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 (99m TcO−) 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 99mTcO− uptake and tp values. The study of kinetics of 99mTcO− in the rabbit knee-joint provides information additional to quantitation of inflammation by 99mTcO4 uptake measurements, since kinetic data characterize the type of joint inflammation.