Standardization of x-ray generators.

Abstract

A relatively simple method was devised which, when applied to the machines in our department, revealed voltage errors as large as 90 per cent in the 20–50 low kVp range (Fig. 1) and smaller errors in the tube current (mA) when measured (Fig. 2). The technic described herein consists of a high-precision bleeder tank to measure the kilovoltage peak, a special high-voltage milliampere probe to measure the tube current (mA) and a high-voltage ampere probe to measure the filament current. The inherent filtration of the tube and collimator system as given by the manufacturer was checked and found to be accurate in all cases tested. The resultant flux is measured in the usual way by using a properly calibrated R meter. A high-voltage bleeder tank was constructed and connected to an oscilloscope to measure the kilovoltage peak. The tank/scope combination was calibrated with a high voltage D.C. power supply. A precalibrated A.C. power supply was used to check the tank/scope calibration. The bleeder tank was calibrated to sample accurately 1/2000 the voltage from the high-tension side of the transformer. Two special, current-measuring, high-voltage probes were constructed to measure directly the high-tension secondary current (mA) and the filament current through the x-ray tube. The use of this system reveals startling differences among machines in our x-ray department. This system makes it possible to calibrate accurately the high voltage, milliamperage, and filament current of an x-ray generator. It will permit the production of uniform quality and quantity radiations if the same technical factors are used, including total filtration, distance, and the like, from machine to machine within any department.