A comparison of 99mTc-MDP and 99mTc-pertechnetate by computerized quantitative joint scintigraphy.

Computerized, quantitative joint scintigraphies were performed using both 99mTc-MDP and 99mTc-pertechnetate. 17 joint pairs with asymmetric active arthritis were selected for the study. The joint activity ratio was calculated by dividing the curve peak value of the inflamed joint by the curve maximum of the contralateral symptomless joint. A very high joint activity ratio with 99mTc-MDP was observed in the case of septic arthritis with osteolytic lesions. In all the rheumatoid joints the activity ratios were higher with 99mTc-MDP than with 99mTc-pertechnetate. In reactive arthritis the mean joint activity ratio was equal with both tracers. It appears that 99mTc-MDP is more sensitive in detecting active rheumatoid arthritis than 99mTc-pertechnetate and that high 99mTc-MDP values might be prognostic of destructive changes.