The clinical demands for accuracy of roentgen generator scales were investigated in order to define suitable levels of tolerance to be required during calibration procedures and preventive maintenance on modern equipment. Radiographs of various film densities were made of four body parts. As test observers 59 radiologists and 53 radiologic technicians were asked to judge which radiographs they considered acceptable or not acceptable. Ninety-five per cent of the radiographs were accepted with the ***under- or overexposure of one mAs step. The spread of the estimations of suitable exposure data made by 38 radiologic technicians was also investigated. From these data the clinically acceptable tolerance of roentgen generator exposure parameters could be derived. It is suggested that the tolerance of tube voltage (kV) should be less than ±5 per cent, current-time product (mAs) −20 to +25 per cent and automatic exposure control systems (AEC) −20 to +25 per cent.
A routine quality assurance test for CT automatic exposure control systems