Bellezzo Murillo, Baeza José A, Voncken Robert, Reniers Brigitte, Verhaegen Frank, Fonseca Gabriel P
Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands; Centro de Engenharia Nuclear, Instituto de Pesquisas Energéticas e Nucleares IPEN-CNEN/SP, São Paulo, Brazil.
Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
Brachytherapy. 2019 Nov-Dec;18(6):852-862. doi: 10.1016/j.brachy.2019.06.005. Epub 2019 Jul 18.
The Bravos afterloader system was released by Varian Medical Systems in October of 2018 for high-dose-rate brachytherapy with Ir sources, containing new features such as the CamScale (a new device for daily quality assurance and system recalibration), channel length verification, and different settings for rigid and flexible applicators. This study mechanically evaluated the Bravos system precision and accuracy for clinically relevant scenarios, using dummy sources.
The system was evaluated after three sets of experiments: (1) The CamScale was used to verify inter- and intra-channel dwelling variability and system calibration; (2) A high-speed camera was used to verify the source simulation cable movement inside a transparent quality assurance device, where dwell positions, dwell times, transit times, speed profiles, and accelerations were measured; (3) The source movement inside clinical applicators was captured with an imaging panel while being exposed to an external kV source. Measured and planned dwell positions and times were compared.
Maximum deviations between planned and measured dwell positions and times for the source cable were 0.4 mm for the CamScale measurements and 0.07 seconds for the high-speed camera measurements. Mean dwell position deviations inside clinical applicators were below 1.2 mm for all applicators except the ring that required an offset correction of 1 mm to achieve a mean deviation of 0.4 mm.
Features of the Bravos afterloader system provide a robust and precise treatment delivery. All measurements were within manufacturer specifications.
瓦里安医疗系统公司于2018年10月推出了Bravos后装治疗系统，用于铱源高剂量率近距离放射治疗，该系统具有一些新特性，如CamScale（一种用于日常质量保证和系统重新校准的新装置）、通道长度验证以及针对刚性和柔性施源器的不同设置。本研究使用虚拟源对Bravos系统在临床相关场景下的机械精度和准确性进行了评估。
在进行三组实验后对该系统进行了评估：（1）使用CamScale验证通道间和通道内驻留的可变性以及系统校准；（2）使用高速摄像机在透明质量保证装置内验证源模拟电缆的移动，测量驻留位置、驻留时间、传输时间、速度曲线和加速度；（3）在临床施源器暴露于外部千伏源时，用成像板捕获源的移动。比较测量和计划的驻留位置及时间。
源电缆计划和测量的驻留位置及时间之间的最大偏差，CamScale测量为0.4毫米，高速摄像机测量为0.07秒。除环形施源器外，所有临床施源器内的平均驻留位置偏差均低于1.2毫米，环形施源器需要1毫米的偏移校正才能使平均偏差达到0.4毫米。
Bravos后装治疗系统的特性提供了可靠且精确的治疗输送。所有测量均在制造商规定的规格范围内。
