Effect of 99mTc-MDP administration on dual-energy X-ray absorptiometry bone mineral density measurements

The effect of a diagnostic dose of (99m)Tc-MDP on bone mineral density (BMD) estimations in the lumbar spine and the neck of femur was assessed in 20 patients using a Hologic QDR4500 scanner. Each patient underwent a DXA assessment prior to and 1 h following injection of (99m)Tc-MDP (mean dose-910 MBq). For comparative purposes, the precision of BMD estimation without the presence of a radioisotope was assessed by performing two sequential DXA studies on 30 volunteers and was found to be less than 0.01 g/cm(2). No significant change in BMD reading was detected following (99m)Tc-MDP injection for either measurement site and the precision of the readings was similar to that observed for the 30 volunteers. This study has shown that any effect produced by a typical bone scan dose of (99m)Tc-MDP is small in comparison with the intrasubject variance when estimating BMD using a Hologic QDR4500 scanner.