Laser Imaging Techniques for Follow-up Analysis of Joint Inflammation in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most frequent chronic inflammatory arthropathy that often leads to joint destruction. Essential for the progress of the disease are both an early diagnosis and a sensitive follow-up of synovitis. In this paper, we present new laser based imaging techniques for the transillumination of small finger joints. The "Laserscan" technique allows the transillumination of small finger joints using red laser light with a wavelength of 675nm. The laser is positioned above the finger joint and a CCD camera detects the scattering distribution below the joint. After processing the data through a statistical machine learning method, we could show in a preliminary clinical study that it was possible to correctly classify the inflammatory status of 62 of 72 joints from 22 patients with RA compared to precise clinical examination. Sagittal optical tomography is a further development of "Laserscan". In this technique, a red laser is moved in sagittal plane above the proximal interphalangeal finger joint while a detector underneath the joint measures the scattered light distribution in the same plane. Using model-based iterative image reconstruction algorithms, sagittal cross-sectional images are obtained based on the acquired data. These images reflect the distribution of scattering and absorption properties within and around the joint cavity of a first healthy volunteer.