A Comparative Analysis for DQA of VMAT Treatment Plans using ArcCHECKTM Diode Array and EPID Portal Dosimetry

Abstract

Author(s): Sang-Wook Lee, Yi-Seong Lee, Jeong-Koo Kim*

Background: As Volumetric Modulated Arc Therapy (VMAT) treatment plans become more complex and highly modulated, robust and precise dosimetric quality assurance (DQA) is essential to ensure accurate and safe radiation dose delivery. Objective: This study aimed to evaluate the effectiveness of DQA for VMAT plans delivered with the Halcyon™ linear accelerator, by comparing the performance of the ArcCHECK™ diode array and EPID-based portal dosimetry. Methods: DQA was conducted for six patients with tumors at various anatomical sites. Gamma passing rates were evaluated using both 3%/3 mm and 2%/2 mm gamma criteria, with ArcCHECK™ and EPID portal dosimetry on the Halcyon™ system. Results: The ArcCHECK™ system yielded average gamma passing rates of 99.50 ± 0.414% (3%/3 mm) and 98.50 ± 0.485% (2%/2 mm). EPID portal dosimetry produced comparable results, with passing rates of 99.01 ± 0.260% and 98.30 ± 0.165%, respectively. Statistical comparisons revealed significant differences in gamma passing rates between ArcCHECK™ and EPID in some tumor sites, but both systems showed high dosimetric agreement (mean >98%), making them suitable for clinical DQA of VMAT plans. Conclusion: Both ArcCHECK™ and EPID portal dosimetry demonstrated high accuracy and consistency in DQA for VMAT treatment planning with the Halcyon™ linear accelerator. These results confirm their clinical applicability as complementary and reliable tools in radiation therapy QA.

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