A Verification of Electron Dose Calculation of a Treatment Planning System Using Monte Carlo Algorithm

Abstract

A part of efficiency of treatment is strongly depending on accuracy of dose calculation, which should be evaluated before implement in a clinical service. The object of this study was to verify the accuracy of electron dose calculation for treatment planning system using Monte Carlo algorithm at depth Dmax, R90 and R50.  The test cases following AAPM TG 53, including seven geometries, namely standard source to surface  distance (SSD), extended SSD, irregular field, irregular surface 30บ slopes, irregular surface 90 ํ step, internal  heterogeneity and adjacent beams were used to verify. This study compared in two types of difference which  using Van Dyk’s criteria of acceptability to evaluate for accuracy. The first was percentage of dose difference  that was compared between the result of calculation and measurement at central axis in water with  ionization. The second was comparison dose distribution by gamma passing rate using 2D array detector in  solid water phantom. The result of percentage of dose difference between calculation and measurement for  standard SSD and extended SSD were -1.5% to 0.5%. Irregular field was -0.1% to 2.8%. The gamma passing  rate was 100% in all geometry with gamma index 4%/4 mm. The average relative error of all these  geometries was acceptable and the electron dose calculation of treatment planning system had accuracy that was acceptable from Van Dyk’s criteria and could be used in the clinical service.