Evaluation of MAGIC-f polymer gel dosimeter for dose profile measurement in small fields and stereotactic irradiation

Abstract

Background and purposeThe use of small fields in modern radiotherapy treatment techniques is increasingly growing, which has aroused the interest of researchers to use more polymer gel in small field dosimetry. Polymer gel dosimeters contain radiation-sensitive materials that are polymerized under irradiation as a function of absorption dose, and the spatial information of the radiation dose distribution is extracted by imaging of polymer gel. In this study, the performance and capability of MAGIC-f polymer gel dosimeter were evaluated for small field dosimetry and the temporal stability was investigated. MethodsMAGIC-f polymer gel was manufactured and it was poured into phantoms and calibration vials, and then phantoms were irradiated with 6 MV photons with small fields. The values of R2 maps and dose distribution in irradiated gel phantoms were obtained using MRI images taken from the gel phantoms at 1 day and 14 days after irradiation. Also, EBT3 film was used for the measurement of dose profiles at the same field shapes. The transverse dose profiles measured with polymer gel dosimeter were compared with the results of EBT3 film. ResultsThe slope of fitted lines on dose-response data at 1 day and 14 days after irradiation were equal to 0.6005 and 0.6147 respectively. By comparing the results of MAGIC-f gel and EBT3 film, the relative difference in FWHM for profile curves was observed 12.1%, 6.1%, and 4.3% for 0.5, 1.0, and 1.5 cm field size respectively. The gamma index pass rates between dose profile of polymer gel and film with criteria of 1%/0.5 mm were more than 77.1%. In the case of temporal stability, the penumbra measured by MAGIC-f at 14 days after irradiation was almost equal to that at 1 day after irradiation but in terms of FWHM, it was greater at 14 days. ConclusionThe results of this study show that the MAGIC-f polymer gel has good reliability and stability characteristics for small field dosimetry but it must be benchmarked against other dosimeters to become a three-dimensional dosimeter in small field dosimetry.