METHODS AND APPARATUS FOR REMOVAL OF SKIN PIGMENTATION AND TATTOO INK

Abstract

Methods and apparatus for dermatological laser treatment, e.g. for the removal of unwanted tattoos or other skin pigmentation. Removal of multiple colors with a single pulsed laser beam may be achieved using intensities in excess of about 50 GB/cm.sup.2. Methods for reducing the pain and tissue damage associated with laser tattoo removal include using a spot size of less than 2 mm with a fluence in the range of 0.5-10 J/cm.sup.2. Scanning the laser beam over an area of skin to be treated allows such areas to be treated accurately with scanning patterns calculated to promote rapid dissipation of heat away from treated portions of the skin. Multiple treatment rooms may be served by a single pulsed treatment laser by beam toggling, splitting or pulse-picking to minimise downtime of the laser.

Claims

1. A laser based system for medical, dermatological or ophthalmic treatment, in which the system includes: (i) a laser located in a first part of a treatment facility; (ii) a beam splitter or beam selector that receives laser pulses from the laser and directs the laser pulses to two or more treatment rooms or areas in a different part or parts of the treatment facility; and the system further includes, in each of the treatment rooms or areas, a laser work head that receives laser pulses from the laser.

2. The laser based system of claim 1 in which the beam selector is configured to sequentially direct laser pulses to different laser work heads, each in a different treatment room or area.

3. The laser based system of claim 2 in which a beam selector directs laser pulses to one treatment room or area, and then to a different treatment room or area.

4. The laser based system of claim 2 in which the beam selector is a motorized flip mirror.

5. The laser based system of claim 2 in which the beam selector includes a set of modulators, such as Pockels cells, that are each selectively turned on by a control unit to down-sample the pulses from the laser and direct the down-sampled pulses to separate treatment rooms or areas.

6. The laser based system of claim 1 in which the beam splitter is configured to generate substantially simultaneous multiple laser pulses, each directed to different laser work heads, each in a different treatment room or area.

7. The laser based system of claim 6 in which the laser generates a single high frequency pulsed treatment laser beam that is multiplexed into a plurality of separate treatment rooms or areas in parallel by the beam splitter, configured for pulse-picking.

8. The laser based system of claim 1 which includes a series of two or more beam splitters or beam selectors.

9. The laser based system of claim 1 in which a beam dump is configured to receive laser pulses that are not sent to a laser work head.

10. The laser based system of claim 1 in which the laser is a femto-second laser, such as a 800 nm Ti:Sapphire laser.

11. The laser based system of claim 10 in which the laser emits 100-30,000 femtosecond pulses, with 1-10 millijoule energies at 1 Khz pulse repetition rate.

12. The laser based system of claim 1 in which there is a second laser, also located in the first part of the facility, that is not a femto-second laser.

13. The laser based system of claim 12 in which the second laser is a 1064 and 532 nm Nd:YAG laser that emits sub nanosecond pulses at 1-10 millijoule energies and 500 Hz pulse repetition rates.

14. The laser based system of claim 1 in which the first part of the facility is a laser room configured to ensure that optimal conditions for the laser are maintained.

15. The laser based system of claim 1 in which the laser has a laser output which is connected to an optical system for directing laser beams produced by the laser into the treatment rooms or areas where they are supplied to a work station comprising a work head.

16. The laser based system of claim 1 in which there are multiple treatment rooms or areas and each treatment room or area includes an articulating arm that is fixed to the wall or floor of the treatment room or area for stability, and a patient treatment chair.

17. The laser based system of claim 1 in which a dividing wall separates a laser room, housing the laser, from each treatment room or area.

18. The laser based system of claim 1 in which the system is configured to operate to sequentially treat patients in different treatment rooms or areas with the laser pulses.

19. The laser based system of claim 1 in which treatment room or area includes an articulating arm that terminates in a work head that includes a laser beam scanning system.

20. The laser based system of claim 19 in which each articulating arm includes an internal mirror system positioned at a joint to reflect a laser beam, generated by the laser, that is passed internally through the arm and to the work head to deliver laser pulses to skin or tissue to be treated.

21. The laser based system of claim 20 in which the laser beam is reflected at the internal mirror to pass through a limb of the arm, and when that limb rotates through an angle, then the mirror is mounted on a gear or mechanism that provides for the mirror to rotate through half that angle.

22. The laser based system of claim 1 in which the work head is configured to automatically scan or move the laser beam in a defined pattern and/or velocity across the skin or tissue to be treated.

23. The laser based system of claim 22 in which the work head is configured to be manually placed by a human operator at the correct region and the scanning head then automatically steers or moves the laser beam within that region.

24. The laser based system of claim 22 in which the work head steers the laser beam using galvanometric mirrors or any other beam steering method, such as acusto optical beam steering.

25. The laser based system of claim 22 in which the defined pattern is a scanning pattern over a tattoo or a region of a tattoo and the system is configured to remove that tattoo.

26. The laser based system of claim 22 in which the defined pattern is selected to ensure no significant thermal heating of the skin or tissue is achieved by the laser beam.

27. The laser based system of claim 1 in which a camera or imaging system displays the skin or tissue to be treated on a display or monitor, illuminated by an alignment laser that shows the perimeter, border or region to be treated by the laser.

28. The laser based system of claim 1 in which the work head includes a camera or imaging system that optically images the area to be treated and automatically enables the laser to be incident on the tissue to be treated only when the system automatically determines that the laser beam is correctly aimed.

29. A method of using a laser for medical, dermatological or ophthalmic treatment, comprising the steps of: (i) providing a laser located in a first part of a treatment facility; (ii) sending laser pulses from the laser to a beam splitter or beam selector, in which the beam splitter or selector directs the laser pulses to two or more treatment rooms or areas in the treatment facility; (iii) providing, in each of the treatment rooms or areas, a laser work head that receives laser pulses from the laser and, in use, directs them to a patient.

30. A method of tattoo removal comprising the steps of: (i) providing a laser located in a first part of a treatment facility; (ii) sending laser pulses from the laser to a beam splitter or beam selector, in which the beam splitter or selector directs the laser pulses to two or more treatment rooms or areas in the treatment facility; (iii) providing, in each of the treatment rooms or areas, a laser work head that receives laser pulses from the laser and, in use, directs them to a tattoo to be removed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0142] In the drawings:

[0143] FIG. 1 is a schematic side view of a dermatological laser treatment facility which includes laser treatment apparatus according to a first embodiment of the present invention.

[0144] FIG. 2 is a schematic section side view of an optical path and scanner head of the dermatological treatment apparatus of FIG. 1 which is shown connected to a pulsed laser via an articulating arm for laser beam delivery to a subject. The work head includes a galvanometric x-y scanner as a beam steering apparatus. The beam is then focused to reach a desired size on subject’s skin.

[0145] FIG. 3 is a side elevation of a manually movable scanner work head forming part of the dermatological laser treatment apparatus of FIG. 1.

[0146] FIG. 4 is a rear elevation of the work head of FIG. 3.

[0147] FIG. 5 shows various scanning fields of different sizes and shapes which are selectable in the work head of the system in FIG. 1

[0148] FIG. 6 is a flow chart of the operation of the dermatological laser treatment apparatus of FIG. 1

[0149] FIG. 7 is a flow diagram of a method for removing a tattoo or other pigmentation from a subject’s skin in accordance with the present invention.

[0150] FIG. 8A illustrates treatment of an area to be treated in accordance with a prior method. FIG. 8B illustrates shape/size optimisation of the scanning field in accordance with the present invention In the prior method as shown in FIG. 8A, an exemplary thin stem of a rose-shaped tattoo requires a very small spot size; a large number of spots with exact placement are needed to cover the entire stem. By contrast, in the scanning method of the present invention, the scanning field may be programmed to any desired shape. An elongated rectangular scanning field, for example, may be more efficient and faster for treating long, thin tattoo lines.

[0151] FIG. 9 is a flow chart of a method for determining a required working fluence (intensity) for pigment removal using pulsed laser light of different pulse widths.

[0152] FIG. 10 is a chart of measured ablation threshold fluence vs. pulse width for various colours of pigment. It is evident that shorter pulse widths require less fluence, and difference in threshold between different colours is smaller.

[0153] FIG. 11 shows an example of multicolour tattoo removal in accordance with the present invention using a high intensity laser as compared with a prior method using a low intensity laser. Depicted are photographs showing actual removal results in a controlled experiment performed on live porcine skin.

[0154] FIGS. 12A and 12B show skin temperature profiles over time. FIG. 12A shows the temperature profile resulting from an high energy large spot. FIG. 12B shows the temperature profile resulting from a low energy small spot. Onset of heat diffusion is noticeable at time scales of about 10 s for the large spot. For a small spot, diffusion of heat is noticeable after less than about 0.1 s.

[0155] FIG. 13 is a chart showing the temperature at the centre of a volume of a heated tissue as a function of time. The thermal relaxation time (50% of initial temperature delta) for a 1 mJ, 0.22 mm spot is about 0.12 s; for a 5 mJ, 0.5 mm spot, the thermal relaxation time is about 0.7 s; and the thermal relaxation time for a 500 mJ, 5 mm spot is about 70 s.

[0156] FIG. 14 is a chart showing thermal relaxation time vs. pulse energy for a given fluence of 2.5 J/cm2.

[0157] FIGS. 15A and 15B illustrate schematically raster scanning vs. interlacing of an area of skin to be treated in accordance with the present invention. FIG. 15A shows standard raster scanning with time T between adjacent lines. FIG. 15B shows an interlacing scan by skipping K lines and returning after bottom line to the top. Time between rows is T*K.

[0158] FIG. 16 is a cross-sectional side view of a holder for a scanning head in accordance with a second embodiment of the present invention.

[0159] FIG. 17 is an exploded view of a separator assembly which forms part of the holder of FIG. 16 and is capable of testing scanner, laser and optical alignment prior to treatment.

[0160] FIG. 18 is a flow chart which illustrates operation of the holder to perform a test routine.

[0161] FIG. 19 is an illustration of an automated scanning work head connected to a balanced articulating arm positioned over a treatment chair in accordance with a third embodiment of the invention.

[0162] FIG. 20A is a schematic drawing of an underside of the scanning work head of FIG. 19.

[0163] FIG. 20B is a side view of the scanning work head of FIGS. 19 and 20A, including a schematic drawing of a subject with pigment to be removed.

[0164] FIG. 21A to 21E illustrate an example of an image acquisition, verification and tattoo-removal treatment sequence in accordance with the present invention. In FIG. 21A, an aiming beam indicates a scanning field outline to an operator. In FIG. 21B, a contour of a target area to be treated is measured and scanning parameters are calculated. FIG. 21C illustrates a preview of a scanning field/sequence using the aiming beam or an on-screen display. FIG. 21D and 21E illustrate the tattoo-removal sequence.

[0165] FIGS. 22A and 22B illustrate the effect of topography on the attainable scanning field. In FIG. 22A a flat target is shown and the whole scanning field of the scanner head can be used. In FIG. 22B, a non-flat target reduces the accessible scanning field. A spherical topology is shown for simplicity.

[0166] FIG. 23 illustrates schematically treatment of a pigmented area to be treated that is larger than an attainable scanning field. A stitching algorithm is used to treat the entire area in a plurality of scanning segments using pattern recognition of untreated areas with overlap.

[0167] FIG. 24 perspective view of a 6-axis robot mounted with a scanner head.

[0168] FIG. 25 is a schematic drawing of a dermatological treatment facility in accordance with a fourth embodiment of the invention in which a single pulsed laser beam from a single treatment laser can be selectively toggled between a plurality (in this case two) different treatment areas.

[0169] FIG. 26 is a schematic drawing of a dermatological treatment facility in accordance with a fifth embodiment of the invention in which a single high-energy pulsed treatment laser beam is split and steered in parallel into a plurality of different treatment areas.

[0170] FIG. 27 is a schematic drawing of a dermatological treatment facility in accordance with a sixth embodiment of the invention in which a single high frequency (pulse repetition rate) pulsed treatment laser beam is multiplexed into a plurality of separate rooms in parallel by pulse-picking.

[0171] FIG. 28 is a timing diagram for the pulse-picking used in the dermatological treatment facility of FIG. 27.

[0172] FIG. 29 is a schematic drawing of the electrical and electronic components and connectivity of a dermatological laser treatment apparatus according to the one embodiment of the present invention shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

[0173] FIG. 1 of the accompanying drawings shows schematically a dermatological treatment facility in accordance with one embodiment of the present invention. The facility is provided in two adjacent rooms 12, 13 separated by a dividing wall 21. One of the rooms 12 is a treatment room; the other is a laser room 13 housing first and second treatment lasers 1, 2. In the present embodiment, the first laser 1 is a 800 nm Ti: Sapphire laser that produces ultra-short pulses, and the second laser 2 is a 1064 and 532 nm Nd:YAG laser. The Ti sapphire laser emits 100-30,000.00 femtosecond pulses, with 1-10 millijoule energies at 1 Khz pulse repetition rate. The Nd-Yag laser emits sub nanosecond pulses at similar energies and 500 Hz pulse repetition rates. It will be understood that different lasers may be used in other embodiments of the invention. An aiming beam 5 is coupled optically to the treatment lasers 1, 2 as described below to assist in placing a work head 4 as described in more detail below in a correct position over an area of a subject’s skin to be treated. A power and control unit 6 is provided, which includes a computer, power supply and dedicated controllers for system operation.

[0174] The laser room 13 ensures optimal conditions for the lasers 1, 2 are maintained. The treatment room 12 contains only operator and subject-accessible equipment.

[0175] Each of the first and second treatment lasers 1, 2 has a laser output 23 which is connected to an optical system 22 for directing laser beams 11 produced by the lasers 1, 2 through the dividing wall 21 into the treatment room 12 where they are supplied to a work station 25 comprising dermatological treatment apparatus in accordance with the invention. The optical system 22 may be any suitable arrangement of mirrors lenses and other optical components known to those skilled in the art (described below) and is received in a protective conduit where it passes through the dividing wall 21.

[0176] In the treatment room 12, adjacent the work station 25 there is provided a treatment chair 10 for a subject to be treated (not shown).

[0177] The work station 25 comprises a console 7 and an articulating arm 3 that is fixed to the wall or floor of the treatment room 12 for stability. The articulating arm 3 carries the above-mentioned work head 4 at its free end. The articulating arm 3 is capable of directing the treatment laser beams and the aiming beam optically (by using mirrors and joints assembly) into an optical input on the work head 4 at any point in a certain volume of the treatment room.

[0178] The work station 25 is connected to a foot pedal 8 for controlling laser output.

[0179] Referring to FIG. 2, the treatment laser 31 (previously referred to as lasers 1 and 2 in FIG. 1 ) is controlled by a dedicated controller 44. For clarity only one treatment laser 1 is depicted, but arrangement of the second laser 2 is similar. Each treatment laser output 31 is monitored in real time by a fast detector 32 which is operable to sample a small percentage of the beam 42 using a beam sampler 35 (which also serves as an aiming beam coupler in this embodiment). The controller 44 is configured to shut down the laser power and close a shutter 33 automatically in the event that the output of the treatment laser deviates from maximal or minimal pulse energy.

[0180] The aiming beam 34 is coupled to the treatment laser beam optical path by a coupling mirror 35. Beam path then travels through a beam expander 36 for propagation through the rest of the system. Travelling through the articulating arm 43, both beams arrive at the work head 37.

[0181] The work head 37 includes a detachable spacer 38 and a galvanometric scanner 41. In use, the laser beam travels into the galvanometric scanner 41 where it is directed by motorized mirrors 40 to pass through lenses 39 and onto a subject’s skin. The spacer 38 extends away from the work head and terminates in a smooth distal end for contacting the subject’s skin. The scanner galvanometric mirrors 40 are rotated so that the beam arrives at the focus lens assembly 39 at an angle. This angle is translated to a position on the subject’s skin through the focus lens assembly. The lenses create a desired spot size on the surface of the skin, which can be resized by an operator to attain required fluence. In the present embodiment a spot size of 0.7 mm is used for a 4 J/cm2 fluence, but it will be understood by those skilled in the art that any spot size of less than about 2 mm, preferably less than about 1 mm may be used, with a fluence in the range of about 0.5-50 J/cm2, preferably about 1-30 J/cm2. The scanner 41 then steers the spot across the skin within a scanning field of adjustable size and shape. The distance between adjacent spots is configurable and is typically less than about 0.1 mm. In some alternative embodiments, overlapping spots having a gaussian profile may be used. The amount of overlap may typically be about 0.1 mm. Different selectable rectangular scanning fields are shown in FIG. 5 by way of example. In particular, in the present embodiment, the galvanometric scanner 41 is operable to scan a configurable rectangle of from about 1 mm to about 10 mm in the length and/or width. It will be understood that in other embodiments, the scanning field may have any predetermined or arbitrary shape within the limitations of the scanner 41. The distance to the area of the subject’s skin may be determined by the spacer 38.

[0182] The work head also contains a motion sensor 26. During operation of the main laser, if the motion sensor detects motion above a predefined threshold it signals the control unit 6 to stop main laser immediately. This helps prevent unintended or uncontrolled lasing.

[0183] The work head 37 includes an outer shell 20 as best shown in FIGS. 3 and 4 which is designed as an ergonomic, plastic assembly that includes a scanning field size selector knob 14, an outline switch 15 to activate the aiming beam 34, indication lighting 19 and a replaceable spacer 18 (38 in FIG. 2).

[0184] The scanner mirrors are programmed to scan one of a set of predefined rectangles FIG. 5 45-54 in sizes ranging from 1 to 10 mm with various aspect ratios. Each rectangle corresponds to a specific setting of the field selector knob 14. In other embodiments of the invention the scanner mirrors may be operable to produce scanning fields of different sizes and/or shapes other than rectangles, e.g. circular scanning fields.

[0185] As best seen in FIG. 29, the controller unit 6 includes a power supply 401 with power lines 401, a processor 402 with memory for storing software and data 404, and real time controller 405, and programmable logic device 403. Combined, these assure smooth and safe operation of the system with acceptable redundancy. Signals and data are connected to various system components (1, 2, 5, 4, 37 etc) as shown through power and data lines 411. The real time controller 405 and processer 402 communicate with a digital scanner controller 406, which in turn operates an analogue scanner driver 407. Those supply both power and control to the galvo mirror scanner 41 in the work head 37. For clarity many connections and details have been omitted.

[0186] The system follows the logic depicted in the diagram of FIG. 6. During power up 61, several safety checks are performed, followed by the idle state 62. Once the outline switch 15 is switched on by the operator, the system moves to outline mode 63. The system remains in outline mode, continuously scanning the rectangle outline (i.e. one of 45-54) with the aiming beam 34, until the outline switch 15 is turned off or until the foot pedal 8 is depressed. Once the foot pedal is depressed, the main laser is turned on and pulses of laser light are scanned across the rectangle scanning area in a full scan mode 64. Once the entire area has been irradiated by laser pulses, the laser is switched off and the system returns to outline mode 63.

[0187] During application of treatment, the operator inspects the shape and size of the pigment to be removed 70. Once the operator turns on the outline scan the aiming beam then outlines the rectangle currently chosen on the subject skin 73 as shown in FIG. 7. This allows for visual feedback and accurate alignment of the scanner on to the treated area. Operator adjusts the field selector so that the rectangle fits the pigment shape and size and places the work head accurately over the pigmented area 77. Once the operator is comfortable with the set scanning field placement, the foot pedal 8 is depressed, and main laser then irradiates the subject’s skin by covering the entire area of the scanning field with laser spots -one spot in each location 79. In the present embodiment, the full scan duration is shorter than 1 second, typically 0.5 second. After the full scan, the main treatment laser is switched off and the aiming beam 34 outlines treated area again 81. Treated areas are usually visible due to a frosting effect of pulsed laser and skin interaction 82. To achieve optimal results, a laser set point is chosen as described in Example 2 below.

[0188] The throughput benefit of adapting the scanning field shape to the tattoo or other area of pigment can be appreciated by comparing the examples shown in FIG. 8A and B. To cover an elongated shape such, for example, as a stem of a rose, using appropriate rectangles 86 requires five scans. For a square or circular shape 85, the number of scans is about 3x greater. Since a single field scan is very fast, the placement process of the operator is the main contributing factor for total treatment time. Thus 3x fewer fields translates to ~3× faster treatment time. For a 3 mm thick and 50 mm long stem, for example, using a 500 Hz pulse repetition rate and a 0.6 mm spot size with no overlap, we arrive at approximately 830 spots, which equals 1.7 seconds of net scanning time. Using a 3x3 mm field (see FIG. 8A), there are approximately 17 separate fields to scan. Assuming a well-trained operator with a field placement time of the order of 0.75 second, we have 12.75 seconds of placement time and 14.45 seconds of total treatment time. When using a rectangular field of 3x10 mm as shown in FIG. 8B, we have ~5 placements, so total treatment time is 5.45 seconds. Although the difference between 15 and 5 seconds is not prohibitive for a treatment session, by repeating this analysis for much larger pigmented areas with complex shapes and features, it is evident that by optimizing the field shape, a huge reduction in treatment time can be achieved. Example 5 below takes this concept further to achieve even shorter treatment times.

Example 2

[0189] Using ultra-short and ultra-high intensity radiation in accordance with the present invention is beneficial for removing several colours with one wavelength, beyond linear absorption which is highly colour selective. When designing a new system one must determine the proper laser working point in order to achieve multi-colour pigment removal. A working point comprises fluence, pulse width and intensity. The intensity is required to be high enough for multi-colour removal, and it is usually determined by the combination of fluence (energy density) and pulse width. Fluence should be high enough to support the intensity, but not too high as to create excessive damage (typically about 0.5-10 J/cm.sup.2). Pulse width should be short but is usually limited by the specific laser design. Preferred pulse widths are of the order of about 0.5-30 picoseconds. Pulse energy is discussed below in Example 3. The optimal working point depends on the wavelength of the specific laser, the target colours (the more the better, usually) and the available laser pulse width of a specific laser system. To find a proper working point, we measure the reaction threshold of different ink colours/skin pigments in a lab setup. The test is repeated for each target pigment. A test target is created by mixing Gelatine, water and pigment. Referring to FIG. 9, the target is then scanned with a set of fluences, where for each fluence, pulse width is modulated (in effect modulating intensity). Once interaction is witnessed in the target (usually according to damage in the target) the threshold fluence for a specific pulse width is determined. By finding the highest intensity needed for the hardest to damage colour, we have arrived at a required intensity that covers all colours. It should be noted that in this method, intensity and fluence are tested independently though pulse width modulation, and is inherently different from prior art methods, where fluence and intensity are coupled since pulse width is constant.

[0190] In FIG. 10 shows an actual lab measurement result. As pulse width increases, more and more fluence is required for effective interaction with a target pigment. The spread of different fluences required for different colours also increases considerably. Prior art laser systems typically work at >250 ps pulse width and lower intensities. For a given fluence at pigment location in the tissue of say ~1 J/cm2 (indicated by reference numeral 100 in FIG. 10), a system might be able to remove green and black for example, but would not be able to remove red and yellow colours. This is because yellow and red have a considerably higher fluence threshold for that pulse width. Alternately one can state that “they do not absorb enough” in the given wavelength and pulse width. By decreasing the pulse width below ~25 ps in accordance with the present invention, the same fluence 101 is capable of removing successfully all colours in this case. This is because at this pulse width, the threshold for interaction is below the given fluence. It should be noted that the same wavelength as in the prior art is now capable of removing all colours as a result of the greater intensity.

[0191] The above method is applicable per specific laser wavelength, where different lasers require different maximal intensities and/or fluences depending on target colours vs. used wavelength. But once the threshold intensity is used, all target colours will be removed by that specific laser.

[0192] By “removal” herein it is intended that full clearance of colour from skin (to naked eye) may be achieved after a finite number of sessions. The number of sessions might vary from one target colour to the next, but in any case, the number of sessions from one colour to the next will not vary by more than a factor of about two.

[0193] Commercial lasers are available for the prescribed parameter set. See for example PicoLaser ltd “Pico-1M” laser with 8 mJ and 8 ps pulse width, or Amplitude Laser ltd “Magma” laser with 30 mJ and 1.5 ps pulse width.

[0194] FIG. 11 depicts actual removal results in a controlled experiment performed on live porcine skin, as an example of the above stated method and system. The target is a multi-coloured square, including areas coloured green 111, blue 112, cyan 113, orange 114, red 118, yellow 117, purple 116 and black 115. Middle of target is untattooed, while boundaries are outlined black.

[0195] Using various pulse width and several treatments in the span of two months, pre- and post-images are shown 101-106. Laser A used a pulse width of 6 ns; laser B 0.6 ns; and laser C employed 1-15 picosecond pulse width (100-1000x shorter). Lasers A, B used 4 J/cm2 fluence, while Laser C used 2 J/cm2 fluence;. The intensity of each of lasers A/B was 0.7 /7 GW/cm2, while laser C had an intensity above 50 GW/cm2. With lasers A, B noticeable removal is achieved in outline black (101 vs. 102 and 103 vs. 104). For the short pulse laser C, all tattoo colours responded and above 80% clearance was achieved (105 vs. 106). Quantitative clearance levels are shown at 107.

Example 3

[0196] The process of laser pigment removal, although targeting pigment, creates local heating in the tissue surrounding the pigment. Although local damage in tissue holding pigment is unavoidable, the surrounding tissue, not directly damaged by pigment radiation absorption, will suffer from secondary heating. The duration of local elevated heating is at the root of higher damage to surrounding tissue. In the following example we will quantify these effects.

[0197] During irradiation of pigmented tissue, the following occurs: Initially, on the time scale of laser pulse width, radiation is absorbed in parts of the tissue that are absorbing, usually in specific chromophores that are targeted for treatment. These can achieve very elevated temperatures (even thousands of degrees) in very short time scales of pico or nano seconds. This usually leads to plasma creation, mechanical breakdown and/or other violent events, which are usually the desired effect of the treatment. Nevertheless, after a short time, all this energy is converted finally to heat: plasma radiation is re absorbed after pulse is over, kinetic particles are slowed through collisions to a halt. Except for chemical alteration (usually an undesired effect), eventually all of the incoming radiation is converted to heat.

[0198] For time scales much longer than pulse width we can use a bulk heat approximation for absorbing layer to estimate the temperatures induced in the tissue. Considering, for example, an average 2.5 J/cm.sup.2 fluence, 500 mJ pulse energy and a 5 mm spot diameter. Tattoo ink, for example, which absorbs laser radiation, is usually/predominantly at a depth from 300 to 700 .Math.m below skin surface. We assume all radiation is absorbed in that thickness, within a cylinder of diameter as of the input pulse (for simplicity) and use water specific heat as a good estimation. Using ΔT=E/M•C we arrive at a temperature elevation of approximately 15° C. above ambient skin temperature of ∼34℃ (outer) to 36.8° C. (inner)

TABLE-US-00001 Water specific heat [C] 4.18 J/gr/deg C specific weight 1000 gr/liter spot diameter 0.50 cm pulse energy [E] 500 mJ absorption depth 0.04 cm fluence 2.5 J/cm^2 volume 8.00E-03 cm^3 Mass [M] 8.00E-03 gr ΔT 15 Deg cell

[0199] This is also true for a 5 mJ pulse energy with 0.5 mm diameter (100x lower energy and 10x smaller diameter). The same average heating will always occur in this approximation if fluence is similar.

[0200] The advantage of applying only small, low energy pulses is clear by looking at heat diffusion over time. After a very quick initial heating process (in the order of nanoseconds or less), heat starts to diffuse away from the initial heated volume. Considering that the subject body is an infinite heat reservoir compared to the total pulse energy even in the high pulse energies, the diffusion will gradually reduce the temperature of heated volume back to natural body temperature. The rate of this cooling effect depends greatly on the volume of the heated tissue, which is very different in the above examples. More precisely, the rate is determined by the ratio of volume to surface area of the heated tissue. A small volume will cool down much more rapidly than a large volume.

[0201] To quantify relevant time scales, consider the case of two pulses with same fluence as in Example 2 above. Assuming just one pulse hitting the tissue, at what rate will the heat diffuse? Solving the linear heat diffusion provides us with the radial profile of the temperature at different times after initial heating at time t=0. Temperature profile of high energy, large spot (FIG. 12A) and low energy, small spot (FIG. 12B) are shown in FIGS. 12. After about 1 second, there is only a minor change in elevated temperature for the 500 mJ pulse 121, while the 5 mJ pulse temperature has dropped by approximately 50% 122. For 500 mJ pulse, it takes in the order of 100 seconds for the temperature to drop by 50%.

[0202] Thermal relaxation time may be defined herein as the time at which the temperature delta has dropped by a factor of 2x. Temperature of centre of heated tissue volume as a function of time is plotted in FIG. 13. For a 1 mJ pulse with 0.22 mm spot, thermal relaxation time is about 0.12 seconds. For a 5 mJ, 0.5 mm spot, relaxation time is about 0.7 s, while for a 500 mJ, 5 mm spot relaxation time is about 70 s.

[0203] FIG. 14 is a chart showing thermal relaxation time vs. pulse energy for a given fluence of 2.5 J/cm2. Box 142 shows a working point according to a prior method using 200-1000 mJ pulses. Relaxation times of 30-200 seconds are typical. In box 141 much shorter relaxation times of 0.1-8 seconds are provided in accordance with the invention using smaller pulse energies of 1-30 mJ. Skin damage thresholds are plotted in 143,144.

[0204] Given that the skin can withstand only about 6 s at 51° C. before damage occurs as discussed previously 144, it is thus clear in the above example, using a 5 mJ pulse, the skin can sustain a 15° C. temperature elevation to around 51° C., since it is dissipated in less than 1 second. For a 500 mJ pulse, with the same temperature elevation, damage will occur since the relaxation time is about 70 s, much longer than the damage threshold. The same analysis is true for skin temperature of 50 degrees, which can be tolerated for 24 seconds before damage occur. It is also known that pain appears before damage occurs. The pain threshold is lower than the damage threshold, but the temperature dependence is similar (Yarmolenko).

[0205] For this reason, pain and damage are both reduced or completely avoided by using small energy pulses (1-30 mJ) instead of large pulses above 200 mJ.

[0206] The above calculation reflects a comparison of high energy pulse to low energy pulse, at the same fluence. In order to gain for the benefit of fast relaxation time when scanning a large area with multiple spots, it is important to provide adequate time between adjacent pulses. This can be achieved by employing dedicated scanning techniques. As an example of smart scanning technique to increase available relaxation time for adjacent spots is shown in FIG. 15B. In a normal raster scan of N lines (FIG. 15A) each thick line 150 is composed of multiple spots. The time it takes to complete a line is T. This means that after time T, each spot will have a new neighbour below and this is in addition to its neighbours left and right in its own line. Now lets us use an interlacing scan (FIG. 15B): this means that instead of scanning lines continuously, we scan the top line 151 and then skip M lines down to mark the next line 152 much further away. We continue this until we reach the edge of the scanning field, were we return to the second line from the top 154 and repeat the process. This gives adjacent lines a relaxation time of K*T, K=floor(N/M) which can be potentially much longer for larger fields.

Example 4

[0207] In order to assure proper functionality of the system and safety of subject and operator, the system in Example 1 may be adapted to include specialized test hardware and sequence in a dedicated work head holder which may be located in the treatment room 12. The holder 27 of the invention includes a work head interface 164, optical lenses 167, a perforated separator 169, and an optical power meter 161.

[0208] Referring to FIG. 16 the work head 4 is connected to the right side of the holder 164 as shown in the drawing. It should be noted that the connection is identical mechanically to the connection of the spacers 18 as described above with reference to FIG. 3 used for treatment.

[0209] To the left of 164 is a lens 166 for adapting the optical distance to the power meter 161. Above the power meter there is a separator 169, were several holds have been drilled to allow the laser radiation to reach the power meter.

[0210] FIG. 17A shows the separator left side 170 in the direction of the detector and also an arrangement of several holes 172 that extend through the separator. FIG. 17B shows the right side of the separator 171 in the direction of the work piece.

[0211] The test sequence is shown in FIG. 18. The sequence starts only when the proper controls have been applied, mainly aiming beam switch 15 on and food pedal 8 is pressed. The scanner mirrors 40 are then moved to positions corresponding to hole positions in the separator 172. In each position, the main laser ½ is turned on, and power is measured in the power meter 161.

[0212] Once all predefined positions and power measurements are performed, the measured power is compared to a predefined table with allowable ranges. Test is successful if all measurements are in the predefined ranges.

[0213] Several favourable aspects should be noted. The first aspect is that the power meter 161 (or any other relevant sensor) is located in a plane that is optically equivalent to the plane of the treated skin using a spacer 18. This is in contrast to prior systems where the laser radiation is usually measured closer to the laser output and not at the output of the system. This ensures that subject receives exact radiation parameters, and accounts for failures occurring anywhere along the optical path: from inside the laser, through the optical elements, the scanner and the lenses in work head (see FIG. 2).

[0214] Second, the different separator holes in different positions require the scanner mirrors 40 to arrive to predefined locations. This ensures the scanner mirrors, their actuators and their control electronics are all performing as expected. It also ensures that the optical beam has not wandered out of alignment in the angle or position, which will correspond to partially or completely missing the separator holes (just like a mirror actuator failure) and resulting in low power measurement.

[0215] Also, by creating holes of different diameters, the divergence of beam can also be accounted for. This divergence will result in different power levels measured compared to predefined ones in holes of different diameter.

[0216] In addition, during the test, real time sensors located next to laser output 32 (see FIG. 2) are compared to the holder sensor, insuring they are consistently measuring pulse energy.

[0217] Finally, the sequence requires operation of user controls in the same manner as the normal operation during treatment, and accounts for any failures in switches or controls.

[0218] It will be understood that the test apparatus does not necessarily need to incorporate a holder for the work head. In other embodiments, the sensors may be mounted to a supporting structure that is not designed to hold the work head as such, but has a work head engaging portion that is configured to engage the work head to locate it stably relative to the sensors for testing. Instead of the perforated separator as described above, the sensors may include at least one position sensitive detector for detecting the position and power of the laser beam.

Example 5

[0219] FIG. 19 illustrates a treatment room of a dermatological treatment facility which includes laser treatment apparatus adapted for automated scanning of an area of a subject’s skin to be treated according to another embodiment of the present invention. Above a treatment chair 190, a large optical work head 191 is suspended through a balanced articulating arm 192. The apparatus in a laser room (not shown) is similar to the apparatus described in Example 1 above, but the treatment room work head in the present embodiment is larger and utilizes imaging and other sensors to scan automatically a large area to be treated (compared with manually scanning small areas in Example 1).

[0220] Laser scanning is widely known from industrial material processing applications. As opposed to industrial application of laser scanning, where the same target material and sample are scanned repeatably in large quantities, in the present invention, however, a subject is only scanned once (at least per treatment), and a required scanning pattern is very rarely similar, as no two subjects and no two lesions are ever identical. Additionally, the cost of error is unacceptable and safety considerations are paramount. The following description shows how these complications may be addressed in accordance with the present invention to provide fast, accurate and safe scanning of lasers for treating dermatological indications.

[0221] In FIGS. 20A and 20B, components of the working head 191 are shown in two cross sectional views. Laser radiation enters the work head input 200 from one or more treatment lasers in the laser room through the articulating arm 192 and passes a motorized adjustable focusing lens 208. It then enters the scanner 201. This scanner is larger than the scanner in Example 1 and directs the laser beam through a 160 mm f-teta lens 202 to cover an area of 100x 100 mm on the subject’s skin 204 which is typically maintained at a constant distance of about [DISTANCE] from the work head 191. Scanner, integrated focusing and f-theta lens are readily available for example from ScanLab Germany or Cambridge technology MA, USA. A camera 207 mounted in the work head is operable for imaging the treatment area, while illumination LEDs 206 supply specific illumination conditions. The camera 207 is also capable of 3D measurement of depth and in addition to imaging the area to be treated can generate a height map of the area. 3D cameras are readily available, for example RealSense from Intel, USA.

[0222] The treatment sequence is described in FIG. 21A-E . Initially, an operator manipulates manually the work head 191 to be placed roughly above the target area. The articulating arm is balanced such that there is little friction and operator can easily manipulate the work head. An aiming beam shows an available scanning field by outlining it (see FIG. 21A) to help the operator position the centre of the available scanning field to coincide approximately with the target area. Using image processing, the system then detects the pigmented areas based on images of the area captured by the camera 207. The 3D camera also measures the contours of the target area and scanning parameters are calculated (FIG. 21B). Once a scanning plan is defined, the operator is shown the planned area to be treated. This can be done with a dedicated computer interface but in this example it is shown directly on the subject target area: using only the aiming beam, the exact planned pattern as will be performed by the main treatment laser is scanned repeatedly (FIG. 21C) . The operator then approves the scanning plan by pressing a button in a user interface screen and then the work head scans the approved area with the treatment laser (FIG. 21D). Following this scan, the system returns to outlining the available field while treated area typically appears white as a result of frosting as described above (FIG. 21E).

[0223] It should be noted that all the pigmented skin within the scanning field is treated at once, without further operator involvement. This ensures accuracy of laser treatment while achieving very fast treatment time compared to manual placement (up to 40 seconds for a 100x100 mm tattoo, typically much less).

[0224] The system may use the premeasured and real time depth data to adjust the focusing lens 208 in order to account for scanner-skin distance and contours of skin surface. In some instances, the contours of the target area may be curved such that scanning the entire area is not possible: a bracelet tattoo around the wrist, for example. During the depth measurement (FIG. 21B), a pigmented area that is too curved to be treated (due to angle above 20 degrees or due to depth that is beyond the focus range of the system, typically 35 mm) is omitted from the planned scan. FIGS. 22A and 22B illustrate an example of this feature: in FIG. 22A a flat target is scanned, and the entire available scanning field 221 can be utilized. In FIG. 22B a curved surface below the scanner 220 implies that a smaller area of surface 223 can be scanned as compared to the larger area of the flat surface 221.

[0225] An image processing algorithm for detecting pigmented areas to be treated may be divided between tattoos, using first order derivative (sobol) operator for edge detection, while pigmented lesions with softer edges may utilize a trained neural network algorithm. These algorithms are easily understood by those skilled in the art. As accuracy of either algorithm is not 100%, the operator may use a suitable computer interface (not shown) to correct the algorithm results and manually adjust the scanning pattern if required. The pattern is then updated to the pre-scan (FIG. 21C).

[0226] When treating an area larger than maximal scanning field or a curved area that cannot be treated in one scan, the treatment may be divided into several segments. The operator manually positions the scanner above each segment and starts the pattern recognition algorithm. Based on previous images compared to current image a suitable stitching algorithm identifies previous segments that were treated and so avoids treating areas twice or missing some areas. This algorithm is shown in FIG. 23A-E. In a first step (FIG. 23A), a scanner is placed above a top-left region of an area to be treated. The camera 207 captures area 230, which is larger than scanner maximal field 231. A pattern recognition algorithm identifies the pigmented area and treatment is then administered to this area 235. Scanner is then moved rightwards as shown in the drawings by the operator (FIG. 23B). The operator needs to verify that there is some overlap in new camera image 236 with previous camera image 230. This overlap is explicitly shown in 234 and 232 (previous and current image overlap area). Using this overlap, images 231 and 236 are stitched, and a new treatment area is now identified by the pattern recognition algorithm, but the area already treated in previous step 235 is masked. Thus the new scan area 237 is defined and scan is performed with no overlap with the previous scan (FIG. 23C). The operator then moves the scanner to the middle-left of the area (FIG. 23D). This time an overlap is found with area 233 of the first image compared to area 239 in new image. The stitching algorithm defines area 240 for treatment and scan is performed (FIG. 23E). It should be noted that the stitching algorithm relies on untreated skin, since treated skin is sometimes significantly different in appearance due to skin whitening (also referred to as frosting) as is frequent in laser treatment if skin.

[0227] When treating contoured areas, the above process may be repeated with an intermediate step of projection of a camera image into a flattened image using the measured curvature data. These algorithms are known to those skilled in the art. Combining large and/or contoured treatment areas is then straightforward.

[0228] Additionally, based on a predefined rule set (usually lasers for specific colours) pattern recognition algorithm identified specific pigment colours and recommends treatment laser wavelength.

[0229] During the main laser scan, which can take several seconds or more depending on tattoo size (see above), the subject may move. For this reason, the camera may continuous image the treatment area and monitor for movement. In order not to be blinded by reflection from the main the laser during scanning, a motorized optical filter 209 (see FIGS. 20) may be used during the treatment scan to block the various laser wavelengths.

[0230] The illumination sources 206 (FIGS. 20) are specially selected LEDs. Some of the LED may emit mainly visible range “white” light. These are used for pattern recognition of pigmented areas by the algorithm. In some embodiments, other LEDs may be specific to the UV range and/or others may be specific to the IR range. Several images may be taken using different illumination sources. UV images extract information on various pigmentation in the skin, while the IR images are used to assess the absorption of the IR wavelength laser.

[0231] This system may be integrated with a 6-axis robot to perform the placement automatically (FIG. 24). This may further increase utilization and accuracy of the system.

Example 6

[0232] As clinical experience shows, in a laser treatment session, there may be a minimum period of 10 to 20 minutes of subject preparation and post-treatment care. The actual net laser treatment time can be equivalent or much faster: approximately 20 minutes for tattoos of 200 cm2 area using the system in Example 1 above; less than about 2 minutes when using the system of Example 5 (200 cm2 is the most common tattoo area to be removed based on clinical experience). This implies low utilization of the laser and system which incurs lower return rate on investment.

[0233] A solution to mitigate the above is a 2-treatment room facility in accordance with the invention, supported by a single treatment laser system. Referring to FIG. 25, the system includes one treatment laser system (with several wavelengths) 253, a control unit 254, two work heads 256,257 (e.g. as described in Example 1 or Example 5) in two treatment rooms 251,252 and a motorized flip mirror 255. Each treatment room also contains a treatment chair and all that is needed to administer treatment. In the present embodiment, the flip mirror, when in position, steers the laser radiation to the work head of room #1 252. When the flip mirror is out of the optical path, laser is directed to second treatment room and scanner head 256. The optical details and flip mirror are well known to those in the art and are not described in detail here. The control unit may be very similar to those described in Examples 1 or 5, with the additional control of a flip mirror. The work head is identical to the one described in the previous examples: articulating arm, scanner etc.

[0234] As one subject is being treated in the first room 252, a second subject may be prepared for treatment in second room 251. The control unit 254 is operable to accept operator commands from the first room work head 257 while commands from second room work head 256 are ignored. Once treatment is finished in first room (signalled by an operator turning off the work head), the controller toggles the flip mirror and diverts its control commands to be received from second work head 256. The subject in second room, now ready for treatment, starts treatment, and the first subject in first room may receive post-treatment care. The first room is afterwards cleaned, and next subject is prepared for treatment, so he/she is ready for treatment once the subject in second room finishes treatment.

[0235] This facility layout improves utilization by approximately a factor of two for either work head of Examples 1 or 5. For a system like the one of Example 1, with a 20-minute average treatment time, utilization may be above 90% as overhead (pre- post- subject care) and treatment times may be similar. Using a scan head similar to the one of Example 5 (automated area scanning) comparatively low utilization still results, as the time the treatment laser is actually scanning is still low (about 4 minutes in every 20-30 minutes). This will be addressed in the following examples.

Example 7

[0236] As discussed in Example 6, it is beneficial to increase overall utilization, lowered by subject pre-and post- care. The most expensive component in the system is the treatment laser. A system for increasing the system utilization by 3x is now described with reference to FIG. 26.

[0237] Using a laser capable of 3-4x higher pulse energy than is required for treatment (i.e. a laser capable of 10-150 mJ), the laser beam is split passively between three treatment areas 261, 262, 267 that are set up to work independently.

[0238] The laser 263 emits a powerful pulse which is split by a ratio of 1:2 in energy by a dedicated beam splitter 264. The smaller pulse (⅓ of the original) propagates to a first treatment room 262. The larger pulse (⅔ or original) continues to propagate in the direction of a second beam splitter 265, where it is split 1:1 and directed to a second room 261 and a third room 267 in parallel. Thus all three treatment rooms receive about 33% of original pulse energy.

[0239] In each treatment room, laser radiation is modulated independently according to control signals from each room separately. This may be achieved using a Pockels cell optical modulator 266 for room 267, for example. Thus three independent work heads are operational in three separate areas. The treatment laser 263 works continuously, and thus any optical modulator used at its output is not required. In effect, this modulator is actually placed in each of the three rooms. Unused pulses are dissipated in beam dump and the end of each optical modulator.

[0240] Thus the utilization of the laser is increased by 3x, at the cost of a more expensive laser and three dedicated optical modulators.

[0241] It will be self-evident to combine this embodiment with the previous one to achieve, e.g. a 6x improvement in utilization with a six-room facility.

Example 8

[0242] In Example 7 above, a treatment laser with 3-4x higher pulse energy is split into three treatment rooms in parallel. Whilst scaling pulse energy is generally advantageous for reducing laser down-time, it may not always the best approach, as laser costs typically scale with pulse energy. In contrast, increasing pulse repetition rate while keeping same pulse energy (i.e. increasing average power) usually scales more favourably. This is because increasing average power involves (to a first order approximation) scaling pump sources and dealing with thermal load, while scaling pulse energy involves in addition dealing with laser induced optical damage to internal laser surfaces, which is mitigated by scaling beam area and thus increasing size and cost of optical components.

[0243] In the present example, a clinic supporting three treatment areas with a single laser is described. Here a laser of 3x higher repetition rate e.g. 600-3000 Hz but similar pulse energy 1-30 mJ (compared to a single room clinic laser) is used.

[0244] Referring to FIG. 27, a laser room 270 contains the above specified treatment laser 271, three fast optical modulators (Pockels cell) 273, 274, 275, a control unit 292 and a beam dump 276. The modulators are normally switched off, allowing laser output 272 to travel undisturbed to the beam dump 276. When one of the modulators 273, 274, 275 is turned on, all of the radiation is deflected by about 90 degrees in the direction of the corresponding treatment room. Radiation then reaches the work head in that treatment room.

[0245] The modulators are selectively turned on by a control unit 292 at one-third of the nominal laser frequency and have a phase of one cycle time between them, meaning a first one of the modulators can only opened once in every three pulses, a second one of the modulators can be opened only for the next pulse and then every 3rd pulse from the second, and so on. In effect, the modulators in combination are down-sampling the pulse train from the laser, with each treatment room receiving every the first, second or third pulse out of every three pulses.

[0246] In addition to down-sampling, the modulators only steer the pulses when there is a demand for lasing from their corresponding treatment room. A detailed timing diagram is shown in FIG. 28. Laser pulses are depicted as dark rectangles 310, while the x axis represents time. The original pulse train from laser output 272 is shown at 300. Reference numeral 301 indicates a signal from the first treatment room work head, requesting a treatment scan at two separate time periods. At 302, the output of the first modulator 272, reaching the work head 292 in treatment room 281 is shown. Every third pulse from the laser is steered to the first room, when there is a request from the corresponding work head. The remaining pulses 303 continue in the direction of the second modulator 274. At 304, a requested treatment signal from the second room work head 279 is shown along with the pulses that are deflected by the second modulator 274 in the direction of the second treatment room 278 and eventually reach the work head 279. Undeflected pulses 305 continue toward the third modulator 275. Numeral 306 indicates a requested treatment signal of the third work head and the resulting pulses reaching the third room. Undeflected pulses 307 arrive eventually in the beam dump 276 where they are absorbed.

[0247] To summarize, three fast optical modulators utilize a high pulse repetition rate laser to treat simultaneously and independently three treatment rooms, thus achieving high utilization of the laser and creating a favourable return on investment. Whilst three modulators are used in the present embodiment to steer successive pulses of laser light to work heads three corresponding treatment areas, those skilled in the art will appreciate that in other embodiments, depending on the original pulse repetition rate of the laser, fewer or more modulators may be used to steer the beam selectively into two or four or more treatment rooms.

Computing Devices and Systems

[0248] The computing devices and systems described and/or illustrated herein broadly represent any type or form of computing device or system capable of executing computer-readable instructions. In their most basic configuration, these computing device(s) may each include at least one memory device and at least one physical processor.

[0249] In some examples, the term “memory device” generally refers to any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. Examples of memory devices include, without limitation, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, Hard Disk Drives (HDDs), Solid-State Drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, or any other suitable storage memory.

[0250] In some examples, the term “physical processor” generally refers to any type or form of hardware-implemented processing unit capable of interpreting and/or executing computer-readable instructions. Examples of physical processors include, without limitation, microprocessors, microcontrollers, Central Processing Units (CPUs), Field-Programmable Gate Arrays (FPGAs) that implement softcore processors, Application-Specific Integrated Circuits (ASICs), portions of one or more of the same, variations or combinations of one or more of the same, or any other suitable physical processor.

[0251] The process parameters and sequence of the steps described and/or illustrated herein are given by way of example only and can be varied as desired. For example, while the steps illustrated and/or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various exemplary methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.

[0252] Features from any of the embodiments described herein may be used in combination with one another in accordance with the general principles described herein. These and other embodiments, features, and advantages will be more fully understood upon reading the foregoing detailed description in conjunction with the accompanying drawings and claims.

[0253] The preceding description has been provided to enable those skilled in the art to utilise various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the spirit and scope of the present disclosure. The embodiments disclosed herein should be considered in all respects illustrative and not restrictive. Reference should be made to the appended claims and their equivalents in determining the scope of the present disclosure.

References

[0254] Anderson, R. R., & Parrish, J. A. (1983). Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science, 220(4596), 524-527. [0255] Goldman, M. P., Fitzpatrick, R. E., Ross, E. V., Kilmer, S. L., & Weiss, R. A. (Eds.). (2013). Lasers and Energy Devices for the Skin (2nd ed.). Taylor & Francis Group, LLC. Pierce County Emergency Medical Services. (n.d.). Disaster Burn Training. Retrieved May 30, 2019, from Pierce County: https://www.piercecountywa.gov/DocumentCenter/View/3352 [0256] Shannon-Missal, L. (2016, February 10). Tattoo Takeover: Three in Ten Americans Have Tattoos, and Most Don’t Stop at Just One. Retrieved from The Harris Poll: https://theharrispoll.com/tattoos-can-take-any-number-of forms-from-animals-to-quotes-to-cryptic-symbols-and-appear-in-all-sorts-of-spots-on-our-bodies-some-visible-in-everyday-life-others-not-so-much-but-one-thi/ [0257] Yarmolenko, P. S. (n.d.). Thresholds of thermal damage and thermal dose models. Retrieved May 31, 2019, from The International Commission on Non-Ionizing Radiation Protection (ICNIRP) : https://www.icnirp.org/cms/upload/presentations/Thermo/ICNIRPWHOThermo_2015_Y armolenko.pdf