Magnetic resonance imaging of rheumatoid arthritis in metacarpophalangeal joints

To report the development of high-resolution targeted magnetic-resonance imaging (MRI) techniques (not using injections of contrast media) to investigate and monitor rheumatoid arthritis (RA) in the metacarpophalangeal (MCP) joints.

A total of 25 RA patients (age range 30-68 years) with varying degrees of disease severity ranging from early onset through active disease to the burnt-out stage, were imaged. (One patient subsequently underwent surgery and histological data was obtained.) A series of 10 control subjects were also studied--two for each 10-year age range. All the RA subjects were assessed for disease activity using standard clinical criteria and radiography as part of normal procedures. MRI was carried out using a targeted system and novel radiofrequency coil. Images of the MCP were performed at very high resolution with 1.5 mm slice thickness and in-plane resolution 130 microns. Standard gradient-echo (GE) sequences were used for anatomical imaging, multiple-echo GE sequences used to produce effective spin-spin relaxation time (T2*) maps and optimised binomialpulse presaturation used in conjunction with a GE sequence to generate magnetization-transfer (MT) ratio maps.

High-quality high-resolution images of the MCP joints were obtained which highlighted normal anatomy and key features characterising the disease state (e.g. pannus, bone erosions, vascularity). Accurate measurements of T2* and MT with variations of +/- 4% and +/- 2% respectively were achieved. In active disease, variations in T2* and MT could be determined throughout areas of pannus, clearly demonstrating the heterogeneity of this erosive tissue. Pannus in MCP joints with active destruction was found to have high values of T2* varying from 25 ms to 40 ms with pockets up to 100 ms, whereas pannus present in chronic destruction, or burnt-out disease, had T2* values ranging from 21 to 29 ms. MT-active tissue was uniformly distributed in burnt-out disease, which was confirmed histologically in one case, compared with a more heterogeneous distribution in active disease.

The MRI sequences and targeted system developed allow high-resolution studies of RA disease progression and activity. The data confirm the variable pattern of the disease and, in particular, heterogeneity of pannus.