Department of Radiotherapy, Cancer center, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China , gfb803@fjmu.edu.cn
Abstract: (16 Views)
Background: This study investigates the dosimetric response of the Delta4 system to varying field sizes and assesses its accuracy in dose verification. Materials and Methods: Output factors for fields ranging from 1 × 1 cm² to 20 × 20 cm² were measured using PTW 60019 detector, PTW 60018 detector, and the Delta4 system. The PTW 60019 measurements were considered the gold standard and were compared with those from the other two detectors. Two test plans were developed to compare the dose verification results of the Delta4 system, both with and without output factor correction. Results: The PTW 60018 and IBA CC13 detector measurements, using the daisy-chaining method, demonstrated strong agreement with the gold standard. However, the Delta4 system showed an underestimation in the output factor of the 1×1 cm² field, with deviations of -2.259% for the 6 MV flattening filter (FF) beam and -3.343% for the 6 MV flattening filter free (FFF) beam. After correcting the output factor, the gamma passes rate (3%/2mm) for test plan 2 featuring 1 × 1 cm² sub-fields improved from 67.3% to 95.7% for the 6 MV FF beam. Conclusions: The Delta4 system exhibits a dosimetric response issue when managing small fields. Output factor corrections are recommended for Delta4 dose verification results when dealing with field sizes less than 4 cm and a high number of sub-fields.
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