POLYMERIC GEL DOSIMETER CHARACTERIZATION FOR APPLICATION IN INTRAOPERATIVE RADIATION THERAPY WITH INTRABEAM

Intraoperative radiation therapy (IORT) is a technique whose goal is to deliver the prescribed dose in a single fraction during surgical procedure. Intrabeam equipment, dedicated to IORT, conforms the dose distribution, generated from your low energy x-ray beam, to treatment site through applicators. The change in the dose distribution caused by the applicators contributes to a high dose gradient that must be better studied, including with three-dimensional techniques. Polymeric gel dosimeters have been used for quality control in external beam and brachytherapy, with the possibility of evaluation of three-dimensional dose distribution. The goal of the present work is the characterization of MAGIC-fm polymeric gel dosimeter response to IORT beam, allowing its use in studies of greater complexity. The irradiation was performed with Intrabeam equipment, using the 4.0 cm surface applicator placed in contact with the surface of a phantom filled with MAGIC-fm gel. The phantom has cylindrical shape, 8.0 cm of inner diameter and 8.0 cm of height and was placed over 4.0 cm of solid water. Gel response was evaluated through Magnetic Resonance images, performed in a 3 T scanner. Response linearity and depth dose distribution were evaluated, the latter was compared with data from the institution. Gel response in function of dose indicates a linear behavior for the analyzed dose range, with sensitivity of 0,24 s-1/Gy. The maximum difference between depth dose percentage is of about 10 pc at treatment reference depth of 1.0 cm. This difference can be explained by backscattering effects, given the phantom size used in the study, that influence both the dose-response curve and the dose distribution. The results show the necessity of sensibility correction for dose distribution evaluation and of use of adequate phantom for the technique. In general, the MAGIC-fm dosimeter showed appropriate sensibility for IORT studies, enabling dosimetric studies and quality control for the technique.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
23 October 2019