Novel in vivo dosimetry of the tongue using EPSON Perfection V39II Flatbed Scanner and Gafchromic RTQA2

Abstract Presently, films and flatbed scanners used for in vivo dosimetry protocols are very expensive which causes many facilities to opt out of potentially useful film in vivo dosimetry programs. The current study seeks to test the viability of the use of a different kind of film that already comes with linear accelerator purchases in the Philippines and are less expensive than the more common EBT line of films: the RTQA2. It also aims to test the use of the inexpensive Epson Perfection V39II scanner in its effectivity for acceptable film scan readout for image analysis (via imageJ). A calibration curve was obtained by exposing the RTQA2 to known doses with the resulting second order polynomial equation of the curve correlating the dose (y) to the netOD (x) of the films. The fit equation was used to obtain the dose for each sample film’s net OD after irradiation and the calculated dose was compared to the TPS-determined point dose for the region where the films were placed. The results for all the plans, namely the step-and-shoot IMRT, dynamic MLC IMRT and VMAT plans yielded errors of less than 5% when compared with the TPS, which is in accord with current recommendations by the IAEA for novel in vivo dosimetry protocols. Similar results were obtained when Gafchromic EBT4 was used instead of RTQA2 as an added layer of protocol verification. These results open the doors for in vivo dosimetry frameworks that need not rely on very expensive gear to be useful in-clinic.