Patent Application
20090149930
The invention generally relates to apparatus and methods for treating tissue with electromagnetic energy and, more particularly, relates to apparatus and methods for cooling a treatment device used to deliver electromagnetic energy to a patient's tissue.
Energy delivery devices that can non-invasively treat tissue with electromagnetic energy 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. Such non-invasive energy delivery devices emit electromagnetic energy in different regions of the electromagnetic spectrum for tissue treatment.
High frequency treatment devices, such as radio-frequency (RF)-based devices, 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's epidermal layer. 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.
Typically, treatment devices include a treatment tip that is placed in contact with, or proximate to, the patient'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, 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.
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.
Although conventional apparatus and methods for delivering cryogen sprays have proved adequate for their intended purpose, what is needed are improved apparatus and methods for cooling superficial tissue in conjunction with non-invasive treatment of deeper tissue with electromagnetic energy.
In one embodiment, an apparatus is provided for treating tissue with electromagnetic energy. The apparatus comprises an energy delivery device configured to transfer the electromagnetic energy to the tissue. The energy delivery device includes a manifold body, a channel in the manifold body, an inlet to the channel, and an outlet from the channel. A closed-loop cooling system is coupled in a circulation loop with the inlet and the outlet of the channel. The closed-loop cooling system includes a pump configured to pump the fluid in the circulation loop to the inlet of the channel and through the channel to the outlet from the channel. A heat exchange member is disposed in the circulation loop between the pump and the inlet to the channel. The heat exchange member is configured to heat the fluid before the fluid enters the inlet of the channel.
In another embodiment, a method is provided for treating tissue with electromagnetic energy. The method comprises pumping the fluid at a first temperature from a reservoir to an energy delivery device and circulating the fluid at a second temperature through the energy delivery device. The fluid is heated at a location between the reservoir and the energy delivery device to the second temperature, which is greater than the first temperature. The method further comprises returning the fluid from the energy delivery device to the reservoir and delivering the electromagnetic energy from the energy delivery device to the tissue beneath the skin surface.
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.
With reference to
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'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.
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.
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.
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'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.
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'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.
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With reference to FIGS. 2 and 5-8, fluid connections are established with the inlet passage 70 and the outlet passages 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. The inlet passage 70 is coupled by a short conduit or tube 86 with an outlet 88 from a heat exchange member 90, which is physically located inside the handpiece 12 in the representative embodiment. An inlet 92 of heat exchange member 90 is coupled with a supply line 94 in the form of an inlet conduit or tube. The return line 84 and the supply lines 94 extend from the heat exchange member 90 out of the handpiece 12 and are routed to the console 16. The outlet 88 and inlet 92 of the heat exchange member 90, as well as the inlet passage 70 and the outlet passages 72, may include fittings (not shown) that facilitate the establishment of fluid-tight connections.
With reference to
Extending just inside the outer perimeter of the second plate 100 is an o-ring groove 108, which is occupied by a sealing member 110, such as an o-ring. When the first and second plates 96, 100 are secured together using the fasteners, the sealing member 110 is compressed by contact between the first and second plates 96, 100 to an extent sufficient to establish a liquid-tight seal for the channel 98. The first and second plates 96, 100 are formed from a material, such as aluminum, that has a relatively high thermal conductivity to promote efficient heat transfer from the heater 102 to the fluid flowing in the heat exchange member 90.
The heater 102, which is thermally coupled with the first plate 96, includes a substrate 112 of a dielectric material and heating element 114 in the form of a serpentine electrically resistive trace carried on the substrate 112. Opposite ends of the heating element 114 include solder pads 115a, 115b representing external connections that are electrically connected with wiring 117a, 117b leading from the handpiece 12 to a temperature controller 116 located in the console 16. The substrate 112 electrically isolates the heating element 114 from the first plate 96, but permits efficient heat transfer from the heating element 114 to the first plate 96. In one representative embodiment, the heating element 114 may include a flexible polyimide film that measures approximately 1 inch (approximately 2.5 centimeters) by approximately 2 inches (approximately 5.1 centimeters), has an operating voltage of 24 volts, and is adhesively bonded using a layer of a pressure sensitive adhesive to the exterior surface of the first plate 96.
Temperature controller 116 is electrically coupled by a cable 119 for bi-directional communication with system controller 18. The temperature controller 116 includes a power supply that powers the heating element 114. A temperature sensor 118 may be configured to measure the temperature of the coolant in the supply line 94 upstream from the heat exchange member 90. A temperature sensor 120 may be configured to measure the temperature of the coolant in the supply line 94 downstream from the heat exchanger. The temperature sensors 118, 120, which are electrically coupled with the temperature controller 116, are configured to communicate electrical output signals representative of the coolant temperature to the temperature controller 116.
In an alternative embodiment, the temperature sensors 118, 120 may be electrically coupled directly with the system controller 18. In another alternative embodiment, the temperature controller 116 may be consolidated into the system controller 18 to define a single integrated controller. In yet another alternative embodiment, fluid temperatures in the fluid reservoir 122 and in the treatment tip 14 may be utilized to provide the representative coolant temperatures used by the temperature controller 116 to control the heating of the fluid by the heating element 114.
The power delivered to the heating element 114 of heater 102 heats the plates 96, 100 of the heat exchange member 90. Heat energy is transferred from the plates 96, 100 to the coolant flowing in the channel 98, which elevates the output temperature of the coolant at the outlet 88 above its input temperature at the inlet 92. The power delivered to the heating element 114 can be modulated to modify the temperature change of the coolant while the coolant is resident in the channel 98 of the heat exchange member 90. The temperature controller 116 samples the signals from the temperature sensors 118, 120 and supplies output signals representing the temperature difference as feedback to the system controller 18. The system controller 18 determines a desired output temperature for the coolant and provides the output temperature to the temperature controller 116. Based upon the output temperature, the temperature controller 116 adjusts the power supplied to the heating element 114 and, therefore, the amount by which the coolant is heated while flowing through the heat exchange member 90.
The channel 98 has a serpentine path configuration in which the channel 98 includes serpentine convolutions between inlet 92 and outlet 88. Alternatively, the channel 98 can be configured in any non-parallel configuration effective to achieve a similar effect. Specifically, the serpentine path configuration of channel 98 optimizes the residence time of the fluid flowing inside the heat exchange member 90 and maximizes the heat transfer to permit higher fluid flow rates.
With reference to
Heat generated in the treatment tip 14 by energy delivery from the treatment electrode 22 and heat transferred from the patient'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 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's skin and the underlying depth of heated tissue. The cooling, at the least, assists in regulating the depth over which the tissue is heated to a therapeutic temperature by the delivered electromagnetic energy.
The coolant is chilled by a separate circulation loop 125 that pumps coolant from the reservoir 122 through separate supply and return lines to a coldplate 126. A pump 128, which may be a centrifugal pump, pumps the coolant under pressure from the reservoir 122 to the coldplate 126. In an alternative embodiment, the coldplate 126 may be placed directly in the return line 84 if permitted by the capacity of the coldplate 126 and flow constrictions.
In a representative embodiment, the coldplate 126 may be a liquid-to-air heat exchanger that includes a liquid heat sink with a channel (not shown) for circulating the coolant, a thermoelectric module (not shown), and an air heat sink (not shown). A cold side of the thermoelectric module in coldplate 126 is thermally coupled with the liquid heat sink and a hot side of the thermoelectric module in coldplate 126 is thermally coupled with the air heat sink. The cold side is cooled for extracting heat from the coolant 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 heat sink. The air heat sink of the liquid-to-air heat exchanger dissipates the heat extracted from the coolant circulating in the liquid heat sink to the surrounding environment. The air heat sink may be any conventional structure, such as a fin stack with a fan promoting convective cooling.
A temperature controller 130 inside the console 16 is electrically coupled with the coldplate 126 and is also electrically coupled with the system controller 18. The system controller 18, which is electrically coupled with a temperature sensor (not shown) used to measure the coolant temperature in the reservoir 122, supplies command signals to the temperature controller 130 in response to the measured coolant temperature. Under the feedback control, the temperature of the coolant in the reservoir 122 is regulated by controlling the operation of the coldplate 126.
In use and with reference to
The over-cooling is necessary as the coolant will inevitably warm as it passes through supply line 94 from the console 16 to the handpiece 12. This warming can be minimized by insulating the exterior of the supply line 94 to limit heat gain from the environment, but cannot be eliminated. Further complicating the problem, the amount of heat transferred to the coolant will vary based on the ambient room temperature and fluid flow rate. By cooling the coolant to a temperature lower than desired, then warming in the handpiece 12 just prior to delivery to the treatment tip 14, coolant can be delivered to the treatment tip 14 at the desired temperature at much greater accuracy than without this process.
The coolant is continuously pumped by pump 124 through the supply line 94 from the reservoir 122 to the handpiece 12. The system controller 18 relies on the upstream and downstream temperatures measured by the temperature sensors 118, 120 to regulate the power supplied to the heating element 114. Based upon the output signals from the temperature sensors 118, 120, the system controller 18 calculates a temperature differential of the coolant upstream and downstream of the heat exchange member 90. The system controller 18 communicates control signals to the temperature controller 116 based upon the temperature differential. The temperature controller 116 translates the control signals into a power level for the heating element 114 of heater 102, which powers the heating element 114 to heat the heat exchange member 90. The temperature of the coolant is elevated by heat transferred from the heat exchange member 90 to a desired temperature before delivery to the treatment tip 14. Because the heating is occurring locally in the handpiece 12 and based upon measured temperatures of the coolant in the handpiece 12, the coolant temperature can be accurately regulated.
The coolant, which is at the desired temperature, 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's skin surface in the contacting relationship with the contact side 32 of the substrate 28. Spent coolant is directed from the channel 66 into the return line 84 and returned to the reservoir 122.
The treatment electrode 22 is energized by generator 38 to deliver high frequency energy to the target tissue. The continuous stream of coolant flowing through the channel 66 in the manifold body 55 continuously cools the adjacent tissue contacted by the treatment electrode 22. The 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 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.
Using the same mechanism, the tissue is also cooled by the continuous stream of coolant 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.
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's general inventive concept.
