Quantification of diphosphonate uptake based on conventional bone scanning

Up to now there has been no routinely used and easy-to-perform method for the quantification of bone uptake. Therefore, we have evaluated the clinical practicability of a new and simple method for the measurement of bone uptake based upon conventional three-phase bone scanning. In 13 patients with normal bone scans, whole-body scintigrams were obtained at 3 min and 1, 2, 3, 4, 5, 6 and 24 h after injection of 600 MBq technetium-99m hydroxymethylene diphosphonate (HMDP). Using a conventional region of interest technique, fitted time-activity curves of soft tissue and urinary excretion were established, and bone uptake was calculated from these data as the total whole-body activity minus both soft tissue activity and urinary excretion. Subsequently, the new method was tested in routine patient management: 32 healthy patients and five patients with different types of metabolic bone disease were investigated, measurements being performed only at 3 min and 3-4 h p.i. during conventional three-phase bone scanning. In the multi-imaged patient subset, soft tissue activity decreased exponentially, reaching a plateau after 6 h with a residual activity of about 14% of initial total whole-body activity. Bone uptake reached quite a stable plateau of about 27% as early as 3 h p.i., with no significant changes up to 24 h. Healthy patients of the two scan group showed no differences in bone uptake (mean uptake values were 24.1% in women and 26.9% in men), whereas in patients with metabolic bone disease bone uptake was significantly higher, with a mean of 48% (P <0.05). Thus, the results of this method are in good agreement with the findings of standard 24-h whole-body retention measurements. The new method, however, is easy to perform, allows assessment of pure bone uptake instead of whole-body retention, and permits calculation of bone uptake by only two measurements during routine three-phase bone scanning.