SU‐E‐T‐76: Dose Verification of IMRT Using Radiochromic Film with Triple Channel Correction Method

Purpose: Triple channel correction (TCC) method is a new method to evaluate radiochromic film dosimetry, and allows for the split signal into dose dependent and dose independent part. This study demonstrates the utility of Gafchromic EBT2 film with TCC method for the quality assurance of the prostate IMRT or RapidArc and the head and neck (H&N) IMRT. Methods: 30 prostate IMRT or RapidArc fields and 20 H&N IMRT fields were measured with EBT2 and the dose distributions were calculated from film image using single channel correction (SCC) method and TCC method. They were evaluated using dose difference (DD) of 2% and gamma analysis of 3%/2mm. Results: The average DD pass rate of SCC method and TCC method were 79.16% and 92.45% for the prostate, and 75.15% and 87.12%for the H&N, respectively. The average gamma analysis pass rate of SCC method and TCC method were 98.47% and 99.81% for the prostate, and 94.57% and 98.86% for the H&N, respectively. In all regions, the DD of TCC method was smaller than that of SCC method. Conclusions: TCC method can separate dose independent parts from a film signal. EBT2 film dosimetry allows high accuracy evaluation of the dose distributions when TCC method was used rather than SCC method.