2D dose reconstruction of IMRT patient-specific QA based on log file

Abstract

This study aims to reconstruct the 2D dose distribution based on log file and use it for IMRT patient-specific QA. Log files retrieved from Varian Unique Linear Accelerator was extracted to calculate the MU fluence and converted into 2D dose distribution using the modified Clarkson integration (MCI) method. All calculations were performed using the MATLAB scripts and functions. This reconstruction assumed that the cube water phantom was irradiated by 6 MV photon at source surface distance (SSD) 98.5 cm and at depth of 1.5 cm. This 2D dose reconstruction was compared with EclipseTM treatment planning system (TPS) calculation. The evaluation was done based on isocenter point and 2D gamma index analysis. The evaluation was separated by the split field (large IMRT field) and non-split field (small IMRT field). The isocenter dose evaluation results were 89% and 36% of data for non-split field and split field had deviation under 3%. The gamma pass-rate results for non-split field with 2%/2 mm, 3%/3 mm and 4%/4 mm criteria were above 84%, 90% and 95%. On the other hand, the gamma pass-rate results for split field with 2%/2 mm, 3%/3 mm and 4%/4 mm criteria were above 78%, 85% and 90%. These results show that log file information can be used to reconstruct 2D dose distribution and potentially to be used for IMRT patient-specific QA.