QUANTITATIVE ASSESSMENT OF SYNOVIAL INFLAMMATION BY DYNAMIC GADOLINIUM-ENHANCED MAGNETIC-RESONANCE-IMAGING - A STUDY OF THE EFFECT OF INTRAARTICULAR METHYLPREDNISOLONE ON THE RATE OF EARLY SYNOVIAL ENHANCEMENT

The effect of temporary inflammatory suppression on synovial membrane enhancement, as determined by dynamic and static gadolinium-DTPA enhan ced magnetic resonance imaging (MRI), was studied. MRI of 18 arthritic knees was performed before and 1, 7, 30 and 180 days after intra-arti cular methylprednisolone injection until clinical relapse. MRI of anot her six knees was performed twice within 2-4 days in order to assess i nterobserver and inter-MRI variation. The rate of early enhancement of the entire synovial membrane of a pre-selected central sagittal slice (REE(syn,tot)), determined by dynamic T1-weighted FLASH MRI, decrease d in all knees within the first post-treatment week and remained low d uring remission, although gradually (syn,tot) increased to pre-treatme nt levels. The interobserver plus inter-MRI variation increasing. In c ases of clinical relapse, REE. was maximally 27%. The predictive value s of a REE(syn,tot) below/above 1.0%/s were 0.94 and 0.91, respectivel y, with respect to the absence/presence of clinical synovitis. Evaluat ion of small synovial areas revealed marked regional heterogeneity. St atic spin echo MRI was not informative. The study indicates that the r ate of early synovial enhancement reflects synovial inflammatory activ ity. Subclinical changes may be revealed. Evaluation of large synovial areas increases reproducibility and reduces the effect of regional he terogeneity. Dynamic MRI may prove a clinically useful measure of syno vial inflammation.