls the rotational speed of a rotor assembly <NUM> of the pump head <NUM>. Thus, based on the input to the motor <NUM> from the generator <NUM>, the pump head <NUM> rotor assembly speed is modulated to adjust the flow rate of the cooling fluid delivered to the distal end <NUM> of the probe assembly <NUM>. That is, the tubing <NUM> extending through the pump head <NUM> is acted on by the pump head rotor assembly <NUM> to pump the cooling fluid through the cooling circuit <NUM> and to the distal end <NUM> (either internally within the probe assembly <NUM> or externally at the treatment site). Accordingly, varying the rotational speed of the rotor assembly <NUM>, which is controlled by the motor <NUM>, varies the flow rate of the cooling fluid through the tubing <NUM> and the lumen <NUM>.

Referring now to <FIG>, methods for controlling a flow rate of fluid through a cooling circuit of a medical probe assembly will be described, according to exemplary embodiments of the present subject matter. As shown at <NUM>, the exemplary method <NUM> includes communicating parameters such as pumping speed, rotational direction, motor acceleration, and motor deceleration to the control unit <NUM>. As previously described, the generator <NUM> includes a controller or control module <NUM> that controls various aspects of a procedure performed using one or more probe assemblies <NUM> of the system <NUM>. The generator controller <NUM> thus determines the cooling flow needed for the particular procedure, and communicates the relevant parameters to the control unit <NUM> to achieve the needed flow rate of the cooling fluid. In exemplary embodiments, the generator <NUM> communicates the parameters to the microcontroller <NUM> over the communication pathway <NUM>. As shown at <NUM> and <NUM> of <FIG>, the microcontroller <NUM>, or other appropriate controller or control module of the control unit <NUM>, interprets or processes the parameters from the generator <NUM> and outputs a motor speed signal to the motor controller <NUM>, or other suitable controller or control module of the control unit <NUM>. As illustrated at <NUM>, the motor controller <NUM> then modulates the motor power supply to control the motor rotational speed based on the motor speed signal, i.e., the input parameter to the motor controller <NUM> derived from the output parameters from the generator <NUM>. The motor <NUM>, which is directly coupled to the rotor assembly <NUM> of the pump head <NUM>, determines the pumping action by the pump head <NUM>. Thus, once the motor <NUM> is activated at a given rotational speed, the cooling system <NUM> begins pumping the cooling fluid from the fluid reservoir <NUM> through the tubing <NUM> to the <NUM> lumen to deliver the cooling fluid to the distal end <NUM> of the probe assembly <NUM>, as shown at <NUM> of <FIG>.

As depicted at <NUM>, the method <NUM> includes sensing the flow rate of the cooling fluid, i.e., using the flow sensor <NUM> disposed between the pump head <NUM> and the probe assembly <NUM> as described herein. That is, as the cooling fluid flows through the cooling circuit <NUM>, the flow sensor <NUM>, which may be installed inline in either the tubing <NUM> or lumen <NUM> such that the cooling fluid enters through the inlet port <NUM> and exits through the outlet port <NUM>, receives the flow of cooling fluid and determines its flow rate. As shown at <NUM>, the flow sensor <NUM> communicates a flow rate signal to the control unit <NUM>, e.g., over the communication pathway <NUM>. As such, the flow sensor <NUM> measures the flow rate of the cooling fluid and outputs the flow data to the control unit <NUM>, e.g., to the microcontroller <NUM>, as an analog or digital flow rate signal. The control unit <NUM>, e.g., the microcontroller <NUM>, processes the flow rate signal to produce a processed flow rate signal, as shown at <NUM> in method <NUM>. For example, the microcontroller <NUM> applies signal processing techniques in real time and outputs the processed signal to the generator <NUM>. The control unit <NUM> then communicates the processed flow rate signal to the generator <NUM>, e.g., over the communication pathway <NUM>, as shown at <NUM> in method <NUM>.

Depending on the power and other ablation or treatment requirements, the generator <NUM> can use the processed flow rate signal to then control the rotational parameters of the pump assembly <NUM> in real-time, e.g., to optimize the treatment procedure. More particularly, as shown at <NUM> in <FIG>, the generator <NUM> determines whether to adjust the speed of the motor <NUM> based on the processed flow rate signal that has been communicated to the generator <NUM> and the desired or optimal parameters of the treatment procedure, i.e., whether a different flow rate of the cooling fluid is needed to achieve a desired effect. If the generator <NUM> determines the motor speed (and thus the flow rate) should be adjusted, the method <NUM> returns to <NUM> of method <NUM>, where the generator <NUM> communicates a motor speed signal to the control unit <NUM>, e.g., to the microcontroller <NUM>, which processes the motor speed signal as shown at <NUM>. The microcontroller <NUM> outputs the processed data to the motor controller <NUM> as illustrated at <NUM>, which modulates the motor power supply and, thus, the rotational speed of the pump head rotor assembly <NUM> to adjust or change the flow rate of the cooling fluid pumped through the cooling circuit <NUM> to the distal end <NUM> of the probe assembly <NUM>, as shown at <NUM>. However, if the generator <NUM> determines the motor speed and cooling fluid flow rate should not be adjusted, the flow sensor <NUM> continues sensing the flow rate as depicted at <NUM>, and the flow rate data is continually communicated to the generator <NUM> such that the flow rate may be adjusted when appropriate or desired, e.g., based on the operational parameters of the treatment procedure.

Although described herein as including a control unit <NUM> that performs particular functions, it will be appreciated that, in some examples not part of the invention the control unit <NUM> may be omitted and its functions may be performed by, e.g., the controller <NUM> of the generator <NUM>. That is, the microcontroller module <NUM> and motor controller module <NUM> may be part of the generator <NUM> rather than a separate control unit <NUM>. Further, although described herein only with respect to a single pump assembly <NUM> and probe assembly <NUM>, it will be understood that the present subject matter may be applied to more than one pump assembly <NUM> and probe assembly <NUM> of the system <NUM>. More particularly, where the system <NUM> includes more than one probe assembly <NUM> and associated pump assembly <NUM> for providing cooling fluid to the distal end <NUM> of the probe assembly <NUM>, each probe assembly <NUM> or a portion of the probe assemblies <NUM> may include a cooling system <NUM> as described herein. Each cooling system <NUM> may operate independently to provide a cooling fluid flow rate required for its associated probe assembly <NUM>, i.e., the flow rate of cooling fluid provided to each probe assembly <NUM> may be different or the same, based on the needs or requirements of the treatment procedure.

Accordingly, the present subject matter provides cooling systems for providing cooling fluid to medical probe assemblies and methods for controlling a flow rate of cooling fluid to a medical probe assembly. As described herein, the cooling systems and methods utilize a flow sensor installed in a cooling circuit through which the cooling fluid flows to measure or sense the flow rate of the cooling fluid through the cooling circuit. The flow sensor communicates the flow data to one or more controllers or processors, which process the flow data and determine whether the speed of a motor, which controls the rotor assembly of a pump head, should be modulated or adjusted to change the flow rate of the cooling fluid through the cooling circuit. That is, the motor speed determines the pumping speed of the associated pump, which determines the flow rate of the cooling fluid through the tubing extending through the pump. Therefore, the methods and systems described herein utilize a direct measure, closed loop feedback approach for determining and controlling the flow rate of cooling fluid to a medical probe assembly. Such a direct measure approach is more accurate than other indirect or open loop non-feedback approaches for controlling the fluid flow rate, such as using only the rotational speed of the pump to control the flow rate. The indirect or open loop systems require high tolerance pumps and components that are capable of repeatedly being accurately set up. Therefore, the direct measure or closed loop approach can reduce the costs of the system, e.g., by utilizing cheaper pumps because high pump tolerances are not required. Of course, as described herein, other advantages and benefits in addition to more accurate flow rate control and reduced system costs may be realized from the present subject matter.

A system of the present subject matter may be used in various medical procedures where usage of an energy delivery device may prove beneficial. Specifically, the system of the present subject matter is particularly useful for procedures involving treatment of back pain, including but not limited to treatments of tumors, intervertebral discs, facet joint denervation, sacroiliac joint lesioning or intraosseous (within the bone) treatment procedures. Moreover, the system is particularly useful to strengthen the annulus fibrosus, shrink annular fissures and impede them from progressing, cauterize granulation tissue in annular fissures, and denature pain-causing enzymes in nucleus pulposus tissue that has migrated to annular fissures. Additionally, the system may be operated to treat a herniated or internally disrupted disc with a minimally invasive technique that delivers sufficient energy to the annulus fibrosus to breakdown or cause a change in function of selective nerve structures in the intervertebral disc, modify collagen fibrils with predictable accuracy, treat endplates of a disc, and accurately reduce the volume of intervertebral disc tissue. The system is also useful to coagulate blood vessels and increase the production of heat shock proteins.

Using liquid-cooled probe assemblies <NUM> with an appropriate feedback control system as described herein also contributes to the uniformity of the treatment. The cooling distal tip regions <NUM> of the probe assemblies <NUM> helps to prevent excessively high temperatures in these regions which may lead to tissue adhering to the probe assemblies <NUM> as well as an increase in the impedance of tissue surrounding the distal tip regions <NUM> of the probe assemblies <NUM>. Thus, by cooling the distal tip regions <NUM> of the probe assemblies <NUM>, higher power can be delivered to tissue with a minimal risk of tissue charring at or immediately surrounding the distal tip regions <NUM>. Delivering higher power to energy delivery devices <NUM> allows tissue further away from the energy delivery devices <NUM> to reach a temperature high enough to create a lesion and thus the lesion will not be limited to a region of tissue immediately surrounding the energy delivery devices <NUM> but will rather extend preferentially from a distal tip region <NUM> of one probe assembly <NUM> to the other.

As has been mentioned, a system of the present subject matter may be used to produce a relatively uniform lesion substantially between two probe assemblies <NUM> when operated in a bipolar mode. Oftentimes, uniform lesions may be contraindicated, such as in a case where a tissue to be treated is located closer to one energy delivery device <NUM> than to the other. In cases where a uniform lesion may be undesirable, using two or more cooled probe assemblies <NUM> in combination with a suitable feedback and control system may allow for the creation of lesions of varying size and shape. For example, preset temperature and/or power profiles that the procedure should follow may be programmed into the generator <NUM> prior to commencement of a treatment procedure. These profiles may define parameters (these parameters would depend on certain tissue parameters, such as heat capacity, etc.) that should be used to create a lesion of a specific size and shape. These parameters may include, but are not limited to, maximum allowable temperature, ramp rate (i.e. how quickly the temperature is raised) and the rate of cooling flow, for each individual probe. Based on temperature or impedance measurements performed during the procedure, various parameters, such as power or cooling, may be modulated, to comply with the preset profiles, resulting in a lesion with the desired dimensions.

Similarly, it is to be understood that a uniform lesion can be created, using a system of the present subject matter, using many different pre-set temperature and/or power profiles which allow the thermal dose across the tissue to be as uniform as possible, and that the present subject matter is not limited in this regard.

It should be noted that the term radiopaque marker as used herein denotes any addition or reduction of material that increases or reduces the radiopacity of the device. Further, the terms probe assembly, introducer, stylet etc. are not intended to be limiting and denote any medical and surgical tools that can be used to perform similar functions to those described. In addition, the subject matter is not limited to be used in the clinical applications disclosed herein, and other medical and surgical procedures wherein a device of the present subject matter would be useful are included within the scope of the present subject matter.

Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the present subject matter has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the broad scope of the appended claims.

Claim 1:
A cooling system (<NUM>) for a medical probe assembly (<NUM>), the system comprising:
a pump assembly (<NUM>) comprising:
a control unit (<NUM>) having a motor controller (<NUM>),
a motor (<NUM>), and
a pump head (<NUM>) driven by the motor;
a fluid reservoir (<NUM>);
a lumen (<NUM>) for delivering a cooling fluid to a distal end (<NUM>) of the medical probe assembly (<NUM>);
a tubing (<NUM>) for conveying the cooling fluid from the fluid reservoir to the lumen, the tubing extending through the pump head;
a flow sensor (<NUM>) for sensing a flow rate of the cooling fluid; and
a radiofrequency (RF) generator (<NUM>) in bi-directional communication with the control unit (<NUM>) of the pump assembly (<NUM>), the RF generator comprising a generator controller (<NUM>) having a set of parameters for a treatment procedure stored thereon,
wherein the pump head (<NUM>) is disposed between the fluid reservoir (<NUM>) and the medical probe assembly (<NUM>) to pump the cooling fluid from the fluid reservoir to the lumen (<NUM>) through the tubing (<NUM>),
wherein the flow sensor (<NUM>) is disposed between the pump head (<NUM>) and the medical probe assembly (<NUM>) to sense the flow rate of the cooling fluid, the flow sensor configured to transmit a flow rate signal to the control unit (<NUM>) in order to generate, by the motor controller (<NUM>) of the control unit, a processed flow rate signal,
wherein the generator controller (<NUM>) determines whether to modify at least one of a speed or a direction of the motor (<NUM>) based on the set of parameters for the treatment procedure and the processed flow rate signal, and
wherein the generator controller (<NUM>) is configured to transmit a control signal to the control unit (<NUM>) to cause the motor controller (<NUM>) to modify one of the speed or the direction of the motor (<NUM>) responsive to a determination to modify the speed or the direction of the motor.