Measurement of x-ray tube potential in the mammographic region

In mammography it is important to be able to measure x-ray tube potential with an accuracy of ±1 kV or better. Mammography x-ray sets generally use molybdenum for both target and filter. Consequently, a high proportion of the x-ray spectrum consists of characteristic radiation from the target. Devices for estimating tube potential such as penetrameters and digital kV meters, which depend on the relation between tube potential and the filtered x-ray spectrum, could be affected in their performance unless calibrated on similar x-ray sets. This paper reports tube potential measurements on a Mo/Mo x-ray set from 25 to 37 kV using the fluorescence technique, a manufacturer's potential divider, two penetrameters of different design and two digital meters of a single design. Agreement between all four techniques was good, being within the various combined experimental errors associated with each, from 37 down to 28 kV, below which the results diverged only slightly. (author)