[Relative uptake of 99mTc-diphosphate and its temporal change in bone diseases]

Quantitative regional measurements of the distribution of a bone seeking radiopharmaceutical is performed easily together with a bone scan using a scintillation camera. Comparative measurements of regional radioactivities yield a ratio of relative uptake. The time change of such a relative uptake ratio is obtained by repeating the regional comparison measurements after a 4--8 weeks interval. The time change of the relative uptake ratio was found to be a clinically useful parameter in the follow-up of skeletal diseases. A decrease in the relative uptake ratio was found with healing fractures, with receding osteomyelitis and during radiation therapy of bone metastases; an increase was observed with spreading metastases, developing osteomyelitis, developing pseudathrosis, and in the beginning of normal fracture healing.