Examining Beam Matching in the Commissioning of a Halcyon Accelerator

• Published in: Nuclear science and engineering Vol. 199; no. 2; pp. 314 - 324
• Main Authors: Thanh Tai, Duong, Tuan, Hoang Duc, Xuan Hai, Nguyen, Ngoc Anh, Nguyen, Bradley, David, Sandwall, Peter, Chow, James C. L.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 01.02.2025
• Subjects: commissioning of treatment unit; gamma index analysis; golden beam data; Halcyon; photon beam models
• ISSN: 0029-5639; 1943-748X
• DOI: 10.1080/00295639.2024.2366733

This study aims to describe the steps needed to be made in developing a commissioning report of a Halcyon linear accelerator utilizing the manufacturer's golden beam data (GBD) as a reference in making the evaluation. The platform herein has determined the performance alignment of our local machine with the GBD obtained through comprehensive analyses. This made use of the gamma index and relative dose difference. This paper details the methodologies and outcomes of comparing local measurements against GBD during commissioning. For the Halcyon linear accelerator, dosimetric data, including percentage depth doses, dose profiles, and output factors, were acquired using a three-dimensional scanning water tank and various ionization chambers. The GBD were exported from the treatment planning system and compared to the measurements. To evaluate the agreement between the GBD and measurements, gamma index and relative dose difference analyses were conducted. For field sizes greater than 4 × 4 cm 2 , percentage depth doses and beam profiles, the gamma indices between GBD and measurements were less than 1%/1 mm. The gamma indices were found to be slightly greater for field sizes 2 × 2 cm 2 and 4 × 4 cm 2 , remaining within 2%/2 mm, satisfying the American Association of Physicists in Medicine Medical Physics Practice Guideline 5 for commissioning and quality assurance of mega-volt photon beams. Deviations in the output factor between the GBD and measurements were not significant, remaining within 1%. The GBD data were evaluated in the commissioning of a Halcyon linear accelerator, with analyses being made of the gamma index and relative dose difference. The gamma index analysis is shown to be an effective method for comprehensively evaluating deviations between the GBD and measurements in the beam matching process.