WO2010061339A1

WO2010061339A1 - Device and method for optically examining the interior of a turbid medium

Info

Publication number: WO2010061339A1
Application number: PCT/IB2009/055329
Authority: WO
Inventors: Rik Harbers; Michael C. Van Beek; Wouter H. J. Rensen
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-11-26
Filing date: 2009-11-25
Publication date: 2010-06-03

Abstract

A device for optically examining the interior of a turbid medium is provided. The device comprises: a light source unit (2) adapted to emit light for irradiating the turbid medium (5); a detector unit (6) adapted for detecting light emanating from the turbid medium (5); and a support (4) adapted for supporting the turbid medium during examination. The support comprises a support surface (3) against which the turbid medium rests during examination. The support surface (3) is provided with a deformable layer (9) of a light- blocking substance.

Description

Device and method for optically examining the interior of a turbid medium

FIELD OF INVENTION

The present invention relates to a device for optically examining the interior of a turbid medium and to a method for optically examining the interior of a turbid medium.

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 optically examining means examining by means of light, e.g. by transillumination. The term turbid medium is to be understood to mean a substance consisting of a material having a high light scattering coefficient, such as for example intralipid solution or biological tissue. The term body part means a part of a human or animal body, e.g. a hand, an arm, a leg, a foot, etc.

In recent years, several different types of devices for optically examining the interior of turbid media have been developed in which the turbid medium under examination, such as a body part, is illuminated with light from a light source and light emanating from the turbid medium is detected by a detector unit in transmission or reflection geometry. In such devices, the detected light is used to gather information about the interior of the turbid medium. Depending on the type of device for optically examining the interior of a turbid medium, e.g. two-dimensional or three-dimensional images of the interior of the turbid medium can be reconstructed or information about concentrations of different substances inside the turbid medium can be extracted from the detected light.

US 5 415 655 shows a medical device for examining tissue by means of light. The medical device has a flexible light guide having a light energy input end adapted for connecting to a light energy source and a light energy output end. The light energy output end outputs a beam of light energy.

Recently, it has been suggested to use devices for optically examining the interior of turbid media to optically detect disease activity of joint diseases such as rheumatoid arthritis (RA) by illuminating both the joints and intermediate tissue of a body part under examination with light and detecting light emanating from the body part. 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. 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 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. Conventionally, rheumatologists use the so-called Disease Activity Score (DAS-28) for diagnosis and treatment monitoring. Since this method is time- consuming, operator-dependent, and has limited sensitivity, there is a demand for suitable devices for detecting disease activity. Use of devices for examining the respective body parts by means of light shows promising results as disease activity monitors.

According to a device for optically examining the interior of a turbid medium by transillumination known to the applicant which device is specifically adapted for detecting disease activity of joint diseases, a turbid medium (in particular a body part, such as a human hand), is placed on a plate made of a transparent material. For examination, the turbid medium is illuminated with an extended light source positioned below the plate and, in transmission geometry, light is detected by a detector unit situated on the opposite side of the turbid medium with respect to the light source. For example, the detector unit may be formed by a CCD camera. However, in such an arrangement, e.g. in a case in which the turbid medium is a body part such as a hand which is a typical situation for joint disease activity monitoring, light used for illuminating the turbid medium will also be transmitted from the light source to the detector unit without passing through the turbid medium. For example, the light will be transmitted between the fingers in the case of the turbid medium being formed by a hand. Since such light will not have been attenuated in the turbid medium, the intensity on the detector unit of this part of the light will be high as compared to the other part of the light which has passed through the turbid medium. Thus, the light not having passed through the turbid medium can saturate the detector unit such that, as a result, the relevant light which has passed through the turbid medium can only be detected with less accuracy. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and a device for optically examining the interior of a turbid medium in which light attenuated by the turbid medium can be detected with higher accuracy and unattenuated light is prevented from saturating the detector unit.

This object is solved by a device for optically examining the interior of a turbid medium according to claim 1. The device comprises a light source unit adapted to emit light for irradiating the turbid medium; a detector unit adapted for detecting light emanating from the turbid medium; and a support adapted for supporting the turbid medium during examination. The support comprises a support surface against which the turbid medium rests during examination. The support surface is provided with a deformable layer of a light- blocking substance. Thus, the support surface against which the turbid medium is to be rested during examination is provided with the deformable layer of a light-blocking substance. In the context of the present application, the term "light-blocking substance" is used for a substance which does not necessarily have to block 100 % of the light from the light source unit. It can still be sufficient if the optical properties of the light-blocking substance are chosen such that, at the initial thickness of the deformable layer of the light-blocking substance, the light attenuation with respect to light from the light source unit is at least similar to or higher than the attenuation of the turbid medium to be examined. In this case, overexposure of the detector unit is already reliably prevented. Thus, the light-blocking substance comprises light attenuation with respect to the light from the light source unit such that the deformable layer (having the initial thickness) attenuates the light from the light source unit at least to the extent to which the turbid medium under examination attenuates the light, preferably to a higher extent. As a consequence, the light-blocking substance is adapted such that it blocks (or substantially attenuates) light from the light source so that no light (or only a small amount) from the light source can pass at positions at which the light-blocking substance is present. Since the layer of the light-blocking substance is deformable, a turbid medium to be examined which rests against the support surface (and against the layer of the light-blocking substance) will deform and move aside (or displace) the light-blocking substance such that the turbid medium comes to direct contact with the support surface (without light-blocking substance remaining between the turbid medium and the support). In case of the layer of the light-blocking substance not blocking 100 % of the light from the light source, small residues of the light-blocking substance remaining between the support surface and the turbid medium will not disadvantageously affect the measurement. Thus, at positions at which the turbid medium contacts the support surface, the turbid medium can be reliably illuminated through a transparent support while, at positions at which the turbid medium does not contact the support surface, light from the light source unit which does not illuminate the turbid medium is reliably prevented from reaching the detector unit at intensities negatively influencing measurement accuracy. In this way, unattenuated light is prevented from saturating the detector unit and light attenuated by the turbid medium can be detected with higher accuracy. The deformable light-blocking substance can be formed by a fluid (either gaseous or liquid) or by a gel which can easily be displaced and reliably fills remaining gaps between positions at which the turbid medium contacts the support surface. Thus, the deformable light-blocking substance comprises a certain flowability enabling displacement by the turbid medium. However, the viscosity of the light-blocking substance can vary over a wide range as will become clear.

According to one aspect, the deformable layer of the light-blocking substance is provided by a transparent flexible container filled with the deformable light-blocking substance which is arranged on the support surface. In this case, the deformable light- blocking substance is reliably held in place by the transparent flexible container, which may e.g. have the shape of a pillow or pad, and the deformable light-blocking substance can be reliably replaced by replacing the flexible container by a new one. Further, since the flexible container is transparent, the material of the flexible container substantially does not affect light transmission from the light source unit to the turbid medium. Such a realization allows using a light-blocking substance which does not keep its shape, such as a liquid, without specific adaptation of the support surface.

According to another aspect, the deformable layer of the light-blocking substance is formed by the deformable light-blocking substance directly applied to the support surface as a layer. In this case, the light-blocking substance can e.g. be formed by a gel or fluid which is directly applied to the (appropriately adapted) support surface. In this case, no further material has to be arranged between the support surface and the light- blocking substance such that substantially undisturbed light transmission to the turbid medium is achieved at positions where the turbid medium displaces the light-blocking substance. In this case, the light-blocking substance should be reshaped or removed after each use. For instance, the light-blocking substance in form of a gel can be removed and replaced by a new layer after use. Alternatively, the light-blocking substance can be leveled (or uniformly distributed) after examination of a turbid medium and before placing the next turbid medium on the support.

Preferably, the deformable layer is structured such that, at positions at which a turbid medium rests against the support surface, the light-blocking substance is moved aside to expose the support surface. In this case, the support surface becomes reliably exposed at positions at which the turbid medium is present such that the turbid medium can be illuminated through the support. Further, at positions at which no turbid medium is present, the light from the light source unit is reliably blocked or at least strongly attenuated by the remaining light-blocking substance. Preferably, the light-blocking substance is a fluid, i.e. in the liquid or gaseous state, or a gel. In this case, the light-blocking substance can reliably fill gaps between parts of the turbid medium, e.g. between fingers in case of a hand forming the turbid medium.

According to an aspect, the light source unit and the detector unit are arranged on opposite sides of the support and the support is transparent with respect to the light from the light source unit. In this case, transillumination of the turbid medium is possible and the light from the light source unit (either before illuminating the turbid medium or after transmittance through the turbid medium) can be transmitted through the support. Preferably, the device for optically examining the interior of a turbid medium is adapted for transilluminating a turbid medium to be examined. Preferably, the light source unit and the support are arranged such that the support surface provided with the deformable layer of the light-blocking substance is located between the light source unit and the turbid medium, when a turbid medium to be examined is placed on the support for examination. In this case, since the deformable layer of the light- blocking substance is situated between the support and the turbid medium, the arrangement is such that light only enters the turbid medium at positions at which turbid medium rests against the support such that the deformable layer is moved aside. On the other hand, light exiting the turbid medium under examination can be detected in a plurality of positions, since the detector unit side of the turbid medium is not covered by light-blocking substance.

If the device is adapted for examining a body part comprising at least one joint as a turbid medium, the device is particularly suited for joint disease monitoring.

Preferably, the device for optically examining the interior of a turbid medium is a medical image acquisition device.

The object is also solved by a method for optically examining the interior of a turbid medium according to claim 11. The method comprises the steps: Placing a turbid medium to be examined onto a support surface of a support provided with a deformable layer of a light-blocking substance such that the light-blocking substance is pushed aside at positions at which the turbid medium rests against the support surface; Illuminating the turbid medium with light and detecting light emanating from the turbid medium. The method achieves the advantages described above with respect to the device for optically examining a turbid medium.

Preferably, the support is transparent and the turbid medium is illuminated through the support. In this case, it is ensured that light from the light source only exits through the support surface and into the turbid medium at positions at which the turbid medium rests against the support surface. Preferably, the light emanating from the turbid medium is detected in transmission geometry.

If the turbid medium is a body part comprising at least one joint, the method is particularly suited for monitoring joint diseases.

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 interior of a turbid medium according to the embodiment. Fig. 2 schematically shows a human hand as a turbid medium to be examined with specific regions of interest indicated.

Fig. 3 schematically shows a support with a deformable layer of a light- blocking substance arranged on the support surface.

DETAILED DESCRIPTION OF AN EMBODIMENT

An embodiment of the present invention will now be described with reference to Figs. 1 to 3. Fig. 1 schematically shows the general setup of the device for optically examining the interior of a turbid medium 1 according to the embodiment. In the embodiment, the device for optically examining the interior of a turbid medium is specifically adapted for examining body parts by transillumination, in particular for examining body parts comprising at least one joint such as a human hand. Thus, the shown device is particularly adapted for joint disease activity monitoring and joint disease analysis.

As can be seen in Fig. 1 , a turbid medium 5 to be examined is placed on the support surface 3 of a transparent support 4. The support can e.g. be made from glass or a transparent plastic material. In the example, the turbid medium 5 is formed by a human hand and the support 4 is formed by a transparent plate. Fig. 2 exemplary shows the regions of interest for joint disease activity monitoring, namely the joints 7 present in the turbid medium 5. Although in the example shown in Fig. 2, the body part 5 is formed by a human hand, other body parts comprising at least one joint can be examined for examining the condition of joints.

Below the support 4, i.e. on the opposite side of the support with respect to the turbid medium 5, a light source unit 2 emitting light 8 for illuminating the turbid medium 5 is located. The light source unit 2 comprises at least one light source emitting the light used for illuminating. The light source can e.g. be formed by a broadband light source, such as an incandescent lamp, or by a single-color light source such as an LED (light emitting diode) or a laser. A plurality of light sources can be provided in the light source unit, e.g. an LED array or a laser array.

On the opposite side of the turbid medium 5 as seen from the light source unit 2, a detector unit 6 is arranged for detecting light emanating from the body part 5 (again schematically indicated by arrows). The detector unit 6 can e.g. be formed by a CCD camera or by another array of light detectors capable of acquiring a spatially resolved two- dimensional image.

As has been described above, in such an arrangement generally the problem arises that light from the light source unit 2 may arrive at the detector unit 6 without having been attenuated by the turbid medium 5. For example, this can be caused by a portion of the light from the light source unit 2 passing between the fingers in case of the turbid medium 5 being formed by a human hand. Since such an unattenuated portion of the light can cause saturation of the detector unit 6 and prevent a successful measurement, there is a need to overcome this problem.

In order to overcome the problem, according to the embodiment a deformable layer of a light-blocking substance is arranged on the support surface 3, i.e. on the side of the support 4 against which the turbid medium 5 rests during examination. The light-blocking substance is chosen such that illumination light from the light source unit 2 is reliably blocked or at least strongly attenuated at positions at which the light-blocking substance is present. For example, the light-blocking substance can be adapted to absorb the light having wavelengths in the relevant wavelength range. The layer 9 of the light-blocking substance is deformable to such an extent that the light-blocking substance can be displaced at positions at which an object is pressed against the layer 9. According to a first example, the light- blocking substance is a gel and the layer 9 is formed by applying the light-blocking substance directly to the support surface 3. In this case, for example a layer of the light-blocking substance having a substantially even thickness is distributed on the support surface 3. Due to the deformability of the layer 9 of the light-blocking substance, if the turbid medium 5 to be examined is placed on the support surface 3 (and thus also on the layer 9), the light-blocking substance is moved away at positions at which the turbid medium 5 rests against the support surface 3. Further, the light-blocking substance is displaced by the pressure exerted by the turbid medium 5 such that the space on top of the support surface 3 which is not filled by the turbid medium 5 is reliably filled by the light-blocking substance. Thus, if the turbid medium 5 is a human hand, for example, the space between the fingers is reliably filled by the light- blocking substance.

At positions at which the turbid medium 5 rests against the support surface 3, substantially no light-blocking substance remains between the turbid medium 5 and the support surface 3. Thus, at these positions light from the light source unit 2 can reliably be coupled into the turbid medium 5 through the transparent support 4 (and through the support surface 3), while the other positions will be reliably filled by the light-blocking substance such that light from the light source unit 2 is prevented from traveling to the detector unit 6 without having passed through the turbid medium 5. The situation with the turbid medium 5 placed on the support surface 3 of the support 4 is schematically shown in Fig. 3 with respect to a human hand as a turbid medium under examination. As can be seen in Fig. 3, the fingers (schematically indicated by ellipses) of the turbid medium 5 contact the support surface 3 without light-blocking substance interposed, while the space between the fingers is filled with the light-blocking substance of the layer 9. It should be noted that, in the case of a light- blocking substance which does not completely block the light from the light source unit but only strongly attenuates the light, small residues of the light-blocking substance between the turbid medium and the support surface 3 do not adversely affect the measurement.

To summarize, according to the embodiment light from the light source unit 2 which passes through the transparent support 4 at positions at which the turbid medium 5 does not rest against the support surface 3 (and the layer 9) is reliably blocked or at least strongly attenuated by the light-blocking substance. In contrast, at positions at which the turbid medium 5 rests against the support surface 3, the light-blocking substance is displaced such that the turbid medium 5 directly contacts the support surface 3 (without light-blocking substance in-between or at least substantially without light-blocking substance) such that light from the light source unit 2 is coupled to the turbid medium 5 via the transparent support 4.

According to the embodiment, for optical examination the turbid medium 5 placed on the support 4 is selectively illuminated with light from the light source unit 2 and light which has traveled through the turbid medium 5 is detected by the detector unit 6 in transmission geometry. Thus, the turbid medium 5 is transilluminated during examination. After transillumination, the turbid medium 5 is removed from the support 4. Before a further examination can take place, e.g. of a different turbid medium, the deformable layer 9 of the light-blocking substance has to be either reshaped (e.g. by leveling the light-blocking substance again) or replaced by a new layer of light-blocking substance.

With reference to Figs. 1 to 3 a situation has been described in which the light- blocking substance (e.g. formed by a gel) is directly applied to the support surface 3. However, according to an alternative, the layer of the light-blocking substance can also be realized differently. According to an alternative, the layer 9 of the light-blocking substance is formed by a flexible, transparent bag which is filled with the light-blocking substance and arranged on top of the support surface. In this case, the light-blocking substance needs not be stable in shape. In particular, the light-blocking substance can be formed by a fluid or a gel. According to the alternative, the flexible, transparent bag filled with the light-blocking substance has a shape such that it can be spread on the support surface 3 to form layer of the light-blocking substance (with the transparent material of the bag arranged around the light- blocking substance and keeping the shape). For example, the deformable layer 9 of the light- blocking substance can be formed by a transparent pad filled with the light-blocking substance and arranged on the support surface 3.

Similar to the situation described above with respect to the embodiment, when the turbid medium 5 to be examined (such as a human hand) is placed on the support 4, at the positions at which the turbid medium 5 rests against the support surface 3 the light-blocking substance is displaced. The positions at which the turbid medium 5 does not rest against the support surface 3 (e.g. between the fingers in case of a hand being the turbid medium 5) are reliably filled by the displaced light-blocking substance. Thus, during optical examination, the turbid medium is selectively illuminated through the transparent support 4 (and the transparent material of the bag) at positions at which the turbid medium 5 rests against the support surface, while at the other positions the light from the light source unit 2 is not allowed to reach the detector unit 6 with intensities bearing the risk of overexposure. As a consequence, overexposure of the detector unit 6 by light from the light source unit 2 which has not traveled through the turbid medium 5 is reliably prevented and the light portion which has traveled through the turbid medium 5 can be reliably detected with high accuracy. It should be noted that the positions of the light source unit 2 and of the detector unit 6 can also be interchanged such that the support 4 is situated between the body part 5 and the detector unit 6. Further, it should be noted that the support 4 need not necessarily be provided as a separate unit but may also be integrated to the light source unit 2 or to the detector unit 6.

Claims

CLAIMS:

1. Device for optically examining the interior of a turbid medium, comprising: a light source unit (2) adapted to emit light for irradiating the turbid medium

(5); a detector unit (6) adapted for detecting light emanating from the turbid medium (5); and a support (4) adapted for supporting the turbid medium during examination; the support comprising a support surface (3) against which the turbid medium rests during examination; wherein the support surface (3) is provided with a deformable layer (9) of a light-blocking substance.

2. Device according to claim 1, wherein the deformable layer (9) of the light- blocking substance is provided by a transparent flexible container filled with the deformable light-blocking substance which is arranged on the support surface (3).

3. Device according to claim 1, wherein the deformable layer (9) of the light- blocking substance is formed by the deformable light-blocking substance directly applied to the support surface (3) as a layer.

4. Device according to any one of claims 1 to 3, wherein the deformable layer (9) is structured such that, at positions at which a turbid medium (5) rests against the support surface (3), the light-blocking substance is moved aside to expose the support surface.

5. Device according to any one of claims 1 to 4, wherein the light-blocking substance is a fluid or a gel.

6. Device according to any one of claims 1 to 5, wherein the light source unit (2) and the detector unit (6) are arranged on opposite sides of the support (4) and the support is transparent with respect to the light from the light source unit.

7. Device according to any one of claims 1 to 6, wherein the device for optically examining the interior of a turbid medium is adapted for transilluminating a turbid medium to be examined.

8. Device according to any one of claims 1 to 7, wherein the light source unit (2) and the support (4) are arranged such that the support surface (3) provided with the deformable layer (9) of the light-blocking substance is located between the light source unit (2) and the turbid medium (5) when a turbid medium to be examined is placed on the support for examination.

9. Device according to any one of claims 1 to 8, wherein the device is adapted for examining a body part comprising at least one joint (7) as a turbid medium (5).

10. Device according to any one of claims 1 to 9, wherein the device for optically examining the interior of a turbid medium is a medical image acquisition device.

11. Method for optically examining the interior of a turbid medium comprising the steps: - Placing a turbid medium (5) to be examined onto a support surface (3) of a support (4) with the support surface provided with a deformable layer (9) of a light-blocking substance such that the light-blocking substance is moved aside at positions at which the turbid medium rests against the support surface;

Illuminating the turbid medium with light and detecting light emanating from the turbid medium.

12. Method according to claim 11, wherein the support (4) is transparent and the turbid medium (5) is illuminated through the support (4).

13. Method according to claim 10 or 12, wherein the light emanating from the turbid medium (5) is detected in transmission geometry.

14. Method according to any one of claims 10 to 13, wherein the turbid medium

(5) is a body part comprising at least one joint (7).