Application of MRI normoxic polymer gel dosimetry for the evaluation of radiation dose distribution in external beam radiotherapy

Abstract

The objective of this work is to study the ability of MRI normoxic polymer gel dosimetry system to verify the computed dose distribution in clinical radiotherapy. To accomplish the objective of this study, normoxic polymer gel was composed. A perspex phantom and five calibration test tubes were also prepared. The test tubes were filled in with the gel. This phantom was then CT scanned and, using the obtained CT data as input, a dose plan was product. The gel phantom and the calibration test tubes were then irradiated .Prior to irradiation, MR scans were performed on the phantom to measure the background value of R2 of the gel. Immediately after irradiation new images of the gel phantom (and calibration test tubes) were obtained using the MR scanner. Finally, from the MRI images in MATLAB environment R2 maps were calculated. In the bladder cancer treatment, the four-field technique produced a homogenous absorbed dose distribution within a phantom planning target volume using dosimeter gel and TPS. In this study, and in the region of interest the difference between the TPS and gel dosimeter data was +0.7% ( SD = 1.8% ). In this study, a clinical treatment procedure investigated using the MRI normoxic polymer gel dosimetry and TPS. The TPS calculations compared with polymer gel dosimeter measurements and found the dose distributions calculated with the TPS is in very good agreement with the Polymer gels measuring. © 2009 Springer-Verlag.