Proof of principle of helium-beam radiography using silicon pixel detectors for energy deposition measurement, identification, and tracking of single ions
Proof of principle of helium-beam radiography using silicon pixel detectors for energy deposition measurement, identification, and tracking of single ions
复制标题
DOI：
10.1002/mp.12723
复制
发表时间：
2018-02-01
期刊：
影响因子：
3.8
通讯作者：
Martisikova, Maria
中科院分区：
文献类型：
--
作者：
Gehrke, Tim;Gallas, Raya;Martisikova, Maria
目的：强子疗法具有向肿瘤区域提供高剂量构象的能力。然而，它需要准确的目标定位。因此，期望在治疗期间精确监测患者的解剖定位。为此目的，强子束质子（pRad）和离子（iRad）射线照相术可能是一个有吸引力的工具，补充传统的成像技术。在通往设想的临床应用的道路上，必须解决几个挑战。其中包括在存在多重库仑散射（MCS）的情况下实现所需的空间分辨率，在临床适用的剂量水平下以足够的厚度分辨率进行射线照相，以及寻找特别合适的强子和探测器的组合。这些主题是在这项工作中的检测系统的基础上硅像素detectors.Methods：在薄层能量沉积测量的基础上的iRad的方法进行了研究。它利用了一个由三个平行的硅像素探测器组成的探测系统，该系统还可以进行粒子跟踪和识别。氦离子，其表现出不太明显的MCS比质子，被选为成像辐射。在海德堡离子束治疗中心，用173 MeV/u氦离子束对平均水当量厚度（WET）为192 mm（最大WET变化为+/- 6 mm）的PMMA体模进行成像。以2.3 mm x 2.3 mm步长形式的WET差异旨在可视化并在体模后面测量的能量沉积图像中解析。该检测系统被放置在成像对象的下游，以检测单个离子离开it. The组合的测量信息的能量沉积，离子类型，和后面的跟踪体模用于图像formation. Results的组合，采用自行开发的数据处理程序：结果表明，氦束射线照相与报告的检测系统是可行的。引入的数据预处理从探测器伪影中净化探测器信号，提高图像质量。此外，来自核相互作用的氢离子的排斥被证明使对比度噪声比（CNR）增加至少2.5倍。这使得在诊断X射线图像的典型剂量水平下，相对厚度差异的分辨率为1.2%。通过考虑单个氦离子离开体模的方向，提高了空间分辨率。一个空间分辨率（MTF 10%）至少为1.15p mm（-1）为所提出的实验setup.Conclusion：一个成功的可行性研究氦束射线照相与引进的检测系统进行。iRad的方法是基于薄硅层中的能量沉积测量。单离子的跟踪和离子识别的方法被证明是重要的氦束照相的空间分辨率和CNR。(C)2017年美国医学物理学家协会
Purpose: Hadron therapy has the capability to provide a high dose conformation to tumor regions. However, it requires an accurate target positioning. Thus, the precise monitoring of the patient's anatomical positioning during treatment is desirable. For this purpose, hadron-beam radiography with protons (pRad) and ions (iRad) could be an attractive tool complementing the conventional imaging technologies. On the pathway to an envisaged clinical application, several challenges have to be addressed. Among them are achieving the desired spatial resolution in the presence of multiple Coulomb scattering (MCS), performing radiographs with a sufficient thickness resolution at clinically applicable dose levels, and the search for combinations of particularly suitable hadrons and detectors. These topics are investigated in this work for a detection system based on silicon pixel detectors.Methods: A method of iRad based on energy deposition measurements in thin layers is introduced. It exploits a detection system consisting of three parallel silicon pixel detectors, which also enables particle tracking and identification. Helium ions, which exhibit less pronounced MCS than protons, were chosen as imaging radiation. A PMMA phantom with a mean water-equivalent thickness (WET) of 192 mm, containing maximal WET-variations of +/- 6 mm, was imaged with a 173 MeV/u helium ion beam at the Heidelberg Ion-Beam Therapy Center. WET-differences in form of 2.3 mm x 2.3 mm steps were aimed to be visualized and resolved in images of the energy deposition measured behind the phantom. The detection system was placed downstream of the imaged object in order to detect single ions leaving it. The combination of the measured information on energy deposition, ion type, and the track behind the phantom was used for the image formation, employing a self-developed data-processing procedure.Results: It was shown that helium-beam radiography is feasible with the reported detection system. The introduced data preprocessing purified the detector signal from detector artifacts and improved the image quality. Additionally, the rejection of hydrogen ions originating from nuclear interactions was shown to increase the contrast-to-noise ratio (CNR) by at least a factor of 2.5. This enabled the resolution of relative thickness differences of 1.2% at a dose level typical for diagnostic x-ray images. The spatial resolution was improved by taking into account the direction of single helium ions leaving the phantom. A spatial resolution (MTF10%) of at least 1.15p mm(-1) for the presented experimental set-up was achieved.Conclusion: A successful feasibility study of helium-beam radiography with the introduced detection system was conducted. The methodology of iRad was based on energy deposition measurements in thin silicon layers. The tracking of single ions and the method of the ion identification was shown to be important for helium-beam radiography in terms of spatial resolution and CNR. (C) 2017 American Association of Physicists in Medicine