A Feasibility Study Of IMRT Dosimetric Verification Using Radiochromic Film

The purpose of this study is to investigate the dose response characteristic of EBT2 film which is scanned with different light sources. Then the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 scanner and FilmQA dosimetry analysis software was applied in clinical.The EBT2 film was placed in solid water phantom, radiated with 6MV photon beam whose delivered dose are span from 0 to 280 cGy. Then the film was scanned with flatbed color scanner, and the scanned images were separated into red, green and blue images. The characteristic of image's dose response was analyzed respectively. The scanner's scanning uncertainty and film orientation effect were tested to evaluate the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software. Then the system was applied in a NPC case in experimental trial as well. 10 cases were tested by this system and mapcheck, the results were analyzed with DTA and Gamma index. The advancement of EBT2 film in IMRT dosimetric verification was investigated by setting various parameters to DTA and Gamma index.The results showed that sequence of dose response sensitivity of the EBT2 film is red, green and blue when scanned in different lights. Cubic polynomial fitting method can satisfy the requirement of dose response curve. The Uniscan C880 scanner's single and multiple scanning uncertainties were 0.22% and 1.12% respectively. Film orientation had a big effect on scanner's readout. The IMRT dosimetric verification system composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software was easy to use, and the results got from this system were accurate. Compared with mapcheck, EBT2 have a higher spatial resolution; can check out more spatial point's dose difference.The IMRT dosimetric verification system based on radiochromic film EBT2 is easy to use and can acquire an accurate result. Due to the advantages of high spatial resolution, it is suitable to use in IMRT dose verification and is valuable for clinical application.