Darne Chinmay D, Robertson Daniel G, Alsanea Fahed, Collins-Fekete Charles-Antoine, Beddar Sam
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Division of Medical Physics, Department of Radiation Oncology, Mayo Clinic Arizona, Phoenix, AZ 85054, USA.
Nucl Instrum Methods Phys Res A. 2022 Mar 11;1027. doi: 10.1016/j.nima.2021.166077. Epub 2021 Dec 16.
Research on proton-based imaging systems aims to improve treatment planning, internal anatomy visualization, and patient alignment for proton radiotherapy. The purpose of this study was to demonstrate a new proton radiography system design consisting of a monolithic plastic scintillator volume and two optical cameras for use with scanning proton pencil beams. Unlike the thin scintillating plates currently used for proton radiography, the plastic scintillator volume (20 × 20 × 20 cm) captures a wider distribution of proton beam energy depositions and avoids proton-beam modulation. The proton imaging system's characteristics were tested using image uniformity (2.6% over a 5 × 5 cm area), stability (0.37%), and linearity (R = 1) studies. We used the light distribution produced within the plastic scintillator to generate proton radiographs via two different approaches: (a) integrating light by using a camera placed along the beam axis, and (b) capturing changes to the proton Bragg peak positions with a camera placed perpendicularly to the beam axis. The latter method was used to plot and evaluate relative shifts in percentage depth light (PDL) profiles of proton beams with and without a phantom in the beam path. A curvelet minimization algorithm used differences in PDL profiles to reconstruct and refine the phantom water-equivalent thickness (WET) map. Gammex phantoms were used to compare the proton radiographs generated by these two methods. The relative accuracies in calculating WET of the phantoms using the calibration-based beam-integration (and the PDL) methods were -0.18 ± 0.35% (-0.29 ± 3.11%), -0.11 ± 0.51% (-0.15 ± 2.64%), -2.94 ± 1.20% (-0.75 ± 6.11%), and -1.65 ± 0.35% (0.36 ± 3.93%) for solid water, adipose, cortical bone, and PMMA, respectively. Further exploration of this unique multicamera-based imaging system is warranted and could lead to clinical applications that improve treatment planning and patient alignment for proton radiotherapy.
基于质子的成像系统研究旨在改善质子放疗的治疗计划、内部解剖结构可视化以及患者定位。本研究的目的是展示一种新的质子射线照相系统设计，该系统由一个整体式塑料闪烁体和两个光学相机组成，用于扫描质子笔形束。与目前用于质子射线照相的薄闪烁板不同，塑料闪烁体（20×20×20厘米）能捕获更广泛的质子束能量沉积分布，并避免质子束调制。通过图像均匀性（在5×5厘米区域内为2.6%）、稳定性（0.37%）和线性度（R = 1）研究对质子成像系统的特性进行了测试。我们利用塑料闪烁体内产生的光分布，通过两种不同方法生成质子射线照片：（a）使用沿束轴放置的相机对光进行积分，以及（b）使用垂直于束轴放置的相机捕获质子布拉格峰位置的变化。后一种方法用于绘制和评估质子束在束路径中有或没有模体时的百分比深度光（PDL）曲线的相对偏移。一种曲波最小化算法利用PDL曲线的差异来重建和完善模体水等效厚度（WET）图。使用Gammex模体比较了这两种方法生成的质子射线照片。使用基于校准的束积分（和PDL）方法计算模体WET的相对精度，对于固体水、脂肪、皮质骨和聚甲基丙烯酸甲酯分别为-0.18±0.35%（-0.29±3.11%）、-0.11±0.51%（-0.15±2.64%）、-2.94±1.20%（-0.75±6.11%）和-1.65±0.35%（0.36±3.93%）。有必要对这种独特的基于多相机的成像系统进行进一步探索，这可能会带来改善质子放疗治疗计划和患者定位的临床应用。
