Device and method for determining a disease activity

1. A system for determining a disease activity of arthritis with respect to an area of interest of a body, the system comprising:

a perfusion manipulator adapted to vary a blood perfusion in the area of interest, wherein the area of interest includes a joint;

an irradiation unit adapted to irradiate the area of interest with light; and

a detection unit adapted to detect intensities of light reflected and/or transmitted by the area of interest under at least two different perfusion conditions in the area of interest; and

a controller adapted to:

record an intensity curve of detected intensities of light over time;

derive features from the detected intensities of light by fitting at least a part of the intensity curve by a fit function having fit parameters and using at least some of the fit parameters as the features for determining the disease activity; and

determine the disease activity of arthritis as a single value or a scalar value based on the features by using a predetermined regression vector,

wherein the controller is adapted to derive the features from the detected intensities of at least one predetermined wavelength or at least two predetermined wavelengths;

wherein the controller is adapted to determine the disease activity using an inner product of the regression vector and a feature vector; and

wherein the feature vector comprises at least the features derived from the intensity curve of the predetermined wavelength or intensity curves of the at least two predetermined wavelengths.

2. The system of claim 1 , wherein the irradiation unit is adapted to irradiate the area of interest with light of at least one wavelength or at least two wavelengths.

3. The system of claim 2 , wherein the irradiation unit is adapted to sequentially irradiate the area of interest with the at least two predetermined wavelengths.

4. The system of claim 1 , wherein the detection unit is adapted to differentiate between different wavelengths.

5. The system of claim 1 , wherein the perfusion manipulator is adapted to cyclically vary the blood perfusion in the area of interest.

6. The system of claim 1 , wherein said at least one predetermined wavelength or at least two predetermined wavelengths correspond to a wavelength or wavelengths that are determined to be the most significant wavelengths for determining the disease activity.

7. The system of claim 1 , wherein the wavelength or wavelengths include:

one wavelength of ca. 666±10 nm.

8. The system of claim 1 , wherein the features derived from the detected intensities of light include at least one of a maximum intensity, a minimum intensity, a drift, an intensity amplitude, a drop time, and an inflection point, or any combination thereof.

9. The system of claim 1 , wherein the detected intensities of light relate to optical measurements performed for more than one area of interest, and the controller is adapted to derive the features from the detected intensities of light for each area of interest.

10. The system of claim 1 , wherein the controller is adapted to:

determine at least one regression vector indicative for the disease activity by analyzing intensities measured for a plurality of patients having different levels of disease activity at a plurality of different wavelengths; and

select the at least two predetermined wavelengths corresponding to extrema in a spectrum of the regression vector.

11. The system of claim 1 , wherein the wavelength or wavelengths include two wavelengths of ca. 666±10 nm and 808±10 nm.

12. The system of claim 1 , wherein the wavelength or wavelengths include four wavelengths of ca. 666±10 nm, 808±10 nm, 835±10 nm, and 864±10 nm.

13. The system of claim 1 , wherein the wavelength or wavelengths include six wavelengths of ca. 586±10 nm, 638±10 nm, 666±10 nm, 808±10 nm, 835±10 nm, and 864±10 nm.

14. A method for determining a disease activity with respect to an area of interest in a body, the method comprising:

varying a blood perfusion in the area of interest wherein the area of interest includes a joint;

irradiating the area of interest with light; and

detecting intensities of light reflected and/or transmitted by the area of interest under at least two different perfusion conditions in the area of interest;

recording an intensity curve of detected intensities of light over time;

deriving features from the detected intensities of light by fitting at least a part of the intensity curve by a fit function having fit parameters and using at least some of the fit parameters as the features for determining the disease activity;

deriving the features from the detected intensities of at least one predetermined wavelength or at least two predetermined wavelengths; and

determining the disease activity of arthritis as a single value or a scalar value based on the features by using an inner product of a predetermined regression vector and a feature vector wherein the feature vector comprises at least the features derived from the intensity curve of the predetermined wavelength or intensity curves of the at least two predetermined wavelengths.

15. The method of claim 14 , wherein irradiating the area of interest with light comprises irradiating the area of interest with light of at least one wavelength or at least two wavelengths.

16. The method of claim 14 , wherein the wavelength or wavelengths include two wavelengths of ca. 666±10 nm and 808±10 nm.

17. The method of claim 14 , wherein the wavelength or wavelengths include four wavelengths of ca. 666±10 nm, 808±10 nm, 835±10 nm, and 864±10 nm.

18. The method of claim 14 , wherein the wavelength or wavelengths include six wavelengths of ca. 586±10 nm, 638±10 nm, 666±10 nm, 808±10 nm, 835±10 nm, and 864±10 nm.