Rawiwan Nuttida, Chatchumnan Nichakan, Vimolnoch Mananchaya, Kingkaew Sakda, Oonsiri Sornjarod
Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Division of Radiation Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand.
Int J Part Ther. 2023 Nov 8;10(2):105-110. doi: 10.14338/IJPT-23-00016.1. eCollection 2023 Fall.
This study aimed to determine the characteristics of 2D ionization chamber array and the confidence limits of the gamma passing rate in pencil beam scanning proton therapy.
The Varian ProBeam Compact spot-scanning system and the PTW OCTAVIUS 1500XDR array were used as a proton therapy system and detector, respectively. Our methods consisted of 2 parts: (1) the characteristics of the detector were tested and (2) patient-specific quality assurance was performed and evaluated by gamma analysis using dose-difference and distance-to-agreement criteria of 3% and 2 mm, respectively, with 123 treatment plans in head and neck, breast, chest, abdomen, and pelvic regions.
The PTW OCTAVIUS 1500XDR array had good reproducibility, uniformity, linearity, repetition rate, and monitor unit per spot within 0.1%, with accuracy, energy dependence, and measurement depth within 0.5%. The overall uncertainty of the PTW OCTAVIUS 1500XDR array was 2.49%. For field size and range shifter, using gamma analysis, the passing rate was 100%. The overall results of patient-specific quality assurance with the gamma evaluation were 98.9% ± 1.6% in 123 plans and confidence limit was 95.7%.
The PTW OTAVIUS 1500XDR offered effective performance in pencil beam scanning proton therapy.
本研究旨在确定二维电离室阵列的特性以及笔形束扫描质子治疗中伽马通过率的置信限。
分别使用Varian ProBeam紧凑型点扫描系统和PTW OCTAVIUS 1500XDR阵列作为质子治疗系统和探测器。我们的方法包括两部分：（1）测试探测器的特性；（2）对123个头部、颈部、胸部、腹部和盆腔区域的治疗计划进行患者特异性质量保证，并分别使用3%剂量差异和2 mm距离一致性标准通过伽马分析进行评估。
PTW OCTAVIUS 1500XDR阵列具有良好的重复性、均匀性、线性、重复率，每个点的监测单位在0.1%以内，精度、能量依赖性和测量深度在0.5%以内。PTW OCTAVIUS 1500XDR阵列的总体不确定度为2.49%。对于射野大小和射程移位器，使用伽马分析，通过率为100%。123个计划中伽马评估的患者特异性质量保证总体结果为98.9%±1.6%，置信限为95.7%。
PTW OTAVIUS 1500XDR在笔形束扫描质子治疗中表现出有效的性能。
