Noninvasive 3D MR microscopy as a tool in pharmacological research: application to a model of rheumatoid arthritis.

Magnetic resonance microscopy (MRM) was applied to noninvasively image skeletal structures in the hindpaw of the live rat to characterize the progression of a heterologous type II collagen-induced arthritic process. Using a resonator, with optimized filling factor, three-dimensional (3D) gradient-echo images with voxel dimensions of 94 x 81 x 60 micron3 were acquired in 54.6 min. Three-dimensional MRM reduces the slice positioning problem, which is critical in longitudinal studies. Moreover, due to the much smaller slice thickness of images derived from 3D data sets, partial volume effects are less pronounced than in corresponding 2D images. Distinct pathomorphological changes associated with the collagen-induced arthritic process (e.g., increase of metatarsophalangeal joint space, and bone and cartilage erosion) could thus be analyzed under in vivo conditions.