WO2010064200A1

WO2010064200A1 - Method and device for optically examining the condition of joints

Info

Publication number: WO2010064200A1
Application number: PCT/IB2009/055458
Authority: WO
Inventors: Wouter H. J. Rensen; Malcolm A. Luker; Alison C. Sundset; Nicholas Y. Kent
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-12-05
Filing date: 2009-12-02
Publication date: 2010-06-10

Abstract

A device for optically examining the condition of joints is provided. The device comprises: a light source unit (21) adapted for illuminating a body part (5) comprising at least one joint (6) with light; a detector unit (24) adapted for detecting light emanating from the body part (5); and a control unit (1) adapted for controlling operation of the device. The device is adapted to acquire an image comprising morphologic information of at least a portion of the body part and store the image comprising the morphologic information in a memory unit (100). The device is further adapted to acquire information with respect to an actual level of inflammation of the at least one joint (6).

Description

Method and device for optically examining the condition of joints

FIELD OF INVENTION

The present invention relates to a method for optically examining the condition of joints and to a device for optically examining the condition of joints.

BACKGROUND OF THE INVENTION

In the context of the present application, the term light is to be understood to mean non-ionizing electromagnetic radiation, in particular with wavelengths in the range between 400 nm and 1400 nm. The term optical examination or optical examining means examination by means of light. The term body part means a part of a human or animal body. In general, the present invention relates to optical detection of joint conditions, in particular to the optical detection of joint diseases such as rheumatoid arthritis (RA). The treatment of such joint diseases is staged. Usually, a patient first receives pain killers. These are frequently followed by non- steroid anti- inflammatory drugs (NSAIDs) and disease modifying anti-rheumatic drugs (DMARDs). In many cases, the last stage in treatment with drugs is the use of biological therapies. In particular the last category is expensive and treatment can cost tens of thousands of dollars per year per patient. Additionally, the drugs used in later stages of treatment often cause more severe side effects. With respect to such joint diseases, medical professionals base their decisions on changes in therapy on disease activity which is given by the number and the severity of inflamed joints. Currently, rheumato Io gists use the Disease Activity Score (DAS-28) for diagnosis and treatment monitoring. However, this method is time-consuming, operator-dependent with associated reproducibility issues, and has limited sensitivity.

Since rheumatoid arthritis is a progressive disease and early diagnosis and start of treatment can help postponing adverse effects and high costs of treatment, there is a demand for objective, reproducible methods and devices for providing satisfactory information about the condition of joints and which assist a medical professional to come to a conclusion with respect to the actual joint condition.

It has been found in time-dependent measurements using non-targeted fluorescent dyes administered to the patient that perfusion dynamics in diseased joints are different as compared to normal healthy joints. However, in the clinical practice of rheumatologists, administration of contrast agents is impractical in most cases.

As an alternative, it has been proposed to use Diffuse Optical Tomography (DOT) to image joints for providing information about their condition. In a research project, venous blood flow to a body part has been temporarily obstructed by means of a pressure cuff and a joint has been imaged by means of DOT. In such studies, it has been found that optical parameters exist which correlate with the presence of rheumatoid arthritis (RA) activity. For example, it is known that inflammation can be recognized by a change in perfusion. Blood constituents, in particular both oxygenated and deoxygenated hemoglobin have distinct optical characteristics compared to other constituents of the human or animal body and thus can be optically detected.

US 6 424 859 B2 discloses a near infrared spectroscopic technique for characterizing the condition of a joint. The results from a spectroscopic measurement are compared to a database in which measurement results for a plurality of arthritic and healthy joints are stored in order to assist a medical professional to come to a conclusion with respect to the joint condition.

According to a method for optically examining the condition of joints known to the applicant, blood flow to and/or from a body part comprising at least one joint is temporarily blocked or occluded and distinct local attenuation measurements are performed at different times before, during, and after blocking of the blood flow. The local attenuation measurements are performed using at least two different wavelengths such that information about the actual disease activity can be attained. It has been found that such a method is capable of providing the desired information about disease activity.

However, the actual disease activity is only one factor which provides relevant information to a medical professional. A second factor which is relevant in monitoring joint diseases such as rheumatoid arthritis is the deformation of joints as a result of chronic inflammation. The known devices for optically examining the condition of joints which provide information about the disease activity are not capable of providing information about joint deformation. Currently, the deformation of joints is measured by x-ray imaging in order to achieve the additional relevant information. However, joint deformation measurements by means of x-ray comprise a number of disadvantages such as the harmfulness of this ionizing radiation and the necessity to additionally consult a radiologist and/or perform x-ray measurements in a different hospital department or at the place of a different medical professional. Due to these disadvantages, joint deformation measurements are currently not performed at every patient visit to a rheumatologist such that structural changes of joints are often not optimally tracked. This non-optimum tracking of structural changes of joints as a result of joint diseases can cause substantial delays in preventative treatment and thus increase the chance of irreversible damage to joints.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a device and a method capable of providing a medical professional with more detailed information about the condition of joints. This object is solved by a device for optically examining the condition of joints according to claim 1. The device comprises a light source unit adapted for illuminating a body part comprising at least one joint with light; a detector unit adapted for detecting light emanating from the body part; and a control unit adapted for controlling operation of the device. The device is adapted to acquire an image comprising morphologic information of at least a portion of the body part and store the image comprising the morphologic information in a memory unit. The device is further adapted to acquire information with respect to a level of inflammation of the at least one joint. Thus, the device is adapted such that both morphologic information and information with respect to the level of inflammation of a joint is acquired using light. Thus, both types of information are acquired with one device and without requiring the use of harmful ionizing radiation. Since the morphologic information is stored in the memory unit, it is available later and can be used by a medical professional for decisions with respect to treatment of joint diseases. Preferably, the information with respect to the level of inflammation is also stored in the memory unit. The information with respect to the level of inflammation can e.g. be acquired by selectively illuminating the body part with light of at least two different wavelengths and detecting the respective light emanating from the turbid medium. Further, the information can e.g. be acquired by temporarily (at least partially) obstructing blood flow to and/or from the body part and performing measurements at times before, during and/or after obstruction of blood flow.

Preferably, the information with respect to the level of inflammation of the at least one joint is information about perfusion dynamics and/or oxygenation. It has been found that such information can reliably be acquired by optical examination. Further, such information enables a reliable determination of the actual level of inflammation, which is correlated to perfusion dynamics and oxygenation. Preferably, the device is adapted to visualize changes between a first image comprising morphological information of the body part acquired at a first point in time and a second image comprising morphological information of the body part acquired at a second point in time. In this way, deformation of joints over time (which can e.g. be caused by chronic inflammation) can reliably be tracked by comparison of images comprising morphologic information acquired at different points in time. Preferably, the device is adapted that the second point in time differs from the first point in time by at least several days. Further, it is possible to visualize changes between images acquired at more than two different points in time. In this way, it will also be possible to track changes over longer time intervals and to determine changes in the speed at which the deformation proceeds.

If the device is adapted to visualize the changes by providing an overlay image showing the second image together with the first image, changes in the deformation of joints can easily be identified by a medical professional.

Preferably, the light source unit is adapted such that light of at least two different wavelengths is selectively emitted. In this case, perfusion dynamics and oxygenation can reliably be determined by selecting appropriate wavelengths such that reliable information about the level of inflammation is provided.

If the device is adapted to visualize changes between the level of inflammation determined at a first point in time and the level of inflammation determined at a second point in time, changes in the level of inflammation over time can easily be tracked and made available to a medical professional. Further, these changes can be compared to changes in morphology determined from the images comprising morphologic information. For example, the changes in the level of inflammation over time can be depicted in a graph (e.g. on a display). This is particularly advantageous if the changes are tracked for more than two points in time over a longer time interval. Preferably, the first and second points in time differ by at least a few days.

Preferably, the device comprises a unit for at least partially blocking the blood flow to and or from the body part. In this case, the information about the actual level of inflammation can reliably be acquired by optical examination. Preferably, the detector unit is formed by a two-dimensional detector array. In this case, the same detector unit is suited for both acquisition of the morphologic information and the information with respect to the actual level of inflammation. The two-dimensional detector array can e.g. be formed by a CCD camera or CMOS camera. If the device is adapted such that the body part under examination is trans- illuminated, the bone structure in the body part can be visualized in the image comprising the morphologic information. In this realization, it is advantageous to use a wavelength at which attenuation by tissue is low for illumination, e.g. a wavelength in the range between 600 nm and 900 nm. According to an alternative, the device is adapted such light is detected by the detector unit in reflection geometry. This alternative is particularly easy to realize.

Preferably, the light source unit is adapted such that the wavelength of the light used for illuminating is in the range from 400 nm to 1400 nm.

Preferably, the device is a medical image acquisition device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will arise from the detailed description of embodiments with reference to the enclosed drawings.

Fig. 1 schematically shows a device for optically examining the condition of joints.

Fig. 2 schematically shows details of a measurement unit according to an embodiment.

Fig. 3 schematically shows a human hand as an example for a body part with the positions of joints indicated. Fig. 4 schematically shows an overlay image visualizing morphological changes which have occurred between two points in time.

Fig. 5 schematically shows the set-up according to a second embodiment realizing reflection geometry.

Fig. 6 schematically shows visualization of changes in disease activity and structural changes over time in form of graphs.

DETAILED DESCRIPTION OF EMBODIMENTS

FIRST EMBODIMENT An embodiment of the present invention will now be described with reference to the figures. The device according to the embodiment can be operated in at least two modes, a first mode adapted for providing information about disease activity (e.g. actual inflammation of joints) and a second mode adapted for acquiring an image comprising structural information (morphologic information; e.g. information about joint deformation). Fig. 1 schematically shows a set-up for the optical detection of the condition of joints. In the illustration, a human body 4 is schematically shown as a body and a hand forms the body part 5 to be examined. However, it should be noted that the invention is not restricted to human bodies and e.g. animal bodies may be subjected to examination. Further, the body part 5 is not restricted to a hand but may also be formed by other body parts comprising at least one joint 6 such as arms, legs, feet, etc.

FIRST MODE OF OPERATION

First, the first mode of operation for providing information about actual disease activity, i.e. the present inflammation of joints, will be described. In the embodiment shown, the device for optical detection of the condition of joints comprises a measurement unit 2, a blood flow blocking unit 3, and a control unit 1. The control unit 1 is provided to control the operation of the device and data acquisition. In the first mode, the measurement unit 2 can be operated to irradiate portions of the body part 5 under examination with light and measure the local attenuation of the light at different positions of the body part 5. For example, in the embodiment shown the measurement unit 2 is formed by a measurement head which will be described in more detail below. It should be noted that Fig. 1 only provides a very schematic illustration without containing further information about the construction of the measurement unit 2. The blood flow blocking unit 3 is provided for temporarily blocking the blood flow to and/or from the body part 5 under examination. In the embodiment, the blood flow blocking unit 3 is provided by a pressure cuff surrounding the arm to which the hand under examination belongs and obstructing the blood flow by application of pressure to the upper arm. It should be noted that the blood flow blocking unit 3 may be adapted differently in order to allow temporarily at least partial blocking of the blood flow to and/or from body parts 5 other than a hand.

The construction of the measurement unit 2 according to the embodiment will be described in further detail with reference to Fig. 2.

The measurement unit 2 schematically shown in Fig. 2 is adapted for attenuation measurements in transmission geometry. The measurement unit 2 comprises a light source unit 21 emitting a beam of light for irradiating the body part 5. The light source unit 21 comprises at least one light source and appropriate light guides to direct the beam of light to the body part 5. The light source may be formed by a lamp or by one or more lasers and the light guides may for instance be formed by optical fibers or other light guiding elements known in the art. The light source unit 21 is adapted to be capable to emit light of at least two different wavelengths, preferably in the red to near infrared, wherein one wavelength is chosen such that blood has a high absorption and another wavelength is chosen such that the absorption of blood is low or comparable to surrounding tissue. Suitable wavelengths are for instance 600 nm and 805 nm but other wavelengths fulfilling these criteria are possible as well. Wavelengths in the wavelength range between 550 and 980 nm are particularly suitable. Further, an optical component 22 which e.g. may be formed by a lens is provided for directing the light to the body part 5. It should be noted that a lens is only one possibility for achieving the desired concentration to a specific area of interest and other possibilities are known to skilled persons. The optical component 22 is capable of concentrating the light (irradiation light 25) on a specific area of interest (or several specific areas of interest; i.e. specific positions) of the body part 5 as will be described below. A second optical element 23 is provided to collect light emerging from the specific area (or areas) of interest and direct the collected light 26 to a detection element 24. The detection element 24 may for instance be formed by a photodiode, a CCD, an optical guide such as a fiber connecting to a photodiode, or another light detection scheme known in the art.

Preferably, the detection element 24 can be a two-dimensional detection array such as a CCD camera or CMOS camera which can also be operated in the second mode without requiring a separate further detection unit as will become clear from the description with respect to the second mode of operation. The measurement unit 2 is adapted such that, in the first mode of operation, distinct local attenuation measurements for at least two different portions of the body part 5 can be performed.

The control unit 1 is adapted such that it controls at least partial blocking of the blood flow to and/or from the body part 5 by means of the blood flow blocking unit 3. Further, it controls the measurement unit 2 such that local attenuation measurements are performed before the blood flow is blocked, local attenuation measurements (at the same positions) are performed during the blocking of blood flow, and local attenuation measurements (at the same positions) are performed after restoring the blood flow.

The attenuation measurements in the three time intervals (before, during, and after occlusion) are performed continuously to achieve time-resolved measurements. In such measurements, the measured intensity drops after blocking the blood flow and rises again after restoring of the blood flow. The height of the drop and the time relation between the blocking/restoring of blood flow and change in the measured intensity provide important information about the condition of the joint 6 under examination. In the first mode, for example, attenuation measurements can not only be performed for a single joint 6 but at least one joint and at least one other portion of the body part under examination can be measured simultaneously, i.e. within the same cycle of normal blood flow, obstruction of blood flow, and restoration of the blood flow. This can be achieved by simultaneously performing distinct local attenuation measurements at the position of the at least one joint 6 and at the position of the at least one other portion of the body part 5. The at least one other portion of the body part may be another joint or a portion which is not a joint and serves as a reference portion. For each of the positions, attenuation measurements can be performed for the at least two different wavelengths of the irradiation light for one of which blood has a high absorption and for the other one of which absorption of blood is low or comparable to surrounding tissue. Preferably, attenuation measurements for multiple joints of a patient are performed simultaneously. In a preferred embodiment, all joints in both hands are measured simultaneously.

As a result, the following steps can for instance be performed in the first mode according to the embodiment: distinct local attenuation measurements for at least one joint and at least one other portion of the body part 5 are performed; the blood flow to the body part 5 under examination is temporarily blocked by means of the blood flow blocking unit 3 and distinct local attenuation measurements for the at least one joint and the at least one other portion are performed; and the blood flow is restored and distinct local attenuation measurements for the at least one joint and the at least one other portion of the body part 5 are performed. In each of the intervals, several attenuation measurements can be performed to achieve a time-resolved measurement. Further, the time dependent behavior of the at least one joint and the at least one other portion of the body part 5 can be analyzed both independently and with respect to each other. Exploiting the measurements for at least two different wavelengths allows analyzing the perfusion dynamics and oxygenation.

Preferably, multiple joints are measured simultaneously and the time dependent behavior of these multiple joints with respect to each other is analyzed. Still more preferably, all joints of a body part 5 are measured simultaneously. Fig. 3 shows a hand as an example for a body part 5 to be examined and the positions of joints 6 are indicated by crosshairs (it should be noted that not all joints are provided with reference signs). The indicated positions can be used as positions for the local attenuation measurements and additionally positions between these indicated positions can be used for reference attenuation measurements. In the embodiment shown in Fig. 1, via the measurement unit 2, the control unit 1 detects the spectral characteristics of the body part 5 containing joints 6. After a baseline measurement, the blood flow is (at least partially) blocked by the blood flow blocking unit 3. The measurement unit 2 now detects spectral changes related to the reduced blood flow. After some time, e.g. 30 seconds, the blood flow is restored by operating the blood flow blocking unit 3 appropriately (e.g. releasing the pressure cuff). The measurement unit 2 detects how fast the perfusion is restored in the joints and in which order the perfusion is restored. Preferably, the perfusion recovery is also compared between joints and other areas of the body part 5. Inflamed joints will have a different perfusion and oxygenation as compared to healthy joints. As a result, the dynamic spectral behavior which is measured by the measurement unit 2 will be different. The results of these measurements provide information from which a medical professional can come to conclusions with respect to the actual disease activity, i.e. the number of inflamed joints and the severity of inflammation.

The time-dependent behavior of individual joints, the behavior of joints with respect to each other and with respect to other parts (that can act as a reference) can be analyzed.

Thus, in the first mode the device for optically examining the condition of joints is operated to provide information about the actual disease activity. The information may be provided such that the device outputs a computed result indicating a certain disease activity (or level of inflammation) or the information may be provided such that further analysis by a medical professional is necessary to gather the disease activity information.

The control unit 1 comprises a memory unit 100 in which the obtained information about the actual inflammation and thus the actual disease activity is stored. For example, information which has been automatically computed can be stored or a conclusion with respect to the actual disease activity by a medical professional (based on the results from the measurement) which is input via an input device (not shown) can be stored in the memory unit.

SECOND MODE OF OPERATION The second mode of operation is specifically adapted to allow detection of joint deformation (which may result from chronic inflammation). In order to achieve this, the measurement unit 2 is operated to illuminate the body part 5 in a "full view" mode, i.e. in contrast to the first mode not only distinct local positions of the body part are illuminated but the body part is illuminated over a wide area, e.g. a substantial part of the body part or the whole body part is illuminated with light from the light source unit 21. This can e.g. be achieved by an appropriately adapted optical component 22 or by removing the optical component 22 for operation in the second mode. At the detector side, a wide area image of the body part 5 is acquired by the detection element 24. Preferably, the detection element 24 is adapted to acquire a two-dimensional image which can e.g. be achieved by the detection element 24 being formed by a CCD array or a CMOS detector array. Detection of the wide area image of the body part 5 (which may be an image of the whole body part or of a substantial portion of the body part) can e.g. be achieved by an appropriately operable second optical element 23 or by removing the second optical element 23 for the second mode operation.

Thus, in the second mode of operation an image of the body part 5 providing structural information is acquired. In other words, the morphology of the body part 5 under examination is established. In the case of the transmission geometry described with respect to the first embodiment, it is possible to visualize the bone structure in the body part 5 albeit with a lower resolution compared to x-ray imaging.

The image of the body part 5 acquired in the second mode of operation is stored in the memory unit 100 provided in the control unit 1.

JOINT DISEASE MONITORING It has been described above that both the results with respect to disease activity acquired in the first mode of operation and the results providing morphological information acquired in the second mode of operation are stored in the memory unit 100 of the control unit 1. The control unit 1 of the device is adapted such that the results from the first and second modes of operation acquired with respect to a specific body part 5 under examination are stored in the memory unit 100. For example, the results are stored together with information enabling identification of a patient to which the body part 5 under examination belongs.

The device is further adapted such that, when, at a second point in time, a body part 5 is examined which has already been examined before at a first point in time, the information with respect to disease activity and the morphological information acquired at the first point in time are brought in relation to the corresponding information acquired at the second point in time. The device is adapted such that changes that have occurred since the first point in time, i.e. changes in disease activity and/or changes in morphology are visualized. For instance, the respective changes can be highlighted on a monitor (not shown). For example, with respect to the images achieved in the second mode of operation at different points in time, the images acquired at different points in time can be overlaid (e.g. by established overlaying techniques) in order to visualize morphologic changes which have occurred. An example for such an overlay image is shown in Fig. 4 in which an image acquired at a first point in time tl in the second mode of operation is schematically shown together with an image acquired at a second point in time t2 in the second mode of operation. As can be seen in Fig. 4, morphologic changes which have occurred can easily be identified from such a combined image. In Fig. 4, it can be seen that the morphology of the body part under examination is different at the second point in time t2 as compared to the first point in time tl. In order to come to meaningful results with respect to joint deformation due to chronic inflammation and with respect to changes in disease activity on larger time scales, the respective measurements in the first and second modes are repeated for a plurality of times with several days, weeks, months, or years between the individual measurements. At every point in time at which the body part 5 of interest is examined, both the examination in the first mode and the examination in the second mode are performed and the respective results are stored in the memory unit 100. Thus, the changes in disease activity occurring over time and the structural changes of the joint can be tracked by visualizing the changes over time. The device according to the embodiment is adapted for visualizing the changes over time based on measurements performed at a large number of different points in time.

A possibility of visualizing the changes in disease activity which have occurred over time and visualizing the morphologic changes which have occurred is provided in Fig. 6. In Fig. 6, graphs are shown in which the results achieved with respect to disease activity and with respect to morphologic changes for a large number of points in time are presented. Further, in Fig. 6 the time points at which changes in therapy have taken place are indicated by triangles. The upper graph shows the structural change in arbitrary units as a function of time, while the lower graph shows the disease activity in arbitrary units as a function of time. For example, the device according to the embodiment is adapted such that these graphs are shown on a display connected to the device (not shown in the Figures). With this type of visualization, the device provides a representation of the patient history providing improved information to a medical professional for deciding on future therapy.

Thus, according to the embodiment both information about changes in disease activity and information about structural changes of a body part under examination are visualized and provided to a medical professional and thus can assist in making treatment decisions.

The described device for optically examining the condition of joints is a combined objective disease activity monitor and structural change monitor which is particularly suited for patients suffering from Rheumatoid Arthritis. The objective disease monitor provides information about the current level of inflammation and the structural change monitor indicates the cumulative historic damage to the joints. Both parameters assist the rheumatologist in making treatment decisions. All these advantages are achieved without necessitating examination by means of x-rays.

SECOND EMBODIMENT

In the first embodiment, the measurement unit 2 of the device for optically examining the condition of joints realizes a transmission geometry in which the light source unit and the detector unit are arranged on opposite sides of the body part 5 under examination, i.e. the body part is irradiated from one side and the light having passed through the body part is measured on the opposite side. In contrast, in the measurement unit 2 according to the second embodiment the light source unit and the detector unit are arranged on the same side of the body part such that light is detected in reflection geometry. Such an arrangement is schematically shown in Fig. 5. With respect to the second embodiment, only the differences to the first embodiment will be described and the description of common features will not be repeated. The second embodiment only differs from the first embodiment in the implementation of the measurement unit 2 and thus only this difference will be described.

As can be seen in Fig. 5, the body part 5 under examination is placed on a support 102 and illuminated with light from a light source unit 21. Although a light source unit 21 comprising two individual light sources is shown in Fig. 5, other realizations are possible. For example, only one single light source can be provided or more than two light sources can be provided. The light sources can be formed as has been described above with respect to the first embodiment. In contrast to the first embodiment, the detection unit 24 is arranged on the same side of the body part 5 as the light source unit. For example, the detection unit 24 can be formed by a CCD camera or another suitable two-dimensional detector array as has been described above with respect to the first embodiment. In such reflection geometry, the optical components 22 and 23 described with respect to operation in the first mode in the first embodiment can be combined. It is advantageous to separate the diffuse reflected light from the illumination light. This can be achieved e.g. by orthogonal polarized spectral imaging (OPSI) or darkfield imaging or other suitable techniques known in the art.

Similar to the first embodiment, the control unit 1 is adapted to operate the device in the first and second modes and store the measurement results in the memory unit 100. Further, the device is adapted to visualize the results as has been described with respect to the first embodiment.

Thus, the second embodiment differs from the first embodiment only in that the light emanating from the turbid medium is detected in reflection geometry in the second embodiment, while the light is detected in transmission geometry in the first embodiment. Besides that, the second embodiment comprises the same features and realizes the same advantages as the first embodiment described above.

It should be noted that, in the embodiments in the first mode, the blood flow need not be completely blocked but a substantial reduction of the blood flow may suffice. A plurality of different ways for implementing the measurement unit 2 exists.

It is an essential feature that the local collection of light from multiple portions of the body part 5 under examination can be measured in the first mode. This can e.g. be achieved by illuminating a single spot at a time and detecting a corresponding single spot on the body part 5 and scanning the position of the illumination and detection spot over the body part 5. A further, more preferred possibility for the first mode of operation is to illuminate the whole body part 5 and to image the transmitted (or reflected) light with a CCD camera or another suitable camera. This has the advantage, that the same detector unit can be used for the first and second mode of operation. However, due to the diffuse transmission, in this case the resolution of the image is limited and light traveling e.g. between fingers may overload the detector as far as no appropriate counter-measures are taken.

Another possibility for the first mode is to illuminate a discrete number of spots on the body part 5. This implementation has the advantage that less stray light reaches the detector which leads to a higher resolution and that the intensity of all the spots can be adjusted such that only a limited dynamic range is required for the detector. A plurality of different realizations for illuminating only a discrete number of spots in the first mode exists as a skilled person will understand.

Further, to detect different wavelengths in the first mode, it is possible to alternate the illumination wavelength. It is also possible to illuminate with all required wavelengths simultaneously and separate the different wavelengths in the detection path, e.g. using filters or a spectrograph.

In a preferred implementation, multiple body parts (e.g. both hands) can be measured simultaneously. Although it has been described that at least two wavelengths are used for illumination in the first mode, e.g. a larger number of discrete wavelengths can be used or even a complete spectrum over a certain range of wavelengths (e.g. 650 to 1000 nm). However, acquiring a complete spectrum requires more costly components as compared to a few distinct wavelengths. If several types of tissue components (such as fat, water, etc.) shall be discriminated, it might be advantageous to use more than two distinct wavelengths. Using more wavelengths helps improving the accuracy of the device, however, at increased cost and complexity.

Claims

CLAIMS:

1. Device for optically examining the condition of joints, comprising: a light source unit (21) adapted for illuminating a body part (5) comprising at least one joint (6) with light; - a detector unit (24) adapted for detecting light emanating from the body part

(5); and a control unit (1) adapted for controlling operation of the device; wherein the device is adapted to acquire an image comprising morphologic information of at least a portion of the body part and store the image comprising morphologic information in a memory unit (100); and the device is further adapted to acquire information with respect to an actual level of inflammation of the at least one joint (6).

2. Device according to claim 1, wherein the information with respect to the level of inflammation of the at least one joint (6) is information about perfusion dynamics and/or oxygenation.

3. Device according to claim 1 or 2, wherein the device is adapted to visualize changes between a first image comprising morphological information of the body part (5) acquired at a first point in time (tl) and a second image comprising morphological information of the body part acquired at a second point in time (t2).

4. Device according to claim 3, wherein the device is adapted to visualize the changes by providing an overlay image showing the second image together with the first image.

5. Device according to any one of claims 1 to 4, wherein the light source unit (21) is adapted to selectively emit light of at least two different wavelengths.

6. Device according to any one of claims 1 to 5, wherein the device is adapted to visualize changes between the level of inflammation determined at a first point in time and the level of inflammation determined at a second point in time.

7. Device according to any one of claims 1 to 6, wherein the device comprises a unit (3) for at least partially blocking the blood flow to and or from the body part.

8. Device according to any one of claims 1 to 7, wherein the detector unit (24) is formed by a two-dimensional detector array.

9. Device according to any one of claims 1 to 8, wherein the device is adapted such that the body part (5) under examination is transilluminated.

10. Device according to any one of claims 1 to 8, wherein the device is adapted such light is detected by the detector unit (24) in reflection geometry.

11. Device according to any one of claims 1 to 10, wherein the light source unit (21) is adapted such that the wavelength of the light used for illuminating is in the range from 400 nm to 1400 nm.

12. Device according to any one of claims 1 to 11, wherein the device is a medical image acquisition device.