It is estimated that in the USA 1.5 million people suffer from systemic lupus erythematosus (SLE). This autoimmune disease often involves joints, and more than 90% of those affected will experience joint pain, stiffness and swelling at some time during the course of their illness. It is currently difficult to both diagnose and estimate the severity of lupus, because signs and symptoms vary considerably from person to person and there is no single diagnostic test for it. We explored the clinical utility of frequency-domain optical tomography (FDOT) to distinguish finger joints affected by SLE from healthy ones of volunteers. The proximal interphalangeal joints (PIP) of the 2nd to the 5th digit from both hands of 10 SLE patients and 4 healthy volunteers were examined. This resulted in a total of 80 joints affected by SLE and 32 healthy joints. The FDOT system was operated at a frequency of 600MHz. The laser diode employed produced a 1-mm beam at 670nm light, which was guided to 11 positions on the top of the PIP joints. At every location, using an exposure time of 80 ms for 16 phase steps, transmission images were acquired using an ICCD camera. First results of the analysis of the amplitude and phase shift of the images acquired show a sensitivity of 100% and a specificity of 80% to distinguish between joints of healthy volunteers and SLE patients.
We have developed a system of flexible optical imaging bands that can be used to assess the effects of systemic lupus erythematosus (SLE) on finger joints. Each imaging band consists of four pairs of light sources and a photodetector. The light sources contain three different light emitting diodes with wavelengths of 530 nm, 655 nm and 940 nm. Two of these imaging bands are wrapped around the proximal interphalangeal (PIP) joints of the index-, middle-, and ringfingers. The imaging bands gather transmitted and reflected light intensities from the tissues for ~ 4 minutes including two venous occlusions. This results in hemodynamic time traces for all source-detector pairs. From theses traces a rise, plateau, and fall time are calculated. We found that, on average, signals obtained from SLE patients displayed a shorter rise time and longer plateau time as compared to signals from healthy controls. Performing a two-dimensional linear discriminant analysis on the rise and plateau times, we obtained the best specificity of 89% and the best sensitivity of 76 %. Area under the receiver operating characteristic (ROC) curve is 0.86.