Comparison of the isocenter verification methods and calculating imaging offset of medical linear accelerators.

The aim of the presented work was to compare two methods of verification of the medical accelerator’s isocenter and determine the imaging offset. Two methods were used for verification - Machine Performence Check (MPC) application with the IsoCal phantom and the Artiscan software with the PTW Isoball Phantom. Each of the analyzed methods provides an alternative way to the time-consuming and costly verification of the isocenter on radiochromic or gafchromic dosimetry films. 
                Measurements were performed for ten days and the obtained data were compared for both methods. Using statistical tests, concordance was determined for the results obtained by the two methods. The data were presented in trend function graphs. 
                Analysis of the results shows that it is not possible to unequivocally state that the methods are not equivalent. In addition, the AAPM TG 142 report assumes that MPC is not a sufficient test for checking medical linear accelerator’s isocentre.