EP2897520A1

EP2897520A1 - Device and method for characterization of tissue

Info

Publication number: EP2897520A1
Application number: EP13771041.4A
Authority: EP
Inventors: Nils Reinke; Andreas FASTRICH; Mathias BONMARIN
Original assignee: Dermolockin GmbH
Current assignee: Dermolockin GmbH
Priority date: 2012-09-18
Filing date: 2013-09-17
Publication date: 2015-07-29
Also published as: CH706988A1; WO2014043822A1

Abstract

A device and a method are made available for characterization of tissue, in particular of skin lesions. The device comprises a stimulator for thermal stimulation of the tissue, a modulator for modulating the temperature of the tissue, an infrared camera for recording modulated infrared images, a computing unit connected to the infrared camera and used to demodulate the modulated infrared images, and a display module for displaying the images demodulated by the computing unit. The modulator and the infrared camera are synchronized in such a way that a modulated infrared radiation radiated from the tissue can be recorded by means of the infrared camera during the thermal stimulation of the tissue.

Description

Device and method for the characterization of tissue

Reference to related applications

This application claims the benefit of Swiss Patent Application No. 01684/12, filed on Sep. 18, 2012, the entire disclosure of which is hereby incorporated by reference.

background

The invention relates to a device and a method for characterizing tissue, in particular skin lesions, according to the independent claims.

State of the art

Methods for characterizing tissue are known in many fields of technology. For example, such methods are used in the characterization of skin to detect skin lesions. So far, in this area, the methods have been limited to a visual examination of the skin. This method is subjective and a diagnosis of skin lesions, such as after a visual characterization of the skin, ie after a subdivision of the skin into areas with different properties, such as e.g. Cancer cell areas, highly depends on the experience of the respective doctor.

Some devices and techniques have been proposed to simplify this characterization and to perform with higher accuracy. Such a technique is based on active thermography.

Active thermography is based on heating or cooling of a sample to be examined Tissue area and on a subsequent spatially resolved recording of the surface temperature of the tissue. The heating or cooling generates a non-stationary temperature gradient within the tissue to be examined, which in turn influences the distribution of the surface temperature. Has a region of the tissue, especially below its surface, different thermo-physical

Properties compared to its environment, e.g. a different density, heat capacity, thermal conductivity, etc., this area influences the heat flow and consequently the time-dependent surface temperature. By monitoring the time-dependent surface temperature, it is therefore possible to detect areas with different thermo-physical properties below the surface. In active thermography, the object under investigation is heated by conduction, convection or absorption or cooled by conduction or convection. The energy transfer can be continuous or periodic. The principles of active thermography can be found e.g. in the document "Infrared thermal imaging" by M. Vollmer and K. P. Möllmann, Wiley-VCH, 2010.

In the study of skin some have

Lesions types have different thermo-physical properties than healthy skin. In particular, in the case of cancerous lesions, higher metabolic heat development and a higher blood perfusion rate at the site of the lesion are expected.

WO 2010065052 A1 discloses a medical diagnostic system in which the skin surface is cooled by supplying cold air for a maximum of one minute. A high-sensitivity stationary InSb infrared camera records the thermal behavior of the skin after thermal stimulation. After a post-processing of the infrared images for compensation By moving the patient, the time-dependent temperature of the skin is calculated and the result compared with a computer model for heat transfer. It has been shown that the thermal signature of melanoma is very different from that of healthy tissue or benign melanocytic nevi. Furthermore, it has been found that the main thermo-physical parameter affecting thermal behavior is blood perfusion, the other parameters mentioned above playing a rather minor role.

In DE 19515317 AI, the skin temperature is measured by contact thermometry or non-contact after stimulation, the document makes no statement about the procedure for the measurement.

The methods mentioned measure the temperature of the skin surface after stimulation, whereby the results are relatively inaccurate. Furthermore, the measurement in WO 2010065052 AI is cumbersome, since the patient must be positioned so that it is not too far from the infrared camera on the one hand and on the other hand, the examined skin area for the camera visible.

DESCRIPTION OF THE INVENTION It is an object of the invention to provide the abovementioned

Disadvantages to be eliminated or minimized.

This object is achieved in the aforementioned device for characterizing tissue, in particular skin lesions, characterized in that the device comprises a stimulation device for thermal stimulation of the tissue, a modulation device for modulating the temperature of the tissue, an infrared camera for detecting modulated infrared images, with the arithmetic unit connected to the infrared camera for demodulating the modulated infrared images and a display module for displaying the images demodulated by the arithmetic unit. The The modulation device and the infrared camera are synchronized in such a way that a modulated infrared radiation emitted by the tissue can be detected by means of the infrared camera during the thermal stimulation of the tissue.

Furthermore, the object with a method for the characterization of tissue, in particular of skin lesions, by means of an inventive

Device solved. First, a portable inspection head is placed on the fabric. Subsequently, the thermal stimulation is applied to the tissue by means of the stimulation device and the image capture of the infrared camera is activated. Thereafter, a frequency of image acquisition with the

Modulation frequency of the modulation device synchronized and detected modulated infrared images by means of the infrared camera. The modulated infrared images are then demodulated by means of the arithmetic unit and the demodulated infrared images are displayed on the display module. The modulated infrared images of tissue-emitted, modulated infrared radiation are detected during thermal stimulation.

By means of the device according to the invention and the method according to the invention, it is possible to obtain considerably more precise results of the tissue behavior in the stimulation with heat, since the behavior of the tissue is recorded directly during the stimulation and the time-dependent temperature patterns obtained thereby can be much better correlated with the stimulation pattern , The present device is therefore more sensitive than previous solutions.

The fact that the thermal radiation of the tissue and not the tissue temperature is recorded results in the advantage that the demodulation of the infrared images can take place directly through the use of images of the thermal radiation of the skin. A calculation of the absolute tissue temperature is difficult this requires information on parameters such as tissue emissivity, air-transmission coefficients, etc.

Further advantageous embodiments will become apparent from the other dependent claims.

In a particularly advantageous

Embodiment, the infrared camera is disposed within a portable inspection head, which is placed on the fabric. In this case, the inspection head comprises at least one channel for supplying the thermal stimulation to the tissue. This arrangement has the advantage of a compact design of the inspection head. The fact that the infrared camera is installed in the inspection head, the range of action of the device is extended and the objects to be examined need not be placed in a certain position or position beforehand. Furthermore, in this arrangement, the camera is always in a substantially constant compared to known solutions, small distance from the tissue to be examined. As a result, the measurement accuracy improves significantly, since external temperature influences or air currents, such as drafts, play a negligible role in the examination room.

In a further particularly advantageous embodiment of the device, the stimulation device and / or the modulation device are designed for periodic stimulation or modulation of the temperature of the tissue. This considerably increases the sensitivity of the measurements or the evaluation of the measurement results.

Brief description of the drawings

Exemplary embodiments of the invention will be explained in more detail below with reference to the figures. It shows Figure 1 shows an embodiment

device according to the invention;

Figure 2 shows a first embodiment

Inspection head;

Figure 3 shows a second embodiment

Inspection head;

Figure 4 shows a third embodiment

Inspection head;

Ways to carry out the invention

FIG. 1 shows an embodiment of the device 1 according to the invention. It comprises a stimulation device for thermal stimulation of a tissue 8. The stimulation device comprises an air conditioner 3 for producing an air flow guided onto the tissue 8 as thermal stimulation. Furthermore, the device 1 comprises a modulation device 4 for modulating the temperature of the air flow and thus of the tissue 8. The air conditioner 3 is connected to the modulation device 4 for modulation of the air flow. In this embodiment, the modulation ^¬ device 4 is arranged at the air outlet of the air conditioner 3. In another embodiment of the device 1, the modulation device 4 can be arranged in an inspection head 2 to be described in more detail, which can be placed on the fabric. The air conditioner 3 is connected by means of at least one flexible, thermally insulated hose 7 with the at least one channel of the inspection head 2. The inspection head 2 includes at least one channel for delivering thermal stimulation to the tissue 8. An infrared camera 14 is disposed within the portable inspection head 2. The infrared camera 14 is connected via a data cable 10c to a computing unit 5 for demodulation of the modulated infrared images. The arithmetic unit 5 is the output side with a display module 6 for the representation of the arithmetic unit demodulated images IIa, IIb connected. A control unit 9 serves to control the modulation device 4 to generate the desired periodic stimulation. It is connected on the one hand via a cable 10b to the arithmetic unit 5 for receiving therefrom a user-defined type of modulation in the form of digital signals, and on the other hand to the modulating device 4 for supplying an electrical signal for the generation of periodic modulation in the modulating device 4 to transfer these.

Fig. 2 shows a first embodiment of the inspection head 2, which is in contact with a fabric 8. It comprises in a housing 2a a channel 13 for supplying the periodic, modulated, thermal stimulation 12a, via the tube 7 of FIG. 1 from the air conditioner 3 in conjunction with the

Modulation device 4 is generated. The channel 13 carries the thermal stimulation 12a on the tissue 8, wherein the thermal stimulation 12a escapes after contact with the tissue through an evacuation port 17, which is shown by the arrows 12c. Thus, hot or cold gas can escape from the interior of the inspection head 2, so that it does not heat up unnecessarily. Part of the heat is taken up by the fabric 8 and emitted from the fabric surface 8a towards the camera 14, which is indicated by the arrows 12b. The infrared camera 14, which is in particular a microbolometer camera or a semiconductor-based infrared camera 14 or a QWIP camera, records the time-dependent thermal radiation 12b of the tissue 8 or the tissue surface 8a via the objective 15. In an advantageous embodiment, the infrared camera 14 is isolated in its radiation detection range by means of a window 16 from the environment, the window 16 is transparent to the radiated from the fabric 8, modulated infrared radiation 12b. The window 16 is between the lens 15 and the fabric 8 arranged and serves on the one hand as a filter for the radiation 12b and on the other hand as protection of the infrared camera 14 against dust and against the thermal stimulation 12a. The window 16 may be made of an infrared transparent material.

The infrared camera 14 converts the thermal emission or radiation 12b of the tissue 8 or the tissue surface 8a into infrared images at a defined image rate. The modulated infrared images are transmitted via the cable 10c from FIG. 1 to the arithmetic unit 5 and digitally demodulated there. Alternatively, a wireless transmission of images via Bluetooth or WLAN is possible. The infrared images are demodulated according to the lock-in principle. The lock-in thermography is known and is therefore not explained here. This results in a phase image IIa and an amplitude image IIb for each infrared image (see FIG. These images IIa, IIb characterize the tissue 8 or its thermal behavior as a result of the periodic stimulation 12a and are displayed on the display device 6 as grayscale or pseudocolor images. In the images IIa, IIb, zones with abnormal phase or amplitude values can then be identified as possible lesions. The amplitude image IIb represents the temperature variations on the tissue surface 8a and the phase IIa shows a representation of the phase shift between the modulation signal and the time-dependent

Fabric surface temperature. To identify the above zones, the phase and amplitude images IIa, IIb can be correlated with the localized thermo-physical properties of the tissue. Due to the averaging properties of the lock-in

Thermography can be achieved a significantly better sensitivity in image processing. For example, temperature differences of less than 1 mK can be detected. In comparison, at conventional static temperature measurements only sensitivities of about 17 mK can be achieved. Another advantage is the intrinsic insensitivity of parameters such as a variation in the emissivity of the tissue, nonhomogeneous heating / cooling of the tissue, unwanted reflections from other infrared sources, etc. When the modulation frequency is chosen high enough, eg in the range of ImHz-lkHz, Lock-in thermography can suppress lateral heat diffusion from the demodulated images IIa, IIb, so that a more precise localization of the lesion and detection of the lesion margin becomes possible.

For the choice of suitable

Modulation frequency includes the inspection head 2 means not shown in the figures for changing the modulation and / or the intensity of the thermal stimulation by the user. These can be, for example, means for inputting parameters and means for transmitting adjusted parameters to the arithmetic unit, which then sends the modulation of the temperature of the air flow (stimulation) 12a via the line 10b to the control unit 9 by means of suitable software. This digital signal is converted by the control unit 9 into a periodically modulated voltage, with the aid of which a heating element explained below is heated.

The temperature-modulated air flow 12a is generated by the air conditioner 3 and the modulation device 4. The air conditioner generates air at constant speed and temperature, which are freely adjustable. The air conditioner 3 comprises at least one electromagnetic source for thermal stimulation of the tissue, in particular an infrared source. The infrared source generates infrared radiation, in particular with a wavelength in the range of 0.1 to 15 μm. In an embodiment of the invention explained in connection with FIG. 3, the electromagnetic source, in this case preferably an infrared lamp, arranged in the channel 13 of the inspection head 2, whereby the air conditioner 3 is omitted. Of course, in this case also the modulation device 4 is located in the channel 13 of the inspection head 2, between the electromagnetic source and the tissue 8.

In the embodiment shown, the modulation device 4 heats the air coming from the air conditioner 3 periodically. In this case, the modulation device 4 comprises an electrical circuit comprising arranged in the emission direction of the air conditioner 3, above-mentioned heating element which may be an electrical resistance, which is not shown. In this case, a voltage applied to the resistor can be varied by means of the control unit 9 in such a way that the temperature of the tissue that can be changed by the thermal stimulation can be modulated. In one embodiment, the resistor is disposed in a tube, not shown, wherein the tube is positioned in the airflow 12a such that this airflow passes the resistor. When a voltage is applied to the resistor, resulting in the heating of the resistor, the air passing by is also heated. If the voltage is periodically modulated, then a periodically modulated temperature of the air flow is achieved. By setting various parameters of the periodic voltage, such as frequency, amplitude, shape, it is thus possible to produce a temperature-modulated air flow which is directed to the tissue 8 to be examined. The modulation amplitude is chosen to set the minimum and maximum airflow temperatures. The greater the modulation amplitude, the greater the temperature gradient in the tissue 8 and the greater the time-dependent thermal signal (radiation). In practice, the maximum temperature is chosen so that the tissue temperature does not exceed 42 ° C during the measurement. It is further advantageous to keep the minimum temperature above the dew point of water, so that no undesirable condensation effects occur. The thus modulated air flow is sent via the flexible hose 7 to the inspection head 2 and enters the channel 13 of the inspection head 2 a.

The inspection head 2 is designed such that the thermal stimulation takes place without touching the tissue by the stimulation and the modulation device. In particular, only one bearing surface of an outer housing of the inspection head 2 touches the tissue surface 8a. The support surface is formed by exchangeable support modules, which are not shown here, with contour adaptable to curvatures of the tissue surface.

In particular, silicone can be used for these bearing surfaces, which is known to have a flexible structure.

FIG. 3 shows a second embodiment of the inspection head 2. This embodiment corresponds to that of FIG. 2 with the difference that the evacuation opening 17 is not arranged laterally of the camera in the vicinity of the support surface, but behind the camera and parallel to the channel 13. Furthermore, in this embodiment, the stimulation device 3 is arranged in the channel 13. It can be an infrared lamp in this case. The modulation device 4 is arranged in the emission direction of the infrared lamp, ie in the current of the thermal stimulation 12a between the stimulation device 3 and the tissue 8. Of course, this arrangement also in the embodiment of FIG. 2 and for the still to be explained embodiment of FIG Use come. Such an arrangement has the advantage that the flexibility of the device is increased because no stationary air conditioner is needed. 4 shows a third embodiment of the inspection head 2, which in this case has two channels 13a and two lateral evacuation openings 17a arranged in the region of the support surface. In this embodiment, the modulated thermal stimulation is introduced simultaneously through both channels into the inspection head 2.

Depending on which type of air flow is to be generated in the interior of the inspection head 2, a suitable embodiment of the inspection head 2 can be selected. This can e.g. depending on the nature of the tissue area or tissue surface to be examined. For example, if the tissue has one or more bends, the third embodiment of the inspection head 2 may be advantageous because the thermal stimulation comes from two directions and more uniformly stimulates the tissue at the bend. In the first embodiment, the air flow comes from one direction only, so that on one side of the curve there would be a "slipstream side" stimulated less than the airflow-facing side, which would result in greater inaccuracy of measurement To generate as laminar a flow as possible in order to stimulate a uniform stimulation of the whole

To reach tissue surface. In order to avoid turbulent flows as much as possible, a suitable inspection head 2 as a function of

Surface texture of the tissue to be chosen for the investigation.

The invention is not limited to the embodiments described, but it is within the scope of the following claims, a variety of other forms selectable.

Claims

claims

1. A device for characterizing tissue, in particular skin lesions, comprising:

a stimulation device for thermal

Stimulation of the tissue,

a modulation device for modulating the temperature of the tissue,

an infrared camera for the detection of

modulated infrared images,

one connected to the infrared camera

Arithmetic unit for demodulation of the modulated

Infrared images,

a display module for displaying the images demodulated by the arithmetic unit,

characterized in that

the modulation device and the infrared camera are synchronized in such a way that a modulated infrared radiation emitted by the tissue can be detected by means of the infrared camera during the thermal stimulation of the tissue.

2. Apparatus according to claim 1, characterized in that the infrared camera is disposed within a portable inspection head which can be placed on the tissue, wherein the inspection head

includes at least one channel for delivering thermal stimulation to the tissue.

3. Apparatus according to claim 2, characterized in that the modulation device in

Inspection head is integrated.

4. Device according to one of the preceding claims, characterized in that the

Stimulation device, an air conditioner for generating an air flow guided on the tissue as thermal stimulation, wherein the air conditioner for modulating the air flow with the

Modulation device is connected.

5. Apparatus according to claim 2 or 3 and claim 4, characterized in that the air conditioner by means of at least one flexible, thermally insulated hose with the at least one channel of

Inspection head is connected.

6. Device according to one of claims 1 to 3, characterized in that the

Stimulation device at least one

Electromagnetic source for thermal stimulation of the tissue comprises, in particular an infrared source, in particular with a wavelength in the range of 0.1 to 15 μιη, in particular wherein the electromagnetic source is arranged in the channel of the inspection head.

7. Device according to one of the preceding claims, characterized in that the

Modulation device comprises an electrical circuit with an arranged in the emission direction of the stimulation device electrical heating element, wherein a voltage applied to the resistor is variable by means of a control unit (9) that the variable by the thermal stimulation temperature of

Tissue is modulated.

8. Device according to one of the preceding claims, characterized in that the

Stimulation device and / or the

Modulation device are designed for a periodic stimulation or modulation of the temperature of the tissue.

9. Device according to one of the preceding claims, characterized in that the

Infrared camera a microbolometer camera or a

Semiconductor-based infrared camera or a QWIP camera is.

10. Device according to one of claims 2 to 9, characterized in that the inspection head comprises at least one evacuation opening for the evacuation of cold or hot gas from its interior.

11. Device according to one of the preceding claims, characterized in that the

Infrared camera is separated in its radiation detection range by means of a window from the environment, the window being transparent to the tissue

radiated, modulated infrared radiation is.

12. Device according to one of claims 2 to 11, characterized in that the inspection head means for modifying the modulation and / or the

Intensity of thermal stimulation by the user includes.

13. Device according to one of claims 2 to 12, characterized in that the inspection head is designed such that the thermal stimulation takes place without touching the tissue by the stimulation and the modulation device, in particular that only one bearing surface of an outer housing of the

Inspection head touches the tissue.

14. The apparatus according to claim 13, characterized in that the support surface is formed by exchangeable support modules with adaptable to curvatures of the tissue surface contour.

15. Method for the characterization of

Tissues, in particular of skin lesions, by means of a device according to one of Claims 1 to 14, characterized in that:

- a portable inspection head on the

Tissue is put on,

the thermal stimulation is applied to the tissue by means of the stimulation device,

- the image capture of the infrared camera is activated,

a frequency of image acquisition with the modulation frequency of the modulation device

is synchronized,

- Modulated infrared images by means of

Infrared camera to be detected

- The modulated infrared images are demodulated by means of the arithmetic unit, and

the demodulated infrared images are displayed on the display module,

characterized in that

the modulated infrared images of tissue-emitted modulated infrared radiation are detected during thermal stimulation.

16. The method according to claim 15, characterized in that the modulation of the thermal

Stimulation of the tissue is performed periodically.

17. The method according to claim 15 or 16, characterized in that the thermal stimulation without touching the tissue by the

Stimulation device is performed.

18. The method according to any one of claims 15 to

17, characterized in that the demodulation is a lock-in demodulation and that per modulated Infrared image two demodulated infrared images are generated: a phase image and an amplitude image; wherein the two demodulated infrared images are color or gray scale coded for display by the display module.