Quantifying disease activity and damage by imaging in rheumatoid arthritis and osteoarthritis

Traditional imaging, represented by radiographs, provides a very concise description of anatomical pathology of bony structures. Both degenerative and inflammatory joint diseases are characterized by progressive joint destruction, and valid, reproducible measures of disease impact are available. Much effort has been expended to develop scoring systems for joint destruction in both osteoarthritis and rheumatoid arthritis, and the most common internationally accepted semiobjective scores are presented. The anatomical pathology mirrors the past activity of the disease, and advanced imaging gives an impression of the actual disease processes, which subsequently lead to the damage. Such information is required to facilitate the development of efficient therapy against arthritis. Newer technology, exemplified by MRI and ultrasound Doppler, supplements images of structural change with functional data of ongoing disease activity. This chapter focuses on the possibilities for quantification of images in MRI and ultrasound, in which postcontrast enhancement and Doppler information, respectively, are of special interest for the evaluation of the inflammatory changes of arthritis. To save time and eliminate human bias, automation is mandatory. In ultrasound, semiautomatic evaluations are coming that allow for a real-time, reproducible estimate of disease activity. With MRI fully automated algorithms have been developed for processing of data of bony structures, cartilage, and soft tissue, and are currently being implemented into everyday clinical practice.