Objectives-To investigate the potential of quantitative magnetic resonance imaging (MRI) to diVerentiate between therapeutically induced changes in inflammation and synovial proliferation in rheumatoid arthritis (RA) of the knee. Methods-MRI of the knee was performed on patients with RA before and one week after injection with corticosteroid (triamcinolone acetonide, TA group, n=9) and before, four, and 12 weeks after injection with yttrium-90 plus TA (TA+Y group, n=7). MRI scans were analysed by subjective visual grading by a trained observer and by computer aided quantitation for three features: synovial fluid volume, synovial pannus volume, and synovial enhancement after intravenous contrast agent. Results-All TA subjects improved clinically at one week but the eVects of TA+Y were more variable. TA significantly reduced synovial enhancement and eVusion volume, whereas TA+Y at 12 weeks tended to increase synovial enhancement and decrease pannus volume. Quantitative MRI values agreed well with subjective assessment of scans. Comparison of calculated change on MRI scan before and immediately after aspiration with actual volume aspirated showed high correlation (r=0.96). Conclusions-Quantitative MRI correlates with subjective visual assessment and, at least for synovial fluid, is accurate. MRI can diVerentiate actions of two therapeutic modalities on various pathological processes and is sensitive enough to detect change after one week. With the additional advantage of lack of observer bias, it will probably become a useful tool in the development and assessment of existing and novel treatments.

A study was undertaken to examine the accuracy and precision of the measurement of flow by magnetic resonance imaging (MRI) with consideration to the equipment and patient related parameters that might be encountered in vivo. For this purpose, test objects were devised consisting of PVC tubing, in which the internal diameter simulated the size of the arteries in the body. The design of the test objects ensured that steady laminar flow was obtained in the sections being imaged. The calibration study suggests that, using MRI, flow can be measured in vitro with systematic error of better than 7.0 +/- 5.0% and random error of better than 7.5%. In general, flow measurements obtained from MRI were found to correlate well with the known flows. However, the results indicated that there are prerequisite conditions for the validity of the measurements, such as the selection of appropriate flow pulse sequences and velocity limits. Measurements taken at vertically 40 mm away from the isocentre of the magnetic field were significantly different (p less than 0.01) from that at the isocentre.

Velocity measurements in major blood vessels were obtained in studies of volunteers using magnetic resonance imaging (MRI) and compared with Doppler ultrasound (US). The vessels studied were the abdominal aorta, superior mesenteric artery, common carotid artery, superficial femoral artery and middle cerebral artery. Using a paired t-test, no significant difference was found between velocity values estimated by MRI and US (p > 0.08). The relative advantages of each technique in radiological practice are discussed.

This study was carried out to measure the differences produced by change of reconstruction filter in calculations of left-ventricular end-diastolic volumes, end-systolic volumes, stroke-volumes and left-ventricular ejection-fractions from (99)Tc(m) Sestamibi (Bristol-Myers Squibb) gated myocardial perfusion SPECT studies. 30 patients had gated SPECT myocardial perfusion imaging at rest. The acquired projections were separately filtered with two filters, a low-pass filter (Butterworth) and an edge-enhancement filter (Metz). Each study was then further processed to determine left-ventricular end-diastolic volume, end-systolic volume, stroke volume and ejection fraction, and to assess defect size. The results for each patient with the two filters were compared. Calculated end-diastolic volumes, end-systolic volumes and left-ventricular ejection fractions, for each filter, were well correlated. Stroke volumes showed worse correlation. The differences between left-ventricular ejection-fractions, end-diastolic volumes and end-systolic volumes were statistically significant. There was no significant difference in stroke volumes. Ejection fractions were inversely correlated with defect size, but change in ejection fraction due to filter was not. End-diastolic and end-systolic volumes were correlated with defect size, but change in volumes due to filter was not. Thus the results for changes produced by choice of filter are not dependent on defect size. Using different reconstruction pre-filters in gated myocardial perfusion SPECT significantly changes the results of calculations of physiological parameters. Each centre should be consistent in the use of filters as this may affect the clinical consequences of the result.