Pharmacokinetics of technetium-99m diphosphonate.

Increased diagnostic information may be derived with Tc-99m diphosphonate from a detailed kinetic analysis of blood disappearance, urinary excretion, and quantitative assessment of skeletal uptake. Blood and urine determinations were studied in three populations: normal volunteers, patients with negative bone scans, and patients with positive bone scans. Quantitative imaging studies were performed in normal volunteers and patients with a scintillation camera interfaced to a computer. All subjects were scanned in the lower lumbar region up to 1 hr after Tc-99m diphosphonate administration. Blood levels exhibited a triexponential clearance pattern. Significant (p less than 0.05) differences were observed for the 5-min blood and 0-1 hr urine values among the various groups. 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 kidney and soft tissue, with a concomitant increase in bone. Skeletal uptake was different for normal and diseased bone.