Measurement of 24-hour whole-body retention of Tc-99m HEDP by a gamma camera.

Measurement of 24-hr whole-body retention of Tc-99m HEDP, using a shadow-shield, whole-body monitor, has been shown to be a sensitive measure of skeletal metabolism and of value in the diagnosis of metabolic bone disease. A new method of measuring the retention using a gamma camera, with a scanning (fishtail) collimator and patient placed at 2.,3 m distance, has been evaluated in 18 patients undergoing routine bone scans. The patients also had whole-body monitor (WBM), and the two methods correlated well, yielding a regression line GC% = -0.82 + 0.98 WBM%, r = 0.975, p less than 0.001. The limitations to, and repeatability of, the gamma-camera measurements are discussed. This work shows that measurements of whole-body retention can be obtained in any nuclear medicine department possessing a gamma camera with a suitable collimator.