Abstract
The accumulation process in bone of 99mTc-hydroxymethylene diphosphonate (99mTc-HMDP) and 99mTc-methylene diphosphonate (99mTc-MDP) was examined on 9 subjects (5 for 99mTc-HMDP and 4 for 99mTc-MDP) . 99mTc compounds in blood were analyzed with radio-thinlayer chromatography, radioactivity was measured using a scintillation counter, and the uptake of both 99mTc diphosphonates in bone was examined by sintigraphy. The amounts of 99mTc-HMDP and MDP compounds disappeared from blood for 2h after injection were 83% and 87%, respectively, and these were almost unchanged even after 3h. While the greater part of 99mTcO-4 contained in both diphosphonates was disappeared from blood, the small amounts of unknown 99mTc compounds were produced in blood. The ratio of the radioactivity of 99mTc-HMDP in lumbar vertebra to soft tissue near bone was 1.5±0.5 after about 3h, showing that equilibrium occured in the process of the accumulation in bone, and good scintigrams were depicted in all the cases.
These results suggest that the accumulation in bone of both 99mTc diphosphonates may be by both fast chemical adsorption onto the surface of the hydroxyapatite in bone and slow uptake mediated through osteoblast-like cells and organic matters.
