GB2319336A

GB2319336A - Skin malignancy detecting system

Info

Publication number: GB2319336A
Application number: GB9723135A
Authority: GB
Inventors: Gary Rogers
Original assignee: HEDGE TONY
Current assignee: HEDGE TONY
Priority date: 1996-11-08
Filing date: 1997-11-04
Publication date: 1998-05-20
Anticipated expiration: 2017-11-04
Also published as: GB2319336B; GB9623302D0; GB9723135D0

Abstract

In a system for detecting skin and sub-skin malignancies, a movable single infra-red sensor or an array of such sensors is or are used in non-contacting manner over a suspect area of skin. Local body temperatures at points within the suspect area are determined by quantitatively detecting IR radiation from these points, the output signals being processed and displayed in an interpretable form.

Description

System for Detecting Mailenancles This invention relates to a system for detecting skin and sub-skin malignancies, especially but not exclusively melanoma. Reference to "sub-skin" malignancies means malignancies which lie immediately beneath the skin, such as sub-skin growths of mole-like form. The invention is not intended to include detection of deep seated malignancies in respect of which the signal processing techniques hereinafter described would in general be inapplicable.

Melanoma is a highly malignant form of skin cancer which manifests itself as a mole-like lesion on the skin. However, at present, a cancerous lesion is not readily distinguishable from a benign mole without clinical examination at a hospital and after histological examination. Somewhat analogously, some forms of sub-skin breast cancer are not readily distinguishable from sub-surface cysts, and require removal and histological examination for proper identification.

Melanoma, particularly, is currently a major concern to the general public and referals of patients to hospitals by doctors in general practice have multiplied in number to such an extent that in many hospitals services are overburdened with clinical examinations for melanoma and analogous cancers to the detriment of other services which have to be carried out by the same personnel.

It would therefore be highly advantageous if a system was available for use by doctors in general practice and capable of reliably testing skin lesions to determine, at least in some cases, whether or not a particular lesion is malignant, thereby reducing the number of hospital referals.

According to the invention, there is provided a system for detecting skin and subskin malignancies comprising at least one infra-red sensor for measuring the effective local body temperature at a point or points in the region of a skin or subskin lesion by quantitatively detecting infra-red radiation emitted from said point or points, signal processing means for processing the signal(s) obtained from the infra-red sensor(s), and display means for receiving the processed signal(s) and displaying said signal(s) in an interpretable form.

Preferably the sensor(s) are capable of quantitatively detecting infra-red radiation incident thereon with a resolution equivalent to a temperature resolution not less than 1/2 of a degree Centigrade, and most desirably not less than about 1/5th of a degree Centigrade.

The present invention has to be distinguished from that of Patent Application No.

9606124.7, in which thermal imaging is carried out at a skin lesion using an infrared camera producing pixel size data. It also has to be distinguished from Patent Application No. 9602792.5, in which a contact sensor is employed.

Thus, instead of using thermistors to measure skin temperature, which rely upon physical contact with the skin, the present invention uses infra-red sensors that are placed over a lesion, but not in physical contact with it. These sensors take temperature readings (by measuring the incident infra-red) of points on the skin's surface. In effect it provides a series of temperature measurements similar to those obtained from a contact device but not in the same way as a thermal imaging setup which uses infra-red cameras producing data of pixel size.

The advantages of using infra-red sensors over thermistors are as follows: - the sensors do not have to contact the skin, which means that difficult skin contours can be sensed - as there is no contact with skin there is no risk of transfer of contamination - sensing can be performed over a much smaller time span - the sensors can collect data from a wider area at a lesion and its surrounding normal skin.

Preferred sensors are infra red heat sensors such as photodiodes or CCD devices operating in the infra-red spectrum. The sensors can alternatively be based upon a PbS or PbSe detector or any other device that responds to infra-red wavelengths.

The ideal spectral response is in the range 0.9 to 5ym wavelength band, and the device should operate ideally at room temperature.

A single sensor can be used to measure the radiated IR from a single point on the skin's surface or a series of sensors can be used in an array, such as a single line array, although sensors could instead be aligned in a square array or other pattern.

A single sensor can be moved about, sequendally to detect radiant IR from different points of the skin's surface. Such a unit can comprise an infra-red detector, amplifier and data capture equipment integrated onto a compact PC board. The output can be sent to a display device that can display the detected IR against time. Means can be incorporated so as to modulate the incident IR so as to diminish the effects of noise within the system. Such a means can be performed by the use of an optical chopper that revolves in front of the detector, the rotational phase and speed being controlled by an internal oscillator on the PC board. Alternatively, the same effect can be achieved by means of software controlling the recording of the IR readings from the detector or by electrically turning the detector on and off at fixed intervals. In some cn':umstances the noise will desirably not be eradicated and the terature variability recorded without modification.

An array of sensors consisting of a number of elements can be used instead. An example is the InGaAs linear image sensor. Characteristically such arrays may have 128 or 256 elements, although the number of elements possible is unlimited and the arrays do not have to be linear, but can conform to any shape, e.g. square, circular etc. The incident IR can be modulated by means of an optical chopper or software that selectively records data at fixed intervals of time. Moreover, it should be made clear that basic equipment may have an array of only two infra-red sensors, spaced with the aim of one sensor accessing a suspect lesion and one the normal skin adjacent the lesion.

The advantage of the array is that more than one point of the skin's surface can be measured at any one time, and an immediate comparison made between the different areas of skin under investigation. A simple line array, where all the individual sensors are arranged in a sttaight line will usually contain individual sensors that are all of the same type, in that they all respond equally to the same infra-red spectrum.

However, although the individual sensors that make up the line array can be uniform in characteristics, i.e. identical, they do not have to be so. Sensors can be adapted so that they measure different wavelengths of IR and can be arranged in such a way that any one area of skin under study can be imaged by sensors of different wavelength responsiveness. For instance, three types of IR individual sensors, a, b, c, may be employed, each type responsive to a different wavelength of IR. These sensors may be arranged in a line array as follows: abcabcabcabcabc....abcabc etc. Each sensor (abc) of the line may be arranged to sense one region of the skin's surface such that with a 129 sensor in single line array, 43 sections of skin are sensed. Each section of skin is thus sensed by three individual sensors (abc) and thus has data recorded with respect to three different types of IR wavelength emitted by the skin.

There is not a limit to the size of the sectors, which could for instance consist of 25 sensors, each responsive to a different IR wavelength, and which image a single section of skin.

Different ways of obtaining data on different wavelengths are possible, including passing filters in front of the sensor array.

Another type of array can comprise a number of single line arrays, as described above, arranged in parallel. Each single line array may have a unique spectral response and be capable of responding to a different part of the IR spectrum. The line arrays may be arranged such that each point on the skin's surface is recorded by a single individual sensor from each different line array. In this way there is obtained data recorded from each point on the skin's surface with respect to different levels of incident infra-red in different parts of the infra-red spectrum.

In use, the single sensor or array is held over the area of skin to be examined at a fixed and known distance. Data is collected in real time and selected by data capture electonics. It is important to be able to attribute the data that is collected to a particular area of skin. For a single sensor this means knowing from which point of the skin or a lesion the recording is made, and for an array it means knowing which individual sensor reading correlates to which part of the lesion under study.

For a single sensor, a video camera is mechanically coupled to said sensor. This enables the video camera to record an image of the skin lesion and its surrounds under study. It is arranged so that the infra-red sensor is aimed at a common focal point, such that the focus of the infra red detector is aligned with the centre of the cross hair of the video camera. In such a way the temperature and the level of IR radiated from any point on the skin lesion can be recorded and correlated to that point. Recording software can hold an image of the skin lesion and enable temperaeures to be recorded at different areas.

For an array, in conjunction with a video camera, the array's sensors can be arranged so that their temperature readings correlate with the area of skin they measure. This will enable the user to identify those sensor readings that correlate to suspect and non-suspect areas of a lesion and its surrounding skin.

Optical/mechanical coupling as described above enables this correlation to occur, allowance being made so that variable heights of the sensors above the lesion are taken into account.

Data interpretation is also important. In the case of a single sensor, the readings from the single sensor can be recorded against time, as a raw reading which includes noise or as a cleaner modulated reading. Each can be used to read the temperature of the skin in either an absolute or relative manner. In order to obtain an absolute reading, data is required as to the temperature of the environment, distance of sensor from skin, humidity etc., i.e. the measurement data has to be interpreted with the aid of further measurements. In order to obtain relative readings, as the sensor is moved around the lesion, some standardisation is necesary, particularly with regard to distance of the sensor from the skin's surface. The data can be displayed on the image of the lesion recorded from the video camera. Alternatively the variability in the real time recording of the incident IR can be interpreted. Such variability can characteristically determine the benign or malignant nature of the lesion. The time series produced can be interpreted with regard to its chaotic nature, measuring its dimension and Lyapunov exponent, for example, or by analysing the resultant time plot it produces. The time plot can be subjected to transformations that enable the time plot to be adequately modelled or predicted, in such a way as to characterise it.

From a single sensor, infra-red readings can be taken from different parts of the skin lesion and its surrounds and displayed in a variety of ways. These will include plotting the relative or absolute temperature on the video image or by statistical analysis, noting mean temperatures in different parts of the lesion and the surrounds, temperature ranges and variability readings such as standard deviation of a number of points. Graphs can be produced showing the temperature profiles.

In the use of an array of sensors, the resultant data enables infra-red information to be produced for a number of points on the skin's surface. This information can be plotted over the video image, thus showing the temperature profile over the lesion and its surrounds. A graphical display can be made, showing the temperature profile in a three dimensional map if the sensors are arranged in a square or other arrangement. With a line array, the data can be shown as a line plot across the lesion. It is possible, due to the coupling of the video camera, to indicate from which points on the skin's surface individual sensors on the array are recording. In this way data can be attributed to either suspect or non-suspect areas and statistical information gathered and analysed. Hence, the mean temperature from a suspect area can be ascertained as well as the mean temperature from non-suspect areas, and the two compared. Parameters such as variability (standard deviation) within each of these areas can be computed as well as whole area variability. Mean temperature differences between suspect and non-suspect areas can be computed, as well as other statistical information. In a line array there can be produced a line profile of the temperature over a lesion. The shape of this profile is characteristic of the type of lesion under study. The shape of the line plot over a malignant lesion is often different from that of a benign lesion and then again different from that of an inflamed lesion. By analysing the shape of the line plot the nature of the lesion can be appreciated and means may be provided to display this shape and statistical parameters emanating from it. Such parameters are typically the difference in temperature measured at the edge of the lesion and over its centre, in comparison with that of the surg skin.

It is not always necessary to locate the position of the points the detector is measuring by means of the dual use of a video camera. With a knowledge of the array and its performance at different heights above a lesion the sensors that access different areas of skin can be known.

The sensor(s) can be used with a filter placed between them and the skin's surface.

These filters can be of a type such that they filter out particular frequencies of light, or particular IR frequencies. The filters can be made of germanium or any other type of material suitable for work with infra-red light.

Apart from filters, there can additionally be employed optics which can focus on to specific sections of skin, or alternatively disperse an area of skin over a diffuse area on a sensor. Scanning optics can also be introduced to enable a stationary infra-red sensor or sensors to scan one or more lines through a lesion, instead of moving the sensor or sensors across the lesion.

Claims

1. A system for detecting skin and sub-skin malignancies comprising at least one infra-red sensor for measuring the effective local body temperature at a point or points in the region of a skin or sub-skin lesion by quantitatively detecting infrared radiation emitted from said point or points, signal processing means for processing the signal(s) obtained from the infra-red sensor(s), and display means for receiving the processed signal(s) and displaying said signal(s) in an interpretable form.

2. A system according to claim 1, wherein the sensor(s) are capable of quantitatively detecting infra-red radiation incident thereon with a resolution equivalent to a temperature resolution not less than 1/2 of a degree Centigrade, and most desirably not less than about 1/5th of a degree Centigrade.

3. A system according to claim 1 or claim 2, employing photodiodes or CCD devices operating in the infra-red spectrum.

4. A system according to claim 1 or claim 2, using sensors based upon a PbS or PbSe detector that respond to infra-red wavelengths.

5. A system according to any of claims 1 to 4, wherein the spectral response of the sensor(s) is in the range 0.9 to 5ym wavelength band when operating at room temperature.

6. A system according to any of claims 1 to 5, using a single sensor which can be used to measure the radiated IR from a single point on the skin's surface.

7. A system according to any of claims 1 to 5, using a series of sensors in an array, such as a line array, to measure IR radiated from a line or area on the skin's surface.

8. A system according to any of claims 1 to 5, using a single sensor and means for scanning a line or area on the skin's surface.

9. A system according to any of claims 1 to 8, in the form of a unit comprising an infra-red detector, amplifier and data capture equipment integrated onto a compact PC board, and a remote display device that can display the detected IR against time.

10. A system according to claim 9, including means to modulate the incident IR so as to diminish the effects of noise within the system.

11. A system according to claim 10, wherein said modulating means comprises an optical chopper that revolves in front of the detector, the rotational phase and speed being controlled by an internal oscillator on the PC board.

12. A system according to claim 7, using individual sensors in the line array which are uniform in characteristics.

13. A system according to claim 7, using sensors in the line array adapted so that they measure different wavelengths of IR.

14. A system according to claim 13, in which the sensors are adapted to obtain data on different wavelengths by means of optical filters in front of the sensor array.

15. A system according to claim 7, using a sensor array comprising a number of lines or sensors, arranged in parallel.

16. A system according to claim 15, wherein each line of sensors has a unique spectral response so as to be capable of responding to a different part of the IR spectrum.

17. A system according to claim 6, wherein a video camera is mechanically coupled to the sensor.

18. A system for detecting malignancies substantially as hereinbefore described.

18. A system according to claim 17, wherein the infra-red sensor is aimed at a common focal point, such that the focus of the infra red detector is aligned with the centre of the cross hair of the video camera.

19. A system according to claim 7, using a sensor array in conjunction with a video camera, the array's sensors being arranged so that their temperature readings correlate with the area of skin they measure by means of an optical/mechanical coupling.

20. A system according to any of claims 1 to 19, wherein temperature measurements from the sensor or sensors are recorded against time, as a raw reading which includes noise or as a cleaner modulated reading, whereby to read the temperature of the skin in either an absolute or relative manner.

21. A system according to claim 20, wherein the variability in the real time recording of the incident IR is interpreted to determine the benign or malignant nature of the lesion.

22. A system for detecting malignancies substantially as hereinbefore described.

Amendments to the claims have been filed as follows Claims 1. A system for detecting skin and sub-skin malignancies comprising an array of infra-red sensors for measuring the effective local body temperature at points in the region of a skin or sub-skin lesion by quantitatively detecting infra-red radiation emitted from said points, signal processing means for processing the signals obtained from the infra-red sensors, and display means for receiving the processed signals and displaying said signals in an interpretable form.

5. A system according to any of claims 1 to 4, wherein the spectral response of the sensor(s) is in the range 0.9 to tym wavelength band when operating at room temperature.

6. A system according to any of claims 1 to 5, in the form of a unit comprising an array of infra-red detectors, amplifier and data capture equipment integrated onto a compact PC board, and a remote display device that can display the detected IR against time.

7. A system according to claim 6, including means to modulate the incident IR so as to diminisb the effects of noise within the system.

8. A system according to claim 7, wherein said modulating means comprises an optical chopper that revolves in front of the detectors, the rotational phase and speed being controlled by an internal oscillator on the PC board.

9. A system according to any of claims 1 to 8, using individual sensors in a line array, which sensors are uniform in characteristics.

10. A system according to any of claims 1 to 8, using sensors in a line array adapted so that they measure different wavelengths of IR.

11. A system according to claim 10, in which the sensors are adapted to obtain data on different wavelengths by means of optical filters in front of the sensor array.

12. A system according to any of claims 1 to 11, using a sensor array comprising a number of lines of sensors, arranged in parallel.

13. A system according to claim 12, wherein each line of sensors has a unique spectral response so as to be capable of responding to a different part of the IR spectrum.

14. A system according to claim 6, wherein a video camera is mechanically coupled to the unit.

15. A system according to any of claims 1 to 14, using a sensor array in conjunction with a video camera. the array's sensors being arranged so that their temperature readings correlate with the area of skin they measure by means of an opticallmechanical coupling.

16. A system according to any of claims 1 to 15, wherein temperature measurements from the sensors are recorded against time, as a raw reading which includes noise or as a cleaner modulated reading, whereby to read the temperature of the skin in either an absolute or relative manner.

17. A system according to claim 16, wherein the variability in the real time recording of the incident IR is interpreted to determine the benign or malignant nature of the lesion.