Patent ID: 12213797

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT OF THE INVENTION

The exemplary apparatus according to the invention shown inFIG.1has a housing19, in which three measuring instruments are mounted next to each other and directed towards the tested area of skin17with a skin lesion resulting from application of an allergen: a stationary camera1, an infrared thermal imaging camera2and a Doppler sensor4, vertically retractable from the housing. A spacer15, made of transparent plastic and having an opening defining the field of the skin area17to be tested, is attached to the housing19facing the patient's skin surface during the examination. During measurement, the spacer15rests on the patient's skin surface, ensuring that the instruments are kept at a constant distance from the surface of the tested skin area17. At the edge of the opening defining the field of the tested skin area17the spacer15has a heating microelement16integrated with a K-type thermocouple in a feedback loop and coated with a black pigment containing micronized carbon or nanotubes commercially available under the trade name VantaBlack™, imitating the thermal and emission standard of artificial skin. During the measurement, the heating microelement16is in contact with a fragment of the tested skin area skin17. The housing19is provided with a heating and cooling system18, providing constant temperature in the immediate vicinity above the tested skin area17during measurement. On the underside of the housing of the apparatus, above the tested skin area17, a tube is provided in form of a rotating ring containing a built-in 3D skin surface scanner5. Inside the rotating ring of the 3D scanner5is an optical system in form of a pattern projector5awith a LED light source, and a recorder5cof the 3D skin scanner with a broadband full-spectral digital camera.

FIG.2shows the diagram of the rotating 3D skin surface scanner5forming a component of the apparatus according to the invention shown inFIG.1. The 3D scanner5is equipped with a pattern projector Sa with a LED light source, which through a projection grid Sb directs a beam of light in the visible range from 380 to 780 nm to the tested skin area17. As a result of the light beam passing through the projection grid Sb having a vertical pattern, an image of this pattern is displayed on the tested skin area17. In case of the presence of papules or vesicles on the skin surface or swelling accompanying the erythema associated with the type IV allergic reaction, a geometric distortion of patterns2atakes place, so that in the image of reflected radiation registered by the camera matrix of the recorder5ca representation3is formed of distorted patterns on the tested skin area17. Individual pixels3aof the photosensitive matrix of the broadband digital camera record the reflected light beam at each scanned point2of the tested skin surface17.

The embodiment of the apparatus according to the invention is related to a complex module for the hybrid comprehensive imaging of biophysical parameters accompanying the skin allergic reaction appearing in both Prick tests and Patch tests, consists of a coupled optoelectronic system integrated in a single housing and containing the following components:a thermal imaging camera2, installed in the central (vertical) axis of a tube formed by a rotating ring at the bottom of the housing; the camera operating in the infrared band in the range of 7.5×103nm (7.5 μm) to 1.4×104nm (14 μm), and provided with a dedicated optical system in form of a multi-lens objective; anda stationary digital camera1, operating in the visible light spectrum having the electromagnetic wavelength range from 380 nm to 780 nm, provided with a multi-lens objective;a Doppler sensor4with a laser operating in a band not lower than 560 nm and optimally 780 nm, with sampling frequency from 10 Hz to 19 kHz, with two optical fiber bands and at least 46 mm separation of optical fiber channels, for transdermal laser Doppler flowmetry (LDF) in the area of vascular microplexuses of the subpapillary layer of the skin,a 3D skin scanner5consisting of a pattern projector5awith a monochromatic coherent light source in form of a LED diode and a vertical projection grid Sb used to display patterned images on the tested skin, and a recorder5cin form of a full-spectral RGB camera operating in a wide spectrum of electromagnetic waves from 300 nm to 1000 nm, in particular covering the visible light spectrum from 380 nm to 780 nm and provided with a multi-lens objective.

A stationary camera1operating in the visible light spectrum range is provided with a single matrix or a higher even number of photodetection matrices of CMOS type (complementary metal-oxide semiconductor, composed of MOS-type transistors) having a native resolution of at least 640×480 pixels, or a LIVEMOS variant, or a photodetection matrix of the CCD type (charge-coupled device) having a native resolution of at least 640×480 pixels. From the structural aspect, the 3D skin scanner5system consists of a full-spectral camera with a photodetection matrix having a native resolution of 6400×3200 pixels constituting the recorder5c, together with a pattern projector Sa; in an embodiment the camera5with the pattern projector Sa are placed in a single vertical plane, on a movable circular frame moving horizontally with a stepper motor controlled by a computer connected to the apparatus and enabling precise control of yje camera movement over the scanned skin area, so that it would cover the entire tested area with its own field of vision, while also acting as a precise recorder of deformations of the patterns displayed on the skin by the projector Sa. The optical system of the 3D skin scanner5is designed to provide minimum scanning parameters with a spatial resolution of at least 0.1 mm, measuring point densities from 0.01 mm to 0.61 mm with a minimum scanning size of 0.03 mm of the scanned skin surface object.

In the embodiment of the apparatus according to the application, the movement of the full-spectral camera used as a recorder5c, takes place on a circular track of 6.2832 rad (360°) and is coupled with the patter projector5aplaced in the same line but offset to ensure scanning of the entire tested skin area, with the optical axis of the camera being initially set to 0 rad (0°).

In the embodiment a stationary camera1CCD was used with a single photodetector matrix having a native resolution of 6400×3200 pixels moving in a horizontal plane on a circular frame with an angle of 6.2832 rad (360°), with the optical axis of the camera initial setting being 0 rad (0°). The stationary camera1CCD is moved on this frame by means of a stepper motor controlled by a microprocessor of a PC, to which the apparatus is connected via an USB 2.0 or higher, after starting the 3D scanning sequence of the tested skin surface.

The stationary camera1with a CCD matrix is placed in the housing19which is open from the bottom towards the tested skin surface, providing the possibility of taking a digital photograph of the tested skin area with a minimum size of 60×150 mm. Preferably, the inner side of the optical system housing19, in which the lens of the CCD camera is placed, is covered with a black anti-glare layer.

Centrally in the axis of the tube formed by a rotary ring at the bottom of the housing19, next to the stationary camera1CCD, there is an additional thermal imaging camera2, operating in the infrared range of electromagnetic wavelengths from 7.5 μm to 14 μm, containing one or higher, even number of microbolometers, cooled or uncooled, having a native resolution of at least 640×480 pixels. The thermal imaging camera2used in the embodiment of the apparatus according to the invention is permanently fixed in the housing, perpendicularly to the open surface of the housing19and preferably has an uncooled microbolometers with a minimum resolution of 640×480 pixels, with a multi-lens objective providing a distance of 100 to 150 mm, minimum required viewing angles of 53°×38° and including a rectangular measuring field of 111×157 mm and a diagonal of 192 mm, while the thermal imaging camera optics ensures adequate geometric resolution, where the size of the minimum segment of the measuring field projected onto a single pixel of the microbolometer is 0.33×0.33 mm (iFOV=0.33 mm) and MFOV=0.99 mm. These values are essential for correct and sufficiently detailed representation of minimum temperature changes at the programmed resolution of the thermal imaging camera2, directly on the test surface and with maintained integrity of measurement across the entire required test field, the dimension of which is implied by the size of a standard Patch test chamber with sides of approx. 50×140 mm, in which allergenic substances are placed and then attached to the skin, as the dimension of the test field in Prick tests depends exclusively on the physician's decision, who can use either a lancet of pre-determined size or disposable lancets allowing to freely determine the limits of the test field.

If the distance from the optical center of the lens of the thermal imaging camera2to the test surface is greater than approx. 150 mm, it may turn out that the actual spatial resolution of the thermal image will be insufficient, and more specifically that the size of a single segment of the test field distinguishable by a single pixel on the microbolometer, for which the thermal imaging camera2is able to determine the minimum factory set temperature difference, may prove to be much greater than 1 mm×1 mm, in particular greater than 3 mm×3 mm. Appropriate selection of optics in connection with the minimum thermal resolution of the thermal imaging camera2at a level <30 mK with mean measurement error of the thermal imaging camera2at around 1% or 1° C., is possible by applying coupled focal length calculation for the objective, at a specified size of the microbolometer and the test field size, according to the formula:

Od=Md×Df
where Od(Object dimensions) is the edge dimension (height or width or diagonal) of the tested quadrilateral object in mm, distinguishable by a single pixel of the microbolometer, f (focus) is the focal length of the objective lens in mm, D (distance) or MOD (minimum object distance) is the minimum distance in mm of the optical center of the objective from the test field, MD (Matrix dimensions: height, width, diagonal) is the dimension of the rectangular microbolometer (height, width, diagonal) in mm.

Calculation of the above parameters allows to solve the problem of insufficient spatial resolution of thermal imaging camera2, which in known solutions based exclusively on thermal imaging methods was a barrier to correct identification of epicenter of epidermal hyperthermia associated with the application of allergens/haptens and resulted in the fact that despite meeting the technical criteria, thermal imaging cameras used alone were not suitable for biomedical purposes and for imaging of minimal epidermal thermal changes with an accuracy of minimum 0.1° C.

In order to ensure the accuracy of temperature representation in the field of view during each subsequent measurement using the thermal imaging camera2, it is necessary to place in its field of view one or more calibration standards in form of a heating microelement16integrated in the K-type thermocouple feedback loop and covered with a black pigment, including the content of micronized carbon or nanotubes commercially available under the trade name VantaBlack™ imitating the thermal and emission standard of artificial skin, with a surface temperature determined as precisely as possible, facing the objective lens of thermal imaging camera2, and having emissivity preferably close to 1. The standard of temperature and emissivity, in particular in form of a heating microelement16, is quadrilateral in shape, with minimum dimensions of 3×3 mm, optimally 10×10 mm. Before each test, the thermal imaging camera2should be individually calibrated independently of the factory calibration, setting the emissivity as close to 1 as possible or exactly to 1, and using the black heating microelement16as the standard to validate this emissivity setting. If two or four standards are used instead of a single emissivity standard in form of the black heating microelement16, they should be affixed at the vertices of the test field rectangle so that they additionally serve as topographic markers to superimpose a thermal image on a digital image from the CCD stationary camera1. For the sake of better visibility of these markers in the infrared thermal imaging camera2, they should be cooled or warmed by a minimum of 1° C. relative to the mean temperature of the tested skin area17before being affixed to the skin.

Initiating the thermal imaging camera2test involves attaching a suitable plastic spacer15to the device housing19by pressing the button activating the device (e.g. marked as “TERMO SCAN”). The tested skin area17is the area on which the Prick or Patch tests were previously performed. The start of the thermal imaging test is signaled by a sound and flashing of an appropriate (e.g. green) signaling LED on the device housing. At the same time, a photograph of the tested area is also taken by the stationary camera1. Positioning the device on the skin is performed manually according to the reference points applied with an appropriate template, with a preview of the image from the stationary camera1on the screen of the computer connected to the device. Termination of the thermal imaging test is signaled by a sound and the flashing of an appropriate (e.g. red) signaling LED on the device housing. In the exemplary embodiment the test results are saved in bmt graphic file format with the option to export to jpg, png, csv or xls formats, in the internal memory of the device and on a removable micro SD card, then transferred via USB to a computer, where they are further processed by means of dedicated software, which is not the subject of this application. The results of thermal imaging analysis are displayed in form of jpg or gif graphic files, and in a numerical format indicating the thermal dimension of the recorded hyperthermia areas on the skin surface in ° C. [or ° F. —depending on the user's preference], while the thermal image can be favorably superimposed on the image recorded by the stationary camera1in jpg format to highlight a greater number of details of the allergic reaction at the test site. In the applications of the apparatus according to the invention, the measurement of temperature distribution on the tested skin surface is carried out using the differential method, wherein the reference temperature on the material containing the black emissivity standard is measured first.

As already mentioned above, attaching the special spacer15in form of a plastic ring or a prism having neither upper nor lower base to the device housing19ensures repeatable measurement conditions using the apparatus according to the invention, in particular the appropriate distance between the optical system and the tested surface, resulting from the focal length of the objective lenses used in the CCD stationary camera1and the thermal imaging camera2. Preferably, the spacer may be transparent and additionally contain ventilation slots allowing the heated or cooled air to be released from above the tested skin surface. Preferably, the minimum distance from the tested skin surface to the bottom lens of the optics of the CCD stationary camera1and the thermal imaging camera2, once the distance element15is inserted, is 100 mm, and optimally 150 mm. The size of spacer15results from the housing variants used and can be, for example, in form of a ring15ahaving a minimum diameter of 30 mm and a minimum height of 100 mm (optimally 150 mm) from the center of the optics of the CCD stationary camera1and the thermal imaging camera2, or a prism having neither upper nor lower base15bhaving dimensions implied by the minimum size of the test field, i.e. 50 mm×150 mm, but it is also necessary to use an interchangeable, narrowed variant of the spacer15cin form of a cuboid having neither upper nor lower base, for which its dimension at the contact point with the skin shall be reduced to: minimum width of 30 mm and minimum length of 150 mm. An additional function of the spacer15is to provide stable thermodynamic parameters during the thermal imaging test, as it prevents uncontrolled air flow as a cooling/heating medium between the skin and the thermal imaging camera. Moreover, the spacer15in combination with the heating and cooling system18and the temperature sensor: either a contact one—in form of a thermocouple or thermistor, or a contactless one—in form of a pyrometer or a system with a thermal imaging camera, allows to trigger a forced euthermia on the surface tested skin, controlled by means of feedback from the temperature sensor. In the exemplary embodiment of the apparatus according to the invention, the temperature sensor function is performed by the thermal imaging camera2, which, before registering the proper thermal imaging sequence, performs a thermal pre-scan, using it as a basis for determining the average temperature of the tested skin area17.

The controller of the heating and cooling system18located in the housing19initiates the process of cooling or heating the test area with a stream of air until the average temperature of the test skin area17reaches the optimum level for the test. It should be borne in mind that the absolute value of the optimal temperature is individually variable and depends on individual features, while the temperature optimization is carried out by an algorithm implemented by a computer, which is not the subject of this application.

In order to standardize the registration of biophysical parameters in conjunction with the topography of allergens/haptens application points on the skin, it is advantageous to use a template according to which allergens are going to be applied to the tested skin in Prick tests, or the adhesive chambers or patches with haptens are going to be arranged in Patch tests, and according to which the test field boundaries on the skin are going to be marked. A special, appropriately attested hypoallergenic marker should be used for marking points and boundaries according to the template. The template shall be made of a rigid material as biologically neutral for human skin as possible, e.g. plastic or cellulose pulp and shall have dimensions equal to those of the test field corresponding to the test field in Prick and Patch tests. In case of Prick tests, optimally two types of templates: linear and non-linear, are used. The first template enables marking of allergen application points in a narrower field having a width defined by vertices of equilateral triangles with sides equal to min. 30 mm or more and having a minimum length of 150 mm. The second template shall be a rectangle having dimensions of at least 50 mm×150 mm, with holes arranged linearly in two rows with a distance between the centers of the holes of at least 30 mm. For Patch tests, it is optimal to use only the second template type, i.e. a rectangular template with minimum dimensions of 50 mm×150 mm.

Using a template requires placing it on the tested skin area, outlining the contours of the template with a special marker and marking allergens/haptens application points through the holes in the template. The template is not used to standardize the performance of skin tests, nor is it an auxiliary instrument to perform the allergy tests as such, but only to standardize the imaging of biophysical parameters already revealed in allergy tests in the infrared band, so that it is possible to make topographically accurate reference of allergen/hapten application points and the negative and positive control sites, as well as irritant application points, where the thermal camera2recorded a local hyperthermia. Hyperthermia is defined as the local temperature in the test field which is at least 0.1° C. higher than the temperature recorded in the test field at the application site of so-called negative control site in form of a saline or glycerin solution, without the addition of allergens, haptens, histamine or any irritants, where thiper>0.1+tcontr, where thiper, is hyperthermia in ° C., tcontris the temperature at the negative control site in ° C.

The template is used to integrate, i.e. precisely superimpose, a digital image from the CCD stationary camera1onto the digital image from the thermal imaging camera2to obtain a virtual image of skin lesions in form of allergic reaction symptoms associated with a visualized isotherm distribution on the skin around these lesions, as well as around places where no allergic skin reaction occurred, and sites of the negative control performed using saline or glycerin solution and the positive control using histamine hydrochloride solution (at a dilution of 1:1, 1;10 or 1:1000), and test sites using an irritant. Such a complex virtual image is only used as a starting point for further, more accurate testing using a set of sensors integrated in the apparatus housing19. These sensors record parameters for specific pathophysiological anomalies associated directly with type I allergic skin reactions triggered by test application of allergens in Prick tests, wherein to confirm the epidermally registered hyperthermia, as induced by a specific allergen, it is necessary to confirm its source, i.e. dilated vessels of subcutaneous microplexuses including subpapillary plexuses as a result of activation of the H1 receptor by histamine released from the granulation of mast cells induced by the allergen applied. Such confirmation is performed by examination of increased flow in these expanded microvessels by transdermal laser Doppler flowmetry using a Doppler sensor4.

In case of Patch tests reproducing the course of type IV allergic skin reaction, the thermal image due to the inaccuracy of determination of the autonomic marker of this reaction in form of focal hyperthermia, resulting from the very small distance (only 5 mm) between the samples of the tested haptens and therefore the possibility of overlapping isotherms from two different allergic foci, an additional, redundant, objective determination of the presence of other typical allergy indicators in form of epidermal lesions visible as small vesicles and papules, by using 3D scanner5imaging of the skin surface, is necessary. The use of multispectral imaging in a single device not only constitutes a measurement redundancy, but also aims at cascade confirmation of the results of the initial imaging of thermal parameters of the skin allergic reaction in the infrared band by dimensioning specific biophysical parameters of the other components of the skin allergic reaction, the measurement of which requires completely different techniques, separate for type I allergic reactions in Prick tests and for type IV reactions in Patch tests. The mechanism of sequential multispectral imaging in skin allergy tests according to the invention effectively solves the problem of full objectivity of their reading by introducing specific biophysical quantities that can be measured and relate to specific response indicators. The analytical model assumes two-stage confirmation of the presence of hypersensitivity to the tested allergen/hapten, firstly by means of the analysis of the test field in infrared—this is a technique common for both type I and type IV allergic reactions. Then, the measurement of particular pathophysiological specific indicators is performed adapted to the type I allergic reaction, where increased local vascular flow is measured in dilated microvessels of skin plexuses, using laser Doppler flowmetry, confirming the effect of histamine release on H1 receptors located in the endothelium. Similarly, in case of type IV allergic reaction, the presence index of epidermal eruptions in form of vesicles and papules, which are currently the basis for differentiation the allergic reaction, is measured. For this purpose, the apparatus employs the method of reconstructing the surface of the skin in a coherent light using a 3D scanner5, which allows determining the size of these eruptions in mm.

In the exemplary embodiment of the apparatus according to the invention, another integrated measuring instrument arranged in a common housing is the 3D optical scanner system5, which consists of a mobile recorder5cin form of a full-spectral camera with a high resolution CCD photodetector having a minimum resolution of 640×480 pixels, working in a wide range of light spectrum from 300 nm to 1000 nm, as well as a movable pattern projector5ahaving a light source in form of an LED emitting coherent monochromatic blue light of a wavelength of at least 415 nm and a vertical projection grid5benabling to project vertical patterns on the skin surface at a density of at least 10 lines per 1 cm, and an objective lens having a focal length of at least 7.7 mm, allowing to project patterns at the entire tested field with a diameter of at least 30 mm. The 3D optical scanner unit in form of the pattern projector5aand the recorder5cis placed in the movable lower part of the housing19of the apparatus according to the invention, open on the side facing the tested skin, on a circular frame moving by means of a stepper motor controlled by a computer processor, to which the entire apparatus is connected, enabling strictly controlled movement of the camera recorder5cin the horizontal plane, allowing for three-dimensional 360° scanning of the tested skin surface.

The analysis of skin lesions in form of vesicles and papules formed in type IV allergic reactions in Patch tests in form of 3D scans requires an appropriate reconstruction of the depth of the obtained epidermal image, which actually means the reconstruction of the depth corresponding to the detected intersections of virtual planes and rays. The result of the calculation is a set of coordinates of intersection points in the global coordinate system (X; Y; Z), where h, v are the coordinates of the detected intersection point and where n is the sequence number obtained in the indexing phase, corresponding to the plane intersecting the point. Then, a computer can generate an equation for this plane (An, Bn, Cn and Dn coefficients), as well as the directional coefficients of the ray corresponding to this point of the 3D scan image (Δxh and Δyv). This data is further used to solve the equation of the plane xh,v and yh,v from the system of equations of the ray: 0=An·Δxh·zh,v+Bn·Δyv·zh,v+Cn·zh,v+Dn, where the solution is the depth of the point relative to the apparent focal length of the objective of the camera recorder5c(the origin of the coordinate system), whereby the point is considered determined correctly only if zh,v is positive.

In the solution according to the invention, it was assumed that the final effect of the 3D scanner5operation is the reconstruction of the tested skin surface, including the adjustment of the surface to the reconstructed point cloud. As the point cloud projection onto the image sensor of the camera recorder5cis given and it is known that normal point vectors have a z component facing the direction of the objective lens, a solution is possible in two dimensions, by creating a planar graph connecting the points of the projection, which is optimal in comparison to the reconstruction of the topology of the object examined from the point cloud without such a projection. Based on the vertices and edges data, it is possible to create a triangular area for each three points that are connected to each other. The result of this step is an expected three-dimensional skin surface model with possible eruptions in form of vesicles or papules, however this model does not take into account areas that are not visible from the point of view of the objective lens. In the exemplary embodiment, the scans are saved in the Wavefront OBJ format. The coupled optics system of the 3D scanner5, consisting of the pattern projector5aand the recorder5c, must be capable of reproducing objects on the skin surface by ensuring proper movement of the scanning system. In the exemplary embodiment of the apparatus according to the invention, the coupled optical system of the 3D scanner5was placed on a frame in the lower part of the cylindrical housing of the apparatus, so that it can rotate around the vertical axis by 360°, thus ensuring that the 3D scan covers the entire area of the tested skin surface having a minimum diameter of 30 mm. The angular alignment of the optical axis of the projector objective lens5aand the recorder objective lens5cmust take into account the direction of the light stream reflected from the surface of the tested skin area17, onto which vertical patters are projected by means of the pattern projector Sa. The measuring ranges of the 3D scanner5in the example are in the range for the Z axis: 30 mm minimum, for the X axis: 30 mm, linearity (Z axis): +/−0.2% of range, resolution (Z axis): +/−0.04% of range, linearity on X and Y axes: +−0.4% of range, resolution on X and Y axes: up to 1024 points/profile.

The lens of the digital recorder5cof the 3D scanner5introduces geometric image distortions, so it is necessary to correct the distortions of this device's objective lens, where d is a differentiated distortion function, which assigns a point on an image sensor with coordinates (h1, V1) to each point (h, v) of the image (perspective projection with the center in the apparent focal length of the objective lens). Then there is also the reverse function d−1, which in turn assigns the corresponding points of the image to the matrix points. The correction of distortions is therefore reduced to transforming the coordinates of the matrix point using the function d−1. Distortion correction can be performed either in the scanner or using an external program. The former solution has the advantage of avoiding additional numerical errors when interpolating new pixel positions. A fourth-degree polynomial of the r variable, which is the distance from the center of the image, is most commonly used as the function d. Parameters for this polynomial can be obtained automatically by means of heuristic databases from scanned standards, which was used in the design solution of the apparatus according to the invention.

Activating the 3D scanning sequence involves connecting the spacer15to the apparatus housing19, pressing the start button (e.g. “Patch test 3D scan”) and is applicable to a single skin area17to which a hapten was previously applied in a Patch test. The start of the 3D scan is signaled by a sound and flashing of an appropriate (e.g. green) signaling LED on the apparatus housing19. The termination of the 3D scan is signalized by a sound and flashing of an appropriate (e.g. red) signaling LED on the apparatus housing19. In the exemplary embodiment, the 3D scan results are saved in the Wavefront OBJ format in the apparatus's internal memory and on a microSD card, and then transferred via USB to a PC, where they are further processed by a dedicated software, which is not the subject of this application. Results of the analysis of 3D scans are displayed in form of reconstructed jpg or gif graphic files, and in a numerical format indicating the number of registered skin lesions, their type, and extrapolated dimensions in mm.

In the exemplary embodiment of the apparatus according to the invention, the last integrated measuring instrument placed in the common housing is a Doppler sensor system4with a laser working in the band of 560 nm minimum, and optimally 780 nm (i.e. in the near infrared range) having a minimum power of 1 mW, with optical fiber channel spacing of at least 0.25 mm, designed for transdermal laser Doppler flowmetry in the skin microvessels of the subpapillary layer and deeper vascular branches supplying blood to subpapillary plexuses in the tested skin area17, where Prick tests were previously carried out. Integrating the Doppler sensor4in the apparatus according to the invention is dictated by a necessity of ensuring the required measurement redundancy confirming the allergic vascular hyperthermic reaction recorded by the thermal imaging camera2and triggered by stimulation of H1 receptors of the endothelium by histamine released from the granulation of mast cells when a positive result of a Prick test is obtained.

Transdermal laser Doppler flowmetry allows only to measure the average flow velocity in skin microvessels and the strength of the signal called blood cell flux, proportional to the product of the number of cells within the tested tissue fragment and the cell movement velocity, the result being expressed in so-called perfusion units (PU), however, the test does not provide a fully objective result as it does not measure the actual flow within the unit: 1 g of blood/100 g of tissue/1 minute. Transdermal laser Doppler flowmetry is of a comparative nature and presents the change in flow in a given vascular bed under the influence of various stimuli. In the apparatus according to the invention, this stimulus is the vasodilatation effect of released histamine on H1 endothelial receptors. Therefore, the use of the Doppler sensor4plays a confirmatory role, and the test result is correlated with the results of the thermal imaging test, confirming the connection of the recorded focal epidermal hyperthermia with a co-located increase in flow in microvessels in type I allergic skin reaction triggered by Prick tests.

The Doppler sensor4consists of a vertically retractable (by means of a stepper motor) cylindrical head containing optical fiber emitter and receiver-recorder of the beam reflected in the tested tissue, placed inside the apparatus housing at a distance of at least 10 mm from the geometrical center of the housing, as it results from prior experimental works that in case of the examining flow in skin microvessels using this method, in type I allergic skin reaction connected with posthistamine vasodilatation (Hovel et al.Laser Doppler flowmetry for determining changes in cutaneous blood flow following intradermal injection of histamine, Clin. Allergy,17; 1987), the results of measurement at the very point of application of the histamine test, or of the allergen in Prick tests, are inconclusive; optimal flow rates are measured at a distance >10 mm from the point of application, up to approx. 30 mm.

In the exemplary embodiment of the apparatus of the invention, switching a laser operating in the 780 nm band to a laser emitting light with wavelengths of 560 nm, 570 nm and 580 nm was applied in order to additionally determine the epidermal erythema index Eiat the allergy test area. Determination of the epidermal erythema index Eiis performed by evaluating the degree of monochromatic light beam emitted by the laser absorption by hemoglobin, without absorption by the skin pigment—melanin. The index is computed according to the following formula:

Ei=log10(1RG)-log10(1RR)
where RGis the mean reflectance for three monochromatic light beams of 560 nm, 570 nm, 580 nm and RRis the reflectance computed according to the formula:

RR=R650⁢⁢nm+R660⁢⁢nm+12⁢R640⁢⁢nm+12⁢R670⁢⁢nm3
where R650rmis the reflectance for a 650 nm light beamR660rmdenotes reflectance for a 660 nm light beamR640rmdenotes reflectance for a 640 nm light beamR670rmdenotes reflectance for a 670 nm light beam

Starting a test using the Doppler sensor4involves connecting the plastic spacer15to the apparatus housing19, pressing an activation button (e.g. labeled “LDF Prick Test”) and concerns the single test skin area17on which an allergen was previously applied during the skin Prick test. The start of the laser Doppler blood flowmetry is signaled by a sound signal and flashing of an appropriate (e.g. green) signaling LED on the apparatus housing19. At this point, the probe head positioning is performed manually with a PC monitor preview from the stationary camera1, and the probe head automatically pulls itself out and stops upon contact with the tested skin surface. Termination of the test using the Doppler sensor4is signaled by a sound signal and flashing of an appropriate (e.g. red) signaling diode on the apparatus housing. In the exemplary embodiment, the test results are saved as text files in the device's internal memory and on a microSD card, and then transferred via USB to a PC, where they are further processed by a dedicated software, which is not the subject of this application. The test results are displayed as text files and graphs showing the numerical values of the flow in skin vessels in Perfusion Units (PU), where PU is the quotient of the flowing blood cells concentration and the average blood cells flow rate; in the biophysical dimension 1 PU corresponds to 10 mV.