2D and 3D imaging system for skin pigmentation disorders

Description

[0001] The field of the invention is that of imaging pigmentary disorders of the skin.

[0002] Dermatology is facing a growing demand for increasingly early management of skin conditions. Regarding the issue of pigmentary skin disorders, statistics from the World Health Organization (WHO) show: 2 to 3 million carcinomas, 132,000 cases of melanoma worldwide in 2011, a doubling of the number of cases every 10 years since 1945, in 15 to 20% of cases, melanoma develops from a mole, 15% chance of 5-year survival if detection is late, 95% chance of cure if detection is early.

[0003] To diagnose pigmentary skin disorders (moles, benign lesions, malignant lesions, carcinomas, melanomas, etc.), dermatological techniques are based on criteria known as ABCDE. Thus, the progression of a pigmentary disorder to cancer is characterized by: an asymmetry (A) of the melanoma, an irregular border (B), an unusual color (C), a diameter (D) that evolves an unusual evolution (E).

[0004] Furthermore, dermatologists attempt to assess the unevenness of pigmentary disorder thickness using two-dimensional imaging techniques such as dermoscopy or dermatoscopy, which are not suitable for reliably characterizing the depth of the pigmentary disorder. In some cases, to confirm the diagnosis, the costly practice of biopsies and histopathological examinations is performed.

[0005] The challenge for dermatologists is to identify suspicious "moles" as early as possible and to develop a new semiology, that is, the correspondence between what is observed and the pathology.

[0006] In the diagnosis of pigmentary disorders, the most common technique, epiluminescence or dermatoscopy, relies on the use of a video microscope, most often digital, to analyze the image using the well-known ABCD criteria. More recently, new equipment has emerged, such as the Siascope from Astron Clinica and the MelaFind from Electro-Optical Systems. Both are based on multispectral information in the visible and near-infrared ranges and differ in their associated data processing tools.

[0007] The Siascope is associated with a simple physical model and provides the user with calculated images of melanin and hemoglobin. In a more advanced version, the practitioner has access to information on the depth of melanin localization, which is crucial for diagnosing certain pigmented lesions. However, the depth localization is dependent on the accuracy of the mathematical model used. A complete model of light backscattering on the skin and its internal structure remains very difficult to obtain, and very little data is available in the literature to validate this approach.

[0008] The MelaFind system, as its name suggests, analyzes images of pigment spots solely for the purpose of melanoma detection. These pigment spot images are orthoimages. The associated digital tools are not based on a physical model but consist primarily of a classification algorithm that compares any new spot to the existing database and returns a yes / no answer to the operator. This type of system may be suitable for diagnostic purposes, and even for screening or prevention, but not for therapeutic intervention and monitoring.

[0009] In practice, a skin biopsy with histology is used as a complement. However, this approach is not well suited to revealing the subject's biochemical parameters. It remains dominated by the Breslow thickness, which measures the maximum thickness of the tumor on a histological section, and is therefore limited by the number and quality of the sections. Its accuracy is artificially reduced by regressive patterns with standardized margins that are consensual but empirical, depending on the tumor thickness as assessed by Breslow. The margins are not always compatible with the tumor's location (e.g., on the face), they are standardized and depend on the clinically visible size of the tumor (up to 1 cm), and are difficult to define precisely in certain clinical forms (sclerodermiform and micronodular basal cell carcinoma).

[0010] There are many other skin pathologies of diverse origins but often linked to the main chromophores of the skin, with devices dedicated to a single pathology (case of MelaFind, as we described previously).

[0011] Document WO2009 / 115947A1 discloses a skin imaging device comprising a housing equipped with a viewing window, at least one illumination means for illuminating the inside of the housing, at least one near-field image acquisition means, and at least one far-field image acquisition means. Image acquisition is performed in bistatic mode.

[0012] The purpose of the invention is to overcome these drawbacks.

[0013] More specifically, the invention relates to an imaging system for a cutaneous pigmentary disorder which comprises: a 2D image acquisition device for pigmentary disorder comprising: ▪ a light source configured to illuminate said disorder having at least one emitter and ▪ receivers, a unit for processing the acquired images, means for visualizing the processed images.

[0014] It is primarily characterized by the fact that it also includes: means for positioning the receptors according to at least two viewing angles so as to obtain at least one image per viewing angle, and distributed according to a spherical cap, a protective structure for the acquisition device and an operator, comprising a window for positioning the receptors so as to direct them towards the pigmentary disorder, the structure being intended to be positioned on the skin and having an opacified external surface except on the positioning window, in that the processing unit comprises a 3D reconstruction module with reflective Radon transformation so as to obtain a 3D image reconstructed from the processed 2D images, and in that the visualization means further comprise means for visualizing the reconstructed 3D image.

[0015] The dimensions of the protective structure are advantageously compatible with a portable acquisition device.

[0016] According to one feature of the invention, the acquisition device comprises a multi-cell pad with one receiver per cell.

[0017] According to another feature of the invention, the acquisition device comprises a light source emitting in the visible band, and means for acquiring images simultaneously by the receivers.

[0018] The positioning means include, for example, a rail on which one or more receivers are positioned, and means for rotating the rail. The rail may be sliding with a single receiver or a single transceiver.

[0019] The light source may be multi-wavelength in the visible and near-infrared bands, and / or the band of the 1st therapeutic window and / or the band of the 2nd therapeutic window and / or the SWIR band, the receiver(s) corresponding to said wavelengths and being synchronized with the emitters, and the acquisition device comprising means for acquiring images successively by the receivers at a rate of at least one image per wavelength and per viewing angle.

[0020] Thanks in particular to skin illumination in the visible and near-infrared bands (0.4 µm to 1.1 µm) and / or SWIR (Small Wave Infrared, from 1.1 µm to 2.2 µm), and / or those of the 1st or 2nd therapeutic window, this new imaging system allows 2D visualization at various angles of view, 3D volumetric visualization of pigmentary disorders and their cutaneous roots, using a non-invasive optical device and associated 2D and 3D treatment and visualization modules.

[0021] The system, which relies on volume illumination, allows direct observation after three-dimensional reconstruction of the pigmentary disorder in its depth.

[0022] The system according to the invention is sufficiently generic to adapt, if not to all, then at least to a large number of skin pathologies. Due to the volumetric 3D visualization which allows an external but also internal view of the pigmentary disorder, it makes it possible to reveal structures and signs invisible to the naked eye (inside), to improve the performance of the clinical diagnosis of pigmentary lesions, to detect parameters allowing to refine the differential diagnosis between melanomas and nevi (location, quantity or quality of melanin, demonstration of neovascularization phenomena around the melanoma, depth of the melanoma structure...).

[0023] It is possible, through the combination of 3D volumetric imaging with 2D two-dimensional imaging from various viewpoints, to better visualize the three-dimensional boundaries of the pigmentary disorder and the possible tumor, to be certain of the complete excision of the malignant skin tumor, of the conditions of healing and to improve the functional prognosis.

[0024] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example and with reference to the accompanying drawings in which: there figure 1 is an illustration of a pigmentary disorder, for example a nevus, the figure 2 schematically represents an example of an imaging system according to the invention, the figure 3a represents a vertical cross-section of a 2D image acquisition device at various angles in a dome configuration, the figure 3b represents a perspective view of a 2D image acquisition device at various angles in a dome configuration, the figure 3c represents a horizontal cross-section of a 2D image acquisition device at various angles in a dome configuration, the figure 4 schematically represents the functional elements of a 2D image acquisition device, the figure 5a represents a vertical cross-section of a 2D image acquisition device at various angles in a dome version with a skirt, the figure 5b represents a perspective view of a 2D image acquisition device at various angles in a dome version with a skirt, the figure 6a represents a vertical cross-section of a 2D image acquisition device at various angles in a multi-cell dome version with a skirt, the figure 6b represents a perspective view of a 2D image acquisition device at various angles in a multi-cell dome version with a skirt, the figure 7 is an illustration of 2D images of a nevus acquired from various angles and post-processed, the figures 8 form a set of illustrations of three-dimensional reconstruction by voxel rendering of the complete 3D volume of a nevus and zooms of the three-dimensional structure of the nevus in question, with for the figure 8a an image of the surface of the nevus from a specific viewing angle, for the figure 8b an image of the surface of the nevus from another angle, for the figure 8c a deep image of the nevus from a specific angle, for the figure 8d a deep image of the nevus from another angle.

[0025] From one figure to another, the same elements are identified by the same references.

[0026] According to the invention, the pigmentary disorder imaging system described in relation to the figure 2 is intended for use by an operator who may be a healthcare professional, but not necessarily. The imaging system includes the following components: ❖ A 2D image acquisition device A for capturing images at various viewing angles and optionally at various wavelengths for each viewing angle, which generates raw 2D images S1 and associated data (viewing angles and wavelengths). ❖ An image processing unit B that generates processed 2D images S2 from the raw images S1 and associated data, and preferably also generates a 3D reconstruction S3 of the pigmentary disorder and its roots from the processed images S2. ❖ Means D1 for 2D visualization of the pigmentary disorder at various viewing angles from the processed 2D images S2. ❖ Means D2 for 3D visualization of the pigmentary disorder and its reconstructed roots S3.

[0027] The image processing unit B and / or the visualization means D1 and D2 can be located remotely from the acquisition device A.

[0028] The image processing unit B performs RAW conversions to a usable image format (JPEG, PNG, TIFF, etc.), optical aberration corrections, cropping, centering, registration, calibration, scaling, thresholding, and angular indexing of the raw S1 images. The resulting processed S2 images are shown. Examples of S2-processed 2D images of a nevus at various shooting angles (20°, 30°, ..., 160°, 170°) are provided. figure 7 .

[0029] Preferably as shown figure 2 From the processed S2 images (themselves derived from the S1 images representing the intensity levels of electromagnetic radiation reflected or emitted by the object's surface), unit B also performs three-dimensional reconstruction of the pigmentary disorder via an algorithmic process of the reflective tomography type based on the inverse Radon transform. This yields processed S3 images. Regarding this three-dimensional reconstruction, one can refer, for example, to US patent 8,836,762, "Optronic system and method dedicated to identification for formulating three-dimensional images." This type of reconstruction uses data related to the reflection, scattering, or electromagnetic emission of the light wave incident on the structures of the pigmentary disorder (nevus, carcinoma, melanoma, etc.) in its depth; it allows for a complete three-dimensional (tomographic) reconstruction of the pigmentary disorder, as illustrated. figure 8 , without introducing tissue absorption parameters.

[0030] These S3 images are point cloud, isodensity, and voxel rendering types (for example, Maximum Intensity Projection (MIP), as described in patent EP 3 234 914 B1: a method for discriminating and identifying objects in a scene using 3D imaging. The MIP technique allows the visualization of three-dimensional data in a two-dimensional plane. Voxels (Volume Pixels) are projected onto a 2D plane; the voxels are determined by the rays joining the projection plane to the observation point and by applying an imposed intensity threshold to the voxels. Several projection planes are created at successive observation angles to obtain a sense of depth and thus improve the 3D rendering. An illustration of a voxel rendering of the reconstructed 3D volume (S3) of a nevus is given in the figures 8 : THE figures 8a et 8b show an image of the surface of a nevus, taken from two angles of view, the figures 8c et 8d show a detailed image of the nevus taken from two different viewpoints.

[0031] The means D1 and D2 for 2D viewing (of images S2) and 3D viewing (of images S3) are typically PCs, tablets, mobile phones (“smartphones”) or any other means of viewing.

[0032] We will now describe in more detail device A for acquiring 2D images at various viewing angles of the pigmentary disorder, shown figure 3a , 3b And 3c It includes: According to an embodiment that is not part of the invention, a light source configured to illuminate the pigmentary disorder. It comprises one or more emitters directed towards the pigmentary disorder 60 (an example of which is shown). figure 1 The light source can be a visible source emitting in the 0.6 µm–0.8 µm band. Preferably, the light source is single-wavelength and wavelength-controllable, emitting successively in the visible and near-infrared (0.4 µm–1.1 µm) bands, the bands of the first (0.65 µm–0.95 µm) and / or second (1 µm–1.35 µm) therapeutic windows, and / or the SWIR band (1.1 µm–2.2 µm), with one wavelength per band. One or more 303 receptors (shown figure 4 ) adapted to the wavelengths of the emitter(s). At the output of the receivers, we obtain the S1 images.

[0033] According to one embodiment of the invention, devices designated as transmitter-receivers 3 may be provided, integrating the transmission function and the reception function in the same device, as shown in the figures 3a , 3b , 3c , 5a , 5b , 6a An example of a transceiver 3 is detailed. figure 4 It includes a light source 301 in the visible band, and also preferably controllable light sources 302 in the visible and IR bands, connected to a wavelength controller 33 which is itself connected to a time clock 32. The wavelength controller 33 and the time clock 32 can be housed by the processing unit B. The device 3 also includes receivers in the bands corresponding to those of the light sources (visible and IR). means of positioning the receptor(s) (or even the emitter(s)) according to M viewing angles (M≥2) of the pigmentary disorder and distributed according to a spherical cap as can be seen figures 3a , 3b , 5a And 5b, so as to obtain at least one image per viewing angle θn (n varies from 1 to N, with N ≤ M), the images being acquired at the same distance from the pigmentary disorder. The larger θN - θ1 is, the more precise the 2D and / or 3D images will be. Typically, 120° ≤ θN - θ1 ≤ 180°; there are 16 viewing angles on the figure 7 with θ1 = 20°, θN = 170° and θN - θ1 = 150°. The positioning means include, for example, a rail 2 rounded according to this spherical cap, on which a receiver (or even a transceiver 3) can slide to positions Pn ensuring a viewing angle θn. Alternatively, a rail 2 can be used on which receivers are fixed at predetermined positions Pn (therefore there are N receivers), without the need to slide them. The positioning means also include means for rotating rail 2 around its vertical axis Oz (as shown figure 3c on which we can see two positions of the rail 2) at angles φk (k varies from 1 to K, K≤M and NK=M) ensuring positions Pnk of the receiver(s) (or even the transmitter-receivers 3) as shown figure 3b And 3c or around a horizontal axis Ox located in a plane containing the ends of the rail. The larger φK - φ1 is, the more precise the 2D and / or 3D images will be. Typically, 120° ≤ φK - φ1 ≤ 180°. Alternatively, the positioning means are fixed to the protective structure 1 described in more detail below, and it is structure 1 that rotates manually or automatically. Note that θN - θ1 = φK - φ1 = 180° corresponds to a dome-shaped structure as shown in the diagrams. figures 3a And 3b .

[0034] According to one embodiment, the acquisition device comprises a multicellular pad, each cell 6 containing a receptor, or even a transceiver 3. This pad has the shape of the spherical cap as shown figure 6a And 6b ; it can be distributed over a limited area or over the entire inner surface of the cap.

[0035] The acquisition device can be adapted or integrated into a mobile phone (smartphone). The acquisition device further includes a protective structure 1 for the operator 50 and the transmitters and receivers, which generally conforms to the shape of the positioning means as shown in the figures, but other shapes can be considered (cubic, composite, or other). This structure 1 has a positioning window for the acquisition device so as to direct it towards the disorder 60. The positioning window is located at the top of the protective structure 1, at the normal to the disorder 60 along the z-axis (the skin is arranged in an xy plane). Thus, the operator can position the acquisition device by direct visual inspection so that the window faces the disorder 60, as illustrated in the figures. figures 3a And 3bwhile maintaining the protective structure 1 on the skin. This window may include a magnifying lens 4, facilitating visual centering on the pigmentary disorder 60 by the operator 50. The structure 1 is intended to be positioned on the skin by the operator and has an opaque external surface, except for the positioning window, in order to protect the operator from light emissions and also to protect the receptors from stray emissions. For eye safety, the magnifying lens 4 advantageously includes an automatic shutter during transmission and reception.

[0036] We have represented on the figures 3a And 3b A dome-shaped structure (1). According to one variant shown figure 5a And 5b, a skirt 5 is associated with the protective structure 1 to allow support on the skin and openings Ψ adaptable to the dimensions of the pigmentary disorder 60 and / or to its position on such or such part of the body, such as the face for example.

[0037] Preferably, the dimensions of structure 1 are compatible with a portable acquisition device A that can be easily placed on different parts of the body: when structure 1 forms, for example, a dome as shown in the figures, it typically has a radius < 15cm. The structure can also be fixed and of larger dimensions.

[0038] As a non-limiting example, the interface (35) is of the type: memory card slot, USB, Wifi, Bluetooth, ....

[0039] Two image acquisition techniques can be used: According to an embodiment not part of the invention, a "passive" imaging technique is used: it concerns the visible and near-infrared bands. The pigmentary disorder is illuminated by ambient light external to the device passing through the positioning window, which may be equipped with the magnifying lens 4, and which remains transparent to ambient light. The emitter considered is then that of the ambient light. The 2D images are acquired successively for the described device in relation to the figures 5a And 5b Images can be acquired simultaneously by the entire array of multicellular receptors for the acquisition device described in relation to the figures 6a And 6bThe acquisition device then includes means for simultaneous acquisition, such as receiver synchronization means. Ambient illumination allows for obtaining a 3D image of the volumetric surface of the disorder but does not always provide sufficient depth for the reconstructed three-dimensional image. According to one embodiment of the present invention, an "active" imaging technique is used: it concerns the visible and infrared bands. The pigmentary disorder is illuminated by the emitting sources 301, 302 of the transceivers 3, the positioning window no longer being transparent to ambient light outside the device; this window is, for example, masked by the operator or can also be equipped with a shutter as previously described. Illumination can be performed successively at several wavelengths for each viewing angle.The pigmentary disorder is then imaged successively for each wavelength and each viewing angle. The acquisition system includes means for successive acquisition synchronized with the illumination, such as means for synchronizing the receivers with the emitters. This technique makes it possible to obtain a 3D image of the volumetric surface of the disorder and deep three-dimensional imaging of the pigmentary disorder. Advantageously, at each exposure, the emission and reception angles are oriented and equal or nearly equal with respect to the normal to the plane containing the skin. These angles (θ, φ) are illustrated in the figures. figures 3a , 3b And 3cin the (x, y, z) coordinate system. This defines an angular coordinate system relative to the normal, where two angles on either side of the normal can have the same absolute value but opposite signs. Thus, two-dimensional images are collected in a monostatic or quasi-monostatic configuration. The device is designed to use two-dimensional images in monostatic or quasi-monostatic retroflection or reflection to obtain a three-dimensional image from the set of two-dimensional images taken at different angles. Furthermore, the 3D imaging will be more precise the larger the number of collected and precisely referenced two-dimensional images.

[0040] The invention enables the acquisition of a three-dimensional volumetric image by illumination within the "first therapeutic window" (650 nm - 950 nm); this approach leads to increased spatial resolution and minimized background noise. The use of three-dimensional imaging, whose spectroscopic properties (photon absorption and emission) lie within the first therapeutic window, allows access to the imaging of so-called "thick" tissues.

[0041] The "second therapeutic window" (1000 nm - 1350 nm) increases the depth of wave penetration by minimizing photon scattering, thus enabling light transmission to a depth of several millimeters. This emission window provides additional information on the development of the nevus roots and its microvascularization.

[0042] The scattering of the light wave emanating from the different wavelengths used allows a set of three-dimensional reconstructions of pigmentary disorders and therefore a complete and comparative information of pigmentary disorders knowing that the phenomena of scattering of light waves on pigmentary disorders are complementary (depth of scattering, scattering cross sections, determination of the roughness of the scattering structure) according to the wavelengths of illumination used.

[0043] Thus, the two-dimensional images obtained are used to obtain a three-dimensional reconstruction in the depth of the skin, particularly for wavelengths of illumination possessing a strong power of penetration of skin tissues.

[0044] This 2D and 3D imaging system is primarily applied in the biomedical field for the identification of cutaneous or subcutaneous disorders. In the context of non-melanoma skin cancers (basal cell carcinoma, squamous cell carcinoma, for example), the system according to the invention allows for precise visualization of the three-dimensional boundaries of the tumor, thus ensuring complete excision of the malignant skin tumor, which is a prerequisite for a cure.

[0045] Thus, the most frequent simple nodular forms (45 to 60 percent of cases) are very well defined, but within these simple forms, there may be a micronodular form, without peripheral delimitation and requiring larger excision margins, the three-dimensional image allowing a precise representation of these complex forms.

[0046] Thus, three-dimensional imaging makes it possible to reveal structures and signs invisible to the naked eye, improving the performance of the clinical diagnosis of pigmented lesions, to detect three-dimensional parameters allowing to refine the differential diagnosis between melanomas, carcinomas and nevi (location, shape, depth, highlighting of vascularization phenomena around the melanoma / carcinoma, modifications of the microrelief, modifications of the dermo-epidermal junction, vascular modifications, visualization of the limits of the tumor which makes it possible to be certain of the complete excision of the cutaneous tumor).

Claims

1. System for imaging a cutaneous pigment disorder (60) which comprises: - a device (A) for acquiring 2D images of the pigment disorder in a monostatic or quasi-monostatic configuration, comprising at least one transmitter / receiver (3), the transmitter / receiver comprising at least one light source (301, 302), which is configured to illuminate the disorder, and at least one receiver (303), the wavelength of which corresponds to that of the transmitter, - a unit (B) for processing the 2D images acquired (S1) in order to obtain processed 2D images (S2), - means (D1) for displaying the processed images (S2), characterized in that it further comprises: - means for positioning the transmitter / receiver (3) in accordance with at least two viewing angles in order to obtain at least one image per viewing angle, and in a state distributed along a spherical cap, - a structure (1) for protecting the acquisition device (A) and an operator (50), comprising a window for positioning the transmitter / receiver (3) in order to direct it towards the pigment disorder (60), the protection structure being intended to be positioned on the skin and having an opacified outer surface, - in that the processing unit (B) comprises a 3D reconstruction module with reflective Radon transform in order to obtain a reconstructed 3D image (S3) from the processed 2D images (S2), - and in that the display means further comprise display means (D2) of the reconstructed 3D image (S3).

2. System for imaging a cutaneous pigment disorder according to the preceding claim, characterized in that the protection structure (1) has dimensions which are compatible with a portable acquisition device (A).

3. System for imaging a cutaneous pigment disorder according to either of the preceding claims, characterized in that the acquisition device (A) comprises a multicellular pad, each cell (6) containing a transmitter / receiver (3).

4. System for imaging a cutaneous pigment disorder according to the preceding claim, characterized in that, with each exposure, the transmission angle and the receiving angle are orientated and equal relative to the normal to the plane containing the skin.

5. System for imaging a cutaneous pigment disorder according to either claim 3 or claim 4, characterized in that the acquisition device comprises a light source transmitting in the visible range and means for simultaneously acquiring the images (S1) by the receivers.

6. System for imaging a cutaneous pigment disorder according to claims 1 to 3, characterized in that the positioning means comprise a rail (2) on which one (or more) transmitter / receiver(s) is / are positioned and means for rotating the rail.

7. System for imaging a cutaneous pigment disorder according to the preceding claim, characterized in that the acquisition device comprises a single transmitter / receiver (3) on the rail (2) and in that the rail slides.

8. System for imaging a cutaneous pigment disorder according to any one of claims 1, 2, 3, 4 or 7, characterized in that the light source is multi-wavelength in the visible and near-infrared ranges, and / or the range of the 1st therapeutic window and / or the range of the second therapeutic window and / or the SWIR range, the receivers(s) corresponding to the wavelengths and being synchronized with the transmitters, and in that the acquisition device comprises means for acquiring images (S1) successively via the receivers as a result of at least one image per wavelength and per viewing angle.

9. System for imaging a cutaneous pigment disorder according to any one of the preceding claims, characterized in that the positioning window is arranged at the tip of the protection structure (1).

10. System for imaging a cutaneous pigment disorder according to any one of the preceding claims, characterized in that it is portable.

11. System for imaging a cutaneous pigment disorder according to any one of the preceding claims, characterized in that the acquisition device (A) is integrated in a mobile telephone.