Determination of high voltage: methods of measurement, practicality, accuracy and regulations concerning tolerances

The quality of an X-ray image is influenced by the radiation parameters (kV value, filtration) because of their impact on contrast and contrast resolution. Deviations from the nominal high voltage of an X-ray tube may lead to unnecessary exposure of the patient and complicate the comparability of X-ray images, which is why there is interest in an easy to handle, non-invasive method of determining the high voltage of an X-ray tube. For the purposes of constancy, several non-invasive high-voltage test tools have been developed, some of which work on the principle of modified film cassettes with two different intensifying screens or different optical extenuations, while others use a ''two filter method'' with photodiodes (electronic kV meters). The accuracy, reproducibility and practicality of two test cassettes and five electronic kV meters have been investigated and their usefulness with respect to national regulations and physicians' demands is discussed. (author)