An In Vivo Bone Densitometer for use with a Diagnostic X-Ray Set

Abstract

An invivo bone densitometer has been designed to be used with a full wave rectified X ray set. The densitometer has been constructed to give a fast and accurate scan of the ulna with a spatial resolution very much better than hitherto achieved. The ulna was chosen so that a wide range of patients, who might have limited agility could be easily scammed for bone mineral content with a view to the early diagnosis of bone disease and to study progress and response to therapy. To overcome the X ray output fluctuations due to variations of the supply voltage, an electronic compensation technique using two detectors was developed. One of the detectors samples the total incident X ray intensity over a portion of the every half cycle, and the other the X ray intensity transmitted through the ulna. Tests to determine the performance of the compensation mechanism over a wide range of operating conditions were made, The reproducibility of the densitometer has been demonstrated by making scans using simulated dead and invivo bone. Theoretical calculations using a simplified theory have Been made to predict the accuracy of the compensation technique and the expected voltage signals. These calculations are compared with experimental observation.