Normal pharmacokinetics of 99mTc-diphosphonate after intravenous administration

In the past several years bone imaging has become a routine diagnostic tool for the nuclear medicine clinician. However, increased information may be derived by determining the ratio-pharmacokinetic parameters associated with blood, urine, and bone. In an adult male population of normals (N = 5--6) blood clearance, urinary excretion, and skeletal uptake of 99mTc-Diphosphonate were determined as a function of time after intravenous (i.v.) administration. The quantitative imaging studies (lower lumbar region) were performed up to 1 h post administration with a scintillation camera interfaced to a computer. Blood levels exhibited a triexponential clearance pattern and urinary excretion of the radiopharmaceutical was essentially complete by 4 h. The computer-generated images showed an initial early uptake in bone, kidneys, and soft tissue. Thereafter, a parallel fall-off in activity was observed in kidneys and soft tissue, with a concomitant increase in bone.