Pencil beam proton radiography using a multilayer ionization chamber
Pencil beam proton radiography using a multilayer ionization chamber
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DOI：
10.1088/0031-9155/61/11/4078
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发表时间：
2016-06-07
影响因子：
3.5
通讯作者：
Meijers, Arturs
中科院分区：
文献类型：
--
作者：
Farace, Paolo;Righetto, Roberto;Meijers, Arturs
提出了一种利用商用多层电离室（MLIC）和治疗计划系统（TPS）集成的铅笔束质子放射照相（PR）方法。使用Giraffe (IBA dose - metry) MLIC （+/- 0.5 mm精度），在9 × 9的斑点正方形中均匀地以5.0 mm的距离放置斑点，从而获得铅笔束PR。获得了电子密度（具有组织等效插入物）模体和头模体的pr。通过TPS在模拟MLIC的水体积中计算交付点的积分深度剂量（IDD）曲线，并虚拟地添加到幻象出口侧的CT上。对于每个点，测量和计算的IDD重叠，以计算距离误差图。在头部幻像上，估计了PR获取的最大剂量。此外，在头部模体上，估计了在1 mm位置错位的情况下对距离误差图的影响。在电子密度幻象中，软组织杆的距离误差在1 mm以内，而致密杆的距离误差更大。在头部幻象中，整个地图的距离误差为-0.9±2.7 mm，大脑区域的距离误差在1 mm以内。由于对小偏差的敏感性和不准确的TPS剂量计算，在非均匀性界面上观察到更大的误差。1毫米不对准的影响在距离误差图上清晰可见，并产生了距离误差的增加（在整个地图上-1.0 +/- 3.8毫米）。对患者进行此类PR获取的剂量是可以接受的，因为对头部幻像的最大剂量是
A pencil beam proton radiography (PR) method, using a commercial multilayer ionization chamber (MLIC) integrated with a treatment planning system (TPS) was developed.A Giraffe (IBA Dosimetry) MLIC (+/- 0.5 mm accuracy) was used to obtain pencil beam PR by delivering spots uniformly positioned at a 5.0 mm distance in a 9 x 9 square of spots. PRs of an electron-density (with tissue-equivalent inserts) phantom and a head phantom were acquired. The integral depth dose (IDD) curves of the delivered spots were computed by the TPS in a volume of water simulating the MLIC, and virtually added to the CT at the exit side of the phantoms. For each spot, measured and calculated IDD were overlapped in order to compute a map of range errors. On the head-phantom, the maximum dose from PR acquisition was estimated. Additionally, on the head phantom the impact on the range errors map was estimated in case of a 1 mm position misalignment.In the electron-density phantom, range errors were within 1 mm in the soft-tissue rods, but greater in the dense-rod. In the head-phantom the range errors were -0.9 +/- 2.7 mm on the whole map and within 1 mm in the brain area. On both phantoms greater errors were observed at inhomogeneity interfaces, due to sensitivity to small misalignment, and inaccurate TPS dose computation. The effect of the 1 mm misalignment was clearly visible on the range error map and produced an increased spread of range errors (-1.0 +/- 3.8 mm on the whole map). The dose to the patient for such PR acquisitions would be acceptable as the maximum dose to the head phantom was