Dosimetric characterisation of anthropomorphic PRESAGE^® dosimeter and EBT2 film for partial breast radiotherapy

Purpose: Whole-breast external beam radiotherapy results in significant reduction in the risk for breast cancer-related death, but this may be offset by an increase in deaths from other causes and toxicity to surrounding organs. Partial breast irradiation techniques are approaches that treat only the lumpectomy area rather than the whole breast. Quality assurance in the radiation therapy treatment planning process is essential to ensure accurate dose delivery to the patient. For this purpose, this article compares the results from an anthropomorphic PRESAGE^® dosimeter, radiation treatment planning system and from the GAFCHROMIC^® EBT2 film. Materials and methods: A breast dosimeter was created and a three-field partial plan was generated in the Pinnacle³ treatment planning system. Dose distribution comparisons were made between Pinnacle³ treatment planning system, GAFCHROMIC^® EBT2 film and PRESAGE^® dosimeter. Dose-volume histograms (DVHs), gamma maps and line profiles were used to evaluate the comparison. Results: DVHs of gross tumour volume, clinical tumour volume and planning tumour volume for the PRESAGE^® dosimeter and Pinnacle³ treatment planning system shows that both measured and calculated statistics were in agreement, with a value of 97.8% of the prescribed dose. Gamma map comparisons showed that all three distributions passed 95% at the ±3%/±3 mm criteria. Comparisons of isodose line distribution between the PRESAGE^® dosimeter, EBT2 film and planning system demonstrated agreement, with an average difference of 1.5%. Conclusions: This work demonstrated the feasibility of PRESAGE^® to function as an anthropomorphic phantom and laid the foundation for research studies in PRESAGE^®/optical-computed tomography three-dimensional dosimetry with the most complex anthropomorphic phantoms.