The diphosphonate space: A useful quantitative index of disease activity in patients undergoing hexamethylene diphosphonate (HMDP) bone imaging for Paget's disease

Comparison between the plasma levels of intravenously injected technetium 99m hexamethylene diphosphonate (99mTc-HMDP) and chromium 151 ethylenediaminetetraacetic acid (51Cr-EDTA) reflects the uptake of diphosphonate into bone (the diphosphonate space). This can be used as an index of skeletal function in metabolic bone disease. In a series of 49 patients with Paget's disease the diphosphonate space (DPS) correlated well with other indicators of disease activity such as alkaline phosphatase and urinary hydroxyproline levels. The DPS is a good predictor of the volume of skeletal involvement as estimated from bone images. The DPS also provides a sensitive indicator of response to treatment with intravenously administered bisphosphonate. The DPS is simple to perform and is a useful adjunct to routine bone imaging. (orig.)