Abstract:
Apparatus and methods for predictively controlling the temperature of a coolant delivered to a treatment apparatus configured to non-invasively treat a patient&#39;s tissue with doses of electromagnetic energy. The treatment apparatus includes a closed-loop cooling system connected with an energy delivery device used to deliver the electromagnetic energy to the patient&#39;s tissue. Coolant is pumped from a reservoir to the energy delivery device in the closed-loop cooling system. The control temperature of the coolant in the reservoir is adjusted based upon the specific room air temperature. This predictive adjustment promotes better control over the coolant temperature at the energy delivery device by lessening the effects of heat gain in transit from the reservoir to the energy delivery device.

Description:
FIELD OF THE INVENTION  
       [0001]    The invention generally relates to methods and apparatus for treating tissue with electromagnetic energy and, more particularly, relates to methods and apparatus for predictively controlling the temperature of a coolant delivered to a treatment device and used to cool the tissue during tissue treatment with electromagnetic energy delivered from the treatment device. 
       BACKGROUND OF THE INVENTION  
       [0002]    Certain types of energy delivery devices are capable of non-ablatively and non-invasively treating a patient&#39;s tissue with electromagnetic energy. These energy delivery devices, which emit electromagnetic energy in different regions of the electromagnetic spectrum for tissue treatment, are extensively used to treat a multitude of diverse skin conditions. Among other uses, non-invasive energy delivery devices may be used to tighten loose skin so that a patient appears younger, to remove skin spots or hair, or to kill bacteria. 
         [0003]    One variety of these energy delivery devices emit high frequency electromagnetic energy in the radio-frequency (RF) band of the electromagnetic spectrum. The high frequency energy may be used to treat skin tissue non-ablatively and non-invasively by passing high frequency energy through a surface of the skin, while actively cooling the skin to prevent damage to the skin&#39;s epidermal layer closer to the skin surface. The high frequency energy heats tissue beneath the epidermis to a temperature sufficient to denature collagen, which causes the collagen to contract and shrink and, thereby, tighten the tissue. Treatment with high frequency energy also causes a mild inflammation. The inflammatory response of the tissue causes new collagen to be generated over time (between three days and six months following treatment), which results in further tissue contraction. 
         [0004]    Typically, energy delivery devices include a treatment tip that is placed in contact with, or proximate to, the patient&#39;s skin surface and that emits electromagnetic energy that penetrates through the skin surface and into the tissue beneath the skin surface. The non-patient side of the energy delivery device, such as an electrode for high frequency energy, in the treatment tip may be sprayed with a coolant or cryogen spray under feedback control of temperature sensors for cooling tissue at shallow depths beneath the skin surface. A controller triggers the coolant spray based upon an evaluation of the temperature readings from temperature sensors in the treatment tip. 
         [0005]    The cryogen spray may be used to pre-cool superficial tissue before delivering the electromagnetic energy. When the electromagnetic energy is delivered, the superficial tissue that has been cooled is protected from thermal effects. The target tissue that has not been cooled or that has received nominal cooling will warm up to therapeutic temperatures resulting in the desired therapeutic effect. The amount or duration of pre-cooling can be used to select the depth of the protected zone of untreated superficial tissue. After the delivery of electromagnetic energy has concluded, the cryogen spray may also be employed to prevent or reduce heat originating from treated tissue from conducting upward and heating the more superficial tissue that was cooled before treatment with the electromagnetic energy. 
         [0006]    Although conventional methods apparatus and for delivering cryogen sprays have proved adequate for their intended purpose, what is needed are improved methods and apparatus for cooling superficial tissue in conjunction with non-ablative and non-invasive treatment of deeper regions of tissue beneath the skin surface with amounts of electromagnetic energy. 
       SUMMARY OF THE INVENTION  
       [0007]    In one embodiment, a method is provided for treating tissue beneath a skin surface with electromagnetic energy. The method comprises pumping a fluid from a reservoir to an energy delivery device, circulating the fluid through the energy delivery device, and returning the fluid from the energy delivery device to the reservoir. The method further includes measuring a value of a room air temperature proximate to at least one of the energy delivery device or the reservoir, and adjusting a control temperature of the fluid in the reservoir based upon the measured value of the room air temperature. The electromagnetic energy is delivered from the energy delivery device to the tissue. 
         [0008]    In another embodiment, an apparatus is provided for treating tissue beneath a skin surface with electromagnetic energy. The apparatus comprises an energy delivery device configured to deliver the electromagnetic energy to the tissue, a closed-loop cooling system including a reservoir configured to hold a coolant and a coldplate configured to regulate a temperature of the coolant held in the reservoir at a control temperature, and a temperature sensor configured to sense a room air temperature proximate to at least one of the reservoir or the energy delivery device. The closed-loop cooing system is configured to circulate the coolant between the energy delivery device and the reservoir. The apparatus further includes a temperature controller communicatively coupled to the coldplate, and a system controller communicatively coupled to the temperature sensor and to the temperature controller. The temperature controller is configured to operate the coldplate to maintain the coolant at the control temperature. The system controller is programmed to determine the control temperature based upon the room air temperature and communicate the control temperature to the temperature controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
           [0010]      FIG. 1  is a diagrammatic view of a treatment system with a handpiece, a treatment tip, and a console in accordance with an embodiment of the invention 
           [0011]      FIG. 2  is a diagrammatic view of the handpiece, treatment tip, and console of  FIG. 1  showing a closed-loop cooling system of the treatment system. 
           [0012]      FIG. 3  is a rear view of the assembled treatment tip taken generally along line  3 - 3  in  FIG. 2  showing the electrode and temperature sensors. 
           [0013]      FIG. 4  is a perspective view of the handpiece partially shown in phantom in which certain internal components, such as electrical wiring, are omitted for clarity. 
           [0014]      FIG. 5  is an exploded view of the treatment tip of  FIG. 2  in which the treatment electrode is shown in an unfolded condition. 
           [0015]      FIG. 6  is a front perspective view of a manifold body located inside the treatment tip of  FIG. 5 . 
           [0016]      FIG. 7  is a rear perspective view of the manifold body of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION  
       [0017]    With reference to  FIGS. 1-5 , a treatment apparatus  10  includes a handpiece  12 , a treatment tip  14  coupled in a removable and releasable manner with the handpiece  12 , a console generally indicated by reference numeral  16 , and a system controller  18 . The system controller  18 , which is incorporated into the console  16 , controls the global operation of the different individual components of the treatment apparatus  10 . Under the control of the system controller  18  and an operator&#39;s interaction with the system controller  18  at the console  16 , the treatment apparatus  10  is adapted to selectively deliver electromagnetic energy in a high frequency band of the electromagnetic spectrum, such as the radiofrequency (RF) band to non-invasively heat a region of a patient&#39;s tissue to a targeted temperature range. The elevation in temperature may produce a desired treatment, such as removing or reducing wrinkles and otherwise tightening the skin to thereby improve the appearance of a patient  20  receiving the treatment. In alternative embodiments, the treatment apparatus  10  may be configured to deliver energy in the infrared band, microwave band, or another high frequency band of the electromagnetic spectrum, rather than energy in the RF band, to the patient&#39;s tissue. 
         [0018]    The treatment tip  14  carries an energy delivery member in the representative form of a treatment electrode  22 . The treatment electrode  22  is electrically coupled by conductors inside a cable  27  with a generator  38  configured to generate the electromagnetic energy used in the patient&#39;s treatment. In a representative embodiment, the treatment electrode  22  may have the form of a region  26  of an electrical conductor carried on an electrically-insulating substrate  28  composed of a dielectric material. In one embodiment, the substrate  28  may comprise a thin flexible base polymer film carrying the conductor region  26  and thin conductive (e.g., copper) traces or leads  24  on the substrate  28  that electrically couple the conductor region  26  with contact pads  25 . The base polymer film may be, for example, polyimide or another material with a relatively high electrical resistivity and a relatively high thermal conductivity. The conductive leads  24  may contain copper or another material with a relatively high electrical conductivity. Instead of the representative solid conductor region  26 , the conductor region  26  of treatment electrode  22  may include voids or holes unfilled by the conductor to provide a perforated appearance or, alternatively, may be segmented into plural individual electrodes that can be individually powered by the generator  38 . 
         [0019]    In one specific embodiment, the treatment electrode  22  may comprise a flex circuit in which the substrate  28  consists of a base polymer film and the conductor region  26  consists of a patterned conductive (i.e., copper) foil laminated to the base polymer film. In another specific embodiment, the treatment electrode  22  may comprise a flex circuit in which the conductor region  26  consists of patterned conductive (i.e., copper) metallization layers directly deposited the base polymer film by, for example, a vacuum deposition technique, such as sputter deposition. In each instance, the base polymer film constituting substrate  28  may be replaced by another non-conductive dielectric material and the conductive metallization layers or foil constituting the conductor region  26  may contain copper. Flex circuits, which are commonly used for flexible and high-density electronic interconnection applications, have a conventional construction understood by a person having ordinary skill in the art. 
         [0020]    The substrate  28  includes a contact side  32  that is placed into contact with the skin surface of the patient  20  during treatment and a non-contact side  34  that is opposite to the contact side  32 . The conductor region  26  of the treatment electrode  22  is physically carried on non-contact side  34  of the substrate  28 . In the representative arrangement, the substrate  28  is interposed between the conductor region  26  and the treated tissue such that, during the non-invasive tissue treatment, electromagnetic energy is transmitted from the conductor region  26  through the thickness of the substrate  28  by capacitively coupling with the tissue of the patient  20 . 
         [0021]    When the treatment tip  14  is physically engaged with the handpiece  12 , the contact pads  25  face toward the handpiece  12  and are electrically coupled with electrical contacts  36 , such as pogo pin contacts, inside the handpiece  12 . Electrical contacts  36  are electrically coupled with insulated and shielded conductors (not shown) of the electrical wiring  24  also located inside the handpiece  12 . The insulated and shielded wires extend exteriorly of the handpiece  12  inside cable  27  to a generator  38  at the console  16 . The generator  38 , which has the form of a high frequency power supply, is equipped with an electrical circuit (not shown) operative to generate high frequency electrical current, typically in the radio-frequency (RF) region of the electromagnetic spectrum. The operating frequency of generator  38  may advantageously be in the range of several hundred kHz to about twenty (20) MHz to impart a therapeutic effect to treat target tissue beneath a patient&#39;s skin surface. The circuit in the generator  38  converts a line voltage into drive signals having an energy content and duty cycle appropriate for the amount of power and the mode of operation that have been selected by the clinician, as understood by a person having ordinary skill in the art. In one embodiment, the generator  38  is a 400-watt, 6.78 MHz high frequency generator. 
         [0022]    A non-therapeutic passive or return electrode  40 , which is electrically coupled with the generator  38 , is physically attached to a site on the body surface of the patient  20 , such as the patient&#39;s lower back. During treatment, high frequency current flows from the treatment electrode  22  through the treated tissue and the intervening bulk of the patient  20  to the return electrode  40  and then through conductors inside a return cable  41  to define a closed circuit or current path  42 . Because of the relatively large surface area of the return electrode  40  in contact with the patient  20 , the current density flowing from the patient  20  to the return electrode  40  is relatively low in comparison with the current density flowing from the treatment electrode  22  to the patient  20 . As a result, the return electrode  40  is non-therapeutic because negligible heating is produced at its attachment site to the patient  20 . High frequency electrical current flowing between the treatment electrode  22  and the patient  20  is maximized at the skin surface and underlying tissue region adjacent to the treatment electrode  22  and, therefore, delivers a therapeutic effect to the tissue region near the treatment site. 
         [0023]    As best shown in  FIG. 3 , the treatment tip  14  includes temperature sensors  44 , such as thermistors or thermocouples, that are located on the non-contact side  34  of the substrate  28  that is not in contact with the patient&#39;s skin surface. Typically, the temperature sensors  44  are arranged about the perimeter of the conductor region  26  of the treatment electrode  22 . Temperature sensors  44  are constructed to detect the temperature of the treatment electrode  22  and/or treatment tip  14 , which may be representative of the temperature of the treated tissue. Each of the temperature sensors  44  is electrically coupled by conductive leads  46  with one or more of the contact pads  25 , which are used to supply direct current (DC) voltages from the system controller  18  through the electrical wiring  26  to the temperature sensors  44 . 
         [0024]    With continued reference to  FIGS. 1-5 , the system controller  18  regulates the power delivered from the generator  38  to the treatment electrode  22  and otherwise controls and supervises the operational parameters of the treatment apparatus  10 . The system controller  18  may include user input devices to, for example, adjust the applied voltage level of generator  38 . The system controller  18  includes a processor, which may be any suitable conventional microprocessor, microcontroller or digital signal processor, executing software to implement control algorithms for the operation of the generator  38 . System controller  18 , which may also include a nonvolatile memory (not shown) containing programmed instructions for the processor, may be optionally integrated into the generator  38 . System controller  18  may also communicate, for example, with a nonvolatile memory carried by the handpiece  12  or by the treatment tip  14 . The system controller  18  also includes circuitry for supplying the DC voltages and circuitry that relates changes in the DC voltages to the temperature detected by the temperature sensors  44 , as well as temperature sensors  90  and  88 . 
         [0025]    With specific reference to  FIG. 4 , the handpiece  12  is constructed from a body  48  and a cover  50  that is assembled with conventional fasteners with the body  48 . The assembled handpiece  12  has a smoothly contoured shape suitable for manipulation by a clinician to maneuver the treatment tip  14  and treatment electrode  22  to a location proximate to the skin surface and, typically, in a contacting relationship with the skin surface. An activation button (not shown), which is accessible to the clinician from the exterior of the handpiece  12 , is depressed for closing a switch that energizes the treatment electrode  22  and, thereby, delivers high frequency energy over a short delivery cycle to treat the target tissue. Releasing the activation button opens the switch to discontinue the delivery of high frequency energy to the patient&#39;s skin surface and underlying tissue. After the treatment of one site is concluded, the handpiece  12  is manipulated to position the treatment tip  14  near a different site on the skin surface for another delivery cycle of high frequency energy delivery to the patient&#39;s tissue. 
         [0026]    With reference to  FIGS. 5-7 , the treatment tip  14  includes a rigid outer shell  52 , a rear cover  54  that is coupled with an open rearward end of the outer shell  52 , a manifold body  55  disposed inside an enclosure or housing inside the outer shell  52 , and a flange  53  for the rear cover  54 . The flange  53  may be a portion of the manifold body  55 . A portion of the substrate  28  overlying the conductor region  26  of the treatment electrode  22  is exposed through a window  56  defined in a forward open end of the outer shell  52 . The substrate  28  is wrapped or folded about the manifold body  55 . The flange  53  provides a flat support surface over which the contact pads  25  are placed, such that the electrical contacts  36  press firmly against the contact pads  25 . 
         [0027]    As best shown in  FIGS. 5 and 6 , the manifold body  55 , which may be formed from an injection molded polymer resin, includes a front section  60 , a stem  62  projecting rearwardly from the front section  60 , and ribs  64  on the stem  62  used to position the manifold body  55  inside the outer shell  52 . The front section  60  of the manifold body  55  includes a channel  66  that, in the assembly constituting treatment tip  14 , underlines the conductor region  26  of the treatment electrode  22 . The shape of the front section  60  corresponds with the shape of the window  56  in the outer shell  52 . The substrate  28  of the treatment electrode  22  is bonded with a rim  68  of the manifold body  55  to provide a fluid seal that confines coolant flowing in the channel  66 . The area inside the rim  68  is approximately equal to the area of the conductor region  26  of treatment electrode  22 . Channel  66  includes convolutions that are configured to optimize the residence time of the coolant in channel  66 , which may in turn optimize the heat transfer between the coolant and the treatment electrode  22 . 
         [0028]    As best shown in  FIGS. 5-7 , an inlet bore or passage  70  and an outlet bore or passage  72  extend through the stem  62  of the manifold body  55 . The inlet passage  70  and outlet passage  72  are rearwardly accessible through an oval-shaped slot  74  defined in the rear cover  54 . The inlet passage  70  intersects the channel  66  at an inlet  76  to the channel  66  and the outlet passage  72  intersects the channel  66  at an outlet  78  from the channel  66 . The channel  66  is split into two channel sections  80 ,  82  so that fluid flow in the channel  66  diverges away in two separate streams from the inlet  76  and converges together to flow into the outlet  78 . Fluid pressure causes the coolant to flow from the inlet  76  through the two channel sections  80 ,  82  to the outlet  78  and into the outlet passage  72 . 
         [0029]    With reference to FIGS.  2  and  5 - 7 , fluid connections are established with the inlet passage  70  and the outlet passage  72  to establish the closed circulation loop and permit coolant flow to the channel  66  in the manifold body  55  when the treatment tip  14  is mated with the handpiece  12 . Specifically, the outlet passage  72  is coupled with a return line  84  in the form of a fluid conduit or tube. The inlet passage  70  is coupled with a supply line  86  in the form of an inlet conduit or tube. The return line  84  and the supply lines  86  extend out of the handpiece  12  and are routed to the console  16 . The inlet passage  70  and the outlet passage  72  may include fittings (not shown) that facilitate the establishment of fluid-tight connections. 
         [0030]    With reference to  FIG. 2 , the treatment apparatus  10  is equipped with a closed loop cooling system that includes the manifold body  55  located inside the treatment tip  14 . The closed loop cooling system further includes a reservoir  96  holding a volume of a coolant  94  and a pump  98 , which may be a diaphragm pump, that continuously pumps a stream of the coolant from an outlet of the reservoir  96  through the supply line  86  to the manifold body  55  in the treatment tip  14 . The manifold body  55  is coupled in fluid communication with the reservoir  96  by the return line  84 . The return line  84  conveys the coolant  94  from the treatment tip  14  back to the reservoir  96  to complete the circulation loop. 
         [0031]    Heat generated in the treatment tip  14  by energy delivery from the treatment electrode  22  and heat transferred from the patient&#39;s skin and an underlying depth of heated tissue is conducted through the substrate  28  and treatment electrode  22 . The heat is absorbed by the circulating coolant  94  in the channel  66  of the manifold body  55 , which lowers the temperature of the treatment electrode  22  and substrate  28  and, thereby, cools the patient&#39;s skin and the underlying depth of heated tissue. The contact cooling, at the least, assists in regulating the depth over which the tissue is heated to a therapeutic temperature by the delivered electromagnetic energy. 
         [0032]    The coolant  94  stored in the reservoir  96  is chilled by a separate circulation loop  101  that pumps coolant  94  from the reservoir  96  through separate supply and return lines to a coldplate  102 . A pump  100 , which may be a centrifugal pump, pumps the coolant  94  under pressure from the reservoir  96  to the coldplate  102 . In an alternative embodiment, the coldplate  102  may be placed directly in the return line  84  if permitted by the capacity of the coldplate  102  and system flow constrictions. 
         [0033]    In a representative embodiment, the coldplate  102  may be a liquid-to-air heat exchanger that includes a liquid heat sink with a channel (not shown) for circulating the coolant  94 , a thermoelectric module (not shown), and an air-cooled heat sink (not shown). A cold side of the thermoelectric module in coldplate  102  is thermally coupled with the liquid heat sink and a hot side of the thermoelectric module in coldplate  102  is thermally coupled with the air-cooled heat sink. The cold side is cooled for extracting heat from the coolant  94  flowing through the liquid heat sink. As understood by a person having ordinary skill in the art, an array of semiconductor couples in the thermoelectric module operate, when biased, by the Peltier effect to convert electrical energy into heat pumping energy. Heat flows from the liquid heat sink through the thermoelectric elements to the air-cooled heat sink. The air-cooled heat sink of the liquid-to-air heat exchanger dissipates the heat extracted from the coolant  94  circulating in the liquid heat sink to the surrounding environment. The air-cooled heat sink may be any conventional structure, such as a fin stack with a fan promoting convective cooling. 
         [0034]    A temperature controller  104  inside the console  16  is electrically coupled with the coldplate  102  and is also electrically coupled with the system controller  18 . The system controller  18 , which is electrically coupled with a temperature sensor  88  used to measure the coolant temperature in the reservoir  96 , supplies temperature control signals to the temperature controller  104  in response to the measured coolant temperature. Under the feedback control, the temperature controller  104  reacts to the control temperature communicated from the temperature controller to control the operation of the coldplate  102  and, thereby, regulate the temperature of the coolant  94  in the reservoir  96 . 
         [0035]    Because the coolant  94  is at a temperature below room air temperature, the coolant  94  inevitably warms as it flows through supply line  86  from the console  16  through the ambient environment to the handpiece  12 . As a result, the coolant temperature at the manifold body  55  is higher than the coolant temperature at the reservoir  96 . Although the warming can be minimized by insulating the exterior of the supply line  86  to limit heat gain from the environment, the heat gain cannot be eliminated. Further complicating the problem, the amount of heat transferred to the coolant  94  will vary based on the room air temperature and fluid flow rate. Typically, the coolant temperature in the manifold body  55  determines the temperature gradient with depth into the patient&#39;s tissue, which may impact the depth profile of the tissue treatment. 
         [0036]    To compensate for the heat gain, the coolant  94  in the reservoir  96  is maintained at a lower temperature than required at the treatment tip  14 . Generally, the amount of the over-cooling compensation for the coolant  94  in the reservoir  96  will scale upwardly with as the room air temperature increases. Coolant  94  originating from the reservoir  96  with a given initial temperature will experience a greater heat gain if the apparatus  10  is located in a comparatively warmer room. In other words, the heat gained by the coolant  94  flowing in the supply line  92  increases with increasing difference between the coolant temperature and the room air temperature. 
         [0037]    The heat gain can be compensated by adjusting the coolant temperature at the reservoir  96 . The value of the coolant temperature inside the reservoir  96  may be set based upon the temperature of the room air in which the treatment apparatus  10  is immersed. To that end, the room air temperature may be detected by a temperature sensor  90 , such as a thermocouple, or a thermistor located at the console  16 . In one embodiment, the temperature sensor  90  may be associated with the generator  38 . Alternatively, the temperature sensor  90  may be located at other locations proximate to the components of the treatment apparatus  10 , such as attached to the handpiece  12 . The room air temperature measured by the temperature sensor  90  is communicated to the system controller  18  and may be used by the system controller  18  for other purposes, such as controlling cooling fans used to dissipate heat generated inside the console  16 . 
         [0038]    A reference is established to guide the selection of coolant temperature at the reservoir  96 . Specifically, empirical data may be accumulated to assess the heat gain of the coolant  94 , while flowing in the supply line  92  from the console  16  to the manifold body  55 , as a function of room air temperature. In one embodiment, the temperature sensors  44  in the treatment tip  14  may be used to sense the coolant temperature at the manifold body  55  and a temperature sensor  88  may be used to sense the coolant temperature in the reservoir  96 . These temperatures are communicated to the system controller  18 , which determines a temperature change at each value of the room air temperature at which the empirical data is acquired. For example, the temperatures of the coolant  94  at the manifold body  55  and at the reservoir  96  can be measured and the temperature change assessed as the room air temperature is varied from over a range, such as from 60° F. to 85° F. 
         [0039]    The empirical data may be acquired at a single reservoir coolant temperature if temperature change due to heat gain is relatively insensitive to reservoir coolant temperature over the normal range of values used during treatment. Otherwise, the empirical date is acquired at a series of reservoir coolant temperatures. The empirical data may be acquired at a single flow rate if temperature change is relatively insensitive to flow rate over the normal range of values used during treatment. Otherwise, the empirical date is acquired at a series of flow rates for the coolant  94 , as pumped by pump  98 , in the supply line  92 . 
         [0040]    Armed with knowledge of the temperature change due to heat gain by the coolant flowing in the supply line  92  as a function of room air temperature, a control technique for measuring the room air temperature and adjusting the coolant temperature at the reservoir  96  based upon the measured room air temperature is implemented in the system controller  18 . The temperature change is used to adjust the degree of undercooling of the coolant  94  in the reservoir  96 , which effectively makes the coolant temperature at the treatment tip  14  independent of air temperature or, at the least, reduces the dependence of the coolant temperature at the treatment tip  14  on air temperature. Several approaches are available for determining the targeted temperature for the coolant  94  in the reservoir  96  during system operation that compensates for the heat gain experienced by the coolant  94  while flowing in the supply line  92 . 
         [0041]    In one embodiment, the data relating the temperature change as a function of room air temperature is stored as entries in a lookup table and the system controller  18  may include logic that controls the lookup table in the address space of the controller&#39;s random access memory. The lookup table represents a data structure, usually an array or an associative array, that contains multiple entries. Within each individual entry in the database, a temperature change is specified for a given room air temperature, as well as potentially other variables like coolant flow rate. In the latter instance, the data structure of the lookup table is a two-dimensional array or associative array that associates a temperature change with each measured room air temperature. The lookup table, which may be also be stored in a non-volatile memory of the system controller  18 , may be used to replace a runtime computation with a simpler lookup operation that merely requires the software executing on the system controller  18  to access numerical values stored in memory. 
         [0042]    The control temperature for the coolant  94  stored in the reservoir  96  may be established with the assistance of the lookup table. As required, the system controller  18  accesses the lookup table to retrieve a value of temperature change from memory that is correlated in the data structure with the corresponding room air temperature. If the measured room air temperature fails to coincide exactly with one of the values in the lookup table, a temperature change can be interpolated from the numerical values in the table. The system controller  18  may specify an adjustment as an offset to the reservoir coolant temperature when a treatment is initiated and maintain that reservoir coolant temperature at that adjusted reservoir coolant temperature over the duration of the patient treatment. The system controller  18  implements the mathematical relationship in software executing on its processor to determine a control temperature that is communicated to the temperature controller  104  for use in regulating the operation of the coldplate  102  to establish and maintain the coolant in the reservoir  96  at the control temperature. 
         [0043]    In an alternative version of the look-up table embodiment, the system controller  18  may monitor the room air temperature for deviations of significance and perform real-time adjustments during the course of patient treatment. If a significant deviation is detected, the system controller  18  may retrieve a different numerical value of temperature change from the lookup table and implement a revised reservoir coolant temperature by supplying an updated control temperature to the temperature controller  104  for use in adjusting the operation of the coldplate  102 . 
         [0044]    In another embodiment of the invention, the correlation between the measured ambient temperature and the temperature change for use in over-cooling the coolant  94  in the reservoir  96  may be determined by a run-time computation using a mathematical equation or relationship. The mathematical relationship is established from the empirically measured data array associating temperature change as a function of room air temperature. For example, the empirically measured data array may be statistically analyzed by a linear regression to establish a mathematical relationship that is linear such that the temperature change that is used to adjust the reservoir coolant temperature scales linearly with the room air temperature. The system controller  18  implements the mathematical relationship in software executing on its processor to determine a control temperature that is communicated to the temperature controller  104  for use in regulating the operation of the coldplate  102  to establish and maintain the coolant in the reservoir  96  at the control temperature. 
         [0045]    In an alternative version of the equation-based embodiment, the system controller  18  may monitor the room air temperature communicated from the temperature sensor  90  to detect deviations of significance and perform real-time adjustments during the course of patient treatment. If a significant deviation is detected, the system controller  18  may recalculate a different numerical value of temperature change using the mathematical relationship and implement a revised reservoir coolant temperature by supplying an updated control temperature to the temperature controller  104  for use in adjusting the operation of the coldplate  102 . 
         [0046]    In use and with reference to  FIGS. 1-7 , the coolant  94  is circulated by pump  100  between the coldplate  102  and the reservoir  96 . The system controller  18  monitors the temperature of the coolant  94  in the reservoir  96  using temperature information received from temperature sensor  88  and communicates control signals to the temperature controller  104  to establish a control temperature for the coolant  94  in the reservoir  96 . The system controller  18  samples the room air temperature communicated from the temperature sensor  90  and adjusts the coolant temperature in the reservoir  96  to reflect the room air temperature measured with the aid of temperature sensor  90 . Specifically, the system controller  18  communicates the control temperature to the temperature controller  104 , which adjusting the operation of the coldplate  102  to establish the coolant temperature in the reservoir  96 . 
         [0047]    The coolant temperature is established by the temperature controller  104  in the reservoir  96  at a calculated temperature setting that is less than the minimum desired temperature at the treatment tip  14 . In other words, the coolant temperature in the reservoir  96  is set at a value that is colder than the coolant temperature required at the treatment tip  14 . The specific temperature is set based upon the room air temperature measured by temperature sensor  90 . As described above, an offset to the reservoir coolant temperature is either retrieved by the system controller  18  from a lookup table or calculated by the system controller  18  using a mathematical relationship. The calculated or retrieved offset is used by the system controller  18  to adjust the control temperature for the coolant  94  in the reservoir  96 . By cooling the coolant  94  to a temperature less than desired based upon the measured room air temperature, coolant  94  can be delivered to the treatment tip  14  at the desired temperature at much greater accuracy than without this process. 
         [0048]    The treatment electrode  22  is energized by generator  38  to deliver doses of high frequency energy to the target tissue. During patient treatment, coolant  94  is continuously pumped by pump  98  through the supply line  86  from the reservoir  96  to the handpiece  12 . The coolant  94  is delivered to the manifold body  55  and circulated through the channel  66  in contact with the conductor region  26  of treatment electrode  22  on the non-contact side  34  of substrate  28 . This cools the treatment electrode  22 , which in turn cools the tissue immediately beneath the patient&#39;s skin surface in the contacting relationship with the contact side  32  of the substrate  28 . Spent coolant  94  is directed from the channel  66  into the return line  84  and returned to the reservoir  96 . 
         [0049]    The continuous stream of coolant  94  flowing through the channel  66  in the manifold body  55  continuously cools the adjacent tissue contacted by the treatment electrode  22 . The contact cooling prevents superficial tissue from being heated to a temperature sufficient to cause a significant and possibly damaging thermal effect. Depths of tissue that are not significantly cooled by thermal energy transfer to the continuous stream of coolant  94  flowing through the channel  66  in manifold body  55  will be warmed by the high frequency energy to therapeutic temperatures resulting in the desired therapeutic effect. The amount or duration of pre-cooling, after the treatment electrode  22  is contacted with the skin surface and before electromagnetic energy is delivered, may be used to select the protected depth of untreated tissue. Longer durations of pre-cooling and lower coolant temperatures produce a deeper protected zone and, hence, a deeper level in tissue for the onset of the treatment zone. 
         [0050]    Using the same mechanism, the tissue is also cooled by the continuous stream of coolant  94  flowing through the manifold body  55  during energy delivery and after heating by the transferred high frequency energy. Post-cooling may prevent or reduce heat delivered deeper into the tissue from conducting upward and heating shallower depths to therapeutic temperatures even though external energy delivery from the treatment electrode  22  to the targeted tissue has ceased. 
         [0051]    If the system controller  18  detects a significant deviation in room air temperature during treatment, the system controller  18  may optionally determine and communicate an updated control temperature to the temperature controller  104 . 
         [0052]    While the invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.