Evaluation of computed tomography anode voltage in clinical application: the influence of profiled filters

Monitoring of operational parameters of X-ray diagnostic equipment, including computer tomographs, is mandatory during acceptance and periodic tests in medical organizations. The importance of control of anode voltage of X-ray radiator is described (as one of the main technical parameters in diagnostic tests of patients, which can influence the quality of visualization and safe operation of the equipment). Anode voltage is evaluated by non-invasive methods using universal dosimeters in the user mode of equipment operation. The influence of profiled filters of Somatom Definition AS, SOMATOM go.All (Siemens, Germany) scanners on the accuracy of anode voltage measurement was investigated. The tests were conducted in clinic conditions without partial removal of the gantry (a structural element of the tomograph, inside which the system “X-ray emitter – detector” is located) and connection to the high-voltage circuit of the device. The distance between the sensitive elements of the measuring device and the displacement of the center of the sensing area relative to the position of the central axis of the X-ray beam of computed tomography scanner were taken into account. Normalized curves of kerma values, anode voltage values and their approximating analytical functions were obtained using a Piranha R&F/M 657 universal dosimeter (RTI Electronics AB, Sweden) at its displacement relative to the laser centralizer of computed tomography scanner. Based on the scheme for noninvasive estimation of anode voltage value, a formula of the relative deviation of the measured value of the anode voltage associated with the presence of a profiled filter at the output of the X-ray emitter of the tomograph and the displacement of the center point of the sensitive area of the measuring device relative to the central axis of the X-ray beam of the tomograph is obtained. The validity of the data based on the formula is confirmed experimentally. The results of the study will be helpful to technical specialists who maintain or control the X-ray computed tomography operating parameters.