A Method to Monitor Local Changes in MR Signal Intensity in Articular Cartilage: A Potential Marker for Cartilage Degeneration in Osteoarthritis

Osteoarthritis (OA) involves changes in the composition and ultimately the loss of cartilage from articulating joints. MRI has the ability to non-invasively probe the compositional integrity of cartilage, thereby potentially identifying diseased cartilage before loss occurs. In this study we have developed a technique to compare local changes in signal intensity over time in fat suppressed 3D gradient echo MR images of articular cartilage in patients with OA. We have used an Active Appearance Model (AAM) based image registration to correspond locations within the cartilage in the same individual at different times. We have applied the technique to data taken over periods of 1 and 3 years in two groups of patients with established OA of the knee. In both these studies, no significant change in total cartilage volume could be detected but we were able to observe some significant changes in signal intensity. We conclude that in a study of cartilage structure the technique can provide additional information without the overhead of extra scans.