Objective. To develop a method for quantifying acute synovial inflammation in rheumatoid arthritis (RA), utilizing magnetic resonance imaging (MRI).Methods. Gadolinium4iethylenetriamine pentaacetic acid-enhanced MRI was performed in 21 patients with knee synovitis. Changes in synovial membrane signal intensity were identified and quantified by line profile analysis. Multiple synovial biopsies were obtained by a blind biopsy technique, and standard clinical and laboratory measurements of disease activity were recorded.Results. The rate of synovial membrane enhancement correlated with histologic features of acute inflammation (r = 0.63, P < 0.01), but not with clinical or laboratory assessments.Conclusion. Dynamic MRI is a valuable technique for assessing acute synovial inflammation in RA.Magnetic resonance imaging (MRI) allows direct visualization of rheumatoid synovium following intravenous administration of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and has been proposed as a potentially valuable tool for evaluating synovitis (14). Synovial membrane uptake of Gd-DTPA (enhancement) is dependent on tissue perfusion and microvascular permeability, and manifests as increased signal intensity (brightness) on T1-weighted images. Therefore, since both increased tissue perfusion and microvascular permeability are cardinal features of all acute inflammatory processes, quantification of the rate of synovial membrane enhancement Supported by the Arthritis and Rheumatism Council (UK).

Objective-To examine the relation between rate of synovial membrane enhancement, intra-articular pressure (IAP), and histologically determined synovial vascularity in rheumatoid arthritis, using gadolinium-DTPA enhanced magnetic resonance imaging (MRI). Methods-Dynamicgadolinium-DTPA enhanced MRI was performed in 31 patients with knee synovitis (10 patients IAP study, 21 patients vascular morphometry study). Rate of synovial membrane enhancement was quantified by line profile analysis using the image processing package ANALYZE. IAP was measured using an intra-compartmental pressure monitor system. Multiple synovial biopsy specimens were obtained by a blind biopsy technique. Blood vessels were identified immunohistochemically using the endothelial cell marker QBend30 and quantified (blood vessel numerical density and fractional area). Results-Median Conclusions-Gadolinium-DTPAenhanced MRI may prove to be a valuable technique for evaluating drugs that influence angiogenesis.

Although magnetic resonance (MR) imaging has been used to evaluate many musculoskeletal lesions, the MR appearance of pigmented villonodular synovitis (PVNS) has not been described in detail. The authors describe two cases of PVNS in the knee imaged with both computed tomography and MR. In both cases parts of each lesion had very low signal intensity on both short repetition time (TR)/echo time (TE) sequences and long TR/TE sequences. Other portions of both lesions had intermediate signal intensity (equal to or higher than that of muscle but lower than that of fat) on short TR/TE sequences and increasing signal intensity on longer TR/TE images. In one case, the lesion also had a cystic component that showed MR changes typical of complex fluid. The authors propose that the MR signal characteristics demonstrated in these cases may be explained by the unique tissue components of the lesion, particularly hemosiderin and fat.