Tc-99m MDP bone clearance - a new technique designed to evaluate bone metabolism on a quantitative basis

A new technique for the quantitative evaluation of bone metabolism (bone clearance) is described, the diagnostic value of which at the hospital level is rated higher than that of qualitative bone scanning, as it permits metabolic imbalances in the bone to be ascertained at an earlier stage and to reduce the radiation exposure of the patients and hospital staff. Bone clearance was expressed as the ratio between the per minute accumulation of activity in the bone and the plasma activity per ml and calculated on the basis of the measured elimination rate of 99m-Tc MDP from the blood and soft tissues. The latter, in turn, was determined by subtraction of the glomerular filtration rate from the wholebody retention of 113mIn DTPA. The results obtained were corrected for the relative amounts of radioactivity bound to plasma proteins. Considerably increased clearance values were determined for patients showing metabolic or systemic disorders and, in particular, thyrotoxicosis (normal thyroid findings in the scintigrams) as well as in cases of premature ossification of epiphyseal cartilages in a growing organism. Markedly decreased clearance values were seen in patients receiving cortisone. The measured values were easily reproducible and consistent with the relevant hormone levels, while being completely independent of the renal function. (TRV)