DERMATOLOGICAL DIAGNOSIS AND TREATMENT SYSTEM

Abstract

Disclosed is a dermatological diagnostic and treatment system including a light source device, a light flow collecting device, a spectroscopic measurement device, and a computer. The light source device includes a laser source tunable in wavelength inside the spectral range, the laser source being tunable in duration and/or rate and the laser source being adapted to generate a second treatment laser beam of high intensity at said first wavelength towards the epidermal surface. The dermatological diagnostic and treatment system further includes a temperature sensor and a feedback device, the temperature sensor being arranged to record a temperature measurement signal of the epidermal surface as a function of the application of the second laser beam. The feedback device is configured to modify the duration and/or rate of the laser pulses as a function of the temperature measurement signal.

Claims

1. A dermatological diagnostic and treatment system comprising: a light source device (2), a light flow collecting device (4), an absorption spectroscopic measurement device (5, 6), and a calculator, wherein: the light source device (2) is adapted to generate a first low-intensity light beam (20) towards an epidermal surface (8) of a patient, the first light beam (20) extending over a spectral range or being tunable in wavelength over a spectral range, the light flow collecting device (4) being arranged to collect a first light flow by reflection and/or diffusion of the first light beam (20) on said epidermal surface (8), the absorption spectroscopic measurement device (5, 6) is adapted to record a first spectroscopic measurement of the first light flow as a function of the spectral range, and the calculator being adapted to receive the first spectroscopic measurement in the spectral range and to determine a first wavelength associated with an absorption of a pigment of said epidermal surface and a second wavelength associated with an absorption of another tissue constituent of said epidermal surface, and in that the light source device includes a laser source (10) tunable in wavelength inside the spectral range, the laser source being tunable in duration and/or rate and the laser source being adapted to generate a second treatment laser beam (1) of high intensity at said first wavelength towards said epidermal surface (8) and in that the dermatological diagnostic and treatment system further includes a temperature sensor and a feedback device (80, 90, 95), the temperature sensor being arranged to record a temperature measurement signal of said epidermal surface as a function of the application of the second laser beam and the feedback device (80, 90, 95) being configured to modify the duration and/or rate of the laser pulses as a function of the temperature measurement signal.

2. The dermatological diagnostic and treatment system according to claim 1, wherein the second laser beam (1) is consisted of pulses of duration comprised between 30 ps and 10 ns.

3. The dermatological diagnostic and treatment system according to claim 1, wherein the light flow collecting device (4) includes an integrating sphere, and wherein the absorption spectroscopic measurement device (5, 6) includes a photo-detection device (5) and a spectrometer or a monochromator.

4. The dermatological diagnostic and treatment system according to claim 1, wherein the laser source (10) is continuously tunable in wavelength over a spectral range extending over at least 100 nm.

5. The dermatological diagnostic and treatment system according to claim 4, wherein the laser source (10) is adapted to generate the first light beam (20) and the second laser beam (1) and wherein the light source device (2) further includes a device for intensity modulating the laser beam generated by the laser source.

6. The dermatological diagnostic and treatment system according to claim 1, wherein the light source device (2) includes another light source adapted to generate the first light beam (20).

7. The dermatological diagnostic and treatment system according to claim 1, wherein the light flow collecting device (4) is configured to collect a second light flow (50) by reflection and/or scattering of the second light beam (1) on said epidermal surface (8) and wherein the absorption spectroscopic measurement device (5, 6) is adapted to record a second light flow measurement signal at the first wavelength.

8. The dermatological diagnostic and treatment system according to claim 7, wherein the feedback device (80, 90, 95) is configured to modify the duration and/or the rate of the laser pulses as a function of the second light flow measurement signal.

9. The dermatological diagnostic and treatment system according to claim 1, wherein the spectroscopic measurement device includes an image detector having a pixel array adapted to form an hyperspectral image of said epidermal surface in said spectral range, and the calculator being adapted to determine the second laser treatment wavelength corresponding to each pixel of the image detector from said hyperspectral image.

10. The dermatological diagnostic and treatment system according to claim 3, wherein the spectroscopic measurement device includes an image detector having a pixel array adapted to form an hyperspectral image of said epidermal surface in said spectral range, and the calculator being adapted to determine the second laser treatment wavelength corresponding to each pixel of the image detector from said hyperspectral image.

11. The dermatological diagnostic and treatment system according to claim 4, wherein the spectroscopic measurement device includes an image detector having a pixel array adapted to form an hyperspectral image of said epidermal surface in said spectral range, and the calculator being adapted to determine the second laser treatment wavelength corresponding to each pixel of the image detector from said hyperspectral image.

12. The dermatological diagnostic and treatment system according to claim 5, wherein the spectroscopic measurement device includes an image detector having a pixel array adapted to form an hyperspectral image of said epidermal surface in said spectral range, and the calculator being adapted to determine the second laser treatment wavelength corresponding to each pixel of the image detector from said hyperspectral image.

13. The dermatological diagnostic and treatment system according to claim 6, wherein the spectroscopic measurement device includes an image detector having a pixel array adapted to form an hyperspectral image of said epidermal surface in said spectral range, and the calculator being adapted to determine the second laser treatment wavelength corresponding to each pixel of the image detector from said hyperspectral image.

14. The dermatological diagnostic and treatment system according to claim 4, wherein the light source device (2) includes another light source adapted to generate the first light beam (20).

Description

[0034] The following description with respect to the appended drawings, given by way of non-limitative examples, will permit a good understanding of what the invention consists in and of how it can be implemented.

[0035] In the appended drawings:

[0036] FIG. 1 shows spectroscopic measurements of the absorption coefficient (CA) of the main chromophores of the epidermal tissues;

[0037] FIG. 2 schematically shows the different physical phenomena of interaction between a laser beam and an epidermal tissue;

[0038] FIG. 3 schematically shows a cross-sectional view of a reflection or backscattering spectroscopy measurement device;

[0039] FIG. 4 schematically shows a diagnostic and treatment system according to one embodiment;

[0040] FIG. 5 schematically shows a treatment method according to one embodiment;

[0041] FIG. 6 schematically shows a variant of the treatment method according to one embodiment;

[0042] FIG. 7 shows a burning severity diagram as a function of the duration of contact and of the temperature.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0043] Device

[0044] An aspect of the present disclosure consists in determining in what proportion the skin reflects a light radiation so as to determine accurately the laser treatment wavelength the most adapted to the pigment to be decomposed and to the skin of the patient.

[0045] Generally, when an incident light beam 1 reaches the surface of an epidermal tissue 8, a portion of the incident beam forms a reflected beam 11. The remaining of the incident beam propagates in the epidermal tissue 8. Another portion 12 is absorbed by the tissue constituents. Still another portion of the incident beam is scattered towards the rear (backscattered beam 14), towards the front (forward-scattered beam 16) and into the epidermal tissue (lateral scattering beam 15). Finally, a last incident beam portion may manage to path through the tissue volume and to form a transmitted beam 13.

[0046] The optical reflection at the surface of the tissue limits the efficiency of the laser treatment. As a function of the wavelength and the nature of the surface of the tissues 8, the optical reflection may be specular or diffuse. The surface reflection may reach high values. The reflection coefficient of a laser beam on the skin at a wavelength of 488 nm is evaluated at about 30%. The scattering is an interaction of the light with the material during which the direction of the incident beam is modified. The backscattered beam 14 goes out of the tissue 8. On the other hand, the absorbed beam 12 and the scattered beams 15, 16 transform the energy brought by the incident photons into heat.

[0047] The proportion of the reflection, absorption, transmission and scattering phenomena depends, for a given tissue, on the wavelength of the incident beam. In the short ultraviolet and in the far infrared, the absorption is more important than the scattering. In other portions of the spectrum (from 300 nm to 2 m), the scattering influences the geometry of the beam by producing a lateral widening and by reducing the penetration depth of the laser beam.

[0048] In FIG. 3 is shown an absorption spectroscopic measurement device. This device includes a light source device 2, an optical system 3, a device 4 for collecting the reflected and backscattered light beam, a spectrometry device 6 and a photo-detection device 5.

[0049] The light source device 2 emits a low-intensity light beam 20 (from 1 mW to 100 mW of mean power). A light source device 2 emitting over a wide spectrum, a spectral band covering a spectral range able to go up to 100 nm, may be used. By way of example, the source device includes a supercontinuum laser. However, it is generally sufficient to perform measurements at a few discrete wavelengths in the spectral range. In another example, the source device includes several laser diodes of low mean power (from 1 mW to 100 mW) adapted to choose different wavelengths in several spectral bands corresponding to different therapeutic windows (visible: 500-700 nm, infrared: about 1 micrometre). The optical system 3 serves to shape the incident light beam and to adapt the size thereof as a function of the desired fluence.

[0050] This light source device 2 is operable to illuminate the epidermal tissue 8 to be treated under a low light beam so as to avoid deteriorating the epidermal tissue, and to change the optical reflection, absorption, scattering and transmission properties of the epidermal tissue.

[0051] The collecting device 4 allows collecting the light flow reflected or backscattered by the skin. The collecting device 4 is configured so as to collect a maximum of photons under illumination by a low-intensity light source 2. By way of example, the collecting device 4 comprises an integrating sphere.

[0052] The spectrometry device 6 includes for example a spectrometer equipped with a detector 5 configured to operate in the spectral domain of the light source 2 as a function of the wavelengths of interest. In another example, the spectrometry device 6 comprises a monochromator equipped with a detector 5, which analyses directly a wavelength reflected by the patient's skin.

[0053] The spectrometry 6 and photo-detection 5 device may be integrated to the collecting device 4. As an alternative, the spectrometry 6 and photo-detection 5 device is connected by an optical fibre to the collecting device 4, so as to outset the case of the spectrometry 6 and photo-detection 5 device.

[0054] The absorption spectroscopic measurement device is calibrated during the fabrication. A calibration is preferably performed before each later use. The calibration source may be the laser itself, set at a given wavelength or an additional source added in the machine (LED or laser diode). In a first case, the calibration consists in arranging a mirror in front of an opening of the integrating sphere to measure the maximum light intensity reflected. In another example, the calibration consists in arranging a light shaft. The reflection measurements on an epidermal tissue are then added to this maximum light intensity, to obtain relative spectroscopy measurements. The absorption is then calculated by subtracting the reference reflection measurement (with the mirror) from the reflection measurement on the epidermal tissue.

[0055] FIG. 4 shows a diagnostic and treatment system according to a first embodiment. The system includes a treatment laser source device 10, a detection device 50 and a feedback device 80. The laser source device 10 emits a treatment laser beam 1 towards the skin 8 to be treated. In an exemplary embodiment, the laser beam 1 is temporally continuous. Preferably, the laser beam 1 is a pulse beam with pulses of duration comprised between 30 ps and 10 ns. The laser pulse rate may vary between 500 MHz and 500 kHz. This temporal operating domain allows using a laser pulse having both a high peak power and a relatively high mean power. This laser pulse allows combining photo-ablative effects coupled to thermal effects in a particularly innovating manner in dermatology. This selection of a duration and rate temporal domain for the laser pulses opens the way to a new kind of interaction in which the photo-ablative effects and the thermal effects may play complementary roles. This source is based on a so-called mode-locked, high rate (between 10 MHz and 500 MHz) laser architecture. The mode-locked regime may be obtained by the use of a saturable absorber, a modulator or a non-linear rotation of the polarization. The association of this source with an element allowing the extraction of one or several pulses (acousto-optical or electro-optical modulator, Pockels cell) generates a single pulse or packets of several variable-rate pulses. The duration of the pulse is adjusted by modifying the dispersion of the signal emitted by means of a dispersive element (volume or fibre Bragg gratings, dispersive mirror, prism).

[0056] In the spectral range, the laser source device 1 used for the treatment generates several discrete wavelengths or is continuously tunable over a wideband in the visible and/or infrared domains. This is made by inserting in the laser cavity a filter for the infrared radiation. The visible radiation is generated by frequency doubling.

[0057] A feedback device 80 is arranged between the photo-detection device 50 and the treatment laser source device 10. A computing processor analyses in real time the absorption measurements of the tissue 8 in order to determine the wavelength adapted to the skin or to the tattoo. The analysed information is then transmitted to the driver software of the laser source device 1 that is adapted to the wavelength as a function of the absorption peak of the chromophore, the tissue or the tattoo to be treated. As an alternative, the selection of the treatment wavelength is performed before the treatment. For that purpose, a spectral image of the area to be treated is for example acquired, with a recording of the different wavelengths to be provided for the treatment laser as a function of each point of the image.

[0058] Method

[0059] In FIG. 5 is shown an example of dermatological laser treatment system and method. In a first step, another light source 9 generates a low-intensity light beam 19 towards the skin 8 to be analysed. The photo-detection 5 and spectrometry 6 system measures a reflection spectrum of the skin 8. A computer or a microcontroller 70 selects a wavelength, a duration (comprised between 30 ps and 10 ns) and a repetition rate (between 10 MHz and 500 MHz) of the treatment laser 10 as a function of the absorption spectrum measured. A train of treatment laser pulses is applied to the skin 8.

[0060] The other illumination source 9 of the skin sample may be a coherent or non-coherent source emitting a wide spectrum or at least one discrete wavelength. This other light source 9 may be the treatment laser 10 but configured to deliver a low-power and/or low-energy light beam 19 in order not to degrade or deteriorate the skin sample. The light beam 19 illuminates the skin 8 to be analysed and treated. The reflected and/or backscattered beam is collected by means of the collecting device and measured by means of the spectrometry 6 and photo-detection 5 device comprising one or several photo-diodes. The variations of the absorption measurements (deduced from the reflection and/or backscattering measurements) are recorded. It is deduced therefrom one or several spectral bands of absorption mainly by the skin 8. These spectral bands of absorption correspond to the different tattoo colours, to the melanin of the skin and/or to markers used in photodynamic therapy (PDT). The optimum conditions of laser treatment are deduced from this analysis.

[0061] A feedback loop 80 is then coupled with the treatment laser source device 10. The treatment laser source device 10 comprises a laser tunable in wavelength in the visible and infrared spectral domains. As an alternative, the treatment laser source device 10 includes several single-wavelength lasers in the visible and infrared spectral domains. These lasers are continuous or pulse lasers as a function of the applications. Preferably, the treatment laser source device 10 emits laser pulses of duration comprised between 500 femtosecond and 100 microseconds with rates from 1 Hz to 1 GHz. The treatment laser beam has a mean power comprised between 100 mW and 100 W.

[0062] The laser treatment system controlled in real time allows performing many dermatological treatments, such as tattoo removal, depilation, photo-rejuvenation or photodynamic therapy.

[0063] This laser treatment system also allows determining in real time the treatment progress thanks to the amplitude of the collected signal linked to the absorption of the surface. For example, in a detattooing process, the more reduced the pigment concentration, the lower the amplitude of the collected absorption signal. It is hence possible to stop the laser treatment thanks to a direct measurement in situ and not based on the simulations predicting the effects of the treatment.

[0064] In practice, the absorption spectrum of the skin may significantly vary from one patient to another according to his/her phototype. Moreover, from one skin to another, the thermal diffusivity and thermal conductivity coefficients also vary. Hence, the thermal effects induced by a same treatment may vary from one patient to another.

[0065] To control the thermal effects, FIG. 6 illustrates a variant of a laser treatment system. This system includes a pulse laser source tunable in duration and repetition frequency to perform a thermally controlled laser treatment.

[0066] This type of temporal operation has a particularly innovative interest in dermatology, where the combination between relatively high peak power AND mean power in the pulse opens up the way to a new kind of interaction in which the photo-ablative effects coupled to thermal effects may play complementary roles.

[0067] The system of FIG. 6 includes a laser source 10 tunable in repetition rate. The laser source 10 generates laser pulses or pulse packets. This system is based on a so-called mode-locked laser architecture. The mode-locked regime may be obtained by the use of a saturable absorber, a modulator or a non-linear rotation of the polarization. The association of this source with an element allowing the extraction of one or several pulses (acousto-optical or electro-optical modulator, Pockels cell) generates a single pulse or packets of several pulses.

[0068] The laser treatment system herein includes a thermal sensor 90 incorporated in the laser head in contact with the epidermis. The thermal sensor 90 measures the temperature on the treated skin. This information allows adapting the thermal load applied to the patient during the laser treatment in order to avoid the damages generated by a too high temperature and/or duration of exposure.

[0069] Indeed, FIG. 7 shows a curve (a) representative of the appearance of deep burns, respectively the curve (b) of superficial burns, and the curve (c) of a discomfort, as a function of the duration of exposure to the laser treatment and of the surface temperature of the skin.