Analysis of different procedures for absolute dosimetry with EBT3 radiochromic film

Purpose: Absolute dose comparison between different methodologies of multichannel dosimetry in pretreatment quality assurance (QA), including highly modulated techniques in a wide range of doses (180 cGy to 1800 cGy). Methods: Several parametric forms for film dosimetry calibration were studied and compared. Then, different algorithms for radiochromic film dosimetry were implemented in Python code. With the objective of comparing these procedures, several IMRT and VMAT plans were irradiated and studied attending to the gamma criterion. A denoising protocol was developed, removing completely Gaussian noise dependency. In addition, spatial resolution dependency was also removed. Results: The algorithms that account for perturbations gave good results in the gamma analysis. The results could not be associated with noise or resolution. The red channel is inadequate for film dosimetry. Conclusions: The studied methodologies offered good agreement with the absolute gamma analysis, even with the 2%, 2 mm criteria. The proposed modifications reduced noise and resolution dependencies and improved the results.