Intensity-modulated radiotherapy quality assurance by alanine-EPR and gel dosimetry of a simulated prostate treatment with bilateral metallic prostheses

Abstract

The presence of metallic prostheses in patients undergoing prostate radiotherapy treatment can lead to scattered doses, compromising treatment reproducibility. This study aims to assess doses in the Planning Target Volume (PTV) and surrounding areas using a water phantom containing pelvic bones and bilateral metallic prostheses. Intensity Modulated Radiotherapy (IMRT) with optimization tools avoiding input dose to the prosthesis was employed. Experimental verification utilized a modified Fricke xylenol orange gel dosimeter (FXO-f) in a 63 mm diameter, 100 mm height cylinder (310 ml volume) for PTV dose checks, and alanine dosimeters for assessing doses in the PTV vicinity and near metallic prostheses. Evaluating doses near prostheses is vital as post-radiotherapy prosthesis loosening has been speculated, possibly linked to overexposure. Gamma evaluation with FXO-f dosimeter yielded approved gamma indices in 97.7% of data points versus TPS, indicating good agreement with linear accelerator-reproduced results. Alanine dosimeter results ranged between (1.0 ± 0.3), (1.2 ± 0.3) Gy, (1.4 ± 0.3) Gy, and (2.0 ± 0.3) Gy, which are comparable to TPS-calculated doses within the dosimeter volume. This result indicates that the heterogeneity correction applied by the Analytical Anisotropic Algorithm used for dose calculation and the avoidance tool employed in the treatment planning could addressed the problem. In summary, this study demonstrates that the treatment technique entering fields towards prostheses, with optimization tools to produce the desirable results.