99mTc-pertechnetate uptake measurement in the rabbit knee-joint. II. Kinetics of 99mTcO-4 in normal and arthritic rabbit knee-joints.

The kinetics of 99mTechnetium pertechnetate (99mTcO-4) in the rabbit knee-joint were studied by external counting of the radio-isotope after intravenous injection. We studied joints with antigen-induced arthritis in the acute and chronic phase of joint inflammation as well as non-inflamed joints. In both inflamed and non-inflamed joints, a rapid increase in radioactivity was followed by a plateau lasting for at least one hour. The time needed to reach 95% of the plateau count rate (tp) was significantly increased in inflamed as compared with non-inflamed knee-joints. Moreover, tp values were significantly higher in acutely than in chronically inflamed joints. No correlation was found between 99mTcO1 uptake and tp values. The study of kinetics of 99mTcO-4 in the rabbit knee-joint provides information additional to quantitation of inflammation by 99mTcO-1 uptake measurements, since kinetic data characterize the type of joint inflammation.