Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA.
Med Phys. 2018 Jul;45(7):2947-2951. doi: 10.1002/mp.12951. Epub 2018 May 20.
The purpose of this study was to develop a fast method for proton range quality assurance (QA) using a dual step wedge and two-dimensional (2D) scintillator and to evaluate the robustness, sensitivity, and long-term reproducibility of this method.
An in-house customized dual step wedge and a 2D scintillator were developed to measure proton ranges. Proton beams with homogenous fluence were delivered through wedge, and the images captured by the scintillator were used to calculate the proton ranges by a simple trigonometric method. The range measurements of 97 energies, comprising all clinically available synchrotron energies at our facility (ranges varying from 4 to 32 cm) were repeated ten times in all four gantry rooms for range baseline values. They were then used for evaluating room-to-room range consistencies. The robustness to setup uncertainty was evaluated by measuring ranges with ±2 mm setup deviations in the x, y, and z directions. The long-term reproducibility was evaluated by 1 month of daily range measurements by this method.
Ranges of all 97 energies were measured in less than 10 minutes including setup time. The reproducibility in a single day and daily over 1 month is within 0.1 and 0.15 mm, respectively. The method was very robust to setup uncertainty, with measured range consistencies within 0.15 mm for ±2 mm couch shifts. The method was also sensitive enough for validating range consistencies among gantry rooms and for detecting small range variations.
The new method of using a dual step wedge and scintillator for proton range QA was efficient, highly reproducible, and robust. This method of proton range QA was highly feasible and appealing from a workflow point of view.
本研究旨在开发一种使用双楔形物和二维（2D）闪烁器的质子射程质量保证（QA）快速方法，并评估该方法的稳健性、灵敏度和长期重现性。
开发了一种内部定制的双楔形物和 2D 闪烁器来测量质子射程。通过楔形物传输均匀剂量的质子束，然后使用闪烁器捕获的图像通过简单的三角法计算质子射程。在所有四个龙门架房间中，对 97 种能量（包括我们设施中所有临床可用的同步加速器能量）的射程进行了 10 次重复测量，以获得射程基准值。然后，将它们用于评估房间之间的射程一致性。通过在 x、y 和 z 方向上测量±2mm 的设置偏差来评估对设置不确定性的稳健性。通过该方法进行 1 个月的日常射程测量来评估长期重现性。
所有 97 种能量的射程测量包括设置时间在内不到 10 分钟。在单一日和 1 个月内的重复性分别在 0.1mm 和 0.15mm 以内。该方法对设置不确定性非常稳健，在±2mm 床架移位的情况下，测量的射程一致性在 0.15mm 以内。该方法也足够灵敏，可以验证龙门架房间之间的射程一致性，并检测小的射程变化。
使用双楔形物和闪烁器进行质子射程 QA 的新方法高效、高度可重复且稳健。从工作流程的角度来看，这种质子射程 QA 方法是非常可行和有吸引力的。
