Comparison of four methods of analysis of 99mTc pyrophosphate uptake in rheumatoid arthritic joints.

Knees, hands, forearms and thighs in 22 patients with classical rheumatoid arthritis and 18 controls were imaged with 99mTc pyrophosphate. The uptake of 99Tc pyrophosphate in the joints of the hand and knee was quantitated using a gamma camera interfaced to a computer. Quantitative measurements of joint activity were assessed by analyzing resultant data in a number of ways. Counts per unit area normalized for body weight and dose of radiopharmaceutical was found to be the most satisfactory method of quantitating differences in disease activity. However, the sensitivity of the method was not great enough to clearly distinguish normal and rheumatoid joints.