Optimum Tube Voltage for Pelvic Direct Radiography: A Phantom Study

Abstract

Pelvic radiography is a frequently performed radiological examination. Its average effective dose (E) is 0.53 mSv which is comparable to the annual per caput dose from diagnostic radiology, 0.6 mSv. However, existing studies on optimum tube potential for pelvic X-rays tend to be limited to screen-film and computed radiography. The purpose of this study was to determine the tube voltage for dose-image optimisation in pelvic direct radiography (DR). Fifty-four pelvic phantom images were acquired using 50-135 kV at 5 kV increments (three images taken at each kV level) and milliampere seconds determined by automatic exposure control. The signal-to-noise ratio (SNR) and dose were measured for each image. Figure of merit (FOM) defined as the ratio of SNR2 to E was used to determine the optimum tube potential. The FOM indicates 135 kV is the optimum setting for pelvic DR. Using the European Commission tube voltage recommendation (75-90 kV) as a reference point, there was only a slight (5.56%) decrease of image quality in the femoral neck region at 135 kV. However, its E was 0.054 mSv. This appreciable dose reduction potential could be attributed to the improvement of detective quantum efficiency and image processing technology of the recent DR system.