Patent Publication Number: US-2012046653-A1

Title: Pulsed therapeutic light system and method

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application claims benefit of U.S. Provisional Patent Application Ser. No. 61/157,862 filed Mar. 5, 2009, the contents of which is incorporated by a reference herein in its entirety. 
    
    
     BACKGROUND 
     Many light based dermatological treatments are performed currently with lasers or pulsed flashlamps/Intense Pulsed Light (IPL). Some professional grade devices used in dermatological treatments require peak power density between, e.g., 200 and 20,000 W/cm 2  delivered in pulse durations between, e.g., 0.5 and 50 ms. 
     Light emitting diodes (LED) are semiconductor light sources that are typically lower cost and more robust than lasers and IPLs. Their drawback is their relatively lower power density. The peak power specifications of some available state of the art LED devices (e.g. 130 W/cm 2 , reported in Journal of Display Technology 2007, Vol. 3, pages 160-175) approach the low end of the peak power density range for lasers or IPLs. Lower power LED devices are currently used for non-thermal dermatological treatments like photobiomodulation (McDaniel, U.S. Pat. No. 6,663,659). Photobiomodulation and similar low level light therapies are non-thermal modalities based on photo-biological processes that can be induced at normal tissue temperatures. Typical state of the art LEDs do not have enough power density to achieve effective thermal treatment modalities where at least a subset volume of the skin is at an elevated temperature above normal tissue temperature. Thus, there is currently a need in the art for high power LEDs suitable for dermatological treatments. 
     SUMMARY 
     In one aspect, a method is disclosed of delivering therapeutic light to a treatment region to effect heating in the treatment region. The method includes providing a light emitting diode and driving the light emitting diode to generate therapeutic light during a pulse period. The method further includes directing the therapeutic light to the treatment region at an average power density of about 200% W/cm 2  or more at the treatment region during the pulse period and maintaining the light emitting diode in a non-emitting state for a recovery period which is longer than the pulse period. 
     In some embodiments, the pulse period is about 50 ms, 10 ms, 1 ms, or less. In some embodiments, the duration of the recovery period is, at least 10 times, 50 times, or 100 times the duration of the pulse period. 
     In one embodiment, the method further includes, during the pulse period, repetitively cycling the light emitting diode between a light emitting state and a non emitting state to produce a series of sub-pulses of therapeutic light. In another embodiment, the step of repetitively cycling includes repetitively cycling the light emitting diode with a duty cycle of about 50% or less. In yet another embodiment, the sub-pulses have a duration of about 1 millisecond or less. 
     In some embodiments, the light emitting diode is characterized by a catastrophic, failure power level, and wherein, during the subpulses, the light emitting diode is operated at a power level equal to about 30%, 70%, 90%, or more of the catastrophic failure power level. 
     In some embodiments, the step of directing the therapeutic light to the treatment region at an average power density of about 200 W/cm̂2 or more at the treatment region during the pulse period comprises directing the therapeutic light to the treatment region at an average power density of about 500 W/cm̂2, 1,000 W/cm̂2, 5,000 W/cm̂2, 10,000 W/cm̂2, 20,000 W/cm̂2 or more at the treatment region during the pulse period. 
     In one embodiment, the method further includes dissipating heat generated by the light emitting diode using at least one heat sink in thermal communication with the light emitting diode. In another embodiment, the light includes infrared light. 
     In one embodiment, the method further includes effecting heating of the treatment region using the therapeutic light, and wherein the treatment region includes tissue, and wherein the heating results in a chemical or physical change to the tissue. In another embodiment, the chemical or physical change includes at least one selected from the list consisting of ablation, cauterization, inciting, shrinkage, lipolysis, and thermal damage, and wherein the tissue includes collagen, and the chemical or physical change includes heat induced collagen shrinkage. 
     In some embodiments, the treatment region is an external or an internal region of a human or animal subject. In another embodiment, the target region has a characteristic size of 1 cm or greater. 
     In another aspect, an apparatus is disclosed for delivering therapeutic light to a treatment region to effect heating in the treatment region. The apparatus includes a light emitting diode, a controller configured to drive the light emitting diode to generate therapeutic light during a pulse period and maintaining the light emitting diode in non-emitting state for a recovery period which is longer than the pulse period, and an optical delivery system configured to direct the therapeutic light to the treatment region at an average power density of about 200 W/cm 2  or more at the treatment region during the pulse period. 
     In some embodiments, the pulse period is about 50 ms, 10 ms, 1 ms, or less. In some other embodiments, the duration of the recovery period is at least 10, 50, or 100 times the duration of the pulse period. 
     In one embodiment, the controller is configured to drive the light emitting diode to, during the pulse period, repetitively cycle the light emitting diode between a light emitting state and a non-emitting state to produce a series of sub-pulses of therapeutic light. In another embodiment, the controller is configured to drive the light emitting diode to repetitively cycle the light emitting diode between the emitting and non-emitting states with a duty cycle of about 50% or less during the pulse period. 
     In one embodiment, the subpulses have a duration of about 1 millisecond or less. 
     In some embodiments, the light emitting diode is characterized by a catastrophic failure power level, and wherein, during the subpulses, the light emitting diode is operated at a power level equal to about 30%, 70%, 90% or more of the catastrophic failure power level. 
     In some embodiments, the optical delivery system directs the therapeutic light to the treatment region at an average power density of about 500 W/cm̂2, 1,000 W/cm̂2, 5,000 W/cm̂2, 10,000 W/cm̂2, 20,000 W/cm̂2 or more at the treatment region during the pulse period. 
     In one embodiment, the apparatus further includes at least one heat sink in thermal communication with the light emitting diode for dissipating heat generated by the light emitting diode. In another embodiment, the therapeutic light includes infrared light. 
     In one embodiment, the optical delivery system includes a fiber optic configured to receive therapeutic light from the light emitting diode at a proximal end and transmit the light to a distill end to illuminate the treatment region. 
     In one embodiment, the apparatus includes a surgical handpiece which is configured for insertion into a human or animal subject to deliver therapeutic light to an internal region. 
     In another embodiment, the apparatus includes a handpiece for delivering therapeutic light to external region of a human or animal subject. In yet mother embodiment, the target region has a characteristic size of 1 cm or greater. 
     In another aspect, an apparatus is disclosed for delivering therapeutic light to a treatment region to effect heating in the treatment region. The apparatus includes a plurality of light emitting diodes, a controller configured to drive each respective light emitting diode to generate therapeutic light during a respective pulse period and maintaining each respective light emitting diode in a non-emitting state for a respective recovery period which is longer than the pulse period, and at least one optical delivery system configured to direct therapeutic light from the light emitting (nodes to the treatment region at an average power density of about 200 W/cm 2  at the treatment region during a treatment period. 
     In one embodiment, the respective pulse periods of the respective light emitting diodes are staggered relative to each other during the treatment period. In another embodiment, at least one of the plurality of diodes in its respective pulse period during substantially the entire treatment period. 
     In one embodiment, the duration of the respective pulse period of each light emitting diode is 50 ms or less. 
     In another embodiment, the duration of the respective pulse period of each light emitting diode is about 10 times the duration of the recovery period or more. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-3  show therapeutic light delivery systems. 
         FIG. 4  is a schematic of a pulsed LED therapeutic light source. 
         FIG. 5  illustrates a pulse scheme for a pulsed LED therapeutic light source. 
         FIG. 6  illustrates an array of pulsed LED therapeutic light sources 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to the figures, systems and methods for delivering therapeutic light to a treatment region using light emitting diodes (LEDs) is shown. The LEDs may be driven in a pulsed mode to provide power that is above the normal continuous operating level for the LEDs. The LEDs may be turned on at the increased operating level for a short period of time (e.g., from 0.5 to 50 ms), followed by a longer period of time (e.g., hundreds of milliseconds) between pulses, allowing the accumulated heat from the on time to dissipate. This allows for the LED source to be used a suitable light source for a light based dermatological treatments in place of lasers and IPLs. The therapeutic light may heat the treatment region such that the heating results in a chemical or physical change to the tissue in the treatment region (e.g., an ablation, cauterization, melting, shrinkage, lipolysis, thermal damage, or another chemical or physical change). The tissue may include collagen, and the chemical or physical changes may include collagen shrinkage. The heating may include raising the tissue above its normal temperature e.g. by 5 degrees C. or more, by 10 degrees C. or more, etc. 
     Referring to  FIG. 1 , an apparatus  100  for delivering therapeutic light to a treatment region is shown, according to an exemplary embodiment. Apparatus  100  includes source  102 , controller  104 , and handpiece  106 . Source  102  may be a power source for providing power to an LED of handpiece  106  and may be connected to handpiece  106  via optical fiber  110 . 
     Handpiece  106  may include one or more LEDs for providing a light source for providing therapeutic light (e.g., infrared light) for a treatment region  108  (e.g., an external region or internal region of a human or animal subject) for heating treatment region  108 . Handpiece  106  may be operated by a user of apparatus  100  for providing treatment region  108  with therapeutic light from handpiece  106 . According to various exemplary embodiments, handpiece  106  may be of any shape, size, or configuration for providing therapeutic; light from the LEDs. Handpiece  106  may be configured to provide therapeutic light for a target region of a specific size (e.g., 1 cm or greater, according to an exemplary embodiment). According to an exemplary embodiment, handpiece  106  may be similar to the handpiece disclosed in PCT Publications WO 2008/007218 and WO 2008/153999, the entire contents of each of which is incorporated by reference herein in its entirety. 
     Controller  104  may be configured to control the amount of light emitted by the LED and the time intervals for which light is emitted b′ the LED. For example, controller may control the voltage or current applied to drive the LED to emit light. Controller  104  may include instructions for keeping the LED of handpiece  106  in a light emitting state for a specific time frame (e.g., for 50 ms, 10 ms, 1 ms, etc.), then keeping the LED in a non-emitting state for a recovery period (e.g., a time frame ten times the duration of the time the LED was emitting light, a time frame fifty or one hundred times the duration of the time the LED was emitting light, a time frame longer than the duration of the time the LED was emitting light, etc.). 
     Controller  104  may be configured to control the therapeutic light provided to treatment region  108 . For example, the therapeutic light may be provided at an average power density of about 100 W/cm 2  200 W/cm 2  or more at treatment region  108 . According to various exemplary embodiment, the therapeutic light may be provided at an average power density of about 500 W/cm 2 , 1,000 W/cm 2 , 5,000 W/cm 2 , 10,000 W/cm 2 , or 20,000 W/cm 2  or in the range of 200-20,000 is W/cm 2 . Apparatus  100  including the LED may serve a an optical delivery system configured to direct the therapeutic light to treatment region  108  at an average power density specified by controller  104 . In one embodiment, handpiece  106  includes a fiber optic configured to receive therapeutic light from the LED at a proximal end and to transmit the light to a distal end for illuminating treatment region  108 . 
     Controller  104  may receive data from handpiece  106  via link  112  regarding LED usage. Data may include sensor data from a sensor within handpiece  106 , data from the accelerometer of handpiece  106 , or from another source. For example, controller  104  may receive data indicating that the LED has been emitting light for too long and is at risk of failure, and controller  104  may send instructions to the LED to turn off as a result. As another example, the accelerometer of handpiece  106  may provide data relating to the position or velocity of handpiece  106 . Controller  104  may receive the data and may determine to change the state of the LED of handpiece  106  to a reduced power or non-emitting state if, for example, if the accelerometer indicates handpiece  105  has been stationary for a given period, of time emitting therapeutic light in a specific area (indicating a risk of overexposure of the subject to emitted light). 
     Referring to  FIG. 2 , the apparatus  100  for deliver mg therapeutic light to a treatment region is shown, according to another exemplary embodiment. In the embodiment of  FIG. 2 , apparatus  100  includes handpiece  106  providing therapeutic light to an internal treatment region  108 . Handpiece  106  may include a surgical probe (e.g. a cannula) which may be inserted into a patient, e.g., through incision  224  in a skin surface  220 . Optical fiber  112  may extent through the handpiece to a distal end of the probe to transmit therapeutic light to the treatment region. 
     Referring now to  FIG. 3 , an apparatus  300  for providing therapeutic light to a treatment region is shown, according to yet another exemplary embodiment. Apparatus  300  includes flashlight or handpiece  302  shown in greater detail. Flashlight  302  includes an LED source  304  providing as light source through lens  306  to treatment region  310 . LED source  304  may include one or more LEDs configured to provide a therapeutic light source to treatment region  310 . 
     Lens  306  may be used to reflect the therapeutic light provided by LED source  304  for treatment region  310  such that the light directly (or indirectly, if desired) hits the surface of region  310 . According to various exemplary embodiments, other optical elements (e.g. reflective elements, refractive elements, collimating elements, concentrating elements, diffusing elements, diffractive elements etc.) in addition to or in place of lens  306  may be used. The optical element may be used to direct therapeutic light to the treatment region with any desired patter, e.g. in a two dimensional pattern having regions of relatively high intensity and regions of relatively low intensity (e.g. as described in U.S. patent application Ser. No. 11.1347672 fled Feb. 3, 2006, the entire contents of which are incorporated by reference herein. 
     Treatment region  310  may include an area  312  below the surface of region  310 . It may be desired for apparatus  300  to provide therapeutic light for area  312  below the surface of region  310 , and the intensity and/or pattern of the light provided by apparatus  300  may be adjusted such that area  312  receives more therapeutic light. For example, lens  306  may be adjusted, the power provided to LED source  304  may be increased, or otherwise. 
     According to an exemplary embodiment, apparatus  300  or a portion of apparatus  300  may be configured to be inserted in treatment region  310  and area  312  such that an internal region (e.g., area  312 ) may receive the therapeutic light. 
     According to various exemplary embodiments, apparatus  300  may further include a controller or power source as described in  FIGS. 1-2  such that a power supply for apparatus  300  or a configuration for how to provide therapeutic light may be provided within apparatus  300  instead of receiving power from an outside source or a configuration from an outside controller. As in the previously described embodiments, apparatus  300  may include one or more sensors (temperature sensors, inertial sensors, etc) which can provide information to controller, which, in turn can control the application of therapeutic light based on the information. 
     Referring to  FIG. 4 , a light source  400  for providing therapeutic light is shown in greater detail, according to an exemplary embodiment. Light source  400  includes an LED  402 , a support substrate  404 , and a heat sink  406 . LED  402  may be an LED for providing therapeutic light as described in the present disclosure. LED  402  is shown emitting therapeutic light  410 . 
     As indicated by the broad arrows, support substrate  404  may be used to accumulate the heat  412  generated by LED  402 , and heat sink  406  may be used to dissipate, the heat in substrate  404 . According to another exemplary embodiment, light source  400  may include multiple heat sinks instead of a single heat sink. According to various exemplary embodiments, other techniques may be used to provide a dissipation of heat generated by LED  402 . For example, fluid circulated through heat sink  406  may be used to help dissipate the heat. In other embodiments, an active element such as Peltier cooler may be used, etc. 
     Retelling now to  FIG. 5 , graphs illustrating a pulse period for an LED is shown, according to an exemplary embodiment. Graph  500  illustrates a short pulse period  502  where the LED is in a light emitting state followed by a longer recovery period  504  under which the LED is in a non-emitting state. According to an exemplary embodiment, pulse period  502  may be 50 ms or less, 10 ms or less, 1 ms or less, or another time frame, and the duration of recovery period  504  may be ten times longer than the duration of pulse period  502 , fifty times longer than the duration of pulse period  502 , one hundred times longer than the duration of pulse period  502 , or another time frame. The length of pulse period  502  and period  504  may be determined or adjusted based on how long the LED requires to recover between pulses to avoid deleterious effects. 
     Referring further to graph  500 , a continuous operation power level  506  and a catastrophic failure power level  508  are illustrated. Continuous power level  506  represents the power level of the LED for operation in a conventional continuously emitting mode. As shown, during pulse period  502 , the LED is pulsed to power levels above the continuous operation power level, to provide increased emission of light. During recovery period  504 , the LED is shut off (or, alternatively, operated in a reduced power state), and allowed to recover from being “overdriven” during the pulse period. During the period, heat is dissipated from the LED, to avoid overheating which would lead to failure or degradation in performance of the LED. 
     Catastrophic failure power level  508  may indicate a maximum power level above which the LED will fail. According to various exemplary embodiments, the LED may be configured to operate at a power level that is equal to about 30% or more of the catastrophic failure power level, equal to about 50% or more of the catastrophic failure power level, equal to about 70% or more of the catastrophic failure power level, equal to about 90% or more of the catastrophic failure power level, or equal to another power level intermediate between levels  506  and  508 , or otherwise. 
     Referring further to  FIG. 5 , pulse period  502  may further be broken down into sub-periods such that the LED may be operated in a “burst mode” where the LED is on for very short periods of time (e.g., 0.05 to 0.1 ms) alternating with periods (e.g. an equally long periods) off time for a total burst pulse duration of between, for example, 0.5 and 50 ms. For example, also referring to graph  520 , during pulse period  502 , the LED may be repetitively cycled between a light emitting state and a non-emitting state to produce a series of sub-pukes  522  of therapeutic light. The repetitive cycling may include, cycling the LED with a duty cycle of 50%, according to an exemplary embodiment. According to other exemplary embodiments, the duty cycle may be of any other value (e.g. 10%, 25%, 75% etc.) and the sub-pulses may be of varying length (e.g., each sub-pulse may be 1 ms or less). Burst mode operation may further reduce the stress on the LED while operating in at “overdriven” power levels greater than level  506 . 
     Referring now to  FIG. 6 , a block diagram of an array of light sources (e.g., multiple individual LEDs of the type described herein, etc) are shown, according to an exemplary embodiment. A device  600  may include multiple light sources  602 ,  604 ,  606 ,  608 . According to various exemplary embodiments, device  600  may include any number of light sources and may include any number of rows or other configurations of light sources. For example, device  600  may be of any shape, may include less than four light sources, six light sources, eight light sources, or more, and may arrange the light sources in any configuration (e.g., all in a row, in a matrix form, circular form, or otherwise). Sources  602 ,  604 ,  606 ,  608  may be configured to be driven by a single controller for maintaining a pulse period and a non-emitting state for each light source, according to exemplary embodiments. 
     In the embodiment of  FIG. 6 , device  600  may be configured to provide therapeutic light from only one or some of the light sources  602 ,  604 ,  606 ,  608  at any given time. For example, device  600  may only provide therapeutic light from one light source at a time. Light may be provided by source  602  for a short period of time before entering a non-emitting state. Once source  602  shuts down for a cool down period, source  604  may begin providing therapeutic belt until source  604  must enter a non-emitting state. Source  606  and source  608  may then provide therapeutic light in a similar matter, and once source  608  shuts down for its non-emitting state, source  602  may be ready to provide therapeutic light again, therefore providing a cycle such that one light source may be providing therapeutic light at any given time. 
     According to various exemplary embodiments, only one light source at a time may provide therapeutic light in device  600 . According to another exemplary embodiment, more than one light source may provide therapeutic light in device  600 . According to yet another exemplary embodiment, one light source may provide therapeutic light some of the time, and none of the light sources may provide therapeutic light for another period of time. For example, in the embodiment of  FIG. 6 , if each sources  602 ,  604 ,  606 ,  608  require a down time that is ten times longer than the time frame in which each source provides light, device  600  may only provide therapeutic light for 40% of the time, while the other 60% of the time is spent with each of four sources  602 ,  604 ,  606 ,  608  in down time. 
     As will be understood by one skilled in the art, light sources of the type described herein may be used to provide therapeutic light for any suitable application. For example, dermatological treatments that may be administered using the systems and methods of the present disclosure may include, for example, facial rejuvenation, pigmented lesions, vascular lesions, acne and other dermatological applications for which a laser or IPL has been found to be effective. In one embodiment, the LED based device of the present disclosure could be used like a laser or IPL by a highly skilled practitioner, e.g. in a limited number of sessions a few weeks apart. In addition, a method of treatment with a LED based device with a lower peak power is suitable for a home use application with daily treatments for extended periods of time (e.g., weeks or months). For such method of treatment the accumulation of the effect from the multiple treatments may compensate for the lower peak power used in the individual treatment. 
     While this invention has been particular shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 
     One or more of any part thereof of the systems and methods of providing therapeutic light may be implemented in computer hardware or software, or a combination of both. The methods may be implemented in computer programs using standard programming techniques following the systems and methods described herein. Program code is applied to input data to perform the functions described herein and generate output information. The output information is applied to one or more output devices such as a display monitor. Each program may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any ease, the language can be a compiled or interpreted language. Moreover, the program can run on dedicated integrated circuits preprogrammed for that purpose. 
     Each such computer program is preferably stored on a storage medium or device (e.g., ROM or magnetic diskette) readable by a general or special purpose programmable computer, for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. The computer program can also reside in cache or main memory during; program execution. Any analysis method can also be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein.