US 20070093798 A1
A method and apparatus for thermal treatment of tissue by irradiating the skin with electromagnetic energy is disclosed. Sources of electromagnetic energy include radio frequency (RF) generators, lasers, and flashlamps. The apparatus includes either a positional sensor or a dosage evaluation sensor, or both types of sensors. These sensors provide feedback to a controller. The controller may control the electromagnetic source parameters, the electromagnetic source activation, and/or the sensor measurement parameters. An additional scanning delivery unit may be operably coupled to the controller or to the sensors to provide a controlled distribution of electromagnetic energy to the target region of the skin. The use of positional measurement sensors and dosage evaluation sensors permits the controller to automatically determine the proper electromagnetic source parameters including, for example, pulse timing and pulse frequency.
1. An apparatus for controlled fractional tissue treatment comprising:
an electromagnetic source that generates electromagnetic energy;
a manually movable handpiece that delivers the electromagnetic energy to a target region of human skin;
a positional sensor that measures at least one positional parameter of the handpiece; and
a controller operably connected to the positional sensor, the controller adjusting in real-time at least one operational parameter of the apparatus in response to the at least one positional parameter measured by the positional sensor, said adjustment causing the electromagnetic energy to create a fractional treatment for the target region of human skin.
2. The apparatus of
a dosage evaluation sensor that measures a skin response to the fractional treatment created by the electromagnetic energy at the target region of human skin, wherein the controller further adjusts in real-time at least one operational parameter of the apparatus in response to the measurements of the dosage evaluation sensor, said adjustment controlling the fractional treatment created by the electromagnetic energy.
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22. A method for controlled fractional tissue treatment comprising:
directing electromagnetic energy via a handpiece toward a target region of human skin;
manually moving the handpiece across the target region;
sensing at least one positional parameter of the handpiece; and
automatically adjusting in real-time at least one operational parameter of the electromagnetic energy in response to the at least one positional parameter, said adjustment controlling the fractional treatment created by the electromagnetic energy.
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34. An apparatus for controlled fractional tissue treatment comprising:
source means for generating electromagnetic energy;
manually movable handpiece means for delivering the electromagnetic energy to a target region of human skin;
first sensor means for measuring at least one positional parameter of the handpiece means;
second sensor means for measuring a skin response to the fractional treatment created by the electromagnetic energy at the target region of human skin; and
control means operably connected to the first and second sensor means, for adjusting in real-time at least one operational parameter of the apparatus in response to the measurements from the first and second sensor means, said adjustment causing the electromagnetic energy to create a fractional treatment for the target region of human skin.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/712,358, “Method and Apparatus for Monitoring and Controlling Thermally Induced Tissue Treatment,” by Leonard C. DeBenedictis, George Frangineas, Kin F. Chan, B. Wayne Stuart III, Robert Kehl Sink, Thomas R. Myers and Basil Hantash, filed Aug. 29, 2005. The subject matter of all of the foregoing is incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a method and apparatus for dermatological tissue treatment, and more particularly, to controlling dosage from an electromagnetic source based on measurements of a handpiece motion and/or skin tissue response.
2. Description of the Related Art
Many electromagnetic dermatological treatment systems require extensive training before physicians and nurses develop the skills to deliver energy uniformly over a treatment region, such as the face, neck, chest, or back. In many cases, physicians and nurses do not treat uniformly, resulting in uneven treatment, over treatment, or under treatment. There is a need to create more uniform photothermal and/or radio-frequency (RF) treatment, particularly for large areas.
Additionally, not all patients respond the same way to the same level of treatment. So even if precisely the same laser energy dose is delivered to two different patients, the response of each patient may be substantially different. Within a single patient, the skin response may vary from region to region. Treatment of the forehead may respond differently than treatment of the neck, for example. If uniform treatment parameters are used for all patients or for all regions, then the treatment parameters will typically be designed for the most sensitive patient or the most sensitive region in order to avoid undesirable side effects. Designing for the most sensitive region or patient will frequently lead to undertreatment of other regions or patients.
Many medical laser systems for the treatment of dermatological skin conditions function by pressing a footpedal to trigger the delivery of a single pulse of treatment energy. This type of treatment apparatus is slow and has a lot of repetitive motions, which can be tiring to the operator. Other laser treatment systems fire identical pulses at a constant pulse repetition rate as the user moves the handpiece across the tissue. This system requires skill and increases the risks of over- or under-treatment in the hands of an unskilled operator. Therefore, there is also a need for an approach to electromagnetic treatment that provides controlled dosage and adjusts the dosage level in real time to prevent over- and/or under-treatment.
Weckwerth U.S. Pat. No. 6,758,845 describes the use of optical measurements of regularly spaced indicia that are placed on or adjacent to the treatment region, but the concept is limited by the application of regularly spaced indicia that are counted to measure distance traveled by a handpiece. This requires the precise positioning of indicia to avoid errors. In addition, the visible indicia may be difficult to remove following treatment, and may leave an unsightly pattern on the skin following treatment.
Weckwerth '845 and Talpalriu U.S. Pat. No. 6,171,302 describe mechanical roller systems for tracking handpiece travel. These can be unreliable, for example, when used with gel due to a lack of friction between the mechanical roller and the skin surface. This leads to drop outs and errors in measurements of positional parameters. In addition, mechanical rollers can become rusted or gummed up so that they no longer spin easily, which makes dropouts and errors more likely. Wearing out of mechanical parts leads to similar errors.
Weckwerth '845 describes other systems that measure position of the handpiece indirectly, through the interaction with reference planes or points outside the target area, rather than measuring the target area directly. With this approach, the location of the treatment surface relative to the reference surface must be measured or controlled. In addition, these systems only measure one coordinate for the handpiece, which means that motion of the handpiece across the target tissue due to change in orientation of the handpiece may not be accounted for by the sensor systems. This leads to inaccuracies.
For treatment of large areas, an automatic laser control system is needed for adjusting laser treatment parameters in real time in response to the handpiece position, velocity, and/or acceleration or in response to the laser treatment itself. Thus, there is a need for an apparatus and method for a feedback loop that increases the effectiveness of treatment by controllably responding to treatment variables such as treatment speed, handpiece angle, handpiece acceleration, patient to patient variability, region to region variability within the same patient, etc. There is also a need for an apparatus and method that preferably enable faster and more reproducible treatments, that require less training and skill by the operator and/or that controllably respond to treatment variables. The apparatus and method preferably will also increase effectiveness without increasing side effects or invasiveness, treat with lower pain and side effects, directly measure treatment efficacy and/or progress for use in a feedback loop either alone or with other inputs instead of relying primarily on accurate delivery of a predetermined treatment dosage or on measurement of handpiece positional parameters, monitor biological response and treatment variables for improved biological predictability, efficacy, and safety, and/or permit better control of dosage, for example for photo-dynamic therapy (PDT) treatments, laser hair removal, or fractional laser resurfacing.
In general, the present invention comprises an apparatus and a method for treatment using feedback from one or more sensors that are used to measure handpiece positional parameters and/or the skin response to thermal or ablative treatment that is caused by the delivery of electromagnetic energy to the skin. The electromagnetic energy may be radio frequency (RF) or optical. The positional sensors and dosage evaluation sensors can be used separately or they can be advantageously combined to allow treatment to vary in response to a combination of skin response and handpiece positional parameters.
In one embodiment of the invention, a combination of relative and absolute handpiece positional measurements is measured to determine the positional changes of the handpiece relative to the treatment area.
In one embodiment of the invention, skin shrinkage is measured with a dosage evaluation sensor. In other embodiments of the invention, one or more measured responses of the skin include changes in one or more of the following: skin birefringence, skin water content, skin elasticity, skin mechanical damping parameters, skin color, skin features such as blood vessels and pigmented lesions, skin thickness, skin texture, and wrinkles. These and other skin changes may be measured usng one or more types of technology such as capacitive sensors, (hyper-) spectral imaging, terahertz imaging, optical coherence tomography, confocal microscopy, ultrasonic imaging, coherent detection, thermal detectors, thermal imaging systems, etc. Other skin responses and measurements can also be used.
In one embodiment of the invention, the output of an erbium doped fiber laser is collimated and deflected by a scanning delivery unit such as a galvanometer scanner or a starburst scanner as described in pending U.S. Application No. 60/652,891 and in corresponding U.S. Application No. 11/158,907, which are incorporated by reference herein, to create a series of figures at the treatment region.
In another aspect of the invention, the scanning rate of the scanning delivery unit is controlled by a controller to deliver a predefined pattern or dosage even if the handpiece velocity changes within a chosen range.
In one embodiment of the invention, a contrast enhancing agent is used to enhance the signal to noise ratio of the positional sensor. For example, FD&C Blue #1 can be applied to the surface of the skin to create an improved signal for a positional sensor comprising an optical mouse chip, CCD array, or other detector array, preferably with at least 25 elements. Using at least 25 elements as a 5×5 array is preferred because this allows sufficient image resolution to observe the changes in positional parameters and/or dosage response. If fewer detector elements are used, a more sophisticated algorithm and/or more sophisticated electronics generally will be typically required in order to distinguish changes in handpiece positional parameters and/or skin response. Other contrast enhancing agents are fluorescent or provide maximum contrast enhancement with IR or UV illumination. Wavelength selective coatings on the optical elements of the system may be used in conjunction with fluorescent contrast enhancing agents to filter out one or more illumination wavelengths. For example, the wavelength selective coatings can be designed to filter out light that is used to enhance the response of an optical positional sensor in order to improve the signal to noise ratio for a fluorescent emission signal at a different wavelength.
The contrast enhancing agent may be applied as a uniform or nonuniform pattern of similar or dissimilar shapes. This pattern of contrast enhancing agent can be applied using rollers, stamps, sprays, and/or stencils, for example. The contrast enhancing agent may also be applied onto or into an adhesive substance such as used in a temporary tattoo.
In selected embodiments of the invention, the positional sensor comprises one or more of the following: a mechanical mouse wheel or roller ball, non-concentric coils, an accelerometer, a gyroscope, transmitter(s) and receiver(s) that can be used to measure distance, a Doppler radar system, an ultrasonic time of flight measurement, etc.
In another embodiment of the invention, leading and trailing dosage evaluation sensors are used to measure the differential skin response due to thermal treatment.
In another embodiment of the invention, the scanning motion of a scanning delivery unit is not changed, but the pulse rate or pulse timing of the electromagnetic source is changed by the controller in response to measurements by at least one positional sensor and/or at least one dosage evaluation sensor. The pulse timing and scanner patterns may be chosen such that the beam is intentionally dragged across the treatment region to reduce the treatment intensity and/or to increase the size of each treatment zone created by each energy pulse.
In another embodiment of the invention, healthy skin is spared in regions between individual treatment zones to create fractional treatment. The spared tissue helps to promote rapid healing of the wounded area, prevent scarring, and allow higher treatment levels than are otherwise possible without side effects. The measurement of positional parameters can be used to accurately space the treatment zones from one another so that treatment dosage can be properly controlled.
In another embodiment, the density of fractional treatment is controlled through the use of feedback from positional and/or dosage sensors.
Other aspects of the invention include methods, devices, and systems corresponding to the approaches described above, as well as applications of the foregoing.
The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
This invention describes an electromagnetic system with automatic adaptive control of (photothermal and/or RF) treatment parameters and/or activation. A nominal pattern and treatment rate may be defined when the system begins treatment and this treatment pattern can be modified based on algorithms that describe the skin response to treatment and/or the positional parameters of the handpiece. Which positional parameter measurements or skin response measurements are made may depend upon particular measurement results. For example, if the handpiece is moving very rapidly across the skin and treatment power is proportional to relative handpiece speed, then bulk heating of the tissue may be a concern. In this case, the dosage evaluation sensors may be instructed by the controller to measure skin parameters that are associated with blistering due to over treatment. If movement is slow, bulk heating and blistering may be less of a concern and more of the processing power of the controller can be used to make more accurate measurements of velocity with the positional parameter sensors instead. Detailed embodiments of the invention are described in the examples given below.
In some embodiments, a distinction can be made between micro-dosimetry and macro-dosimetry measurements. Micro-dosimetry measurements are substantially limited to one or more zones that are about to be treated by a pulse or a set of simultaneous pulses. For example, measurement of a 1.2 mm diameter area that is cocentered with a 1 mm diameter area that is about to be treated is micro-dosimetry because the measurement is substantially limited to the region that is about to be treated with a future pulse or a future set of essentially simultaneous pulses. In contrast, macro-dosimetry measurements are used to evaluate larger areas of skin to produce an average measurement of regions that include both areas that are about to be treated (or that have just been treated) and adjacent regions. In some embodiments, a dosage evaluation sensor is used to produce micro-dosimetry or macro-dosimetry measurements in accordance with the feedback loops of this invention.
While the operator manually moves the handpiece 100 in direction 101 or after the operator has manually moved the handpiece 100, the positional sensor 180 measures one or more positional parameters of the handpiece 100 and the dosage evaluation sensor 160 measures the skin response to treatment parameters. The positional sensor 180 and the dosage evaluation sensor 160 communicate with the controller 115 and/or with the scanner control 125. The controller 115 and/or the scanner control 125 materially alter the treatment in real time in response to the positional parameter measurements and/or in response to the dosage evaluation measurements.
In some embodiments, the feedback loops comprising the controller 115 and/or the scanner control 125 in combination with the positional sensor 180 and/or the dosage evaluation sensor 160 can be used to provide automated control of treatment parameters such as treatment location, treatment zone overlap, treatment energy, treatment depth, treatment power, treatment zone pattern, treatment cooling (including pre-cooling and post-cooling), etc. These treatment parameters can be controlled through adjustment of device parameters that affect treatment such as optical focus or spot size, pulse width, pulse energy, pulse timing, pulse frequency, laser power, laser wavelength, spray cooling volume, spray cooling timing, etc.
Optionally, the controller 115 may be operably connected to the scanner control 125, which can be helpful for reducing the number of wiring connections from the sensors. The controller 115 may serve the function of both the controller 115 and the scanner control 125 as shown in the embodiment of
Detailed embodiments of several components in
In general, an electromagnetic source 110 is a radio frequency (RF) source, an optical source, or a combination of the two. A RF source generates electromagnetic energy with a frequency in the range of 0.1-20 MHz and preferably in the range of 0.5-8 MHz. An optical source generates light, which is defined for this application as electromagnetic energy with a wavelength in the range of 300 to 12,000 nm. Optical energy is preferred over radio frequency energy because it permits the energy to be directed more accurately and more easily to the desired locations on the skin. RF energy can also be desirable, particularly for applications where deeper penetration or targeting of particular buried layers of skin are desired. The choice of RF or optical energy may also be made to reduce interference with a chosen type of dosage evaluation sensor and/or position sensor.
In a preferred embodiment, the electromagnetic source 110 is a laser and the electromagnetic energy 130 is a laser beam. Examples of lasers are Nd:YAG lasers, diode lasers, erbium fiber lasers, CO2 lasers, Er:YAG lasers, Er:glass lasers, flashlamp-pumped lasers, free electron lasers, thulium fiber lasers, Raman shifted fiber lasers, dye lasers, gas lasers, Argon lasers, and ytterbium fiber lasers.
The skin response can be measured by one or more dosage evaluation sensors 160 employing one or more types of technology such as capacitive sensors, (hyper-) spectral imaging, terahertz imaging, optical coherence tomography, confocal microscopy, ultrasonic imaging, coherent detection, thermal detectors, thermal imaging, etc. In addition, one or more dosage evaluation sensor(s) 160 may measure skin birefringence, skin water content, skin elasticity, skin mechanical damping parameters, skin color, skin features such as blood vessels and pigmented lesions, skin thickness, skin texture, wrinkles, etc. Other types of measurement technology and other dermatological features and tissue properties that can be measured will be apparent to those skilled in the art.
A mechanical mouse or roller wheel with an encoder can also be used as a positional sensor 180. It is preferable, however, to use a non-mechanical positional sensor, which does not rely primarily on moving parts to measure positional parameters. Non-mechanical positional sensors advantageously improve measurement reliability on slippery surfaces and reduce the chance of mechanical failure in comparison to mechanical positional sensors.
In one embodiment of a non-mechanical positional sensor 180 coil sensors are used as described by Ben-Haim et al in U.S. Pat. No. 6,788,967, which is herein incorporated by reference. Three sensor coils that are mechanically coupled to the handpiece 100 in the appropriate orientations can be used to measure positional information, for example up to three dimensions and/or up to three angular orientations for the handpiece when the sensor coils are placed in the magnetic field generated by at least two radiators. Other geometries and numbers of radiators and sensor coils are possible for measurement of one-dimensional to six-dimensional positional parameters of the handpiece. Other non-mechanical positional sensors such as optical positional sensors are described below and may be detachable from the handpiece.
One example of the use of coil sensors is shown in more detail in
In a preferred embodiment, each of the magnetic field source elements 1285A-C and each of the magnetic field sensor elements 1284A-C comprise a loop antenna that is tuned to a desired frequency, for example a frequency of about 10 kHz. The loop antennas 1285A-C for the magnetic field source elements 1282 can each be driven with a current source, for example an op-amp current source. Alternately, a single current source 1288 can be electronically switched to power each of the loop antennas of the magnetic field source elements 1285A-C sequentially. Preferentially, the system is operated in the near field of each of the magnetic field source elements 1285A-C and each of the magnetic field sensor elements 1284A-C, but operation in the far field is also possible. The source elements 1284A-C can be sequentially powered in order to time division multiplex the source signals. The controller 1215 comprises receiver electronics for measuring the response detected by the magnetic field sensors. The receiver electronics portion of the controller may be collocated with the magnetic field sensor elements 1284A-C or may be integrated with the other electronics of the controller 1215. The controller comprises appropriate electronics to demultiplex the received signals to identify the measured magnetic field intensity due to each of the source elements. To synchronize the systems, particularly in the case of time division multiplexing, a common clock can be used for the source and receiver electronics. Other configurations of source, receiver, multiplexing/demultiplexing, and electronic systems will be apparent. For example, additional embodiments and refinements of appropriate magnetic field systems can be found in U.S. Pat. Nos. 4,613,866, 4,737,794, 4,742,356, and 5,307,072, each of which is incorporated herein by reference.
In alternate embodiments, the magnetic field source elements 1285A-C are located at one or more reference points outside the handpiece and the magnetic field sensor elements 1284A-C are attached to the handpiece. The location of and direction of the treatment beam(s) emitted from the handpiece relative to the reference coordinate system is then measured. For treatment on the face, the handpiece 1200 can include the magnetic source 1281, and a small earbud that is placed within the ear of the patient can contain the magnetic positional sensor 1280. To improve accuracy and to determine whether the earbud has fallen out or shifted, a second magnetic positional sensor (not pictured) may be used, for example in the opposite ear of the patient. If there is a discrepancy between the redundant sensors, the system can alert the physician, using for example an audible alarm.
The choice of which of the magnetic source 1281 and the magnetic positional sensor 1280 is located at the reference point(s) and which is located at the handpiece 1200 can be chosen based on the sources of electromagnetic interference and objects of electromagnetic field distortion, such as metal plates. For the example above, it is anticipated that there is a scanning motor element, such as for example used in
In one embodiment of a magnetic field system as described in
In one embodiment of the invention, one or more measured handpiece positional parameters include handpiece position or handpiece angle (angular orientation) or the time derivatives of these two parameters including handpiece velocity, handpiece acceleration, handpiece angular velocity, and handpiece angular acceleration. Handpiece positional parameters can be absolute or can be relative to the treatment region.
To enhance the serviceability of the apparatus and to allow handpieces to be interchanged and thus share expensive components, the handpiece may be detachable from one or more of the following: the electromagnetic source 110, the controller 115, and the scanner controller 125. To reduce the weight of the handpiece, these components may be located outside the handpiece. Alternatively, to enhance portability of the apparatus, these components may be included inside the handpiece.
The scanning delivery unit is configured to receive the electromagnetic energy 130 and deliver the electromagnetic energy 130 to the skin 150 regardless of where the other components are housed. For example, the electromagnetic source 110 may be a laser. The electromagnetic radiation may be coupled into an optical fiber, optical waveguide, or articulating arm for delivery to the handpiece. The handpiece can accept optical energy by using a fiber coupling or a fiber collimator. Similarly, it will be evident to those skilled in the art that the sensors 160 and 180 should be operably coupled to the controller 115, but do not need to be located inside the handpiece.
The controller 115 and scanner control 125 may be separate components as in
In the embodiment of
In the embodiment of
An example of a dosage evaluation sensor 260 is a capacitive sensor as shown in
In an alternative embodiment, the pattern can be intentionally varied according to a predefined algorithm where treatment rate is varied in real time in response to changes in the velocity or acceleration of the handpiece and where the treatment pattern is not predefined. For example, the treatment pattern can be controlled in real time by the user by appropriately adjusting the position, velocity, or acceleration of the handpiece. In some treatments, it is desirable to allow the operator to have control over the level of treatment through the use of velocity. For example, if the user treats quickly, the system may be configured to allow a higher level of treatment response as measured by the dosage evaluation sensor 260. If the user treats slowly, then the maximum allowable treatment response can be reduced. Thus, the user is able to control the treatment settings simply by changing positional parameters of the handpiece. Thus, the treatment pattern, treatment density, treatment intensity, and other treatment parameters may not be predefined, but may be defined through an automated response to measured positional parameters, to measured treatment response, or to both measured positional parameters and measured treatment response. An electronic or computer interface (not pictured) may be provided to allow switching on or off different modes of user control.
In another embodiment, a treatment status map is displayed on a monitor (not shown) for the user or the patient to observe. The positional sensor 280 can be used to measure the location within the treatment region of the tissue response that is measured by the dosage evaluation sensor 260. In this way, a map can display which parts of the treatment region have been treated and how each part of the treatment region has responded to treatment. The user can take the information on this map to make treatment uniform over the entire treatment region or to have treatment vary in a desirable manner such as treating area with deep wrinkles more heavily than less wrinkled areas. Alternatively, the system can be configured to automatically reduce or disable treatment in the regions that have already been adequately treated as the user continues to move the handpiece over the treatment region. A picture or schematic representation of the treatment region, such as line drawing of a face for treatment of wrinkles on the face, can be used as a background for a computer display of the map of the treatment response measurements.
The use of a postional sensor 280 and/or a dosage sensor 260 to create a map can be used beneficially, particularly with small beam sizes less than 1 mm in their smallest dimension. Using such a map, treatment can be turned on or off based on whether treatment has covered that area or not. The advantage of using a beam size of less than 1 mm is that the granularity of the beam size for treatments that are visually apparent after treatment will be less noticeable for such small beam sizes. Thus, the use of a positional sensor 280 and or a density sensor 260 is particularly suited to fractional treatment and/or treatments with a small beam size of less than 1 mm.
Controller 215, optical source 210, and other components may be external to the handpiece 200 instead of being included inside the handpiece as illustrated in
In a preferred embodiment, the electromagnetic source 210 is a single mode pulsed erbium doped fiber laser with a peak output power in the range of 5-50 W and a wavelength in the range of 1.52-1.62 μm. This laser source can be focused to an optical spot size in the range of 30-600 μm and preferably 60-300 μm on the surface of the skin. Pulse energies in the range 2-100 mJ and preferably in the range of 8-20 mJ can be used for these ranges of optical spot size, wavelength, and power. This preferred embodiment does not include surface skin cooling, but such cooling can be included if desired to reduce damage to the epidermis and dermal-epidermal junction.
The scanning delivery unit 220 used in this embodiment is a scanner wheel rotating at least 360° around an axis 221 as described in detail in U.S. Application No. 60/652,891 and in corresponding U.S. application Ser. No. 11/158,907, which are incorporated by reference herein. Other scanner types will be apparent to those skilled in the art. For example, galvanometer scanners, pseudo stationary deflection (PSD) scanners as described in copending U.S. application Ser. No. 10/750,790, which is also incorporated by reference herein, polygonal scanners, light valves, LCD screens, MEMS based reflective scanners, and translation stages can be used for the scanning delivery unit for delivery of optical energy. Multiple scanning delivery units can be used in such systems to control multiple axes of deflection. For example, two galvanometer scanners can be used in series to scan the laser beam in two directions to cover an area on the surface of the skin 250. Alternatively, single scanning units can cause beam deflection in two directions as described in detail in U.S. application Nos. 60/652,891 and 11/158,907.
One algorithm that can be used to control operational parameters of the scanning delivery unit 220 is to adjust the rotational speed of a double or single wheel PSD scanner and the laser firing rate in proportion to the velocity of the handpiece. This allows microscopic treatment zones of fractional resurfacing to be placed in a predefined pattern on the skin.
Another algorithm for controlling treatment is to adjust the firing of the laser in approximate proportion to the relative velocity of the handpiece to create a predefined density of treatment zones. A uniform distribution of treatment zones across a treatment region by overlapping or abutting treatment zones can also be achieved. For example, if the scanner 220 shown in
In another embodiment, the scanner wheel 220 is run at a velocity that drags the optical beam 230 across the treatment region. This wheel velocity may even be in the opposite direction of the direction that would compensate for movement of the handpiece. This intentional dragging of the optical beam 230 across the surface of the skin 250 can be created with either variable-velocity or fixed-velocity scanner systems. With the fixed-velocity system, for example, the pulse duration of the laser beam can be adjusted according to the velocity of the handpiece 200 such that the optical beam is dragged across the skin by approximately the same distance with each pulse. By changing the angular velocity of the scanner wheel 220 or by changing the pulse duration for the optical beam 230, the distance over which the optical treatment occurs for each pulse can be changed. The controlled dragging of the optical beam can, for example, be used to increase the fill factor for a fractional resurfacing treatment by making each microscopic treatment zone larger by increasing the distance over which optical treatment occurs. As the velocity of the handpiece 200 is reduced, the increased pulse duration prescribed by this algorithm may cause a reduction in treatment response as measured by the dosage evaluation sensor 260. Therefore, it may be desirable to increase the pulse energy to keep the tissue response the same.
The contact plate 239 beneficially reduces optical scattering from the skin surface for the treatment beam by creating a smooth surface that can be used to precisely and reproducibly position the skin relative to the focus depth of the optical beam 230. The contact plate 239 can also act as a thermal heat spreader or can conduct heat away from the surface to actively cool the skin when connected to a cooling source (not shown). The contact plate 239 and dichroic mirror 232 can comprise sapphire, fused silica, borosilicate glass, transparent plastic, or other transparent materials. The contact plate 239, dichroic mirror 232, and other optical components may have optical coatings applied on one or more sides to increase the efficiency of energy delivery into the skin or to enhance the reflectivity or transmission of the illumination 283 from the illumination source 282.
In some embodiments, the contact plate 239 may be undesirable and may be omitted. For example, in ablative laser treatments, it may be desirable to have the surface of the skin be mechanically free to enhance the ablation response of treatment.
To enhance the ability of the optical positional sensor 280 to read the positional parameters of the handpiece 200, a contrast enhancing agent 290 can be applied onto or into the skin 250. For example, uniform application of a dye to the surface of the skin 250 can preferentially decorate certain features, such as skin wrinkles or hair follicles, to create shapes that can be detected as objects by the positional sensor 280. The contrast enhancing agent 290 must be non-toxic when applied onto or into a patient's skin in amounts suitable for adequately enhancing measurements by the positional sensor 280. Preferably, the contrast enhancing agent and the materials and geometry chosen for the handpiece 200 and contact window 239 allow the handpiece 200 to slide easily over the surface of the skin 250.
Examples of contrast enhancing agents 290 are carbon particles, India ink, and FD&C Blue #1. Many other dyes, inks, particulates, etc. can be used as contrast enhancing agents when applied to the skin and when used with the appropriate positional sensor 280. The wavelength illumination source 282 can be chosen to maximize the signal to noise ratio of the measurement of the positional parameters of the handpiece 200. For example, a red LED with a peak wavelength in the range of 600 to 640 nm can be used with FD&C Blue #1.
In many cases, the contrast enhancing agent will be chosen such that it has a low absorption of the treatment energy or of the treatment wavelength in the case of optical treatment energy. In this way, the contrast enhancing agent will not interfere with the deposition of the treatment energy in the treatment region. In some cases, the contrast enhancing agent is chosen such that a measurable or observable parameter changes in response to the treatment energy. A change in the contrast enhancing agent can be used to determine where treatment has occurred, which allows the treatment to be touched up in areas where it is not even or uniform.
It is desirable to choose a contrast enhancing agent 290 that can be removed without abrasive or harsh scrubbing. Alternatively, a removal facilitation substance (not shown) can be applied prior to application of the contrast enhancing agent 290 to allow the dye to be removed more easily. Dimethicone, urea, and arginine are examples of removal facilitation substances. These substances may be applied prior to the contrast enhancing agent 290 to facilitate subsequent removal of the contrast enhancing agent 290. These substances can be applied using common solvents such as water, alcohol, or oil. Concentrations of the removal facilitation substance can be used, for example, in the range of 0.001M to 0.1M.
It is desirable to choose a contrast enhancing agent 290 that is not clearly visible when illuminated with typical room light and/or sunlight. Contrast enhancing agents 290 are said to be “hypovisible” if and only if the contrast enhancing agent is not readily visible on otherwise bare skin with the naked eye when illuminated with 400-650 nm light when the contrast enhancing agent 290 is applied such that the response of the detector 280 is beneficially and substantially enhanced when using an illumination wavelength from 300-400 nm or from 700-1100 nm. The use of hypovisible contrast enhancing agents 290 is desirable because the contrast enhancing agent 290 will be less visible after treatment even if not all of the contrast enhancing agent 290 is removed from the treatment region.
Many fluorescent inks, lakes, dyes, and particulates are examples of hypovisible contrast enhancing agents 290. Fluorescing agents are desirable because the wavelength of illumination can be filtered by the dichroic mirror 232 or by other optical components or coatings while the throughput of the fluorescent emission wavelength is maximized to improve the signal to noise ratio of the positional sensor 290. Polymer (PMMA) encapsulated fluorescent dyes are commercially manufactured by NewWest Technologies (Santa Rosa, Calif.). Other fluorescent materials include collagen, elastin, FD&C Orange No. 5, flavin adenine dinucleotide, flavin adenine mononucleotide, folic acid, niacin, nicotinamide, reduced nicotinamide adenine dinucleotide (NADH), porphyrins, pyranine (FD&C Green No. 7), pyridocine hydrochloride, quinine sulfate, riboflavin, riboflavin phosphate, tryptophan, uranine (fluorescein), or combinations thereof. The absorption and emission spectra for these substances are well published in the art. Other fluorescent materials that are well known in the art can also be used as the contrast enhancing agent 290, for example Carbazine, Coumarin, Stilbene 3, Kiton Red.
The intensity of fluorescent emission of pyranine varies with pH. So pyranine can be used to evaluate changes in barrier function and alert the user or automatically stop treatment or reduce treatment intensity if a break in the stratum corneum or a rupture of the skin occurs during treatment. Thus, the contrast enhancing agent 290 may also be used to improve the signal to noise ratio of the dosage evaluation sensor 260.
Indocyanine green (ICG) is an example of a contrast enhancing agent 290. Most contrast enhancing agents 165 can be diluted with water or other solvents to make them easier to apply or cheaper to use. The peak wavelength of ICG varies depending on the solvent and the concentration of ICG. For example, in water, ICG has an IR absorption peak at approximately 700 nm for high concentrations (e.g. 129-1290 μM) and at approximately 780 nm for low concentrations (e.g. 6.5-65 μM). For ICG in blood plasma, there is an absorption peak in the range of approximately 790-810 nm across a broad range of concentrations (6.5-1290 μM). In general, ICG typically has an absorption peak in the range of 650-850 nm for most solvents. ICG also has absorption peaks in the UV range. ICG does not have a strong absorption peak in the range of 400 to 650 nm, which makes it difficult to see with the naked eye. Thus, ICG is an example of a contrast enhancing agent that has low visibility to the human eye, but is easily discernable to a silicon based optical detector when illuminated appropriately. In non-fluorescing contrast enhancing agents, the wavelength (or wavelength range) of illumination can be chosen to be in a region where the peak absorption of the contrasting agent is at least 3 times, or preferably at least 10 times, stronger or weaker than that of skin. It is also desirable to have the peak absorption of the contrasting agent in the chosen wavelength (or wavelength range) to be at least 3 times, or preferably at least 10 times, stronger than the peak absorption within the wavelength range of 400-650 nm.
The contrast enhancing agent can also be applied in a pattern. The pattern may comprise a uniform grid of identical FIGS. 391 in the treatment region 357 as illustrated in
Patterns of contrast enhancing agents can also be attached to the skin using adhesives as used in temporary tattoos. As in a temporary tattoo, a pattern can be created by printing a contrast enhancing agent on or embedding a contrast enhancing agent in an adhesive that attaches to the skin. The adhesive has the advantage of being easier to remove than many of the contrast enhancing agents that can be included in or on the adhesive. Lakes of FDA approved colors such as FD&C Blue #1 (also packaged as Optiguide Blue by Reliant Technologies, Palo Alto, Calif.) can be embedded in a polymer-based tattoo adhesive and painted onto the skin. Following treatment, these adhesive based patterns can be removed with alcohol and light scrubbing. The use of adhesive also allows the use of contrast enhancing agents in doses that would otherwise be toxic to the skin because the adhesive can be designed to provide a barrier between the skin and the contrast enhancing agent.
Alternatively, contrast enhancing agents may be suspended in sugar-based or gel based solutions without patterning. These solutions can desirably be made viscous so that they do not drip outside the treatment area.
Instead of applying a pattern of figures with a contrast enhancing agent, the laser treatment zones may form a pattern of figures that is used to enhance the response of the positional sensor 280. For example, a CO2 laser can ablate portions of the skin to create a pattern of ablated areas interspersed inside nonablated areas. This pattern can be illuminated with an LED to provide visible features that enhance the signal to noise ratio of an optical mouse chip functioning as a positional sensor 280.
Other embodiments of the positional sensor 280 are illustrated in
The positional sensors and dosage evaluation sensors shown in
While the embodiment illustrated in
As shown in
Measurements of acceleration or angular acceleration can be integrated in time to produce measurements of velocity and position or angular velocity and angular position. In many configurations, an initial calibration and periodic recalibrations may be required to reset the reference velocity, angular velocity, position, and/or angular position.
Accelerometers measure absolute positional parameters of the handpiece 400 rather than relative positional parameters of the handpiece 400 with respect to the treatment region of the skin 450. If relative positional parameters are desired, accelerometers can be used when the treatment region is immobilized or when absolute movement of the treatment region is insignificant. Alternatively, the absolute movement of the treatment region of the skin 450 and the absolute movement of the handpiece 400 can both be measured and the relative motion between the handpiece 400 and the treatment region of the skin 450 can be calculated.
Relative measurements of angular position can be used to provide feedback to the system and disable the laser unless the relative angle of the handpiece is within a certain angular range relative to the surface normal from the surface of the treatment region. This may be useful, for example, to align properly a cooling spray and a treatment laser beam on a treatment region. Absolute measurements of angular position are useful if the handpiece 400 has components that are sensitive to gravity, such as fluid-filled cavities that leak if turned upside down. Relative measurements of position can be used to measure distance between locations for pulsing the electromagnetic source 410.
Absolute or relative measurements of velocity, acceleration, angular velocity, and angular acceleration are useful for evaluating whether the handpiece has been dropped or has suddenly slipped in an uncontrolled way, which might lead to undesired treatment outside the desired treatment area. A combination of relative positional parameter measurements and absolute positional parameter measurements can be used to measure movement of the patient. For example, if the patient suddenly moves, the difference between the relative acceleration and the absolute accerlation measurements may be significant. In any of the situations described in this paragraph, the controller 415 may temporarily disable the electromagnetic source 410 to prevent treatment in areas that are not desired by the user.
The number and location of transmitters and receivers determines the positional parameters that can be measured. For measuring the position of the handpiece in three dimensions, three transmitters and one receiver can be used. For measuring the position of the handpiece in up to three dimensions and also measuring the angular position for up to three independent angular directions, a second receiver can be used. For measuring all three dimensions and all three handpiece angles, three transmitters and three receivers are preferably used in order to have redundancy. A simple apparatus comprises two transmitters and one receiver. This apparatus can be used to measure the positional parameters of a handpiece in two dimensions along a predefined surface. In an alternate configuration, two receivers are used with one transmitter to produce the same measurement. The particular geometry and locations of transmitters and receivers can be generalized by one skilled in the art.
For simplicity in the examples described below, receivers are located on the handpiece and transmitters are located inside the treatment region 557 or are mechanically coupled to the treatment region 557 such that the measured positional parameters of the handpiece will be relative to the treatment region and not absolute measurements. Other configurations can be used if absolute measurements are desired. Light based or other electromagnetic communications systems can be used for these types of systems as well.
In one embodiment, three radio frequency transmitters are attached to a cap, preferably made of cloth or latex for ease of use and low cost. For example, transmitters can be attached to EEG caps for this purpose. This type of cap is useful for locating the handpiece when treating wrinkles on the forehead or periorbital areas of the face, for example, because the transmitters can be mechanically coupled to the treatment region. This type of cap can also be used with the coil measurement system described in the text for
One advantage of the accelerometer, magnetic, gyroscope, and transmitter-receiver based measurement systems is that they can easily be used in noncontact mode, which reduces the chance of skin movement during treatment and allows the handpiece to be held at different distances from the skin in order to manually adjust the beam size that is incident on the skin surface.
Multiple positional sensors can also be used, for example, to allow lower quality signals from each of the positional sensors. For example, an optical mouse type sensor can be used with a magnetic radiator coil measurement system. The combination of multiple sensors can also be used to shut the system down if large discrepancies were noted between or among the sensors. If different types of sensors were used, discrepancies can be used to provide additional information, for example, about whether the skin is being stretched. This information can be used to detect situations when the handpiece is not sliding properly and can be used to provide feedback to the system and reduce localized over- and under-treatments.
The ultrasonic transmitter-receiver pairs shown in
During certain types of photothermal treatment, dermal collagen is coagulated, which causes a loss of optical birefringence for the collagen. This change in birefringence can be measured by the imaging sensor 850 and can be used, for example, as the endpoint of a treatment pulse to control the duration of a treatment pulse.
The polarizer 867 may be adjustable (automatically or manually) to make alignment easier or more precise or to allow comparison of cross polarization and parallel polarization images.
The embodiment shown in
In another implementation of the dosage evaluation sensor illustrated in
Using a dosage evaluation sensor 961 before treatment and another dosage evaluation sensor 960 after treatment allows the controller 915 to calculate how much treatment is applied for a particular treatment setting. The controller 915 can then make adjustments as appropriate to adjust the parameters of the electromagnetic source 910. This dosage feedback loop allows real time adjustment of treatment parameters.
An example of a dosage feedback loop uses a first capacitive dosage evaluation sensor 961 and a second capacitive dosage evaluation sensor 960. Each capacitive dosage evaluation sensor measures the percentage of skin that has been treated with a nonablative fractional resurfacing treatment. The first and second capacitive dosage evaluation sensors 961, 960 are positioned in front of and behind the treatment window such that the first capacitive dosage evaluation sensor 961 measures the percentage of skin that had been treated prior to the current pass of the handpiece and the second capacitive dosage evaluation sensor 960 measures the percentage of skin that has been treated after the current pass of the handpiece over the treatment region. The difference between the measurements for the two sensors 960, 961 describes the percentage of skin treated during the current pass of the handpiece over the treatement region. The calculation of the percentage of skin treated during the current pass can be used, for example, to avoid overtreatment caused by bulk heating of tissue by reducing the laser treatment energy when unusually high percentages are calculated. Other examples of appropriate dosage feedback sensors 960, 961 are described in U.S. application Ser. No. 10/868,134, which is incorporated by reference herein.
The characteristics of the generated stress wave vary based on mechanical and optical characteristics of the skin. The probe wavelength can be chosen such that there is a difference in absorption within the skin between untreated and treated skin. Alternatively, the pulse conditions are chosen such that the mechanical response is different for treated and untreated skin. Thus, the stress wave that is created can be measured to determine whether the probed skin is approaching, has reached, or has exceeded a desired level of treatment. Examples of mechanical characteristics of the skin that can be probed using a stress wave include elasticity, tension, and mechanical damping of the skin.
The signature of the stress wave that is generated can be measured using several different techniques. One technique is illustrated in
A second technique for measuring the stress wave is to observe the change in reflectance pattern from a beam incident on the surface of the skin as shown in
The components 1162, 1163, and 1164 are similar to their analogs in
The optional contact window 1165 is preferably comprised of a transparent material, such as fused silica or sapphire, through which the probe beam 1163 passes.
The probe beam 1163 is absorbed by the skin 1150 to create a stress wave in the skin 1 150. As described above for
The coherent illumination source 1172 should be a coherent source, for example a HeNe laser. The angle of the coherent illumination beam 1173 relative to the surface of the skin 1150 and the angle of the imaging system relative to the surface of the skin 1150 and relative to the coherent illumination beam 1173 is preferably aligned to maximize the measurement signal. Once a signal has been measured, the decay constant and resonant frequency of the stress wave can be measured with of the apparatii described by
With the techniques described in
The examples presented here have all illustrated the use of these techniques on human skin. This invention is also applicable to treatment of other tissues of the body. For example, puncturing the surface of toenails for treatment of nail fungus, soft palate for treatment of disorders such as sleep apnea and snoring, hair removal, topical delivery of pharmaceuticals or nutriceuticals, or treatment of heart tissue for laser-based TMR treatments can all benefit from the use of this invention.
Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed in detail above. For example, in many of the examples above, lasers are used as the embodiment, but these can be generalized to RF, flashlamp, or other electromagnetic energy based treatments as well. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims.
In the specification and in the claims, reference to an element in the singular is not intended to mean “one and only one” unless explicitly stated, but rather is meant to mean “one or more.” In addition, it is not necessary for a device or method to address every problem that is solvable by different embodiments of the invention in order to be encompassed by the claims.