Quantifications and sensitivity in bone scanning in the detection of bone metastases.

In a prospective study the whole body retention (WBR) and several bone-soft-tissue ratios (BSR) were determined in 50 consecutive clinical patients. The scans were studied in the usual way. Three independent observers found an increased uptake in 5 scans. The rest activity was calculated by expressing the WBR, measured at 24 h to a percentage of the WBR measured at 5 min. It appeared that in the same 5 patients, being observed visually to show an increased uptake, the rest activity was pathologically higher than the rest activity in the 'normal' patients. The L2-flank ratio also differentiated in the five scans having the observed increased uptake. The same patients with an increased uptake were differentiated by three observers with the help of quantification. The extra use of the WBR and the BSR determinations in the detection of bone metastases appeared to be absent in this study. The sensitivity was not increased.