Patent Publication Number: US-2011060322-A1

Title: Apparatus and method for surface cooling

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from U.S. Provisional Patent Application Ser. No. 61/040,053 filed Mar. 27, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to cooling of a surface region, such as a biological tissue surface, and in particular to method and apparatus which can facilitate such cooling. 
     BACKGROUND INFORMATION 
     There is an increasing demand for repair of skin defects that can be induced by aging, sun exposure, dermatological diseases, heredity, traumatic effects, and the like. For example, some treatment techniques use electromagnetic radiation to generate thermal and/or damage to the skin, which can result in a wound healing response that leads to a biological repair of the damaged skin or other desirable effects. Electromagnetic radiation provided, e.g., by a laser, an intense pulsed light source (“IPL”), a flashlamp, or the like can also be used for hair removal. 
     Application of an electromagnetic radiation to treat skin tissue may often be accompanied by undesirable side effects, including a sensation of pain in the patient being treated. A reduction of pain sensation can be achieved, e.g., by cooling the region of skin tissue being treated before and/or during the treatment. Cooling of skin tissue can also increase the ratio of ablation depth to a thermal affected zone diameter during a laser ablative procedure. For example, a cooled tissue can facilitate targeting of deeper tissue with an ablative laser while reducing thermal damage in adjacent regions along the surface thereof. 
     Techniques for cooling skin tissue can be based on various physical mechanisms. For example, conductive cooling can be achieved by contacting a cold object with the surface of the skin tissue. However, conductive cooling can obstruct electromagnetic radiation being directed to the skin tissue. To avoid this problem, the cold object can be formed of a material which does not significantly absorb or reflect the particular electromagnetic radiation being provided. It is noted that this requirement can limit the choice of materials which can be used to cool the skin surface, and such materials may not have sufficient thermal capacity to provide effective cooling. Accordingly, conductive cooling may be performed on a target region of skin tissue prior to treatment of the tissue with electromagnetic radiation, and may not be suitable for cooling skin tissue during such treatment. 
     Convective cooling can also be used cool a target region of skin tissue by directing a fluid (e.g., a gas) over the target region. Motion of the fluid relative to the tissue surface increases the effective heat transfer coefficient between the tissue and the fluid to enhance the rate of skin tissue cooling. The fluid may optionally be cooled to provide increased cooling. Such flowing fluid may facilitate the electromagnetic radiation to pass therethrough relatively unimpeded, such that convective cooling can be used effectively during treatment of the skin tissue. Systems configured to provide convective cooling may require large cooling arrangements to cool the continuously flowing gas, and thus may be bulky and/or inefficient to operate. 
     Convective cooling may be accompanied by evaporative cooling, where the evaporation of a liquid on the surface being cooled is enhanced by the moving fluid (e.g., gas). Release of the enthalpy of vaporization when the surface liquid evaporates can provide further cooling of the surface. Such liquid may be naturally present, e.g. sweat or perspiration, and/or it may be applied to the surface being cooled. Other liquids, such as alcohols, which tend to evaporate quickly, may be applied to the surface being cooled to increase the rate of cooling. The use of evaporative cooling can be limited by the ability to provide and/or maintain an evaporating liquid on the surface being cooled. 
     Another conventional technique which may be used to cool skin tissue uses a cryospray, which is a cold vapor that is directed to the surface to be cooled. Conventional cryosprays include a cryogenic substance in a liquid form that is maintained under pressure in a container. The cryogenic substance may be present in a gaseous state under normal (e.g., atmospheric) pressure. When the cryogenic substance is controllably released from the container, such as through a valve or nozzle, it converts to a vapor and expands under the lower pressure outside the container, and may cool significantly by operation of the Joule-Thompson effect. Such cryosprays can provide a cold stream of vapor that can be directed to the surface to be cooled. Because the expanded vapor can be very cold, cryospray techniques may be used to generate a series of short bursts of the cold vapor to cool an object. However, it is difficult to maintain a moderate and continuous degree of cooling using cryosprays. For example, portions of skin tissue may freeze when exposed to a cold cryospray for too long of a time. 
     The electromagnetic radiation can be directed onto skin tissue using, e.g., certain types of lasers, to cause ablation of tissue. Ablation generally removes a portion of the tissue exposed to the electromagnetic radiation by vaporization and/or evaporation of tissue components. The laser ablation process can form a plume containing debris from the removed tissue. An object placed over a target area of tissue being ablated, e.g., a conductive cooling mass, may prevent some or all of the plume from being released from the tissue that is treated. This can lead to a dangerous buildup of debris and heat in the target region. 
     The plume formed during tissue ablation can also produce undesirable effects. For example, the plume may interfere with a beam of the electromagnetic radiation provided by the laser, causing partial reflection, absorption, and/or diffusion of the applied beam. The debris itself may also present a health hazard. For example, ablated debris may contain infectious material (e.g., a virus or bacteria), and allowing such debris to enter the environment may be harmful. 
     Accordingly, there may be a need to address and/or overcome at least some of the deficiencies or issues described herein above. 
     SUMMARY OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the present disclosure provide an apparatus for cooling a surface, such as, e.g., a target region of skin tissue, by facilitating a flow of gas over the surface. This cooling can be performed, e.g., during treatment of the tissue by an exposure to an electromagnetic radiation, such as optical energy from a laser or an IPL. Such cooling can reduce the perception of pain during the treatment of the skin tissue. The exemplary embodiment of the apparatus can further provide containment and removal of debris which can be generated from the tissue during treatment, such as a plume formed by exposing tissue to an ablative laser. 
     According to one exemplary embodiments of the present disclosure, a cooling apparatus can be provided that can include a housing with an opening on a lower portion thereof that is configured to enclose a volume over the target region of tissue. In certain exemplary embodiments, the housing can includes one or more windows that facilitates an electromagnetic radiation to pass therethrough with substantially no interaction with the window, and/or that allow or facilitate for a visual observation of the target region from outside the housing. In other exemplary embodiments, the housing can be formed partially or entirely of a material which allows visual observation of the target region and/or transmission of the electromagnetic radiation therethrough. The exemplary apparatus can include one or more inlet arrangements (e.g., ducts) connected to the housing that are configured to facilitate a gas to enter the volume enclosed by the housing, and one or more outlet arrangements (e.g., ducts) that facilitate the gas to be removed from the volume. 
     In still other exemplary embodiments of the present disclosure, the housing can include a hole or an opening on an upper surface thereof that facilitates or allows energy, e.g., a laser radiation, to enter therethrough. For example, an opening may be provided in a portion of the housing that is configured to allow or facilitate a portion of an optical guide or outlet aperture of a laser to be attached thereto. Such exemplary configuration can allow or facilitate the energy to be directed onto the surface without passing through the housing material. In certain exemplary embodiments, a source of directed energy, e.g., a laser aperture or optical waveguide, can be directly coupled to the housing or configured to pass through a portion of the housing, e.g., forming a substantially airtight seal with the housing. The source of directed energy can be movably attached to the housing, such that the energy can be directed to various locations on the surface without moving the housing. 
     A portion of the exemplary housing can also be formed of a material that allows or facilitates an observation of the target region and of an energy-tissue interaction during treatment. The exemplary housing can also be formed using a material can further reduce or eliminate emission of harmful radiation from beneath the housing (e.g., back-reflected radiation from a CO 2  laser). 
     In certain further exemplary embodiments, the apparatus can include a source of low pressure or vacuum configured to pull a gas in from the one or more inlets and out from the volume enclosed by the housing through the outlet duct, e.g., creating a flow of the gas over the surface of the target region. The low pressure source can include a pump arrangement, an evacuated vessel or container, or the like. Such flow can cool the tissue surface by convective and/or evaporative cooling. A filter can also be provided in the outlet duct to remove debris contained in the gas being removed from the volume, such as material in a plume generated by an ablative laser interacting with tissue in the target region. 
     In still further exemplary embodiments, a cooling arrangement can be provided to cool gas entering the volume enclosed by the housing through the inlet duct. A filter may also be provided in the inlet duct to remove contaminants or particulates in the gas before it enters the volume and flows over the target region. In certain exemplary embodiments of the present disclosure, the gas removed from the enclosed volume by the low pressure source can be directed to the cooling arrangement to increase the cooling efficiency thereof. 
     In still further exemplary embodiments, a valve can be provided in the inlet duct to control the flow of the gas through the inlet duct and into the volume enclosed by the housing, and to optionally provide a pulsed flow of the gas over the target region. Such pulsed flow can provide enhanced cooling and/or a reduction of pain sensation. A valve arrangement can also be provided at the outlet duct to control flow of gases exiting the enclosure. 
     The exemplary cooling apparatus can further include a spray nozzle coupled to the housing, and configured to direct a spray or stream of liquid onto the target region being cooled. Evaporation of such liquid by the gas flowing over the target region can provide an enhanced cooling by evaporation. The liquid can include water, an alcohol, an analgesic such as lidocaine, a bactericide or other biologically active substance, or any combination thereof. The spray nozzle, valve arrangements, and/or low pressure source can be controlled to provide alternating pulses of sprayed liquid and flowing gas to increase the effectiveness of the evaporative cooling. In certain exemplary embodiments, the gas flow within the enclosed volume and the liquid spray can each be continuous, e.g., while energy is being applied to the tissue. 
     In another exemplary embodiment of the present disclosure, a method can be provided using which a surface which includes providing a housing to enclose a volume over at least a portion of the surface can be cooled, and a gas out of the enclosed volume between the housing and the surface can be drawn out or removed through one or more outlet ducts to generate a flow of the gas over the surface. One or more inlet ducts can be provided in the housing to allow or facilitate further gas to enter the space enclosed by the housing and allow or facilitate the flow to be maintained for a desired period of time. 
     In further exemplary embodiments of the present disclosure, the flow can be pulsated to create a vibration in the surface being cooled, which can further reduce a sensation of pain if the surface is associated with a biological tissue such as skin. The pulsated flow can be provided by controlling a pump used to draw gas from the enclosed volume, and/or by controlling one or more valves provided in the inlet and/or outlet ducts. 
     In still further exemplary embodiments, at least a portion of the gas can be cooled before entering the enclosed volume to provide additional cooling of the surface. 
     In yet further exemplary embodiments, the surface being cooled can be sprayed with a liquid, and evaporation of the liquid from the surface can provide additional cooling. Such evaporation may be enhanced by the flow of gas over the surface. The sprayed liquid can include water, alcohol, any other liquid which can be evaporated using the gas flow, or a mixture thereof. 
     These and other objects, features and advantages of the present disclosure will become apparent upon reading the following detailed description of embodiments of the invention, when taken in conjunction with the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further objects, features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments, results and/or features of the exemplary embodiments of the present disclosure, in which: 
         FIG. 1  is a schematic diagram of a cooling apparatus in accordance with exemplary embodiments of the present disclosure; 
         FIG. 2  is a schematic diagram of a cooling apparatus in accordance with further exemplary embodiments of the present disclosure; 
         FIG. 3  is a plan view of several exemplary shapes that can be used for an apparatus housing in accordance with exemplary embodiments of the present disclosure; and 
         FIG. 4  is a schematic diagram of a cooling apparatus in accordance with still further exemplary embodiments of the present disclosure. 
     
    
    
     Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the present disclosure will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments and is not limited by the particular embodiments illustrated in the figures. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the present disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An exemplary embodiment of an apparatus  100  which may be used to cool a surface such as skin tissue is shown in  FIG. 1 . The exemplary apparatus  100  can include a housing  105  which is provided with at least one inlet duct  107  and at least one outlet duct  108 . The housing  105  may include a window  110 , which allows or facilitates an observation of a target area  115  of skin tissue  120  to be treated. The window  110  can also allow or facilitate an electromagnetic radiation  125  provided from an energy source  130  to pass therethrough and interact with the target area  115 . A low-pressure source  135  may be provided in communication with the outlet duct  108 . An optional cooling arrangement that can include, e.g., an enclosure  140  and a cooling device  145 , can be connected to the inlet duct  107 . An optional outlet filter  150  may be provided in the outlet duct  108 , and an optional inlet filter  155  may be provided in the inlet duct  107 . 
     The housing  105  of the exemplary apparatus  100  can be configured to be placed over the target region  115  of skin tissue  120  (or other tissue) to be treated, thereby enclosing a volume above the target region  115 . A lower portion of the housing  105  can be configured to contact the surface of the skin tissue  120  surrounding the target region  115 , such that a seal may be formed between the housing  105  and the tissue surface  120 . A resilient material or gel can be provided on the lower portion of the housing  105  to improve contact between the housing  105  and the surface of the skin tissue  120  surrounding the target region  115 . Such resilient material or gel, and/or one or more rollers or other low-friction arrangements can also be provided on the lower portion of the housing to facilitate translation of the housing  105  over the surface of the tissue  120 . In further exemplary embodiments, an ink or other visible substance can be provided along at least a portion of the lower portion of the housing  105 . Such ink can assist in placement of the housing  105  relative to the target area  115 , and can also indicate which areas of the tissue  120  have been treated if the housing  105  is moved over the surface of the tissue  120 . 
     The housing  105  can be provided in any one of a variety of shapes. For example, when viewed in plan, the housing  105  can have a shape that is approximately square, rectangular, oval or ovoid, etc. The housing  105  can include sidewalls which extend from an upper surface of the housing  105  downward to the surface of the skin tissue  120 . Alternatively, the housing  105  can have a contour of a shallow dome that may be round or oval as viewed in plan, or any other configuration that may be selected to cover the target region  115 . The housing  105  can be sized and shaped such that it is large enough to surround an entire area of the tissue  120  to be treated with energy or electro-magnetic radiation. Alternatively, the housing  105  can be relatively small in size and configured to be moved over the surface of the tissue  120  to treat a plurality of areas of the tissue  120 . Top or plan views of several exemplary housing shapes are shown in  FIG. 3 . 
     The housing  105  can have a low profile such that a dimension of the housing  105  along the surface is greater than a dimension thereof, e.g., perpendicular to the surface. This exemplary low profile can facilitate a maintenance of a flow of gas (indicated by arrow  160 ) that is substantially parallel to the surface of the target area  115 . Such exemplary low profile can also facilitate an increase of a velocity of gas over the surface of the tissue  120  for a particular volumetric flow rate of the gas through the inlet duct  107  and/or outlet duct  108 . A higher gas velocity can provide higher rates of cooling and/or evaporation from the tissue surface  120 . 
     The window  110  can be provided in the upper surface of the housing  105  to allow or facilitate the electromagnetic radiation  125  from the energy source  130  to pass therethrough and interact with at least a portion of the skin tissue  120  located in the target region  115 . The window  110  can be formed of or include a material which does not significantly interact or interfere with the electromagnetic radiation  125 , and allows or facilitates such radiation  125  to pass therethrough with substantially no or little absorption or reflection. The window  110  can alternatively or additionally be configured to allow or facilitate visual observation of the target region  115  from above the housing  115 . A plurality of such windows  110  may also be provided in the housing  115 . In certain exemplary embodiments, the entire housing  105  or a substantial portion of the upper surface thereof, may be formed of a material which allows or facilitates a visual observation of the target region  115  and/or substantially unimpeded passage of the electromagnetic radiation  125  therethrough. 
     The inlet duct  107  and the outlet duct  108  are preferably located apart from each other, e.g., at opposed portions of the housing  105 . Such spaced-apart placement of the inlet and outlet ducts  107 ,  108  can facilitate a flow of gas between the inlet duct  107  and the outlet duct  108  that passes over the target region  115 . In certain exemplary embodiments, the housing  105  can be provided with a plurality of inlet ducts  107  and/or a plurality of outlet ducts  108 . 
     The low-pressure source  135 , such as, e.g., a vacuum source, can be connected to the outlet duct  108 . The low-pressure source  135  can include, for example, a pump arrangement, such as a positive displacement pump or a vacuum pump, or any other device which can provide a source of low pressure capable of withdrawing gas from the volume enclosed by the housing  105 . The flow or vacuum capacity of the low-pressure source  135  can be selected based on the size and configuration of the housing  135 , the size and configuration of the inlet duct  107  and the outlet duct  108 , the desired flow velocity over the target region  115  of the tissue  120 , etc. 
     The low-pressure source  135  may be configured to remove gases and any entrained substances (e.g., debris from a plume) from the volume enclosed by the housing  105  through the outlet duct  108 . For example, as gases are removed from this enclosed volume by the low-pressure source  135 , additional gases can be pulled into the enclosed volume through inlet duct  107 . In this manner, a flow of gas (indicated by the arrow  160  in  FIG. 1 ) can be generated or induced over the target region  115 . This flow of gas  160  can provide convective and/or evaporative cooling to the target region  115 . Such cooling can be maintained while the target region  115  is exposed to electromagnetic radiation  125  from energy source  130 . 
     Exemplary embodiments of the present disclosure described herein can provide certain benefits as compared to conventional cooling systems that blow or otherwise direct a flow of air or other gas over the tissue being treated. For example, using the low-pressure source  135  to pull gas from the volume enclosed by the housing  105  can help maintain contact between the housing  105  and the surface of the skin tissue  120 . Such exemplary arrangement and/or configuration also can contain debris and/or other by-products formed when the tissue  120  is exposed to the electromagnetic energy  125 , and allow them to be removed through the outlet duct  108  rather than being released into the surrounding environment. 
     Exemplary embodiments of the present disclosure may also allow or facilitate a more precise control of the flow velocity and geometry over the target region  115  through a suitable choice of the shape of the housing  105 , size and placement of the inlet and outlet ducts  107 ,  108 , control of the low-pressure source  135 , etc. 
     The opening of the inlet duct  107  can be relatively small in size, such that gas flowing through the inlet duct  107  expands when it enters the volume enclosed by the housing  105 . Such expansion can cool the gas as it enters the enclosed volume, which may further enhance the cooling of the target region  115  as the cooled gas flows over the target region  115 . 
     The low-pressure source  135  can be a pumping arrangement that includes controller circuitry for turning the low-pressure source  135  on and off. The controller circuitry can also control the rate at which gases are extracted from the enclosed volume within the housing  115  (e.g., by varying the speed of the pump). The low-pressure source  135  may also generate a slight vacuum in the volume between the housing  105  and the target region  115 . This lower pressure can pull the surface of the target region  115  upward into the volume enclosed by the housing  105 , which can stretch the tissue  120  slightly. Such stretching can be beneficial when exposing the target region  115  to the electromagnetic energy  125 , for example, by increasing the rigidity of the tissue and/or by promoting closure of any holes or incisions formed in the stretched tissue after the tissue  120  is allowed to relax. 
     The energy source  130  can include an intense pulsed light source, a laser, or any other energy source which can direct energy to the target region  115  to produce an interaction with a portion of the skin tissue  120 . The energy source  130  can be an ablative laser, such as a CO 2  laser or an Er:YAG laser, which can ablate a portion of the tissue in the target region  115  and create a plume of debris. This debris and any other substances present in the volume enclosed by the housing  105  can be withdrawn through the outlet duct  108  by the low-pressure source  135  as described herein. 
     In further exemplary embodiments, the outlet filter  150  can be provided in communication with the outlet duct  108  to remove debris from the gases flowing into the outlet duct  108 . Any conventional filter configuration may be used that is suitable for trapping and/or removing the debris from the flowing gas. For example, the outlet filter  150  may include a cartridge containing a fibrous or microporous medium, such that the cartridge can be periodically replaced as it becomes saturated with debris. The outlet filter  150  can be provided in the outlet duct  108  between the housing  105  and the low-pressure source  135  as shown in  FIG. 1 , or alternatively it may be provided at an outlet of the low-pressure source  135 . A plurality of outlet filters  150  may also be provided. 
     The inlet filter  160  can be provided in the inlet duct  107  to remove particles or contaminants from gas entering the volume beneath the housing  105  and flowing over the target region  115 . The inlet filter  155  can be similar in structure to the outlet filter  150 , or it may have a different configuration. A plurality of inlet filters  155  can also be provided. 
     To enhance the convective cooling of the target region  115 , the cooling arrangement can be connected to the inlet duct  107 . For example, the cooling arrangement can include the enclosure  140  and the cooling device  145  that is configured to lower the temperature of the gas contained within and/or flowing through the cooling enclosure  140 . The cooling device  145  can include, for example, one or more Peltier elements, one or more conduits containing a flowing coolant that are provided in contact with the cooling enclosure  140 , a cooled bath surrounding a portion of the cooling enclosure  140 , a phase-change medium, and the like. For example, the phase-change medium can be ice, dry ice, or the like. The cooling device  145  can include, for example, a cold object formed of a material having a large thermal mass. 
     The cooling enclosure  140  may have at least one small dimension (e.g., it can have the form of a narrow tube or flat channel) to improve contact between the cooling device  145  and the gas within the cooling enclosure  140 , and thereby more effectively lower the temperature of the gas. The cooling device  145  can further include control circuitry and a temperature sensor provided, e.g., in the inlet duct  107  or adjacent to the enclosure  105  to facilitate a more precise control of the temperature of the gas flowing through the inlet duct  107  and over the target region  115 . 
     A further exemplary embodiment of a cooling apparatus  200  in accordance with the present disclosure in shown in  FIG. 2 . Similar to the exemplary cooling apparatus  100  shown in  FIG. 1 , the apparatus  200  can include the housing  105  with the inlet duct  107  and the outlet duct  108  attached thereto, the window  110 , the low-pressure source  135 , the inlet filter  155 , and the outlet filter  150 . The exemplary cooling apparatus  200  can also include a heat exchange arrangement  210 , which can include an inner duct  220 , an outer duct  230 , and a chilling arrangement  240 . The exemplary cooling apparatus  200  can also be provided with a spray nozzle  250  attached to the housing  105 , and an optional inlet valve  260  provided in communication with the inlet duct  107 . 
     The operation of the exemplary cooling apparatus  200  is similar to that described above for the exemplary cooling apparatus  100  shown in  FIG. 1 . The low-pressure source  135  may be configured to pull gas through the outlet duct  108  from the volume enclosed by the housing  115 . Further gas can be pulled into this volume through the inlet duct  107 , creating a gas flow  160  that cools the target region  115 . 
     In this exemplary embodiment, the inlet duct  107  can be connected to the inner duct  220  of the heat exchange arrangement  210 . The inner duct  220  can have the form of, for example, one or more tubes or conduits having any of a variety of cross-sectional shapes, e.g., round, rectangular, oval, or the like. The chilling arrangement  240  can be provided in contact with the inner duct  220  to cool gas passing therethrough. The chilling arrangement  240  can include, for example, one or more Peltier elements having the cooling side thereof in contact with and/or forming a portion of the wall of the inner duct  220 , or any other suitable heat exchange device configured to cool the inner duct  220 . Gas which is cooled by the chilling arrangement  240  can be pulled through the inlet duct  107  by the low-pressure source  135  to create the flow  160  of the cooled gas that flows over the target region  115 . 
     In certain exemplary embodiments, an outer duct  230  can be provided in the heat exchange arrangement  210  that is connected to the outlet duct  108  and the low-pressure source  135 . For example, the low-pressure source  135  can be situated between the outlet duct  108  and the outer duct  230  as shown in  FIG. 2 . Other configurations may be used, e.g., the outer duct  230  may be provided between the outlet duct  108  and the low-pressure source  135 . The outer duct  230  can surround at least a portion of the chilling arrangement  240  and/or a portion of the inner duct  220  as shown in  FIG. 2 . For example, the outer duct  230  can have the form of a tube or other passageway that surrounds both the inner duct  220  and the chilling element  240 . 
     Gas pulled through the outlet duct  108  by low-pressure source  135  can flow through the outer duct  230  and over an outer surface or a portion of the chilling arrangement  240 , which can enhance the cooling efficiency of the chilling arrangement  240 . For example, if the chilling arrangement includes a Peltier element, gas flowing over the hot side of the Peltier element through outer duct  230  can facilitate a removal of the heat extracted from the inner duct  220  by the cold side of the Peltier element. The gas flowing through the outer duct  230  may still be slightly cooled after flowing through the housing  105 , which can further increase the cooling efficiency of the heat exchange arrangement  210 . 
     The exemplary cooling apparatus  200  can also include the spray nozzle  250  coupled to the housing  105 . The spray nozzle  250  can be configured to controllably direct a spray of liquid towards the target area  115 . The gas flow  160  can increase the evaporation rate of the liquid on the surface of the target area  115 , and thereby provide enhanced surface cooling by evaporation. The spray of liquid may be continuous, periodic, or pulsed. For example, the spray nozzle  250  can be vacuum-activated, such that a spray of liquid is produced while the low-pressure arrangement  135  produces a flow  160  of gas within the volume enclosed by the housing  105 . 
     The liquid provided by or through the spray nozzle  250  can be water, alcohol, or any other liquid or combination of liquids that will evaporate when exposed to the gas flow  160  to provide enhanced cooling. This liquid can also include other substances which may provide a beneficial effect to the target area before, during, and/or after treatment by exposure to electromagnetic radiation. Such substances can include analgesics (e.g., a lidocaine solution), antibiotics, or other biologically active agents. 
     The exemplary cooling apparatus  200  can also include the inlet valve  260  provided in the inlet duct  107 . The inlet valve  260  can be configured to controllably start, stop, and/or regulate the flow of gas into the volume contained below the housing  105 . For example, the inlet valve  260  can be an electronically-actuated gate valve, a rotating wheel having cut-outs that alternately open and block the flow of gas through the inlet duct  107 , or other valve mechanisms. A rotating wheel which includes regions having different densities of openings or passages therethrough can also be provided, which can generate a smooth variation of pressure changes and flow beneath the housing  105  as the wheel rotates and partially obstructs the inlet duct  107 . 
     Control circuitry for the inlet valve  260  can operate the inlet valve  260  so as to obtain different pulse frequencies and flow patterns in order to achieve a desired flow response (such as, e.g., to match a resonant frequency of the tissue surface in the target region  115 ). Further, circuitry may be provided to adjust other parameters associated with the apparatus in order to achieve desired flow characteristics. Such exemplary parameters can include, for example, the valve diameter, the distance of flow over the target region  115  (e.g., based on the length of the housing  105  and/or the size of an opening provided on a lower surface of the housing  105 ), etc. For example, vibration of the tissue surface induced by flow can provide further analgesia in accordance with gate control theory, where additional sensation associated with the vibration “occupies” local nerve endings and reduces their ability to detect and transmit pain signals. 
     An optional vibration detector can also be provided to detect vibration of the skin surface in the target region  115 . The vibration detector can include, e.g., a lateral diode laser or other light source together with one or more photodiode detectors which are configured to measure the vibration elevation and frequency of the skin surface. The exemplary vibration detector can be coupled to a controller in a feedback configuration which can control the operation of the inlet valve  260 , the low-pressure source  135 , and/or other components of the exemplary cooling apparatus  200  to achieve and/or maintain a desired vibration of the tissue in the target region  115 . 
     The inlet valve  260  can be controlled to allow or facilitate the pulses of gas to flow over the target region  115 , e.g., in-between pulses of electromagnetic energy which may be applied to the target region  115 . The inlet valve  260  can also be provided in communication with the spray nozzle  250 , such that a brief spray of liquid onto the target area  115  is followed by a pulse of gas flowing over the target region  115  to provide an intermittent evaporative cooling. The timing and duration of the liquid spray and gas pulses can be selected to provide a desired cooling of the target region  115 . 
     The inlet valve  260  can also be operated in a continuous pulsed mode such that it allows or facilitate a continuous stream of gas pulses to be pulled through the inlet duct  107  by the low-pressure source  135  and flow through the housing  115 . This can be achieved, for example, by rapidly cycling the inlet valve  260  between open and closed states, while the low-pressure source  135  is operating. The duration of the open and closed states, and the frequency of switching between the states, can be selected to achieve a desired pulsed flow of gas over the target region  115 . For example, the pulse duration can be selected as the length of the cooled portion of the inner duct  220  divided by the flow velocity when the valve is opened. This exemplary procedure can provide a series of pulses, where the gas in each pulse is obtained substantially from the cooled portion of the inner duct  220 . Other criteria may be used to determine the valve operation parameters based on resultant cooling and flow behaviors for particular treatments. 
     The gas entering the inlet duct  107  from the cooling enclosure  140  or the inner duct  220  of the heat exchange arrangement  210  can be, for example, air that is pulled in from the environment surrounding the exemplary cooling apparati  100 ,  200 . Alternatively, such gas can be provided from a controlled source, such as a gas canister. A controlled gas source can allow or facilitate treatment of the target region  115  to be performed under a specified environment. For example, a low-oxygen or oxygen-free gas mixture, a gas containing predetermined amounts of beneficial substances, or any other desired gas composition can be provided. 
     A further exemplary embodiment of a cooling apparatus  400  in accordance with the present disclosure in shown in  FIG. 4 . Similar to the exemplary cooling apparati  100 ,  200  shown in  FIGS. 1 and 2 , respectively, the exemplary apparatus  400  can include the housing  105  with the inlet duct  107  and the outlet duct  108  attached thereto, and the window  110 . 
     A distal portion of the energy source  130 , e.g., an end of a waveguide or a casing enclosing such waveguide, the aperture of the laser or the IPL, a portion of an energy delivery handpiece or the like, can be mechanically coupled to the housing  105  of the exemplary cooling apparatus  400 . This coupling can be rigid, or it can allow or facilitate an angular movement of the energy source  130  relative to the housing to enable the electromagnetic energy  125  to be directed towards various portions of the target region  115 . For example, if the distal portion of the energy source  130  is rigidly coupled to the housing  105 , the electromagnetic energy  125  can be directed towards various portions of the target region  115  by translating the entire housing  105  relative to the target region  115 . Alternatively, conventional optical components or the like associated with the energy source  130  can be used to alter the direction of the electromagnetic energy  125  being emitted from the distal portion of the energy source  130 . 
     The low-pressure source  410  that may be used with the exemplary cooling apparatus  400  (or with other exemplary embodiments of the present disclosure) can be, for example, a container or reservoir enclosing a gas under vacuum or low pressure, e.g., an evacuated container or the like. The low-pressure source  410  may be provided in communication with the outlet duct  108 . A valve  420  can be provided between the outlet duct  108  and the low-pressure source  410 . Withdrawal of gas through the outlet duct  108  from the volume enclosed by the housing  105 , and thus flow of the gas over the target region  115  of the tissue  120 , can be controlled or regulated, e.g., by operation of the valve  420 . For example, debris or effluent that may be produced within the enclosed volume of the housing  105  can be withdrawn through the outlet duct  108  and into the low-pressure source  410 . After use, the low-pressure source  410  may optionally be discarded or cleaned and re-used. 
     In a further aspect, exemplary embodiments of the present disclosure can provide a method for cooling a surface which includes providing a housing to cover a portion of the surface and at least partially enclose a volume between the housing and a surface region to be cooled. A gas can be drawn through the enclosed volume to generate a flow of the gas over the surface region. This flow may provide convective cooling of the surface region. 
     The gas can be withdrawn from the enclosed volume through one or more outlet ducts connected to the housing, and further gas can enter the enclosed volume through one or more inlet ducts connected to the housing. The gas can be air, air mixed with one or more additional components (such as a further gas or a vaporized substance), and/or it can be any other gas which may be provided through the inlet ducts. 
     In further embodiments of the exemplary cooling method, at least a portion of the gas provided to the inlet duct can be cooled before it enters the enclosed volume. Such cooling of the gas can increase the degree and/or efficiency of cooling of the surface. 
     In still further exemplary embodiments of the cooling method, the surface being cooled can be sprayed with a liquid. Evaporation of the liquid from the surface, which may be enhanced by the flow of gas, can provide additional cooling. A variety of liquids can be used including, e.g., water, alcohol, another liquid which can be evaporated using the gas flow, or a mixture thereof. The liquid spray can be continuous, intermittent, or of a finite duration. 
     The foregoing merely illustrates the principles of the invention. Various modifications and combinations of the described embodiments and/or elements thereof will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous techniques which, although not explicitly described herein, embody the principles of the invention and are thus within the spirit and scope of the invention.