Assessing inflammation in the proximal interphalangeal joints of systemic lupus erythematosus patients with a flexible optical imaging system

A common symptom of systemic lupus erythematosus (SLE) is inflammation and joint pain in the fingers. There is currently no technology to objectively quantify the level of inflammation and monitor its progression over time. We evaluated the proximal interphalangeal (PIP) joints of two SLE subjects and two healthy subjects with a flexible optical imaging system (FOIS). FOIS includes eight sets of three light-emitting-diodes (LEDs) (wavelength λ = 880 nm, 660 nm, and 530 nm) and a photodiode to measure transmitted light from the LEDs by the photodetector. During data acquisition, a partial arterial occlusion is induced using a blood pressure cuff inflated to the subject’s diastolic blood pressure. The cuff is then released, and the measurement is allowed to return to baseline. The measurements are used to tomographically reconstruct the distribution of total hemoglobin concentrations (HbT) inside the finger. The SLE subjects’ PIPs were confirmed as diseased using systematic multiplanar grey-scale (GS) and power Doppler (PD) ultrasound. We found that the SLE subjects had a noticeably higher HbT in and around the joint cavities than in the healthy subjects. This suggests that FOIS could be used to assess inflammation in joints of SLE patients.