Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification
Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification
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DOI：
10.1088/0031-9155/60/18/7085
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发表时间：
2015-09-21
影响因子：
3.5
通讯作者：
Beddar, Sam
中科院分区：
文献类型：
--
作者：
Polf, Jerimy C.;Avery, Stephen;Beddar, Sam
为评价康普顿照相机（CC）在临床质子笔形束流输送过程中对瞬发γ射线（PG）的测量能力，以提供对质子笔形束流输送的体内验证，采用114 MeV和150 MeV质子笔形束流对水模体进行辐照。使用临床射束电流，每次辐照输送高达500 cGy的剂量。原型CC放置在距离束流中心轴15 cm处，在照射期间测量了0.2 MeV至6.5 MeV的PG。从测量的数据（2D）图像的PG发射重建。(1D)从PG图像中提取轮廓，并将其与所输送质子笔形射束的测量深度剂量曲线进行比较，CC能够在临床射束电流下测量114 MeV和150 MeV质子射束输送期间的PG发射。PG发射的2D图像被重建为单个150 MeV的质子笔形束以及为114 MeV的笔形束的5 × 5 cm单能层。在2D图像上可检测到布拉格峰（BP）范围的偏移。从PG图像中提取的1D轮廓显示PG发射轮廓的远端衰减与远端BP衰减很好地对齐。在光束范围内小至3 mm的偏移可以从1D PG轮廓中检测到，精度为1.5 mm或更好。然而，与目前的CC原型，需要400 cGy的剂量，以获得足够的PG信号的2D PG图像reconstruction.It是可能的测量PG与我们的原型CC在输送质子笔形束在临床剂量率的相互作用。可以重建PG发射的图像，并且可以检测到BP范围的偏移。因此，在质子治疗输送过程中使用CC进行体内范围验证的PGI是可行的。然而，原型CC检测效率和重建算法的改进是必要的，使其成为临床可行的PGI系统。
The purpose of this paper is to evaluate the ability of a prototype Compton camera (CC) to measure prompt gamma rays (PG) emitted during delivery of clinical proton pencil beams for prompt gamma imaging (PGI) as a means of providing in vivo verification of the delivered proton radiotherapy beams.A water phantom was irradiated with clinical 114 MeV and 150 MeV proton pencil beams. Up to 500 cGy of dose was delivered per irradiation using clinical beam currents. The prototype CC was placed 15 cm from the beam central axis and PGs from 0.2 MeV up to 6.5 MeV were measured during irradiation. From the measured data (2D) images of the PG emission were reconstructed. (1D) profiles were extracted from the PG images and compared to measured depth dose curves of the delivered proton pencil beams.The CC was able to measure PG emission during delivery of both 114 MeV and 150 MeV proton beams at clinical beam currents. 2D images of the PG emission were reconstructed for single 150 MeV proton pencil beams as well as for a 5 x 5 cm mono-energetic layer of 114 MeV pencil beams. Shifts in the Bragg peak (BP) range were detectable on the 2D images. 1D profiles extracted from the PG images show that the distal falloff of the PG emission profile lined up well with the distal BP falloff. Shifts as small as 3 mm in the beam range could be detected from the 1D PG profiles with an accuracy of 1.5 mm or better. However, with the current CC prototype, a dose of 400 cGy was required to acquire adequate PG signal for 2D PG image reconstruction.It was possible to measure PG interactions with our prototype CC during delivery of proton pencil beams at clinical dose rates. Images of the PG emission could be reconstructed and shifts in the BP range were detectable. Therefore PGI with a CC for in vivo range verification during proton treatment delivery is feasible. However, improvements in the prototype CC detection efficiency and reconstruction algorithms are necessary to make it a clinically viable PGI system.