Evaluating assays with optical inhomogeneities
The invention relates to a method and a sensor device ( 100 ) for evaluating an assay with a sample. During the assay, optical measurements are made at a sensing surface ( 112 ), and at least one “homogeneity-image” of the sensing surface ( 112 ) is generated. From this image, an “homogeneity-indicator” is determined for at least one region of interest, and the optical measurements are then evaluated in dependence on said indicator. The homogeneity-indicator may for example be a binary value which indicates if an inhomogeneity was detected or not. If an inhomogeneity was detected, all optical measurements may be rejected, only measurements for the involved region of interest may be rejected, or measurements for a selected sub-area of the involved region of interest (ROI) may be rejected.
1. A sensor device for performing and evaluating an assay with a sample, comprising:
a carrier with a sensing surface that can be contacted by the sample, the carrier comprising a sample chamber, the sample chamber comprising the sensing surface and configured to receive the sample;
an optical sensor unit for making optical measurements at the sensing surface, the optical sensor unit comprising an image sensor by which a homogeneity-image of the sensing surface can be generated, the homogeneity-image including a plurality of pixels, each pixel having an image value; and
an evaluation unit coupled to the optical sensor unit, the evaluation unit comprising digital data processing-hardware executing software to:
determine whether image values of pixels within at least one region of interest in the homogeneity-image of the sensing surface deviate from a given target range of image values, wherein homogeneity is based on image values of the pixels falling within the given target range and inhomogeneity is based on the image values deviating from the given target range;
reject the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating inhomogeneity; and
accept the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating homogeneity.
2. The sensor device according to claim 1 , wherein the optical sensor unit further comprises a light source for emitting a light beam towards the sensing surface.
3. The sensor device according to claim 2 , wherein the light source comprises a light-emitting-diode (LED).
4. The sensor device according to claim 1 , wherein the optical sensor unit further comprises a focusing lens positioned between the sensing surface and the image sensor.
5. The sensor device according to claim 1 , wherein the image sensor comprises a two-dimensional camera.
6. The sensor device according to claim 1 , further comprising a data carrier for storing the software.
7. The sensor device according to claim 1 , wherein the sample chamber further comprises magnetic beads disposed about the sensing surface.
8. The sensor device according to claim 7 , further comprising a pair of magnets disposed about the sample chamber to generate a magnetic field in the sample chamber.
9. The sensor device according to claim 1 , wherein the image sensor is configured to generate the homogeneity-image at the start of the assay, during the assay, or at the end of the assay.
10. The sensor device according to claim 1 , wherein to determine whether the image values of pixels within the at least one region of interest in the homogeneity-image deviate from a given target range, the digital data processing-hardware further executes software to:
generate a histogram of the image values of the pixels within the at least one region of interest; and
determine whether a width of a main peak of the histogram falls within a given range.
11. The sensor device according to claim 1 , wherein the assay detects parathyroid hormone (PTH).
12. The sensor device according to claim 1 , wherein the assay detects cardiac troponin.
13. A sensor device for performing and evaluating an assay with a sample, comprising:
a carrier with a sensing surface that can be contacted by the sample;
an optical sensor unit for making optical measurements at the sensing surface, the optical sensor unit comprising an image sensor by which a homogeneity-image of the sensing surface can be generated, the homogeneity-image including a plurality of pixels, each pixel having an image value; and
an evaluation unit coupled to the optical sensor unit, the evaluation unit comprising digital data processing-hardware executing software to:
determine whether image values of pixels within at least one region of interest in the homogeneity-image of the sensing surface deviate from a given target range of image values, wherein homogeneity is based on image values of the pixels falling within the given target range and inhomogeneity is based on the image values deviating from the given target range;
reject the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating inhomogeneity; and
accept the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating homogeneity;
wherein the image sensor is configured to generate a plurality of homogeneity-images at different times of the assay.
14. A sensor device for performing and evaluating an assay with a sample, comprising:
a carrier with a sensing surface that can be contacted by the sample;
an optical sensor unit for making optical measurements at the sensing surface, the optical sensor unit comprising an image sensor by which a homogeneity-image of the sensing surface can be generated, the homogeneity-image including a plurality of pixels, each pixel having an image value; and
an evaluation unit coupled to the optical sensor unit, the evaluation unit comprising a data carrier and digital data processing-hardware executing software stored on the data carrier to:
determine whether image values of pixels within at least one region of interest in the homogeneity-image of the sensing surface deviate from a given target range of image values, wherein homogeneity is based on image values of the pixels falling within the given target range and inhomogeneity is based on the image values deviating from the given target range;
reject the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating inhomogeneity; and
accept the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating homogeneity;
wherein the digital data processing-hardware further executes software to store as data on the data carrier a shape and a location of an indicated inhomogeneity present on the sensor surface via the homogeneity-image for subsequent comparison with a successively generated homogeneity-image to determine whether servicing, cleaning, or replacing of the sensor device is required.
15. A sensor device for performing and evaluating an assay with a sample, comprising:
a carrier with a sensing surface that can be contacted by the sample;
an optical sensor unit for making optical measurements at the sensing surface, the optical sensor unit comprising an image sensor by which a homogeneity-image of the sensing surface can be generated, the homogeneity-image including a plurality of pixels, each pixel having an image value; and
an evaluation unit coupled to the optical sensor unit, the evaluation unit comprising digital data processing-hardware executing software to:
determine whether image values of pixels within at least one region of interest in the homogeneity-image of the sensing surface indicate homogeneity or inhomogeneity based on a given target range of image values;
reject the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating inhomogeneity; and
accept the optical measurements provided by the optical sensor unit for the at least one region of interest in response to the image values of pixels within the at least one region of interest indicating homogeneity;
wherein the digital data processing-hardware further executes software to determine whether the image values of pixels within at least one region of interest in the homogeneity-image of the sensing surface indicate homogeneity or inhomogeneity by subtractively combining the homogeneity-image with a reference image of the at least one region of interest to generate a difference image and by comparing pixel values of the difference image to the given target range.