Cryogenic Probe Filtration System

[0001] The present application is a Continuation of U.S. Ser. No. 13/741,363 filed Jan. 14, 2013 (Allowed); which application claims the benefit of U.S. Provisional Appln No. 61/586,698 filed on Jan. 13, 2012; the full disclosures which are incorporated herein by reference in their entirety for all purposes.

[0002] The present invention is generally directed to medical devices, systems, and methods, particularly for cooling-induced remodeling of tissues. Embodiments of the invention include devices, systems, and methods for applying cryogenic cooling to dermatological tissues so as to selectively remodel one or more target tissues along and/or below an exposed surface of the skin. Embodiments may be employed for a variety of cosmetic conditions, optionally by inhibiting undesirable and/or unsightly effects on the skin (such as lines, wrinkles, or cellulite dimples) or on other surrounding tissue. Other embodiments may find use for a wide range of medical indications. The remodeling of the target tissue may achieve a desired change in its behavior or composition.

[0003] The desire to reshape various features of the human body to either correct a deformity or merely to enhance one's appearance is common. This is evidenced by the growing volume of cosmetic surgery procedures that are performed annually.

[0004] Many procedures are intended to change the surface appearance of the skin by reducing lines and wrinkles. Some of these procedures involve injecting fillers or stimulating collagen production. More recently, pharmacologically based therapies for wrinkle alleviation and other cosmetic applications have gained in popularity.

[0005] Botulinum toxin type A (BOTOX®) is an example of a pharmacologically based therapy used for cosmetic applications. It is typically injected into the facial muscles to block muscle contraction, resulting in temporary enervation or paralysis of the muscle. Once the muscle is disabled, the movement contributing to the formation of the undesirable wrinkle is temporarily eliminated. Another example of pharmaceutical cosmetic treatment is mesotherapy, where a cocktail of homeopathic medication, vitamins, and/or drugs approved for other indications is injected into the skin to deliver healing or corrective treatment to a specific area of the body. Various cocktails are intended to effect body sculpting and cellulite reduction by dissolving adipose tissue, or skin resurfacing via collagen enhancement. Development of non-pharmacologically based cosmetic treatments also continues. For example, endermology is a mechanical based therapy that utilizes vacuum suction to stretch or loosen fibrous connective tissues which are implicated in the dimpled appearance of cellulite.

[0006] While BOTOX® and/or mesotherapies may temporarily reduce lines and wrinkles, reduce fat, or provide other cosmetic benefits they are not without their drawbacks, particularly the dangers associated with injection of a known toxic substance into a patient, the potential dangers of injecting unknown and/or untested cocktails, and the like. Additionally, while the effects of endermology are not known to be potentially dangerous, they are brief and only mildly effective.

[0007] In light of the above, improved medical devices, systems, and methods utilizing a cryogenic approach to treating the tissue have been proposed, particularly for treatment of wrinkles, fat, cellulite, and other cosmetic defects. These new techniques can provide an alternative visual appearance improvement mechanism which may replace and/or compliment known bioactive and other cosmetic therapies, ideally allowing patients to decrease or eliminate the injection of toxins and harmful cocktails while providing similar or improved cosmetic results. These new techniques are also promising because they may be performed percutaneously using only local or no anesthetic with minimal or no cutting of the skin, no need for suturing or other closure methods, no extensive bandaging, and limited or no bruising or other factors contributing to extended recovery or patient “down time.” Additionally, cryogenic treatments are also desirable since they may be used in the treatment of other cosmetic and/or dermatological conditions (and potentially other target tissues), particularly where the treatments may be provided with greater accuracy and control, less collateral tissue injury and/or pain, and greater ease of use.

[0008] While these new cryogenic treatments are promising, careful control of temperature along the cryogenic probe is necessary in order to obtain desired results in the target treatment area as well as to avoid unwanted tissue injury in adjacent areas. Once the probe is introduced into a target treatment area, cooling fluid flows through the probe and probe temperature decreases proximally along the length of the probe toward the probe hub. It has been found that impurities within the probe can negatively affect temperature along the cryogenic probe and cooling performance. It is believed that the source of the cooling fluid provides much of the impurities, since the source is typically intended for general use in various fields. Therefore, it would be desirable to use a common cooling fluid source and provide a desired level of performance and reliability.

[0009] Embodiments of the invention provide improved medical devices, systems, and methods. Many of the devices and systems described herein will be beneficial for filtering cryogenic cooling fluid from a cryogenic medical device.

[0010] Embodiments of the invention relate to a cryogenic device, which can include a handpiece portion having a cryogenic coolant pathway configured to fluidly couple to a detachable needle probe. A cartridge holder can couple to the handpiece portion and configured for removeably holding a pressurized cartridge. A filter device can couple to the cartridge holder, the filter device can have a distal filter end for fluidly coupling the filter device to the cryogenic coolant pathway and a proximal filter end for fluidly coupling to the pressurized cartridge. The filter device can include at least one particulate filter configured to filter particulates, and a molecular filter configured to capture fluid contaminants received from the cartridge and from the coolant pathway when not in fluid communication with the cartridge. The filter device can also include a filtration media that is modified to be hydrophobic and/or oleophobic.

[0011] Embodiments of the invention relate to a cryogenic device. The device can include a handpiece portion having a cryogenic coolant pathway configured to fluidly couple to a needle probe. A filter device can be included for coupling to a pressurized cartridge to the cryogenic coolant pathway, wherein the filter device comprises at least one of a particulate filter configured to filter particulates and a molecular filter configured to capture fluid contaminants.

[0012] In one aspect of the device, each of the proximal filter end and the distal filter end can include at least one microscreen.

[0013] In another aspect of the device, the at least one microscreen can be a 2 micron screen or less.

[0014] In one aspect of the device, the molecular filter includes filter media.

[0015] In one aspect of the device, the filter media can be a plurality of molecular sieves.

[0016] In one aspect of the device, the molecular sieves comprise pellets having pores ranging in size from 1-20 Å.

[0017] In one aspect of the device, average pore size is 5 Å.

[0018] In one aspect of the device, the proximal end of the filter assembly can include a puncture coupling configured to puncture the cartridge.

[0019] In one aspect of the device, the cartridge holder can include a cartridge receiver affixed to the handpiece and having a cavity for holding the cartridge.

[0020] In one aspect of the device, the cartridge holder can further include a cartridge cover removeably attached to the cartridge receiver.

[0021] In one aspect of the device, the cartridge cover can couple to the cartridge receiver in a first position where the cartridge is held intact by the cartridge receiver, with the cartridge cover being moveable to a second position in which the cartridge is punctured and made fluidly coupled to the filter assembly.

[0022] In one aspect of the device, the cartridge holder further comprises a coupling assembly that has a sealing valve that seals the cryogenic coolant pathway from atmosphere when the pressurized cartridge is not coupled to the cartridge holder.

[0023] In one aspect of the device, the coupling assembly includes a pressure relief valve.

[0024] In one aspect of the device, at least a portion of the cryogenic coolant pathway between the cartridge and the needle probe is hydrophobic and/or oleophobic.

[0025] In one aspect of the device, the filtration media comprises surface modified ePTFE, sintered polyethylene, or metal mesh.

[0038] The present invention provides improved medical devices, systems, and methods. Embodiments of the invention will facilitate remodeling of target tissues disposed at and below the skin, optionally to treat a cosmetic defect, a lesion, a disease state, and/or so as to alter a shape of the overlying skin surface. Embodiments of the invention utilize a handheld refrigeration system that can use a commercially available cartridge of fluid refrigerant. Refrigerants well suited for use in handheld refrigeration systems include nitrous oxide and carbon dioxide. These can achieve temperatures approaching −90° C.

[0039] A commercially produced refrigerant cartridge will typically contain impurities, since such a cartridge is manufactured for uses where such impurities are a minor consideration. Additionally, impurities can be introduced to the fluid as a result of puncturing the cartridge to access the refrigerant, or from the environment in which the system is used. Solid impurities can compromise the performance of the refrigeration system by occluding passageways and/or creating leak paths in sealing mechanisms. Fluid impurities, both liquids and gasses, such as oil, water, oxygen, nitrogen, and carbon dioxide can also be present within the refrigeration cartridge. These impurities may also occlude or restrict refrigerant passageways, and/or chemically alter properties of the refrigerant. This effect of impurities can a be exacerbated with decreased temperature, since lower temperatures make liquids such as oils less viscous perhaps even changing the phase to a solid. This could also occur with gases such as water vapor which could condense into water or even freeze. In particular the effects of these particulates on refrigeration systems relying upon microtubes or micro-orifices would be susceptible to inconsistent performance of the refrigeration process.

[0040] At least some of the embodiments of the present invention may include a filtration device, which may, in at least some instances, addresses one or more of the aforementioned issues. The filtration device may include an element for capturing solids, as well as or alternatively an element for capturing fluids. In addition, or alternatively, the filtration device and/or portions of the handpiece may be modified through to be hydrophobic and/or oleophobic. In a handheld refrigeration system embodiment the filtration device may be optimally sized so that it has sufficient capacity to remove the contaminants within a refrigeration cartridge, but small enough to retain the hand held form factor. The refrigerant and the filtration system may be provided as a single integrated cartridge, however the elements could be provided separately, and the filtration device could also be used in systems that do not have use a refrigerant cartridge. Other options may include implementing the filtration device as an independent element or integrating the filtration into another element of the system such as the valve, or cooling element (for example as an integral part of a disposable probe).

[0041] The filtration device can include a particulate filter, for removing solids, such as a microscreen, explanded PTFE, or sintered plastic disc. Such a filter could be constructed as mesh having passages ranging from 1-3 microns in diameter. The microscreen could include passages sized such that minor particulates can pass through, i.e., particles not capable of occluding a refrigerant pathway or creating a leak path across a seal. As one non-limiting example, for a fluid pathway of 20 microns, a screen that filtered out particulate larger than 2 microns could be used.

[0042] The filtration device can also include a molecular filter for capturing a size range of fluid molecules. Refrigerant contaminants such as oils and water vapor passable through the microscreen could be captured by passing the refrigerant through the molecular filter, which could be a bed of substance such as adsorption media. The pathway could provide for optimum contact of the fluid with the media and have physical characteristics that are suitable for extracting contaminates from the refrigerant. For instance, the media may consist of a cartridge filled with pellets comprising 5 Å molecular sieves. Alternative forms of molecular sieves include spheres or powders, and the pore size could be 1-20 Å. Alternate materials may be selected such as silica or activated charcoal as appropriate for the contaminants selected for extraction.

[0043] In some embodiments, surface portions of the cryogen fluid pathway of the handpiece, including the filter, that come into contact with both the cryogen and the atmosphere can be selected or modified to be hydrophobic or oleophobic. Surface modification process include plasma surface modification or coating via a vapor deposition process or similar process of another highly hydrophobic material.

[0044] In some embodiments, liquid contaminants are removed from the inside of the system prior to treatments by performing a purging step prior to use of the device. By introducing a dry gas or liquid source, such as liquid nitrous, dry carbon dioxide, or other dry gas, the gas can be flowed through the handpiece absorbing and venting liquid contaminants. The drying properties of a gas can be improved by heating the gas before passing it through the handpiece. This can be achieved by using the dry-gas cartridges that are the same form factor as the cryogen cartridges used by the procedure. If the handpiece is held in the vertical orientation (tip pointing up), nitrous oxide leaves the cartridge in the gaseous form. A secondary heater can be optionally installed in the handpiece to further boost the gas temperature thereby improving the drying effect.

[0045] If this purge step is performed with nitrous oxide or other refrigerant and with a treatment tip, or test tip designed with small channels to mimic the treatment tip, the flow of cryogen can be monitored by the system so as to confirm when the flow is regular (if there are contaminants in the system, but flow will be interrupted as contaminants freeze and then resume once they thaw). Internal sensors can monitor the flow by directly measuring flow, measuring pressure drop associated with flow, or measure the cooling power of the exhaust flow.

[0046] In some embodiments, a hand held cryogenic device includes a refrigerant cartridge, puncture pin, and the filtration device that are all part of one assembly. In use, the cartridge can be inserted into the handheld system. The refrigerant cartridge (e.g., an 8 gram nitrous oxide cartridge) would then be punctured and the refrigerant would flow through a lumen of the puncture mechanism. The refrigerant would then pass through the filtration device, which can include filtration media (e.g., 5 Å molecular sieves) and at least one microscreen (e.g., a 2 micron screen or smaller). After passing through the filtration device, the refrigerant would be appropriately pure for use. The refrigerant could then pass through a valve mechanism and from there through a 20 micron lumen within a 27 or 30 g closed tip needle. The refrigerant could be used to cool the needle through the Joule-Thompson effect and potentially the latent heat of evaporation associated with the refrigerant. This extraction of heat could be used to cool tissue that the needle had been inserted into to cause a therapeutic effect, such as tissue modeling.

[0047] At least some of the embodiments of the present invention may be used for the amelioration of lines and wrinkles, particularly by inhibiting muscular contractions which are associated with these cosmetic defects so as so improve an appearance of the patient. Rather than relying entirely on a pharmacological toxin or the like to disable muscles so as to induce temporary paralysis, many embodiments of the invention will at least in part employ cold to immobilize muscles. Advantageously, nerves, muscles, and associated tissues may be temporarily immobilized using moderately cold temperatures of 10° C. to −5° C. without permanently disabling the tissue structures. Using an approach similar to that employed for identifying structures associated with atrial fibrillation, a needle probe or other treatment device can be used to identify a target tissue structure in a diagnostic mode with these moderate temperatures, and the same probe (or a different probe) can also be used to provide a longer term or permanent treatment, optionally by ablating the target tissue zone and/or inducing apoptosis at temperatures from about −5° C. to about −50° C. In some embodiments, apoptosis may be induced using treatment temperatures from about −1° C. to about −15° C., or from about −1° C. to about −19° C., optionally so as to provide a permanent treatment that limits or avoids inflammation and mobilization of skeletal muscle satellite repair cells. In some embodiments, temporary axonotmesis or neurotmesis degeneration of a motor nerve is desired, which may be induced using treatment temperatures from about −25° C. to about −90° C. Hence, the duration of the treatment efficacy of such subdermal cryogenic treatments may be selected and controlled, with colder temperatures, longer treatment times, and/or larger volumes or selected patterns of target tissue determining the longevity of the treatment. Additional description of cryogenic cooling for treatment of cosmetic and other defects may be found in commonly assigned U.S. Pat No. 7,713,266 (Atty. Docket No. 000110US) entitled “Subdermal Cryogenic Remodeling of Muscle, Nerves, Connective Tissue, and/or Adipose Tissue (Fat)”, U.S. Pat. No. 7,850,683 (Atty. Docket No. 000120US) entitled “Subdermal Cryogenic Remodeling of Muscles, Nerves, Connective Tissue, and/or Adipose Tissue (Fat)”, and U.S. Pat. No. 9,039,688 (Atty. Docket No. 002510US) entitled “Method for Reducing Hyperdynamic Facial Wrinkles”, the full disclosures of which are each incorporated by reference herein.

[0048] In addition to cosmetic treatments of lines, wrinkles, and the like, embodiments of the invention may also find applications for treatments of subdermal adipose tissues, benign, pre-malignant lesions, malignant lesions, acne and a wide range of other dermatological conditions (including dermatological conditions for which cryogenic treatments have been proposed and additional dermatological conditions), and the like. Embodiments of the invention may also find applications for alleviation of pain, including those associated with muscle spasms as disclosed in commonly assigned U.S. Pat. No. 8,298,216 (Atty. Docket No. 000810US) entitled “Pain Management Using Cryogenic Remodeling,” the full disclosure of which is incorporated herein by reference.

[0049] Referring now to FIGS. 1A and 1B, a system for cryogenic remodeling here comprises a self-contained probe handpiece generally having a proximal end 12 and a distal end 14. A handpiece body or housing 16 has a size and ergonomic shape suitable for being grasped and supported in a surgeon's hand or other system operator. As can be seen most clearly in FIG. 1B, a cryogenic cooling fluid supply 18, a supply valve 32 and electrical power source 20 are found within housing 16, along with a circuit 22 having a processor for controlling cooling applied by self-contained system 10 in response to actuation of an input 24. Alternatively, electrical power can be applied through a cord from a remote power source. Power source 20 also supplies power to heater element 44 in order to heat the proximal region of probe 26 thereby helping to prevent unwanted skin damage, and a temperature sensor 48 adjacent the proximal region of probe 26 helps monitor probe temperature. Additional details on the heater 44 and temperature sensor 48 are described in greater detail below. When actuated, supply valve 32 controls the flow of cryogenic cooling fluid from fluid supply 18. Some embodiments may, at least in part, be manually activated, such as through the use of a manual supply valve and/or the like, so that processors, electrical power supplies, and the like may not be required.

[0050] Extending distally from distal end 14 of housing 16 is a tissue-penetrating cryogenic cooling probe 26. Probe 26 is thermally coupled to a cooling fluid path extending from cooling fluid source 18, with the exemplary probe comprising a tubular body receiving at least a portion of the cooling fluid from the cooling fluid source therein. The exemplary probe 26 comprises a 30 g needle having a sharpened distal end that is axially sealed. Probe 26 may have an axial length between distal end 14 of housing 16 and the distal end of the needle of between about 0.5 mm and 5 cm, preferably having a length from about 3 mm to about 10 mm. Such needles may comprise a stainless steel tube with an inner diameter of about 0.006 inches and an outer diameter of about 0.012 inches, while alternative probes may comprise structures having outer diameters (or other lateral cross-sectional dimensions) from about 0.006 inches to about 0.100 inches. Generally, needle probe 26 will comprise a 16 g or smaller size needle, often comprising a 20 g needle or smaller, typically comprising a 25, 26, 27, 28, 29, or 30 g or smaller needle.

[0051] In some embodiments, probe 26 may comprise two or more needles arranged in a linear array, such as those disclosed in previously incorporated U.S. Pat. No. 7,850,683. Another exemplary embodiment of a probe having multiple needle probe configurations allow the cryogenic treatment to be applied to a larger or more specific treatment area. Other needle configurations that facilitate controlling the depth of needle penetration and insulated needle embodiments are disclosed in commonly assigned U.S. Pat. No. 8,409,185 (Atty. Docket No. 000500US) entitled “Replaceable and/or Easily Removable Needle Systems for Dermal and Transdermal Cryogenic Remodeling,” the entire content of which is incorporated herein by reference. Multiple needle arrays may also be arrayed in alternative configurations such as a triangular or square array.

[0052] Arrays may be designed to treat a particular region of tissue, or to provide a uniform treatment within a particular region, or both. In some embodiments needle 26 is releasably coupled with body 16 so that it may be replaced after use with a sharper needle (as indicated by the dotted line) or with a needle having a different configuration. In exemplary embodiments, the needle may be threaded into the body, it may be press fit into an aperture in the body or it may have a quick disconnect such as a detent mechanism for engaging the needle with the body. A quick disconnect with a check valve is advantageous since it permits decoupling of the needle from the body at any time without excessive coolant discharge. This can be a useful safety feature in the event that the device fails in operation (e.g. valve failure), allowing an operator to disengage the needle and device from a patient's tissue without exposing the patient to coolant as the system depressurizes. This feature is also advantageous because it allows an operator to easily exchange a dull needle with a sharp needle in the middle of a treatment. One of skill in the art will appreciate that other coupling mechanisms may be used.

[0053] Addressing some of the components within housing 16, the exemplary cooling fluid supply 18 comprises a canister, sometimes referred to herein as a cartridge, containing a liquid under pressure, with the liquid preferably having a boiling temperature of less than 37° C. When the fluid is thermally coupled to the tissue-penetrating probe 26, and the probe is positioned within the patient so that an outer surface of the probe is adjacent to a target tissue, the heat from the target tissue evaporates at least a portion of the liquid and the enthalpy of vaporization cools the target tissue. A supply valve 32 may be disposed along the cooling fluid flow path between canister 18 and probe 26, or along the cooling fluid path after the probe so as to limit coolant flow thereby regulating the temperature, treatment time, rate of temperature change, or other cooling characteristics. The valve will often be powered electrically via power source 20, per the direction of processor 22, but may at least in part be manually powered. The exemplary power source 20 comprises a rechargeable or single-use battery. Additional details about valve 32 are disclosed below and further disclosure on the power source 20 may be found in commonly assigned Int'l Pub. No. WO 2010/075438 (Atty. Docket No. 002310PC) entitled “Integrated Cryosurgical Probe Package with Fluid Reservoir and Limited Electrical Power Source,” the entire contents of which is incorporated herein by reference.

[0054] The exemplary cooling fluid supply 18 comprises a single-use canister. Advantageously, the canister and cooling fluid therein may be stored and/or used at (or even above) room temperature. The canister may have a frangible seal or may be refillable, with the exemplary canister containing liquid nitrous oxide, N₂O. A variety of alternative cooling fluids might also be used, with exemplary cooling fluids including fluorocarbon refrigerants and/or carbon dioxide. The quantity of cooling fluid contained by canister 18 will typically be sufficient to treat at least a significant region of a patient, but will often be less than sufficient to treat two or more patients. An exemplary liquid N₂O canister might contain, for example, a quantity in a range from about 1 gram to about 40 grams of liquid, more preferably from about 1 gram to about 35 grams of liquid, and even more preferably from about 7 grams to about 30 grams of liquid.

[0055] Processor 22 will typically comprise a programmable electronic microprocessor embodying machine readable computer code or programming instructions for implementing one or more of the treatment methods described herein. The microprocessor will typically include or be coupled to a memory (such as a non-volatile memory, a flash memory, a read-only memory (“ROM”), a random access memory (“RAM”), or the like) storing the computer code and data to be used thereby, and/or a recording media (including a magnetic recording media such as a hard disk, a floppy disk, or the like; or an optical recording media such as a CD or DVD) may be provided. Suitable interface devices (such as digital-to-analog or analog-to-digital converters, or the like) and input/output devices (such as USB or serial I/O ports, wireless communication cards, graphical display cards, and the like) may also be provided. A wide variety of commercially available or specialized processor structures may be used in different embodiments, and suitable processors may make use of a wide variety of combinations of hardware and/or hardware/software combinations. For example, processor 22 may be integrated on a single processor board and may run a single program or may make use of a plurality of boards running a number of different program modules in a wide variety of alternative distributed data processing or code architectures.

[0056] Referring now to FIG. 2A, the flow of cryogenic cooling fluid from fluid supply 18 is controlled by a supply valve 32. Supply valve 32 may comprise an electrically actuated solenoid valve, a motor actuated valve or the like operating in response to control signals from controller 22, and/or may comprise a manual valve. Exemplary supply valves may comprise structures suitable for on/off valve operation, and may provide venting of the fluid source and/or the cooling fluid path downstream of the valve when cooling flow is halted so as to limit residual cryogenic fluid vaporization and cooling. Additionally, the valve may be actuated by the controller in order to modulate coolant flow to provide high rates of cooling in some instances where it is desirable to promote necrosis of tissue such as in malignant lesions and the like or slow cooling which promotes ice formation between cells rather than within cells when necrosis is not desired. More complex flow modulating valve structures might also be used in other embodiments. For example, other applicable valve embodiments are disclosed in previously incorporated U.S. Pub. No. 2008/0200910.

[0057] Still referring to FIG. 2A, an optional heater (not illustrated) may be used to heat cooling fluid supply 18 so that heated cooling fluid flows through valve 32 and through a lumen 34 of a cooling fluid supply tube 36. Supply tube 36 is, at least in part, disposed within a lumen 38 of needle 26, with the supply tube extending distally from a proximal end 40 of the needle toward a distal end 42. The exemplary supply tube 36 comprises a fused silica tubular structure (not illustrated) having a polymer coating and extending in cantilever into the needle lumen 38. Supply tube 36 may have an inner lumen with an effective inner diameter of less than about 200 μm, the inner diameter often being less than about 100 μm, and typically being less than about 40 μm. Exemplary embodiments of supply tube 36 have inner lumens of between about 15 and 50 μm, such as about 30 μm. An outer diameter or size of supply tube 36 will typically be less than about 1000 μm, often being less than about 800 μm, with exemplary embodiments being between about 60 and 150 μm, such as about 90 μm or 105 μm. The tolerance of the inner lumen diameter of supply tubing 36 will preferably be relatively tight, typically being about +/−10 μm or tighter, often being +/−5 μm or tighter, and ideally being +/−3 μm or tighter, as the small diameter supply tube may provide the majority of (or even substantially all of) the metering of the cooling fluid flow into needle 26. Additional details on various aspects of needle 26 along with alternative embodiments and principles of operation are disclosed in greater detail in U.S. Patent Publication No. 2008/0154254 (Atty. Docket No. 000300US) entitled “Dermal and Transdermal Cryogenic Microprobe Systems and Methods,” the entire contents of which are incorporated herein by reference. Previously incorporated U.S. Pat No. 8,409,185 (Attorney Docket No. 000500US) discloses additional details on the needle 26 along with various alternative embodiments and principles of operation.

[0058] The cooling fluid injected into lumen 38 of needle 26 will typically comprise liquid, though some gas may also be injected. At least some of the liquid vaporizes within needle 26, and the enthalpy of vaporization cools the needle and also the surrounding tissue engaged by the needle. An optional heater 44 (illustrated in FIG. 1B) may be used to heat the proximal region of the needle in order to prevent unwanted skin damage in this area, as discussed in greater detail below. Controlling a pressure of the gas/liquid mixture within needle 26 substantially controls the temperature within lumen 38, and hence the treatment temperature range of the tissue. A relatively simple mechanical pressure relief valve 46 may be used to control the pressure within the lumen of the needle, with the exemplary valve comprising a valve body such as a ball bearing, urged against a valve seat by a biasing spring. An exemplary relief valve is disclosed in U.S. Provisional Patent Application No. 61/116,050 previously incorporated herein by reference. Thus, the relief valve allows better temperature control in the needle, minimizing transient temperatures. Further details on exhaust volume are disclosed in previously incorporated U.S. Pat. No. 8,409,185.

[0059] Alternative methods to inhibit excessively low transient temperatures at the beginning of a refrigeration cycle might be employed instead of or together with the limiting of the exhaust volume. For example, the supply valve might be cycled on and off, typically by controller 22, with a timing sequence that would limit the cooling fluid flowing so that only vaporized gas reached the needle lumen (or a sufficiently limited amount of liquid to avoid excessive dropping of the needle lumen temperature). This cycling might be ended once the exhaust volume pressure was sufficient so that the refrigeration temperature would be within desired limits during steady state flow. Analytical models that may be used to estimate cooling flows are described in greater detail in previously incorporated U.S. Patent Pub. No. 2008/0154254.

[0060] Alternative methods to inhibit excessively low transient temperatures at the beginning of a refrigeration cycle might be employed instead of or together with the limiting of the exhaust volume. For example, the supply valve might be cycled on and off, typically by controller 22, with a timing sequence that would limit the cooling fluid flowing so that only vaporized gas reached the needle lumen (or a sufficiently limited amount of liquid to avoid excessive dropping of the needle lumen temperature). This cycling might be ended once the exhaust volume pressure was sufficient so that the refrigeration temperature would be within desired limits during steady state flow. Analytical models that may be used to estimate cooling flows are described in greater detail in U.S. Pub. No. 2008/0154254, previously incorporated herein by reference.

[0061] FIG. 2B shows a cross-section of the housing 16. This embodiment of the housing 16 is powered by an external source, hence the attached cable, but could alternatively include a portable power source. As shown, the housing includes a cartridge holder 50. The cartridge holder 50 includes a cartridge receiver 52, which is configured to hold a pressured refrigerant cartridge. The cartridge receiver 52 includes an elongated cylindrical passage 54, which is dimensioned to hold a commercially available cooling fluid cartridge. A distal portion of the cartridge receiver 52 includes a filter device 56, which has an elongated conical shape. In some embodiments, the cartridge holder 50 is largely integrated into the housing 10 as shown, however, in alternative embodiments, the cartridge holder 50 is a wholly separate assembly, which may be pre-provided with a coolant fluid source 18.

[0062] The filter device 56 fluidly couples the coolant fluid source (cartridge) 18 at a proximal end to the valve 32 at a distal end. The filter device 56 includes at least one particulate filter 58. In the shown embodiment, a particulate filter 58 at each proximal and distal end of the filter device 56 is included. The particulate filter 58 can be configured to prevent particles of a certain size from passing through. For example, the particulate filter 58 can be constructed as a microscreen having a plurality of passages less than 2 microns in width, and thus particles greater than 2 microns would not be able to pass.

[0063] The filter device 56 also includes a molecular filter 60 that is configured to capture fluid impurities. In some embodiments, the molecular filter 60 is a plurality of filter media (e.g., pellets, powder, particles) configured to trap molecules of a certain size. For example, the filter media can comprise molecular sieves having pores ranging from 1-20 Å. In another example, the pores have an average size of 5 Å. The molecular filter 60 can have two modalities. In a first mode, the molecular filter 60 will filter fluid impurities received from the cartridge 18. However, in another mode, the molecular filter 60 can capture impurities within the valve 32 and fluid supply tube 36 when the system 10 is not in use, i.e., when the cartridge 18 is not fluidly connected to the valve 32.

[0064] Alternatively, the filter device 65 can be constructed primarily from ePTFE (such as a GORE material), sintered polyethylene (such as made by POREX), or metal mesh. The pore size and filter thickness can be optimized to minimize pressure drop while capturing the majority of contaminants. These various materials can be treated to make it hydrophobic (e.g., by a plasma treatment) and/or oleophobic so as to repel water or hydrocarbon contaminants.

[0065] It has been found that in some instances fluid impurities may leach out from various aspects of the system 10. These impurities can include trapped moisture in the form of water molecules and chemical gasses. The presence of these impurities is believed to hamper cooling performance of the system 10. The filter device 56 can act as a desiccant that attracts and traps moisture within the system 10, as well as chemicals out gassed from various aspects of the system 10. Alternately the various aspects of the system 10 can coated or plated with an impermeable materials such as a metal.

[0066] As shown in FIG. 2C, the cartridge 18 can be held by the cartridge receiver 52 such that the cartridge 18 remains intact and unpunctured. In this inactive mode, the cartridge is not fluidly connected to the valve 32. A removable cartridge cover 62 can be attached to the cartridge receiver 52 such that the inactive mode is maintained while the cartridge is held by the system 10.

[0067] In use, the cartridge cover 62 can be removed and supplied with a cartridge containing a cooling fluid. The cartridge cover 62 can then be reattached to the cartridge receiver 52 by turning the cartridge cover 62 until female threads 64 of the cartridge cover 62 engage with male threads of the cartridge receiver 52. The cartridge cover 62 can be turned until resilient force is felt from an elastic seal 66, as shown in FIG. 2C. To place the system 10 into use, the cartridge cover 62 can be further turned until the distal tip of the cartridge 18 is punctured by a puncture pin connector 68, as shown in FIG. 2D. Once the cartridge 18 is punctured, cooling fluid escapes the cartridge by flowing through the filter device 56, where the impurities within the cooling fluid are captured. The purified cooling fluid then passes to the valve 32, and onto the coolant supply tube 36 to cool the probe 26. In some embodiments the filter device, or portions thereof, is replaceable.

[0068] In some embodiments, the puncture pin connector 68 can have a two-way valve (e.g., ball/seat and spring) that is closed unless connected to the cartridge. Alternately, pressure can be used to open the valve. The valve closes when the cartridge is removed. In some embodiments, there is a relief valve piloted by a spring which is balanced by high-pressure nitrous when the cartridge is installed and the system is pressurized, but allows the high-pressure cryogen to vent when the cryogen is removed. In addition, the design can include a vent port that vents cold cryogen away from the cartridge port. Cold venting cryogen locally can cause condensation in the form of liquid water to form from the surrounding environment. Liquid water or water vapor entering the system can hamper the cryogenic performance. Further, fluid carrying portions of the cartridge receiver 52 can be treated (e.g., plasma treatment) to become hydrophobic and/or oleophobic so as to repel water or hydrocarbon contaminants.

[0069] FIG. 2E shows a coupling assembly 70 that is connectable between the cartridge and filter device 56. The coupling assembly 70 may be integrated into or be separate from various aspects of the housing 16, such as the cartridge receiver 52 or cartridge cover 62. Here, the coupling assembly 70 is threadably engagable with the cartridge cover 62. However, the coupling assembly 70 can be coupled in a number of different ways, such as adhesion, pressure, or welding. An o-ring seal 72 separates and fluidly seals the coupling assembly 70 to the housing 16. A seal 74 applies a force, by way of a spring 76, between the housing 16 and the filter device 56 and the coupling assembly 70. When the nozzle of the cartridge 18 is inserted into the central passage of the coupling assembly, it applies a force against the seal 74 to compress the spring 76, thereby allowing cryogenic fluid to flow around the seal 74. When the filter is removed it is desirable to reduce the pressure inside the system from a high pressure to a low pressure, however it is desirable to maintain a low pressure greater than ambient pressure inside the system to prevent contaminants and atmospheric gases from entering the system. To allow depressurization of the system, a ball and spring valve 78 is included. The spring acts on the ball and holds the ball against a seat. The high pressure refrigerant acts on the opposite side of the ball when the system is pressurized. When the filter is installed, the filter seals against the inside of the chamber distal to the spring valve and vent port, therefore when the filter is installed and the system is pressurized, high pressure refrigerant acts equally on both sides of the ball and thus the spring maintains the ball against the seat in the closed position. When the filter is removed, the vent side of the ball is opened to atmospheric pressure. The spring is designed such that it maintains a low pressure against the ball such that when the ball is acted on by high pressure refrigerant on one side and atmospheric pressure on the other side, the spring depresses and the high pressure refrigerant is vented until the refrigerant pressure equals the pressure imparted by the spring.

[0070] Turning now to FIG. 3A, an exemplary embodiment of probe 300 having multiple needles 302 is described. In FIG. 3A, probe housing 316 includes threads 306 that allow the probe to be threadably engaged with the housing 16 of a cryogenic device. O-rings 308 fluidly seal the probe housing 316 with the device housing 16 and prevent coolant from leaking around the interface between the two components. Probe 300 includes an array of three distally extending needle shafts 302, each having a sharpened, tissue penetrating tip 304. Using three linearly arranged needles allows a greater area of tissue to be treated as compared with a single needle. In use, coolant flows through lumens 310 into the needle shafts 302 thereby cooling the needle shafts 302. Ideally, only the distal portion of the needle shaft 302 would be cooled so that only the target tissue receives the cryogenic treatment. However, as the cooling fluid flows through the probe 316, probe temperature decreases proximally along the length of the needle shafts 302 towards the probe hub 318. The proximal portion of needle shaft 302 and the probe hub 318 contact skin and become very cold (e.g. −20° C. to −25° C.) and this can damage the skin in the form of blistering or loss of skin pigmentation. Therefore it would be desirable to ensure that the proximal portion of needle shaft 302 and hub 318 remains warmer than the distal portion of needle shaft 302. A proposed solution to this challenge is to include a heater element 312 that can heat the proximal portion of needle shaft 302 and an optional temperature sensor 314 to monitor temperature in this region. To further this, the a proximal portion of the needle shaft 302 can be coated with a highly conductive material, e.g., gold, that is conductively coupled to both the needle shaft 302 and heater element 314. Details of this construction are disclosed below.

[0071] In the exemplary embodiment of FIG. 3A, resistive heater element 314 is disposed near the needle hub 318 and near a proximal region of needle shaft 302. The resistance of the heater element is preferably 1Ω to 1 K Ω, and more preferably from 5Ω to 50Ω. Additionally, a temperature sensor 312 such as a thermistor or thermocouple is also disposed in the same vicinity. Thus, during a treatment as the needles cool down, the heater 314 may be turned on in order to heat the hub 318 and proximal region of needle shaft 302, thereby preventing this portion of the device from cooling down as much as the remainder of the needle shaft 302. The temperature sensor 312 may provide feedback to controller 22 and a feedback loop can be used to control the heater 314. The cooling power of the nitrous oxide may eventually overcome the effects of the heater, therefore the microprocessor may also be programmed with a warning light and/or an automatic shutoff time to stop the cooling treatment before skin damage occurs. An added benefit of using such a heater element is the fact that the heat helps to moderate the flow of cooling fluid into the needle shaft 302 helping to provide more uniform coolant mass flow to the needles shaft 302 with more uniform cooling resulting.

[0072] The embodiment of FIG. 3A illustrates a heater fixed to the probe hub. In other embodiments, the heater may float, thereby ensuring proper skin contact and proper heat transfer to the skin. Examples of floating heaters are disclosed in commonly assigned Int'l Pub. No. WO 2010/075448 (Atty. Docket No. 002310PC) entitled “Skin Protection for Subdermal Cyrogenic Remodelling for Cosmetic and Other Treatments”, the entirety of which is incorporated by reference herein.

[0073] In this exemplary embodiment, three needles are illustrated. One of skill in the art will appreciate that a single needle may be used, as well as two, four, five, six, or more needles may be used. When a plurality of needles are used, they may be arranged in any number of patterns. For example, a single linear array may be used, or a two dimensional or three dimensional array may be used. Examples of two dimensional arrays include any number of rows and columns of needles (e.g. a rectangular array, a square array, elliptical, circular, triangular, etc.), and examples of three dimensional arrays include those where the needle tips are at different distances from the probe hub, such as in an inverted pyramid shape.

[0074] FIG. 3B illustrates a cross-section of the needle shaft 302 of needle probe 300. The needle shaft can be conductively coupled (e.g., welded, conductively bonded, press fit) to a conductive heater 314 to enable heat transfer therebetween. The needle shaft 302 is generally a small (e.g., 20-30 gauge) closed tip hollow needle, which can be between about 0.2 mm and 5 cm, preferably having a length from about 0.3 cm to about 0.6 cm. The conductive heater element 314 can be housed within a conductive block 315 of high thermally conductive material, such as aluminum and include an electrically insulated coating, such as Type III anodized coating to electrically insulate it without diminishing its heat transfer properties. The conductive block 315 can be heated by a resister or other heating element (e.g. cartridge heater, nichrome wire, etc.) bonded thereto with a heat conductive adhesive, such as epoxy. A thermistor can be coupled to the conductive block 315 with heat conductive epoxy allows temperature monitoring. Other temperature sensors may also be used, such as a thermocouple.

[0075] A cladding 320 of conductive material is directly conductively coupled to the proximal portion of the shaft of needle shaft 302, which can be stainless steel. In some embodiments, the cladding 320 is a layer of gold, or alloys thereof, coated on the exterior of the proximal portion of the needle shaft 302. In some embodiments, the exposed length of cladding 320 on the proximal portion of the needle is 2 mm. In some embodiments, the cladding 320 be of a thickness such that the clad portion has a diameter ranging from 0.017-0.020 in., and in some embodiments 0.0182 in. Accordingly, the cladding 320 can be conductively coupled to the material of the needle 302, which can be less conductive, than the cladding 320.

[0076] In some embodiments, the cladding 320 can include sub-coatings (e.g., nickel) that promote adhesion of an outer coating that would otherwise not bond well to the needle shaft 302. Other highly conductive materials can be used as well, such as copper, silver, aluminum, and alloys thereof. In some embodiments, a protective polymer or metal coating can cover the cladding to promote biocompatibility of an otherwise non-biocompatible but highly conductive cladding material. Such a biocompatible coating however, would be applied to not disrupt conductivity between the conductive block 315. In some embodiments, an insulating layer, such as a ceramic material, is coated over the cladding 320, which remains conductively coupled to the needle shaft 302.

[0077] In use, the cladding 320 can transfer heat to the proximal portion of the needle 302 to prevent directly surrounding tissue from dropping to cryogenic temperatures. Protection can be derived from heating the non-targeting tissue during a cooling procedure, and in some embodiments before the procedure as well. The mechanism of protection may be providing heat to pressurized cryogenic cooling fluid passing within the proximal portion of the needle to affect complete vaporization of the fluid. Thus, the non-target tissue in contact with the proximal portion of the needle shaft 302 does not need to supply heat, as opposed to target tissue in contact with the distal region of the needle shaft 302. To help further this effect, in some embodiments the cladding 320 is coating within the interior of the distal portion of the needle, with or without an exterior cladding. To additionally help further this effect, in some embodiments, the distal portion of the needle can be thermally isolated from the proximal portion by a junction, such as a ceramic junction. While in some further embodiments, the entirety of the proximal portion is constructed from a more conductive material than the distal portion.

[0078] In use, it has been determined experimentally that the cladding 320 can help limit formation of a cooling zone to the distal portion of the needle shaft 302, which tends to demarcate at a distal end of the cladding 320. This effect is shown depicted in FIG. 3C where non-target tissue, directly above target tissue, including skin and at least a portion of subcutaneous tissue are not made part of the ice-ball. Rather, cooling zones are formed only about the distal portions of the needles—in this case to target a temporal nerve branch. Thus, while non-target tissue in direct contact with proximal needle shafts remain protected from effects of cryogenic temperatures. Such effects can include discoloration and blistering of the skin. Such cooling zones may be associated with a particular physical reaction, such as the formation of an ice-ball, or with a particular temperature required to therapeutically affect the tissue therein.

[0079] Standard stainless steel needles and gold clad steel needles were tested in porcine muscle and fat. Temperatures were recorded measured 2 mm from the proximal end of the needle shaft, about where the cladding distally terminates, and at the distal tip of the needles. As shown, temperatures for clad needles were dramatically warmer at the 2 mm point versus the unclad needles, and did not drop below 4° C. The 2 mm points of the standard needles however almost equalize in temperature with the distal tip.

[0080] An exemplary algorithm 400 for controlling the heater element 314, and thus for transferring heat to the cladding 320, is illustrated in FIG. 4. In FIG. 4, the start of the interrupt service routine (ISR) 402 begins with reading the current needle hub temperature 404 using a temperature sensor such as a thermistor or thermocouple disposed near the needle hub. The time of the measurement is also recorded. This data is fed back to controller 22 where the slope of a line connecting two points is calculated. The first point in the line is defined by the current needle hub temperature and time of its measurement and the second point consists of a previous needle hub temperature measurement and its time of measurement. Once the slope of the needle hub temperature curve has been calculated 406, it is also stored 408 along with the time and temperature data. The needle hub temperature slope is then compared with a slope threshold value 410. If the needle hub temperature slope is less than the threshold value then a treating flag is activated 412 and the treatment start time is noted and stored 414. If the needle hub slope is greater than or equal to the slope threshold value 410, an optional secondary check 416 may be used to verify that cooling has not been initiated. In step 416, absolute needle hub temperature is compared to a temperature threshold. If the hub temperature is less than the temperature threshold, then the treating flag is activated 412 and the treatment start time is recorded 414 as previously described. As an alternative, the shape of the slope could be compared to a norm, and an error flag could be activated for an out of norm condition. Such a condition could indicate the system was not heating or cooling sufficiently. The error flag could trigger an automatic stop to the treatment with an error indicator light. Identifying the potential error condition and possibly stopping the treatment, may prevent damage to the proximal tissue in the form of too much heat, or too much cooling to the tissue. The algorithm preferably uses the slope comparison as the trigger to activate the treatment flag because it is more sensitive to cooling conditions when the cryogenic device is being used rather than simply measuring absolute temperature. For example, a needle probe exposed to a cold environment would gradually cool the needle down and this could trigger the heater to turn on even though no cryogenic cooling treatment was being conducted. The slope more accurately captures rapid decreases in needle temperature as are typically seen during cryogenic treatments.

[0081] When the treatment flag is activated 418 the needle heater is enabled 420 and heater power may be adjusted based on the elapsed treatment time and current needle hub temperature 422. Thus, if more heat is required, power is increased and if less heat is required, power is decreased. Whether the treatment flag is activated or not, as an additional safety mechanism, treatment duration may be used to control the heater element 424. As mentioned above, eventually, cryogenic cooling of the needle will overcome the effects of the heater element. In that case, it would be desirable to discontinue the cooling treatment so that the proximal region of the probe does not become too cold and cause skin damage. Therefore, treatment duration is compared to a duration threshold value in step 424. If treatment duration exceeds the duration threshold then the treatment flag is cleared or deactivated 426 and the needle heater is deactivated 428. If the duration has not exceeded the duration threshold 424 then the interrupt service routine ends 430. The algorithm then begins again from the start step 402. This process continues as long as the cryogenic device is turned on.

[0082] Preferred ranges for the slope threshold value may range from about −5° C. per second to about −90° C. per second and more preferably range from about −30° C. per second to about −57° C. per second. Preferred ranges for the temperature threshold value may range from about 15° C. to about 0° C., and more preferably may range from about 0° C. to about 10° C. Treatment duration threshold may range from about 15 seconds to about 75 seconds and more preferably may range from about 15 seconds to about 60 seconds.

[0083] It should be appreciated that the specific steps illustrated in FIG. 4 provide a particular method of heating a cryogenic probe, according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 4 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0084] The heating algorithm may be combined with a method for treating a patient. Referring now to FIG. 5, a method 100 facilitates treating a patient using a cryogenic cooling system having a reusable or disposable handpiece either of which that can be self-contained or externally powered with replaceable needles such as those of FIG. 1B and a limited capacity battery or metered electrical supply. Method 100 generally begins with a determination 110 of the desired tissue therapy and results, such as the alleviation of specific cosmetic wrinkles of the face, the inhibition of pain from a particular site, the alleviation of unsightly skin lesions or cosmetic defects from a region of the face, or the like. Appropriate target tissues for treatment are identified 112 (such as the subdermal muscles that induce the wrinkles, a tissue that transmits the pain signal, or the lesion-inducing infected tissues), allowing a target treatment depth, target treatment temperature profile, or the like to be determined. Step 112 may include performing a tissue characterization and/or device diagnostic algorithm, based on power draw of system 10, for example.

[0085] The application of the treatment algorithm 114 may include the control of multiple parameters such as temperature, time, cycling, pulsing, and ramp rates for cooling or thawing of treatment areas. In parallel with the treatment algorithm 114, one or more power monitoring algorithms 115 can be implemented. An appropriate needle assembly can then be mounted 116 to the handpiece, with the needle assembly optionally having a needle length, skin surface cooling chamber, needle array, and/or other components suitable for treatment of the target tissues. Simpler systems may include only a single needle type, and/or a first needle assembly mounted to the handpiece.

[0086] Pressure, heating, cooling, or combinations thereof may be applied 118 to the skin surface adjacent the needle insertion site before, during, and/or after insertion 120 and cryogenic cooling 122 of the needle and associated target tissue. Non-target tissue directly above the target tissue can be protected by directly conducting energy in the form of heat to the cladding on a proximal portion of the needle shaft during cooling. Upon completion of the cryogenic cooling cycle the needles will need additional “thaw” time 123 to thaw from the internally created cooling zone to allow for safe removal of the probe without physical disruption of the target tissues, which may include, but not be limited to nerves, muscles, blood vessels, or connective tissues. This thaw time can either be timed with the refrigerant valve shut-off for as short a time as possible, preferably under 15 seconds, more preferably under 5 seconds, manually or programmed into the controller to automatically shut-off the valve and then pause for a chosen time interval until there is an audible or visual notification of treatment completion.

[0087] Heating of the needle may be used to prevent unwanted skin damage using the apparatus and methods previously described. The needle can then be retracted 124 from the target tissue. If the treatment is not complete 126 and the needle is not yet dull 128, pressure and/or cooling can be applied to the next needle insertion location site 118, and the additional target tissue treated. However, as small gauge needles may dull after being inserted only a few times into the skin, any needles that are dulled (or otherwise determined to be sufficiently used to warrant replacement, regardless of whether it is after a single insertion, 5 insertions, or the like) during the treatment may be replaced with a new needle 116 before the next application of pressure/cooling 118, needle insertion 120, and/or the like. Once the target tissues have been completely treated, or once the cooling supply canister included in the self-contained handpiece is depleted, the used canister and/or needles can be disposed of 130. The handpiece may optionally be discarded.

[0088] As discussed with reference to FIG. 5, a power monitoring algorithm 115 can be applied prior to, during, after, and in some cases in lieu of, the treatment algorithm 114, such as the one shown in FIG. 4. One example of a power monitoring algorithm 600 is shown in FIG. 6A, which illustrates a method for monitoring power demand from a heater when cooling fluid is passed through at least one needle. The power monitoring algorithm 600 can be performed during an actual treatment of tissue. At operation 602, the controller (e.g., controller 22) monitors power consumption of a heater (e.g., heater 44), which is thermally coupled to a needle (e.g., needle 26), directly or via a thermally responsive element (e.g., element 50). Monitoring can take place during a tissue treatment procedure, for example, as discussed with reference to FIG. 5, performed in parallel to a treatment algorithm. Alternatively, power monitoring can take place during a diagnostic routine.

[0089] At operation 604, the controller correlates a sampled power measurement with an acceptable power range corresponding to a tissue characteristic and/or operating parameter. This measurement may further be correlated according to the time of measurement and temperature of the thermally responsive element 50. For example, during treatment of target tissue, maintaining the thermally responsive element 50 at 40° C. during a cooling cycle may be expected to require 1.0 W initially and is expected to climb to 1.5 W after 20 seconds, due to the needle 26 drawing in surrounding heat. An indication that the heater is drawing 2.0 W after 20 seconds to maintain 40° C. can indicate that an aspect of the system 10 is malfunctioning and/or that the needle 26 is incorrectly positioned within target tissue or primarily positioned in non-target tissue. Correlations with power draw and correlated device and/or tissue conditions can be determined experimentally to determine acceptable power ranges.

[0090] At operation 606, the controller determines whether the power measurement is correlated within acceptable limits of an expected power draw, or to a power draw indicating a tissue or device problem. If the correlation is unacceptable, then the controller may in operation 608 initiate an alarm to the user and/or halt or modify the treatment algorithm. In some cases, the error is minor, for example, the controller may signal a user indication to modify operator technique, e.g., apply greater or lesser pressure to the skin. In other cases, the error can indicate a major valve malfunction, and signal an alert to abort the process and/or cause a secondary or purge valve to operate. If the correlation is acceptable, then in operation 610 it is determined whether the treatment algorithm is still in process, which will cause the power monitoring algorithm to end or continue to loop. Alternatively, the power monitoring algorithm 600 can simply loop until interrupted by the controller, for example, when treatment algorithm has ended or by some other trigger.

[0091] In some embodiments, the power monitoring algorithm 600 can be performed exclusively for tissue characterization purposes, e.g., to determine proper operating parameters for a later treatment, by only looping between operations 602 and 604 for a predetermined amount of time to collect data. Data can be collected and correlated by the controller to a particular tissue type and further correlated to optimal treatment parameters. For example, the characterized tissue may have a greater or lesser average amount of adjacent adipose tissue, which could require longer or shorter treatment times. This process be performed, for example, by inserting the needle into the target tissue and providing only enough coolant to characterize the tissue, rather than remodel.

[0092] FIGS. 6B and 6C show another power monitoring algorithm 612 for regulating a freeze zone, that can be implemented parallel to or in lieu of a treatment algorithm, such as the one shown in FIG. 4, as well as parallel to another power monitoring algorithm, such as the one shown in FIG. 6A. At operation 614, a valve is or has been previously regulated to provide at least one needle with coolant, with the needle being in contact with tissue, as illustrated in FIG. 6C. After some time, a cooling zone forms within the tissue, and will continue to grow in size as long as the needle is supplied with coolant. Ideally, the cooling zone is limited in size to the area of target tissue, to prevent unintentional treatment of the non-target tissue. While coolant is flowing, power demand from the heater is monitored, which can occur immediately or alternatively after a predetermined amount of time has passed since opening of the valve.

[0093] At operation 618, the controller determines whether a sampled power measurement correlates to a maximum ice-ball size desired for a particular therapeutic effect, such as tissue remodeling. Correlations with power draw and cooling zone size can be determined experimentally to determine acceptable power ranges, and the tissue can be pre-characterized according to a tissue characterization algorithm, such as shown in FIG. 6A This measurement may further be correlated according to the time of measurement and temperature of the thermally responsive element 50. If the power draw does not correlate with the maximum allowable ice-ball size, then the monitoring is continued.

[0094] After a determination that the power demand correlates with the maximum cooling zone size, the valve is regulated to provide the needle with less or no coolant at operation 620. After some time the cooling zone will decrease in size as heat is drawn in from surrounding tissue. During that time, power supplied to the heater is monitored at operation 622. At operation 624, the controller determines whether a sampled power measurement correlates to a minimum ice-ball size required to maintain the desired therapeutic effect. If the power draw does not correlate with the maximum allowable ice-ball size, then the monitoring is continued while the cooling zone continues to decrease in size.

[0095] Eventually, at operation 624, the power measurement will correspond with the minimum cooling zone size. This causes the controller to loop the process and provide more coolant, which causes the cooling zone to grow in size. The valve can be metered in this manner to maintain the cooling zone within acceptable size tolerances, until the procedure is complete.

[0096] A variety of target treatment temperatures, times, and cycles may be applied to differing target tissues to as to achieve the desired remodeling. For example, as more fully described in U.S. Pat Nos. 7,713,266 and 7,850,683, both previously incorporated herein by reference.

[0097] There is a window of temperatures where apoptosis can be induced. An apoptotic effect may be temporary, long-term (lasting at least weeks, months, or years) or even permanent. While necrotic effects may be long term or even permanent, apoptosis may actually provide more long-lasting cosmetic benefits than necrosis. Apoptosis may exhibit a non-inflammatory cell death. Without inflammation, normal muscular healing processes may be inhibited. Following many muscular injuries (including many injuries involving necrosis), skeletal muscle satellite cells may be mobilized by inflammation. Without inflammation, such mobilization may be limited or avoided. Apoptotic cell death may reduce muscle mass and/or may interrupt the collagen and elastin connective chain. Temperature ranges that generate a mixture of apoptosis and necrosis may also provide long-lasting or permanent benefits. For the reduction of adipose tissue, a permanent effect may be advantageous. Surprisingly, both apoptosis and necrosis may produce long-term or even permanent results in adipose tissues, since fat cells regenerate differently than muscle cells.

[0098] While the exemplary embodiments have been described in some detail for clarity of understanding and by way of example, a number of modifications, changes, and adaptations may be implemented and/or will be obvious to those as skilled in the art. Hence, the scope of the present invention is limited solely by the claims as follows.