Patent Application
20100298744
The present disclosure relates to systems and methods for treating tissue with ultrasound energy.
Various devices and methods exist for generating high-intensity, focused shock waves using high intensity focused ultrasound. Most of the devices are experimental and only available in scientific laboratories. Methods employing high-intensity, focused shock waves are generally employed for ultrasonic induction of thermal lesions in cancerous tumors. Those methods involve prolonged sonication times to induce lesions in tissue. Such sonication times range from several seconds to several minutes or even dozens of minutes. In tumor treatment the area of treatment via sonication is generally small relative to the size of a patient's body.
Employing currently available focused ultrasound technology in a less invasive manner and over a relatively large area of a subject's body would take a great deal of time with currently available sonication methods such as are employed in cancerous tumor treatment.
Disclosed herein are method(s) and device(s) capable of generating a small lesion as deep as a few millimeters beneath the skin's surface and covering several cubic millimeters in volume in orders of magnitude less time, for example, in tens of milliseconds. More specifically, in one exemplary embodiment, a method of treating tissue (e.g., skin) is provided which includes generating one or more ultrasound pulses with each pulse having a pulse width shorter than a thermal relaxation time of a tissue treatment volume, and applying one or more of said ultrasound pulses to at least one portion of the tissue treatment volume to generate one or more tissue treatment areas in a region. Methods of treating tissue can include effecting a therapeutic treatment in said region of the tissue, and/or effecting a cosmetic treatment in said target region.
Various ranges of pulse widths are provided herein. For example, the pulses can have a pulse width in a range of about 1 ms to about 70 ms, about 10 ms to about 50 ms, about 10 ms to about 40 ms, about 10 ms to about 30 ms, about 10 ms to about 20 ms, about 5 ms to about 10 ms, etc.
The pulses can also have any of a plurality of frequency ranges. For example, said pulses can have an ultrasound frequency in a range of about 0.7 MHz to about 20 MHz, 3.5 MHz to about 12 MHz, in a range of about 5 MHz to about 12 MHz, in a range of about 3 MHz to about 12 MHz, and/or in a range of about 20 kHz to about 700 kHz, etc.
The method can utilize various embodiments of a transducer configured to provide the desired ultrasound energy to the target tissue. For example, the method can include utilizing at least one transducer having a numerical aperture in a range of about 0.8 to about 1.1 to generate said one or more pulses such that each pulse exhibits a power density in a range of about 800 W/cm2 to about 5000 W/cm2, about 500 W/cm2 to about 5,000 W/cm2, and/or about 40 W/cm2 to about 800 W/cm2 at a focal area in the target region. For example, the method can include utilizing at least one transducer to generate said one or more pulses such that each pulse exhibits an energy density in a range of about 2.5 J/cm2 to about 25 J/cm2, and/or about 4 J/cm2 to about 80 J/cm2 at a focal area in the target region.
The method can also include targeting tissue at various locations and/or targeting various volumes and/or areas of tissue. For example, said target tissue region can be located at a depth in a range of about zero to about 6 mm below the tissue surface. Also, the target tissue region can have a volume in various ranges, for example, a volume in a range of about 1×10−4 mm3 to about 30 mm3.
The method can also include selecting various energy and/or treatment parameters so as to target the desired location. For example, the method can include selecting the ultrasound frequency of the pulses so as to cause damage and/or provide treatment in a tissue region extending from the tissue surface to a depth of about 6 mm below the tissue surface. The method can also include selecting the ultrasound frequency of the pulses so as to cause thermal action in the dermis layer of the tissue. The method can also include selecting the ultrasound frequency of the pulses so as to cause damage in a fatty region of the tissue. For example, this ultrasound frequency can be selected so as to be within a range of about 3 MHz to about 5 MHz, or about 3 MHz to about 12 MHz.
The method can also include focusing said ultrasound pulses into said target region. For example, the step of focusing the pulses can include focusing the pulses into a focal volume having a size in a range of about 0.0001 mm3 to about 30 mm3.
The step of applying ultrasound pulses to the tissue can include applying one or more pulses to each of a plurality of discrete tissue portions in said target region to generate a plurality of treated tissue portions separated from one another by untreated portions of said target region. For example, the treated portions can generate a plurality of separated coagulation lines within the target region. In another example, the treated portions can provide a pattern of separated treatment areas within the target region. Any of said treatment areas can be separated from a neighboring treatment area by any desired distance. For example, the distance between treatment areas can be in a range of about 1 mm to about 5 mm along at least one dimension.
The method can also include applying a substance to the tissue surface so as to enhance coupling of the ultrasound pulses into the tissue. For example, in one embodiment the substance is a gel.
In another aspect of the present disclosure, a method of applying ultrasound energy to the tissue is provided which includes applying at least one diagnostic ultrasound pulse to a tissue treatment volume within a target region, and detecting an echo generated in response to said diagnostic ultrasound pulse. The method can also include analyzing said echo to determine whether it is safe to apply ultrasound capable of generating treatment areas to said tissue treatment volume, and applying one or more ultrasound pulses each having a pulse duration shorter than the thermal relaxation time of the tissue treatment volume to the tissue treatment volume to cause one or more treatment areas therein. In one embodiment, the treatment areas effect a cosmetic treatment in the tissue target region. In another embodiment, the treatment areas effect a therapeutic treatment in the tissue target region.
The diagnostic pulse can be generated so as to have a frequency in any of a number of desired frequency ranges. For example, the frequency can be in a range of about 5 to about 15 MHz. Also, any of a variety of transducers can be configured to provide the desired energy delivery. For example, said diagnostic pulse can be generated by a transducer having a numerical aperture in a range of about 5 mm to about 20 mm. Also, the diagnostic pulse can be generated so as to exhibit any range of desired power density. For example, the power density can be in a range of about 0.1 to about 0.8 W/cm2 at the tissue surface.
The method can also include a step or steps of analyzing said echo to determine the presence or absence of ultrasound obstacles along the propagation path of the diagnostic ultrasound pulse. For example, the method can include analyzing said echo to determine whether bone is present along the propagation path of the diagnostic ultrasound pulse, and/or analyzing said echo to determine whether sufficient coupling exists between the ultrasound pulse and the tissue.
In another embodiment, a method of treating tissue is provided which includes generating one of more ultrasound pulses each having a pulse width of less than about 95 ms. The method also includes applying one of more of said ultrasound pulses to at least one portion of a tissue target region to generate one or more treatment areas in said target region.
In another aspect, a method for applying ultrasound energy to tissue is provided which includes scanning an ultrasound transducer over a tissue surface (e.g., skin) to apply ultrasound energy to the tissue surface, and controlling the transducer so as to deliver the ultrasound energy to a plurality of tissue locations at a substantially uniform depth below the tissue surface. In one embodiment, the step of controlling the transducer includes causing said transducer to apply a substantially constant pressure to said tissue surface as the transducer delivers the ultrasound energy to said tissue locations. The step of controlling the distance can include maintaining a reference location of the transducer at a substantially constant distance relative to the tissue surface as the transducer delivers the ultrasound energy to said tissue locations. The step of scanning the transducer can also include activating the transducer to apply the ultrasound energy to selected locations of the tissue.
In one embodiment, the step of controlling the distance further includes causing the transducer to apply a substantially constant compressive pressure to the tissue surface while the transducer is delivering the ultrasound energy to each of said tissue locations. The method can also include the step of controlling the transducer to remove it from contact with the tissue surface upon termination of delivery of the ultrasound energy to at least one of said tissue locations. The method can include removing the compressive pressure upon termination of delivery of the ultrasound energy to at least one of the tissue locations. In one embodiment, the method can further include the step of raising the transducer relative to the tissue surface upon termination of delivery of the ultrasound energy to at least one of said tissue locations thereby facilitating the movement of the transducer from one treatment site to the next site. Also, the step of controlling the distance can further include causing the transducer to apply a substantially constant compressive pressure to the tissue surface while the transducer is delivering the ultrasound to said locations and raising the transducer a constant amount relative to the tissue surface while the transducer is moving over the tissue surface (e.g., from a one treatment site to another treatment site).
The method can also include the use of a transducer which is activated to apply one or more pulses of ultrasound energy to each of said tissue locations. Like above, various ranges of pulse width are provided. For example, said pulses can include a pulse width in a range of about 1 ms to about 70 ms, in a range of about 5 ms to about 20 ms, in a range of about 10 ms to about 50 ms, in a range of about 10 ms to about 40 ms, in a range of about 10 ms to about 30 ms, in a range of about 10 ms to about 20 ms, in a range of about 5 ms to about 10 ms, in a range of about 5 ms to about 70 ms, etc. Additionally, the method can utilize pulses having various ranges of frequency. For example, said pulse can have a frequency in a range of about 3.5 MHz to about 12 MHz, in a range of about 5 MHz to about 12 MHz, etc.
In yet another aspect, various embodiments of a device for applying ultrasound energy to tissue are provided. In one such embodiment, the device includes a transducer for generating ultrasound energy for application to the tissue. The device can also include a scanner coupled to the transducer for moving the transducer along three dimensions over tissue (e.g., skin) wherein the scanner can include a controller for controlling position of said transducer along a dimension substantially perpendicular to the tissue surface so as to deliver energy to a substantially uniform depth below the tissue surface at a plurality of tissue locations.
The controller can be configured to provide various ranges of motion. For example, the controller can be configured to cause said transducer to apply a substantially constant compressive force to the tissue as the transducer applies ultrasound energy to the tissue. The controller can also include a linear travel mechanism coupled to the transducer and configured to apply a substantially constant force to the transducer in a direction toward the tissue.
The linear travel mechanism can be configured in various manners so as to provide the desired application of force. For example, the linear travel mechanism can include a spring configured to effect application of said force. The linear travel mechanism can also include a pneumatic cylinder adapted to effect application of said force. The linear travel mechanism can also include a solenoid configured to effect application of said force.
In one embodiment, the controller can include a sensor for providing one or more signals indicative of a distance between a reference surface of the transducer and the tissue surface (e.g., skin surface). Various sensors can be utilized. For example, the sensor can be a force sensor, an optical sensor, or an electrical sensor (e.g., capacitance, e-field, inductive, resistive, etc.). The controller can also include a servo system in communication with said sensor wherein the servo system is configured to maintain a distance between said reference surface and the tissue surface at a predetermined value during said at least a portion of the scan based on signals provided by the sensor.
In yet another aspect, various embodiments of a device for applying ultrasound energy to tissue (e.g., a tissue surface, skin) are provided which include a transducer for generating ultrasound energy, and a scanner coupled to the transducer for moving the transducer relative to a reference position, the scanner can move in determined distances relative to the reference position, along at least two dimensions so as to deliver the ultrasound energy to selected locations of the tissue. For example, the scanner can use a reference position to move with known or determined distances relative to those reference positions. The reference position can be, for example, a coordinate relative to the device itself, or a feature (e.g., a spot or wrinkle) on the patient's body. That is, the scanner can be configured to track the transducer relative to its own coordinates or the skin.
In one embodiment, the scanner is configured to control movement of the transducer so as to deliver said ultrasound energy to each of said locations of the tissue a pre-defined number of times during a scan. The scanner can also be configured to control movement of the transducer so as to deliver said ultrasound energy to each of said locations once during a scan. In one embodiment, the scanner can be configured to track said transducer relative to one or more reference locations for controlling delivery of the ultrasound energy to said tissue locations.
In one embodiment, at least two dimensions are substantially parallel to the tissue surface and the scanner is configured to move the transducer along another dimension substantially perpendicular to the tissue surface. The scanner can also be configured to control movement of the transducer along the dimension perpendicular to the tissue surface such that the transducer delivers the ultrasound energy to said locations at a substantially uniform depth below the tissue surface.
In one embodiment, the device can further include a frame to which the transducer is coupled. The frame can be configured for contact with the tissue surface (e.g., skin) at one end thereof, wherein the end includes an opening through which the ultrasound energy generated by the transducer can be applied to the tissue. The frame can also be configured for immobilizing a portion of the tissue facing said opening of the frame when said end of the frame is in contact with the tissue. For example, the frame can be configured to stretch a portion of the tissue facing said opening of the frame when said end of the frame is in contact with the tissue.
In one embodiment, a method of treating tissue is provided which includes determining from an external surface of a skin a location of cellulite, and applying at least one diagnostic technique to a skin portion within the location of cellulite to determine a location of a connective strand. The method also includes applying one or more ultrasound pulses to the connective tissue strand, the one or more pulses having a pulse duration shorter than a thermal relaxation time of a target region treatment volume. As detailed below, a projection of connective tissue strand causes the appearance of cellulite.
Various diagnostic techniques are within the spirit and scope of the present disclosure. For example, the diagnostic technique can be diagnostic ultrasound, palpation, etc.
In yet another embodiment, a device is provided for applying ultrasound energy to tissue. The device includes a phased array of transducers for generating ultrasound energy, a controller coupled to the array wherein the controller is configured to target selected locations of a tissue treatment volume with ultrasound energy, and also configured so as to apply one or more ultrasound pulses each having a pulse width shorter than a thermal relaxation time of a tissue treatment volume.
In one aspect, a method for treating tissue includes applying to a region of tissue (e.g., in the volume of tissue) one or more heating acoustic pulses with a frequency of from about 0.7 MHz to about 20 MHz and with a power density and an energy density sufficient to raise the temperature in the region of tissue by at least about 5° C. The method for treating tissue also includes applying to the region of tissue one or more cavitation acoustic pulse with a frequency range of from about 20 kHz to about 700 kHz with a power density and an energy density sufficient to induce cavitation in the region of tissue (e.g., in the volume of tissue). In one embodiment, the one or more heating acoustic pulse has a frequency, a power density and an energy density sufficient to raise the temperature in the region of tissue from about 5° C. to about 35° C. The heating acoustic pulse can have a power density of from about 500 W/cm2 to about 5,000 W/cm2 and have an energy density of from about 2.5 J/cm2 to about 25 J/cm2. The cavitation acoustic pulse can have a power density of from about 40 W/cm2 to about 800 W/cm2 and have an energy density of from about 4 J/cm2 to about 80 J/cm2. Optionally, the cavitation acoustic pulse can be applied only after the heating acoustic pulse, in this way the region of tissue is heated by the heating acoustic pulse prior to treatment with the cavitation acoustic pulse. In another embodiment, the cavitation acoustic pulse is partially overlapped with the heating acoustic pulse and the delay between the cavitation acoustic pulse and the heating acoustic pulse ranges between about 1% and about 90% of the duration of the heating acoustic pulse.
In another aspect, a device for applying ultrasound energy to tissue includes an ultrasound transducer for generating ultrasound energy for application to tissue and a mechanism for dispensing at least one acoustic coupling medium between the ultrasound transducer and a tissue portion to provide a substantially constant acoustic coupling of the ultrasound energy into said tissue portion during treatment. In some embodiments, the mechanism is configured to continuously replenish the coupling medium during treatment. In other embodiments, the coupling medium is selected such that the speed of sound through the coupling medium is substantially the same as the speed of sound through the tissue. The ultrasound transducer can be disposed within a housing having a distal tip, the tip being sized and configured to dispense a desired amount of said at least one coupling medium onto a surface of said tissue portion (e.g., the surface of the skin). The at least one acoustic coupling medium can be a first coupling medium disposed within the housing. The device can include a reservoir containing a second coupling medium, the reservoir being in communication with the tip to transfer the second coupling medium to the tip to be dispensed onto said surface of the tissue portion.
The first coupling medium and the second coupling medium can be the same coupling medium. The first coupling medium can be a substance with an acoustic impedance substantially similar to an acoustic impedance of water. The first coupling medium can have a viscosity of up to about 500,000 cPs.
In some embodiments, the device further includes a drive mechanism in communication with the reservoir, the drive mechanism configured to drive a desired amount of the second coupling medium from the reservoir to the tissue surface. The drive mechanism may be, for example, a piston. Optionally, the drive mechanism and a viscosity of the second coupling medium are configured to dispense a desired amount of the second coupling medium at a desired rate so as to provide a thin film of the second coupling medium between the tissue surface and tip. In one embodiment, the thin film has a viscosity in a range of about 80,000 cPs to about 100,000 cPs. The thin film can: reduce friction between the tip and the tissue surface, provide cooling of the tissue surface, include an additive configured to provide an indication of prior treatment (e.g., the additive can be configured to change color if subjected to a predetermined amount of ultrasound energy). In one embodiment, the mechanism for dispensing at least one acoustic coupling medium is configured to dispense the coupling medium so as to substantially eliminate imperfections in the acoustic coupling medium during treatment.
In another aspect, a device includes a handheld housing, a source for generating ultrasound energy for application to tissue through a distal end of the housing, a reservoir for containing an acoustic coupling medium, the reservoir having an opening in proximity of the distal tip for dispensing the acoustic coupling medium onto a surface of the tissue to facilitate coupling of the ultrasound energy into the tissue portion. The device also includes a drive mechanism coupled to the reservoir for driving the acoustic coupling medium from the reservoir onto said tissue surface. In some embodiments, the drive mechanism and a viscosity of the acoustic medium are configured to provide a thin film of the acoustic medium onto the tissue surface as the housing is moved over the surface to apply ultrasound energy to said tissue.
In another aspect, a method of applying ultrasound energy to tissue includes providing a device having an ultrasound energy emitter and a reservoir for containing an acoustic coupling medium, the reservoir having an opening for dispensing said medium onto a tissue surface. The method includes moving the device over a tissue surface while dispensing the coupling medium from the reservoir so as to form a thin film of the coupling medium on the tissue surface and activating the emitter to apply ultrasound energy to the tissue surface having said film of the coupling medium. The film of the coupling medium facilitates coupling of the ultrasound energy onto the tissue. In one embodiment, the film has a substantially uniform thickness thereby to provide a substantially constant coupling between the ultrasound energy and different portions of the tissue. In another embodiment, the steps of dispensing the coupling medium and applying the ultrasound energy are performed substantially concurrently.
The present disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure.
Methods, devices, and systems for applying ultrasound energy to tissue, e.g., skin tissue, are disclosed. In some cases, the ultrasound energy can be applied as a plurality of ultrasound pulses to selected tissue locations, e.g., skin tissue at a depth below the skin surface. In some embodiments, the pulse widths are selected to be less than about 70 milliseconds (ms), e.g., in a range of about 0.1 ms to about 70 ms, and/or in a range of about 5 ms to about 50 ms. Further, in some embodiments in which the ultrasound energy is applied to the tissue surface (e.g., to skin tissue), one or more transducers generating the ultrasound energy can be controlled so as to deliver the energy to a substantially uniform depth below the tissue surface (e.g., skin surface). In some cases, the ultrasound energy can be applied via a disclosed device while the device is scanned over the skin surface. To facilitate the scanning of the device over the skin, a suitable substance, e.g., a gel can be dispensed onto the tissue surface, e.g., in a substantially continuous manner and/or at a substantially consistent thickness on the tissue surface. In one embodiment, the gel is dispensed onto the tissue surface from a container attached to the device. The supply of gel onto the tissue surface can lower the friction between at least a portion of the device (e.g., the device tip) and the tissue surface (e.g., the skin). In addition, employing such a gel substance on the surface of the tissue being treated can facilitate the delivery of the ultrasound energy to the tissue by providing acoustic impedance matching.
If the target site is in need of treatment, the method and system can determine the desired treatment (e.g., the desired treatment regimen). As detailed below, the desired treatment regimen can include dose, duration, etc. Prior to initiating treatment, the system and method can be configured to determine if it is safe and/or efficient to deliver energy to the target site. For example, the method can trigger an echo transducer configured to detect the presence or absence of bone, the effectiveness of coupling of the transducer to the tissue (whether the coupling is good or poor), etc. The method can also activate a z-position control mechanism configured to position the head of the energy emitter at a known z-position relative to the target site thereby allowing a known amount of energy to be delivered to a known depth below a tissue surface. Once the transducer is properly positioned, the emitter can be activated and the desired treatment performed. The transducer can then be moved to the next target site for further treatment.
With reference to the step of the determining treatment in the flowchart of
τr=d2/4α
where:
d is characteristic dimension of the area, and
α is the thermal diffusivity (for water-rich tissue such as dermis, α≈1.5*10−3 cm2/s).
In one embodiment, if target dimension of the area d≈z 0.2 mm, then the thermal relaxation time is ˜70 ms. Using relatively short pulses as disclosed herein enables one or more of (1) confinement of the thermal energy within the intended treatment zone, (2) sharp demarcation of the boundaries of the thermal action zone, and (3) treatment with short pitch and high density of the thermal action zones.
In an exemplary embodiment, each pulse has a pulse width in a range of about 1 ms to about 70 ms, and the pulses are applied to at least one portion of a tissue target region to generate one or more treatment volumes in said region. By way of example, in some cases, the pulse widths can be in a range of about 10 ms to about 40 ms, or in a range of about 10 ms to about 30 ms, or in a range of about 10 ms to about 20 ms, or in a range of about 5 ms to about 10 ms, or in a range of about 0.1 ms to about 5 ms. As taught herein, the application of such short ultrasound pulses at proper power densities, such as those disclosed below, can effect a desired cosmetic and/or therapeutic treatment in the tissue while minimizing, and preferably eliminating, discomfort experienced by a subject during application of the pulses. The term “treatment” is used herein to encompass both a cosmetic and a therapeutic treatment. Examples of a cosmetic treatment can include, without limitation, skin rejuvenation (e.g., improving skin color, skin tightening, treatment of rhytides, treatment of wrinkles, etc.) and reduction and/or elimination of cellulite appearance. Examples of a therapeutic treatment can include, without limitation, treatment of tissue in order to illicit a response by which immunity is bolstered or strengthened. While not being bound to any single theory it is believed that therapeutic treatment can be achieved according to the disclosed methods, because treatment of the tissue with the ultrasound energy creates injury and/or stress to the treated tissue, which promotes inflammation and adaptive immunity that is capable of resisting and/or fighting threats to health. In addition, therapeutic treatments can result from an increase in blood supply to the treated area.
In some embodiments, the ultrasound pulses have a frequency in a range of about 3 MHz to about 12 MHz or in a range of about 5 MHz to about 10 MHz or a frequency of about 7 MHz. The frequency of the pulses can be selected based on any of a number of variable factors including, the desired cosmetic and/or therapeutic treatment, the location(s) of the tissue to be treated (e.g., the depth of the skin tissue below the skin surface, whether downtime associated with tissue treatment is desirably minimized and/or avoided), the type of tissue to be treated, among other factors. For example, ultrasound pulses with a frequency in a range of about 3 MHz to about 5 MHz can be employed for treating fatty tissue (e.g., by causing intentional regions of thermal damage in the tissue). Generally, for a set length treatment time (t), the higher the frequency the shallower the depth of penetration in the z direction into the tissue relative to a lower frequency, which results in a deeper depth of penetration in the z direction into the tissue in the same treatment time (t). For example, attenuation of ultrasound in tissue at 12 MHz is from about 5 to about 9 times higher than attenuation at 3 MHz depending on the nature of the tissue (e.g., if the tissue is muscle or fat, attenuation in skin being the largest, then muscle and fat).
In many embodiments, the ultrasound pulses are focused onto the tissue, e.g., into a focal volume having a volumetric size in a range of about 0.0001 mm3 to about 30 mm3, to provide a desired power density. By way of example, the power density of the applied pulses can be in a range of about 800 W/cm2 to about 5000 W/cm2 at the focal area, or a range of from about 1200 W/cm2 to about 2000 W/cm2. In some cases, the pulses are focused onto the tissue with a numerical aperture in a range of about 0.05 to about 0.9, in a range of about 0.5 to about 1.1, in a range of about 0.8 to about 1.1, or about 1.0 (e.g., an aperture of 1.0 in use with 5 MHz).
In the above ultrasound method, the ultrasound energy, e.g., in the form of a plurality of ultrasound pulses, can be applied to a variety of tissue types. In some embodiments, the ultrasound energy is applied to the skin to treat skin tissue, e.g., tissue at a depth in a range of zero to about 6 mm, or from about 2 mm to about 5 mm below the tissue surface (e.g., the skin surface). In some embodiments, the ultrasound energy (e.g., ultrasound pulses) can be applied to each of a plurality of discrete tissue portions in a target tissue region to generate a plurality of treated tissue portions separated from one another by untreated portions of the target region. By way of example, a treatment portion can be separated from a neighboring treatment portion by a distance in a range of about 1 mm to about 5 mm, or from about 2 mm to about 4 mm, or about 3 mm. In some cases, the treated portion provides a pattern of separated treatment regions within a tissue target region. By way of example, the treated portions can generate a plurality of separated coagulation lines within a target region (a region requiring treatment).
With reference to the flowchart of
In some cases, the diagnostic pulse can have a frequency in a range of about 5 MHz to about 15 MHz and can exhibit a power density in a range of about 0.1 W/cm2 to about 0.8 W/cm2 at the tissue surface, or at a focal area when the diagnostic pulses is focused onto the tissue. The focal depth of the diagnostic pulse will range from about zero to about 6 mm, or from about 2 mm to about 5 mm below the tissue surface.
In some embodiments, the generated diagnostic echo can be analyzed to determine the presence or absence of any obstacles along the propagation path of the diagnostic ultrasound. An ultrasound obstacle can include, for example, bone and/or bubbles in a topical substance (e.g., a gel) applied to a tissue surface (e.g., skin surface) for facilitating coupling of the ultrasound energy into tissue and/or regions of inconsistent density in the applied topical substance. In some cases, the echo can be analyzed to determine whether sufficient coupling exists between the diagnostic ultrasound pulse and the tissue (e.g., by analyzing the intensity of the returning echo). The presence of bone within a depth of from about 2 mm to about 3 mm below the focus area risks thermal damage to the bone that can result in, for example, necrosis to the bone. Improper coupling due to, for example, bubbles or inconsistent gel density, can result in inconsistent energy delivery to the focal area resulting in inconsistency or absence of treatment to the focal area in a region of a bubble and/or inconsistent gel density.
With reference to the flowchart of
By way of example, in some cases, the transducer can be controlled to apply a substantially constant compressive pressure to the tissue surface (e.g., skin surface) as the transducer delivers the ultrasound energy to the tissue locations. Upon termination of the application of the ultrasound energy to a tissue location, the compressive pressure can be removed (such that a transducer is removed from contact with the tissue, while the transducer is moved to another location to which the ultrasound energy will be applied). As another example, a reference location (e.g., a radiation-emitting surface) of the transducer, or a reference location of a frame to which the transducer is coupled, can be maintained (e.g., via feedback control) at a substantially constant distance relative to the tissue surface (e.g., skin surface) as the transducer delivers the ultrasound energy to the tissue such that at each irradiation location, the energy is effectively deposited at a substantially uniform depth.
While the various embodiments provided herein describe the treatment of tissue located at some depth below the skin surface, various other such tissues may be treated. Those skilled in the art will appreciate that various other types of tissue are within the spirit and scope of the present disclosure.
The device 10 further includes a calibration unit 28 that can initially calibrate the transducer 20 and confirms that the transducer 20 is functional. The calibration unit 28 is in communication with the computer 26 to provide information regarding the status of the acoustic transducer 20. In some cases, the computer 26 can utilize this information to selectively activate the signal generator 22, and hence the acoustic transducer 20, to apply ultrasound pulse(s) to selective locations of the tissue. For example, in some cases, the computer 26 can compare the information received from the calibration unit 28 to a pre-defined pattern of locations to determine when the transducer 20 needs to be activated. The computer 26 communicates with the scanner 25 to direct the scanner 25 to move the transducer 20 in a desired pattern.
The acoustic transducer 20 can scan over the skin surface and emit focused ultrasound waves to deliver acoustic energy into a plurality of tissue locations at a precise depth in the subcutaneous tissue. In some embodiments, the scanning procedure can include movement of the transducer 20 over the tissue surface with deceleration of the transducer 20 speed at target treatment spots. One or more ultrasound pulses can be fired to treat the treatment spot. After the firing of the ultrasound pulse(s), the transducer 20 can move, e.g., at a predetermined acceleration, to an adjacent target treatment spot to apply ultrasound pulse(s) to that spot.
In some embodiments, the scanning procedure can include continuous movement of the transducer 20 over the tissue surface with energy delivered in a continuous manner, e.g., during at least a portion of the scan. By way of example, the ultrasound energy and the speed of the transducer 20 can be selected such that the continuous movement of the transducer 20 delivers energy in a continuous manner to create a line of coagulation in the tissue without damaging the surface of the tissue (e.g., the skin surface).
In some embodiments, the transducer 20 can receive an electrical energy up to about 30 Watts from the signal generator 22 and the amplifier 24 to generate acoustic power in a range of about 15 Watts to about 20 Watts for application to the skin. As noted above, in many embodiments, the acoustic energy generated by the transducer 20 can be focused into the tissue to provide a power density in a range of about 800 W/cm2 to about 1500 W/cm2 at a focal area of the target region that ranges from about zero to about 6 mm below the tissue surface.
In some implementations, the above exemplary device can operate in two modes: one modality in which predominantly mechanical (non-thermal) energy is used to disrupt fat cells and another modality in which higher frequency ultrasound energy is used to cause thermal action by some increase in temperature in targeted volumes (e.g., small volumes) of subcutaneous connective tissue.
The device 10 can be implemented to generate one or more desired ultrasound frequencies, e.g., in a range of about 3 MHz to about 12 MHz. As the applied ultrasound frequency increases, the length of the focal zone and the volume of tissue coagulation caused by the focused ultrasound decreases. As discussed further below, a prototype device built in accordance with the teachings herein was utilized to apply ultrasound energy to skin tissue at any of a number of frequencies including, for example, about 3.5 MHz, about 5 MHz, and about 12 MHz. The frequency that is applied depends on, for example, the desired size of coagulation. In one embodiment, at a frequency of about 12 MHz, at a time of about 60 ms, relatively small and relatively superficial damage is produced in skin beginning from the surface to a depth of about 1 mm with a maximum diameter of 0.5 mm at the surface of the skin. A frequency of about 5 MHz, at a time of from about 10 ms to about 20 ms, was chosen to produce relatively small (e.g., between about 0.1 mm and about 1 mm in size) damage in the dermis at a depth of from about 1 mm to about 3 mm. A frequency of about 3.5 MHz was chosen to produce relatively large (e.g., about 2 mm in length and about 0.5 mm in diameter) damage in predominantly fatty region during 110 ms under the skin at 7 mm depth.
As noted above, in many embodiments, the ultrasound energy (e.g., the ultrasound pulses) can be focused into tissue. The F-number is a measure of how rapidly the ultrasound energy is focused into the tissue, and is defined as the ratio of the focal length relative to the transducer's active aperture diameter. In general, as the focusing of the ultrasound energy becomes stronger (as the F-number decreases), the smaller is the near-field heating produced by the transducer. In some embodiments, the F-number associated with the focusing of the ultrasound generated by the transducer 10 into the tissue can be, e.g., in a range of about 0.8 to about 1.1. By way of example, in some embodiments, an F-number of about 1 (or smaller) can be utilized to minimize near-field heating that can result from a series of sound impulses. Increasing the frequency of the pulses and/or the delay between successive pulses, as well as decreasing the pulse duration and F-number of the transducer 10, can reduce near-field heating during operation.
In one embodiment, when attached to the cone 48 one side of the tip 50 contacts the patient's tissue surface. The thickness of the tip 50 will determine in part and in combination with the cone 48, how deep into the patient's tissue the focal depth penetrates. A less thick tip 50 will provide a deeper focal depth than a thicker tip, which will provide a less deep or more shallow focal depth. Suitable tips 50 can range in size (e.g., thickness) to achieve depths ranging from zero to 6 mm below the tissue surface. Likewise, suitable cones 48 can be sized to achieve in combination with a tip 50 depths ranging from zero to about 6 mm below the tissue surface. Suitable cones 48 and/or suitable tips 50 may be made from machined metal, a polymer, e.g., a low cost plastic suited to disposability. The cone 48 may be made from the same or different material than the tip 50 to which it mates.
The ultrasound energy that is concentrated in a focal spot (region) can temporarily increase the tissue temperature and cause coagulation of the tissue. In some embodiments, the transducer 20 as well as the focusing element (herein also referred to as a focusing lens) can be configured to create treatment regions (e.g., coagulated tissue regions) with dimensions that can range from about several hundred micrometers to a few millimeters. In one illustrative exemplary study, samples of tissue were sonicated for about twenty milliseconds with focused ultrasound at a frequency of about 3.5 MHz and at an acoustic power density of up to 900 W/cm2 at the focal peak. The ultrasound energy was focused into the tissue at an F-number of about 0.9. An infrared (IR) thermal camera was utilized to measure temperature rise in the tissue due to exposure to the focused ultrasound energy. More specifically,
In some embodiments, referring to
The small transducer 56 is a listening transducer that is capable of receiving a returning echo generated in response to a diagnostic acoustic wave generated by the listening transducer. By way of example, such an echo can be created by the reflection of the acoustic wave from (a) a discontinuity in a topical substance (e.g., gel) applied to the tissue surface to facilitate coupling of the acoustic wave to the tissue, (b) surface of the tissue, (c) bone or other solid object(s) which could be below the tissue surface. The retuning echo can be measured to determine whether at least an object that would interfere with treatment acoustic wave is present in the path of the waves, and if so, to determine how far away the object is, its size, shape, consistency (e.g., whether the object is solid, filled with fluid, or both), and uniformity. Such information can be gleaned, e.g., based on the amplitude (strength), frequency of the echo and the time it takes for the echo to be detected relative to the transmission of the diagnostic acoustic wave. Such analysis of the echo can be performed by a computer (such as a computer 26 shown in the above device 10 in
In practice, one or more diagnostic acoustic pulses are applied to the tissue prior to the application of treatment acoustic energy. If the analysis of one or more echo signals detected in response to such diagnostic pulses indicates that no interfering objects (or conditions such as discontinuity in a topical substance applied to the skin surface) are present, the treatment transducer 54 can be activated to generate treatment acoustic energy (e.g., in the form of pulses) for application to the tissue.
In some embodiments, ultrasound energy can be applied to selected locations of a tissue region requiring treatment to generate treatment portions that are separated from untreated portions within that region. The untreated portions can facilitate the healing process. By way of example, as shown schematically in
In another embodiment, methods, devices, and systems for controlling the movement and positioning of the transducer 20 (or other energy source) relative to a tissue surface (e.g., skin) allow accurate delivery of a pre-determined amount of energy to specific target tissue sites (e.g., target sites 70 in
In this exemplary embodiment, the control module 82 is also in communication with a scanner or scanning mechanism 88. The scanning mechanism 88 is, in turn, in communication with an ultrasound energy emitter (e.g., a transducer) 20. Based on instructions from the control module 82, the scanning mechanism 88 can position the energy emitter 20 above a target site via an x-position control mechanism 90 and/or a y-position control mechanism 92. In many embodiments, the scanning mechanism 88 can also move the transducer 20 along the z direction (typically a direction that is substantially perpendicular to the skin surface) via a z-position control mechanism 94. In some embodiments, the scanning mechanism 88, again in combination with the control module 82, can also determine the height that the transducer 20 should be positioned above the target site so as to ensure that a desired amount of ultrasound energy will be delivered to the target site, and position the energy emitter 20 at this determined height. As detailed below, a sensor 96 in communication with a z-position control mechanism 94, and in further communication with the control module 82, can determine the proper height and move the energy emitter 20 accordingly.
Once the transducer 20 is positioned above a target site, the control module 82 can actuate the energy emitter 20 so as to deliver a desired amount and type of ultrasound energy to the target site for a desired amount of time. The scanner 88 can then move the transducer 20 to position it over another target site to apply ultrasound energy to that site. In some embodiments, the device 10 can also include various additional sensors 98 configured to sense one or more parameters of the tissue surface and/or target site so as to determine if treatment should be stopped in view of some safety concern and/or the effect of the treatment. This information can be transferred to the control module 82 which can then determine based on, for example, some stored treatment protocol and/or algorithm, whether this site should be targeted again, and if so, whether such further treatment should be performed immediately or at some future time point (e.g., the energy emitter can be returned to this initial site after the remaining target sites have been treated). Thus, these features provide the device 10 with a feedback mechanism configured move the energy emitter 20 among the various target sites until each site has been treated once or repeatedly, as needed.
The energy emitter 20 can be coupled to a scanner or scanning mechanism 88 which can move the energy emitter 20 to some desired position relative to the target site(s). The scanning mechanism 88 can be configured to achieve the desired x-, y-, and/or z-position relative to a target tissue site. For example, the scanning mechanism can be in communication with various sensors 96, 98 and/or a control module 82 so as to automatically move the energy emitter 20 from one desired position to the next desired position. Alternatively, the scanning mechanism 88 can be manually manipulated from one desired position to the next desired position. Also, the scanning mechanism 88 can be controlled by some combination of automation and manual control.
In an exemplary embodiment, the scanning mechanism 88 can be configured to control movement of the transducer 20 relative to an x-axis and a y-axis thereby allowing the energy emitter 20 to be positioned in two dimensions substantially above a target site. The scanning mechanism 88 can also be configured to control the height (i.e., z-position control) of the energy emitter 20 relative to a tissue surface thereby ensuring a desired amount of energy is delivered to a desired depth below the tissue surface so as to effectively treat the target tissue.
In this manner, the energy emitter (an ultrasound transducer) 20 can be moved anywhere in an x-y plane (which is typically substantially parallel to the skin surface) to be positioned over a target site. In this way, the x-y movement allows the energy emitter 20 to be positioned anywhere in an x-y plane. Those of ordinary skill in the art will appreciate that various alternative x- and/or y-position control mechanisms are within the spirit and scope of the present disclosure.
As indicated, treatment of various conditions require ultrasound energy to be delivered to a specific depth below a tissue surface so as to target a specific volume of tissue. Also, it is often necessary to deliver a substantially constant amount of energy to numerous such subcutaneous tissue sites located at a substantially uniform depth below the skin surface. One mechanism for repeatedly delivering a substantially constant dose of energy to the various target sites is to position the transmitter 20 at an optimum height above each target site thereby minimizing or substantially eliminating any interference or diminution of energy resulting from the intervening tissue between the tissue surface to the target site.
Referring now to
As indicated in
Referring again to
Various other embodiments of z-position control mechanisms 94 can also be employed. For example, after applying a compressive pressure to the tissue surface via the z-position control mechanism, the z-position control mechanism 94 can remove the transducer assembly 20 from target tissue. Thereafter, the transducer assembly 20 can be moved to the next treatment location along the x, y, and/or z-axis.
As indicated in
In another embodiment, the device 10 can also include a tightening mechanism configured to, taken alone or in combination with the above-described z-position control mechanism 94, apply a tightening force across all or a portion of the tissue surface of the treatment area thereby effectively minimizing any irregularities and/or inconsistencies found in the region of the various target sites (e.g., inconsistencies found above one or more of the various target sites). As explained above, minimizing or obviating any differences among the various regions of tissue in the region of target tissues (e.g., differences found above the corresponding target tissues) can facilitate delivery of a consistent amount of ultrasound energy to the numerous target sites. In this way, multiple target tissue sites are treated at a substantially even depth.
Referring back to
As shown schematically in
The presently disclosed device and system also includes various subsystems and components configured to perform and optimize a desired treatment regimen. For example, in an exemplary embodiment, the device 10 can include some form of sensing or imaging technology 80 configured to identify and define a treatment region having a plurality of target tissue sites located therein. Typically, the treatment area is defined as some surface area of tissue and/or some volume of tissue.
Referring still to
Referring now to
Referring still to
In some embodiments, the presently disclosed device and system can identify and/or select a plurality of target tissue sites e.g., 70a, 70b, 70c from the entire treatment area 72 such that selected treatment of these target sites 70a, 70b, 70c can provide the desired therapeutic effect to the entire treatment area 72. For example, in one embodiment, at least one algorithm can be stored within the control module 82. The stored algorithm can generate some pre-determined pattern and/or number of target tissue sites in view of the previously recorded treatment area. For example, as shown in
In an alternative embodiment, the control module 82 can determine the target sites 70 based on some analysis of information relating to the treatment area. For example, the control module 82 may identify various areas to be treated based on some measured parameter, such as, for example, discoloration, progression of skin condition (e.g., acne), etc. As will be apparent to those of ordinary skill in the art, any such procedures for selecting target tissue areas is within the spirit and scope of the present disclosure.
In an exemplary embodiment, the control module 82 of the device 10 is in communication with the scanning mechanism 88 thereby allowing the control module 82 to position the energy emitter at a desired x-, y-, and/or z-position for a desired period of time so as to effect treatment. That is, upon identifying the number and location of target tissue sites 70 within the treatment area 72, the control module 82 can be configured to activate the scanning mechanism 88 so as to position the energy emitter 20 at a location substantially above the target tissue site 70. Once the energy emitter 20 is positioned at a location substantially above the target tissue site 70 (or concurrently with the x- and y-positioning of the energy emitter 20), the control module 82 can further be configured to active the z-position control mechanism 94 thereby allowing for the energy emitter 20 to deliver a known amount of ultrasound energy to a tissue site located at some depth D below the tissue surface. At this stage, the control module 82 can now be configured to initiate the treatment protocol thereby firing the energy emitter 20 so as to deliver the desired dose (e.g., desired frequency, pulse width, etc.) of ultrasound energy to the target site 70 (e.g., 70a, 70b, 70c of
Referring still to
The presently disclosed device can include various types and/or configurations of such sensors 98. For example, the sensors 98 can be temperature sensors configured to determine the temperature at the tissue surface (e.g., skin surface). The sensor can detect visible damage by optical means (e.g., pigment change, inflammation detection). Those of ordinary skill in the art will appreciate that various other sensors are within the spirit and scope of the present disclosure.
In some embodiments, referring now to
While the above embodiments discuss delivery energy to discrete location thereby providing discrete treatment sites 70a, the device and methods can also be configured to provide continuous treatment. Thus, in some embodiments the transducer 20 can deliver energy while moving relative to the tissue surface thereby producing a treatment site of any desired configuration (e.g., a line-like lesion).
One challenge associated with ultrasound use is achieving good coupling (e.g., contact) of ultrasound energy into the target tissue. In order to couple ultrasonic energy from a transducer to the tissue, a coupling medium can be used. In some embodiments, a coupling medium (e.g., a gel) can be continuously disposed between the ultrasound transducer device and the tissue surface as the device is scanned over the tissue. In one embodiment, the coupling medium is selected such that the speed of sound through the medium is substantially the same as the speed of sound through the tissue. In order for a coupling medium to be effective, the medium should be preferably substantially free from imperfections such as, for example, air gaps, bubbles, or voids. In the case of a focusing transducer, effective coupling is challenging because the transducer is usually a concave shape, and is positioned at some distance away from the surface of the tissue being treated.
In one embodiment, the presently disclosed device provides consistent and effective coupling of ultrasonic energy from a transducer to tissue via a substantially constant coupling of the ultrasonic energy from the transducer to the tissue.
The extension 162 can be a conduit that connects the reservoir 156 (e.g., via tubing 158) to the tip 154. At least a portion of the reservoir 156 is filled with another coupling medium (i.e., a second coupling medium) 62. The second coupling medium 62 (e.g., a gel) can have a viscosity which is low enough such that it can be driven (e.g., via gravity and/or mechanically driven) from the reservoir 156 to the tip 154. Optionally, the viscosity of the second coupling medium 62 is high enough such that is does not flow without being driven out of the reservoir. In one embodiment, the first coupling medium 60 (e.g., the primary gel) is the same viscosity as the second coupling medium 62. In another embodiment, the first coupling medium 60 has a higher viscosity than the second coupling medium 62. Where the first coupling medium 60 has a relatively higher viscosity than the second coupling medium 62, the viscosity of the first coupling medium 60 will be up to about 500,000 cPs. In one embodiment, the first coupling medium 60 has a relatively thick gel-like agar or gelatin-like consistency. The first coupling medium 60 may be molded and shaped such that the second coupling medium 62 is in contact with the transducer 54. The second coupling medium 62 can be capable of forming an extruded film 160 which has a viscosity that ranges from about 80,000 cPs to about 100,000 cPs. In one embodiment, both the first coupling medium 60 and the second coupling medium 62 have a viscosity that ranges from about 80,000 cPs to about 100,000 cPs at [temp/pressure] conditions.
In use, referring again to
Referring to
In an exemplary embodiment, the transducer assembly 20 provides a substantially constantly refreshed supply of a second coupling medium (e.g., extruding gel) 62, substantially avoids breakdown, cavitation bubbles, and/or particulates which otherwise might be present near the concentrated energy focus of the ultrasonic beam. In addition, the supply of an amount of fresh second coupling medium 62 can ensure that the tip 154 and the tissue surface do not touch.
The second coupling medium 62 can serve various functions. For example, the second coupling medium 62 can enhance the coupling of the ultrasound energy from the transducer 54 to the target tissue (e.g., skin). The second coupling medium 62 can also provide some measure of cooling, by displacing gel that might be heated by proximity to the skin being treated. The second coupling medium 62 can also provide a low friction film between the tip 154 and skin, which can be particularly beneficial in scanning operations.
In the application of an ultrasonic scanner system that does not utilize an extruded gel as disclosed herein, where a transducer is moved in discrete steps on the tissue (e.g., skin) and then pulsed, the spatial uniformity of the resulting pulse pattern (array of treatment dots) depends in part on the skin remaining stable. A precise translation of the pulse might not be completely effective if the relatively soft tissue distorts laterally while the head is being scanned. If maintained, such contact between the tip and the tissue surface could provide friction and thereby disrupt the treatment. An alternative to scanning would be to lift the head, reposition the transducer, and lower it between pulses, but that requires a large amount of down time in contrast to scanning, and is potentially unpleasant to the patient (e.g., because of the time required to conduct the treatment procedure). Such up and down “pick in place” type movements could also risk entrapped air bubbles near the tip.
Referring again to
In one embodiment, referring to
An additional benefit of the extruding gel 62 is to provide a visual reference of areas already scanned. In these embodiments, pulse marks are not necessarily visually evident on the skin at the areas previously scanned. This visual reference can be enhanced via color or reflective additives in the gel. In this way, any unintended, repeated scanning can be avoided and/or the area of prior treatment can be made evident to the practitioner.
In almost all cases, any surface of a medical device that contacts a subject must be cleaned, sterilized, or replaced between individual subjects. In one embodiment, the tip 154 of this device can be cleaned with sterilizing solutions, then sufficient amounts of gel can be pumped through the tip to ensure that only fresh material is exposed to the next patient. Alternatively, all or at least a portion of the device may be disposable after a single treatment. For example, the tip 154 might be disposable and replaced between patients. Alternatively, the cone 152 and the tip 154 can be replaced after each patient (or at any other desired time).
In many embodiments, efficient ultrasound delivery requires the first coupling medium 60 to be in direct contact with the transducer 54. Referring to
Referring now to
By applying ultrasound energy to these strands of connective tissue, the tension and/or pressure of the strands of connective tissue can be relaxed and/or eliminated such that the pull of the strands of connective tissue inwards (B) is lessened and/or eliminated. Strands can be thermally effected to be relaxed. For example, the ultrasound energy can be employed to thermally denature one or more structural components such as a protein of the strand. The thermal effect of the ultrasound energy can be used to sever one or more strand such that no tension remains left in the strand. In this way, the “dimpled” or “tufted” appearance on the surface of the skin is diminished or removed (e.g., smoothed out). Thus, ultrasound can be employed to improve the appearance of cellulite. The locations of the strands can be detected with diagnostic ultrasound pulse or another diagnostic technique. In some embodiments, an array of transducers (e.g., a phased array of transducers) can be used (e.g., instead of a scanner), to provide manipulation of the focal point of ultrasonic energy delivery. An array of transducers may be used in addition to a means for mechanical movement of the transducer. Optionally, an array of transducers may be employed without mechanical movement of the transducer.
In order to get a therapeutic effect in tissue one wants to produce lesions of coagulation with a coagulation radius that ranges from about 0.1 mm to about 0.8 mm. Previously such a range of radii (e.g., from about 0.1 mm to about 0.8 mm) was only achievable with a level of pain experienced by the subject that would require at least topical (and more commonly, local) anesthesia. It is desirable to coagulate tissue with a coagulation radius that ranges from about 0.1 mm to about 0.8 mm via ultrasound energy in a manner that induces pain below a threshold tolerable by subjects such that anesthesia may be avoided.
The lesions of coagulation (e.g., the coagulation zone(s)) produced by the method disclosed herein have a shape that is close to an ellipsoid of axial symmetry, with low asphericity (e.g., is substantially spherical). The coagulation radius is the radius of a hypothetical ideal sphere that has the same volume as an actual lesion of coagulation (e.g., the coagulation zone(s)) but that has been approximated as a hypothetical ideal sphere.
In accordance with this method, a combination of treatment parameters that delivers a treatment volume with a coagulation radius that ranges from about 0.1 mm to about 0.8 mm while inducing pain that is below a tolerability threshold such that anesthesia is unnecessary (or may be avoided).
Pain can be measured on a subjective scale of 1 to 10 where 1 is defined as absence of pain and 10 is defined is the worst pain imaginable by the respondent (e.g., the subject). In one embodiment, a pulse width of 15 ms or less, e.g., from about 5 ms to about 15 ms was employed and achieved a pain level of between 3 and 1 (total of 6 subjects), which is viewed as generally “painless” or “negligible pain.” In another embodiment, a pulse width of from about 15 ms to about 50 ms was employed and achieved a pain level of between 5 and 1 (total of 6 subjects), which is viewed at generally as a “tolerable” level of pain that does not require anesthesia.
In one embodiment, dermis tissue was treated with a power level of 250 Watts, a frequency of 5 MHz, and at a pulse width of 15 ms or less (e.g., from about 5 ms to about 15 ms) to achieve an average coagulation treatment radius of between about 0.5 mm to about 0.8 mm (total of 3 subjects) and the subjects rated the pain level between 1 and 3, which is viewed as “painless” or “negligible pain”.
Ranges of parameters suitable for use with the following pulse width's and/or power levels are, for example:
(A) a pulse width range of from about 0.1 ms to about 5 ms; a power level range of from about 10 Watts to about 150 Watts; a frequency range of from about 0.7 MHz to about 20 MHz or a frequency range of from about 2 MHz to about 8 MHz.
(B) a pulse width range of from about 5 ms to about 50 ms; a power level range of from about 150 Watts to about 500 Watts; a frequency range of from about 0.7 MHz to about 20 MHz or a frequency range of from about 2 MHz to about 8 MHz.
(C) a pulse width range of from about 10 ms to about 30 ms; a power level range of from about 200 Watts to about 300 Watts; a frequency range of from about 0.7 MHz to about 20 MHz or frequency range of from about 2 MHz to about 8 MHz.
In one embodiment a transducer is employed to heat a region, e.g., a volume, of tissue to a temperature within a desired temperature range. The heated region can be raised from the temperature range of normal physiological body temperature (e.g., from about 30° C. to about 38° C.) to a temperature in the range of from about 30° C. to about 65° C., from about 40° C. to about 65° C., or from about 40° C. to about 55° C. Thus, the acoustic pulses can heat the region of tissue to cause a temperature rise in the region, e.g., a volume, of tissue of at least 5° C. or from about 5° C. to about 35° C. Thus, transducer heats a volume of tissue to a temperature within the range of from about 30° C. to about 65° C. When heating the volume of tissue the transducer applies a frequency that ranges from about 0.7 MHz to about 20 MHz. The heating acoustic pulse(s) applied by the transducer has a power density of from about 500 W/cm2 to about 5,000 W/cm2 and has an energy density of from about 2.5 J/cm2 to about 25 J/cm2.
A transducer is employed to produce cavitation activity in previously heated tissue region (e.g., in the volume of tissue), more specifically, in the tissue region having a temperature raised by at least about 5° C. by the heating acoustic pulse(s) applied by the transducer transducer employed to heat the region of tissue. To produce cavitation activity, the transducer applies a cavitation acoustic pulse with a frequency that ranges from about 20 kHz to about 700 kHz. The cavitation acoustic pulse(s) applied by the transducer has a power density of from about 40 W/cm2 to about 800 W/cm2 and has an energy density of from about 4 J/cm2 to about 80 J/cm2.
The clinical endpoint of cavitation will vary based on the treatment application. For example, with tattoo removal the clinical endpoint may be a visible blanching of the appearance of the tattoo and/or a change in color of the tattoo in the skin. Combining heating and cavitation as disclosed herein can be used for any of a number of clinical applications such as, for example, 1) tattoo removal 2) fat reduction 3) cellulite treatment 4) skin tightening and 5) treatment of malformations such as lesions, tumors etc.
In one embodiment, a single transducer is employed to apply at least one heating acoustic pulse to first heat the volume of tissue and then the transducer is employed to apply at least one cavitation acoustic pulse to produce cavitation activity in the heated volume of tissue. More specifically, the transducer first applies at least one heating acoustic pulse having a frequency that ranges from about 0.7 MHz to about 20 MHz to heat the volume tissue by at least about 5° C. or from about 5° C. to about 35° C. Once the tissue is heated the temperature of the tissue region (e.g., the volume of tissue) is within the range from about 30° C. to about 65° C., within the range of from about 40° C. to about 65° C., and/or more within the range of from about 40° C. to about 55° C. The same transducer is then switched to a lower frequency such that it applies a frequency that ranges from about 20 kHz to about 700 kHz to produce cavitation activity in the heated volume of tissue (in the region of tissue). The temperature of the volume of tissue may be monitored by any of a number of suitable methods including, for example, one or more of: contact temperature measurements at the skin surface, non-contact (e.g., IR) measurements at the skin surface, invasive (needle) measurements of temperature inside the tissue, and/or non-invasive (e.g., phase-sensitive US, opto-acoustic) measurements of temperature inside the tissue.
Cavitation activity can be determined by various means including acoustical means and optical means. In one embodiment, cavitation activity is determined by acoustical means that employ a hydro phone which transforms an acoustic signal to an electrical signal. The electrical signal produced via the hydro phone informs the user that cavitation activity has been achieved. The amount of cavitation activity can be detected by the electrical signal that is produced. In another embodiment, the cavitation activity is determined by optical means such as by employing sonoluminescence which detects light emitted when cavitation bubbles collapse. The quantity of detected light emission can enable determination of the amount of cavitation activity produced by the transducer. The clinical endpoint of cavitation activity may vary by treatment application (e.g., tattoo treatment can have a cavitation activity endpoint that differs from the cavitation activity endpoint of cellulite treatment). The cavitation activity endpoint may be determined by visually determining when the clinical endpoint has been achieved (e.g., when the tattoo has been blanched). In some embodiments, the cavitation activity endpoint is determined by the quantity of cavitation activity, which may be determined by electrical signal and/or by optical means, for example.
In another embodiment, multiple transducers (i.e., two or more transducers) are employed such that one transducer applies a frequency that ranges from about 0.7 MHz to about 20 MHz to heat the volume tissue and another transducer (i.e., a separate transducer) applies a frequency that ranges from about 20 kHz to about 700 kHz to produce cavitation activity in the heated volume of tissue. In one embodiment, a first transducer is relatively larger than the second smaller transducer.
Optionally, a composite transducer is made up of multiple transducers. For example, in one embodiment, one or more relatively high-frequency transducers and one or more relatively low-frequency transducers are incorporated into a composite transducer. For example, referring now to
In another embodiment, referring to
Heating and cavitation may be done sequentially, simultaneously, and/or sequentially with some overlap such that heating occurs and during the heating process cavitation of the treatment area beings. Sequential, simultaneous, and/or sequential with some overlap can be conducted with a single transducer or with multiple transducers.
Without being bound to any single theory it is believed that elevating the temperature of the tissue modifies the cavitation activity. It is known that the intensity of cavitation in aqueous media varies with temperature of the aqueous media such that cavitation activity generally increases as temperature increases up to a threshold amount. Thus, combining heating of tissue via a frequency applied with a transducer with inducing cavitation activity in tissue via frequency applied with the transducer that heated the tissue or with a different transducer is expected to intensify the cavitation activity of the tissue at the same acoustic power level, therefore producing fewer side effects. Combining heating with acoustic energy and inducing cavitation with acoustic energy enables the threshold for cavitation to be reduced so that cavitation can be induced with a lower power density and a lower energy density than would be required in the absence of heating. In this way, by employing heating acoustic pulse(s) with cavitation acoustic pulse(s) fewer and/or less intense side effects of cavitation result.
In one embodiment of a method for treating tissue a heating acoustic pulse is applied to a region of tissue (e.g., a volume of tissue) to raise the temperature of the region of tissue by at least 5° C. One or more heating acoustic pulse can have a frequency of from about 0.7 MHz to about 20 MHz and have a power density and an energy density sufficient to raise the temperature in the region of tissue at least 5° C. (e.g., from about 5° C. to about 35° C.). One or more cavitation acoustic pulses are applied to the region of tissue (e.g., a volume of the tissue) with a frequency range of from about 20 kHz to about 700 kHz with a power density and an energy density sufficient to induce cavitation in the region of tissue. Optionally, the heating acoustic pulse has a power density of from about 500 W/cm2 to about 5,000 W/cm2 and has an energy density of from about 2.5 J/cm2 to about 25 J/cm2 and the cavitation acoustic pulse has a power density of from about 40 W/cm2 to about 800 W/cm2 and has an energy density of from about 4 J/cm2 to about 80 J/cm2.
Cavitation activity is determined through the concentration of cavitation bubbles in a cavitation zone. It is difficult to initiate cavitation in certain regions of tissue, for example, initiating cavitation in a dense and viscous area of the skin tissue can be challenging. In tissue that has blood vessels and capillaries the blood vessels and/or capillaries would be the first places affected by the cavitation activity (which may not be a desired outcome). In difficult treatment areas, for example, areas where there are blood vessels and/or capillaries that are not the targeted areas for treatment, the transducer energy can be focused at the target areas (i.e., focused at tissue such that the transducer energy avoids capillaries and blood vessels). Such focusing can be achieved by employing a focusing transducer and/or an array of transducers with synthetic aperture capabilities. A focusing acoustic transducer is described herein in relation to
To illustrate the efficacy of the above methods for treating tissue by application of ultrasound energy and for preliminary safety evaluation of such tissue treatments the results of a number of in-vitro experiments are presented below. Direct and indirect evidence of the formation of coagulation zones (lesions) was obtained. Coagulation lesions were created ex vivo in dermis and fatty tissue of pig and human skin. The appearance of the lesions in vitro was demonstrated with H&E and NBTC staining techniques and photography using a microscope. The following parameters were employed for the ultrasound pulses:
Frequency: 3.4 and 5 MHz,
Electrical power max: 250 W,
Acoustic spatial focal peak intensity: 800-1000 W/cm2,
Pulse widths: 10-70 ms.
Experiment 1: Treatment of Pig Skin
Samples of pig skin were sonicated with 3.4 MHz focused ultrasound with a single pulse of 40 ms in duration. The ultrasound energy corresponded to the spatial peak intensity of about 800 to about 1000 W/cm2 (without considering attenuation and nonlinear effects in tissue and water). The F-number was 0.9 and the focal spot was located at another 2.5 mm below the skin surface. As shown in
The first signs of coagulation appeared at about 1 mm to about 2 mm under the skin surface and disappeared beneath about 4 mm to about 5 mm of the skin surface, the maximum diameter of the coagulation spot ranged from about 0.8 mm to about 1.5 mm, or about 1 mm. The depth (e.g., the z direction) of the coagulation lesion ranged from about 4 mm to about 1 mm. The length of the lesion (
When sonication times go above certain values, it can result in skin burns (
Therefore, at selected acoustical power and transducer configurations, two important parameters are the time of the surface damage and focal damage. Threshold time of the surface damage is important for safety of the technique and the focal damage is important for efficacy of the treatment. Both of the parameters depend on the focal place under the skin (e.g., the focal depth).
A sample of a freshly excised 1 cm thick piece of human abdomen skin was sonicated with 3.4 MHz focused ultrasound. Temperature below the skin sample was kept at 37° C. (the temperature of the human body), the temperature at the surface of the skin was 27° C. The location of the sonicated spot was removed with a biopsy punch, and stained with the H&E technique. Device parameters were about 250 W of electrical output power, 900 W/cm2 of acoustic spatial focal peak intensity and 40 ms pulse lengths. The focal depth was 2 mm below the skin surface and the F-number was 0.9. As shown in
The treatments of the pig and human skin show that the focused ultrasound device is able to generate coagulation lesions at a depth while leaving the upper skin layers intact. Our experiments show that the tissue layers lying deeper than the focal area also remain intact. Acoustic exposure times to produce such lesions were experimentally determined at different positions of the ultrasound focal area beneath the skin surface. Experiments with in-vitro porcine skin and NBTC stain technique verified that the disclosed device can create such lesions in a reproducible manner and the coagulated lesions lie from about 1 mm to about 2 mm below the skin surface at the specified settings, the coagulated skin is about 2 mm to about 3 mm long and about 1 mm in diameter. Additional experiments demonstrate that this approach to creating coagulation lesions works in ex-vivo human skin and acoustic parameters for coagulated lesion generation in ex-vivo human skin are close to the parameters used in the pig skin model.
Thermo-coagulated fractions (e.g., islets) may be formed in skin using focused ultrasound. Using ultrasound, a matrix of lesions, with few micrometers or millimeters separation between, may be positioned in the dermis of skin (
With reference to
With reference to
One skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/174,201, which was filed on Apr. 30, 2009. This provisional application is herein incorporated in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61174201 | Apr 2009 | US |
