Study of non-invasive instruments for the measurement of pulsed X-ray high voltage tube

Abstract

Non-invasive instruments (kVp meters) are widely used in radiology with diagnostic and guidance systems. Placed in the x-ray beam, they combine detectors and filters, to determine X-ray tube voltage and exposure time, which are the most important quantities in radiology and diagnostic quality control. Calibration of these instruments were limited by reference bench capabilities. General Electric Medical System France and LNE (The national metrology institute in France) have developed a reference bench for the characterization of kVp meters. The set up includes a fast high voltage generator associated with its internal measuring systems and an X-ray tube. The measurements are compared with an invasive reference standard. The set-up is installed in a Faraday cage, precautions have been taken in order to carry out accurate measurements and special adaptations have been made to avoid stray capacitances, which affect the dynamic performance of the generator. Results have shown a good agreement with the internal measuring system of the generator but the kVp meters have shown both good and bad results depending the exposure time, the current and the positioning.