Three dimensional reconstruction of therapeutic carbon ion beams in phantoms using single secondary ion tracks
Anna Merle Reinhart, Claudia Katharina Spindeldreier, Jan Jakubek, Maria Martisikova
备注：
This is an author-created, un-copyedited version of an article published in Physics in Medicine and Biology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6560/aa6aeb
Carbon ion beam radiotherapy enables a very localised dose deposition. However, already small changes in the patient geometry or positioning errors can significantly distort the dose distribution. A live monitoring system of the beam delivery within the patient is therefore highly desirable and could improve patient treatment. We present a novel three-dimensional imaging method of the beam in the irradiated object, exploiting the measured tracks of single secondary ions emerging under irradiation. The secondary particle tracks are detected with a TimePix stack, a set of parallel pixelated semiconductor detectors. We developed a three-dimensional reconstruction algorithm based on maximum likelihood expectation maximisation. We demonstrate the applicability of the new method in an irradiation of a cylindrical PMMA phantom of human head size with a carbon ion pencil beam of 226MeV/u. The beam image in the phantom is reconstructed from a set of 9 discrete detector positions between -80 and 50 degrees from the beam axis. Furthermore, we demonstrate the potential to visualise inhomogeneities by irradiating a PMMA phantom with an air gap as well as bone and adipose tissue surrogate inserts. We successfully reconstructed a 3D image of the treatment beam in the phantom from single secondary ion tracks. The beam image corresponds well to the distribution expected from the beam direction and energy. In addition, cylindrical inhomogeneities with a diameter of 2.85cm and density differences down to 0.3g/cm$^3$ to the surrounding material are clearly visualised. This novel 3D method to image a therapeutic carbon ion beam in the irradiated object does not interfere with the treatment and requires knowledge only of single secondary ion tracks. Even with detectors with only a small angular coverage, the 3D reconstruction of the fragmentation points presented in this work was found to be feasible.
Development of a Full Monte Carlo Therapeutic Dose Calculation Toolkit for Halcyon Using Geant4
目的：在Geant4（10.7版）中开发一个用于最近发布的环形门架直线加速器的蒙特卡罗（MC）治疗剂量计算工具包，用于放射治疗计划的二次剂量验证。研究方法：对于Halcyon（Varian Medical Systems），对DSMLC进行建模，并使用Geant 4模拟DSMLC和患者体模中的辐射传输。辐射源从相空间文件中采样，用于DSMLC上方的直线加速器头。使用Varian提供的基于云的Monte Carlo（MC）模拟器VirtuaLinac（VL）获得相空间文件。不同方野宽度（2x2、4x4、6x6、8x8、10x10、20x20和28x28 cm 2）的剂量曲线，即，百分比深度剂量（PDD）曲线和横向剖面进行了模拟，并与实验剖面进行了比较。还使用开发的工具包计算了两个解剖部位（前列腺和脑）的IMRT（调强放射治疗）计划，并与TPS计算的剂量进行了比较（Acuros，Eclipse 15.6）。使用3D剂量差和3D伽马分析来评价与TPS计算剂量相比的模拟准确度。结果如下：对于所有模拟射野尺寸，水模中模拟的侧向剂量分布和PDD曲线与测量值匹配良好，相对差异为± 2%。对于前列腺和脑调强放射治疗计划，模拟剂量与TPS计算剂量显示出良好的一致性。两个前列腺和脑计划的3D伽马通过率（3%/3mm）分别为98.08%和95.4%。结论：开发的Halcyon全MC剂量计算工具包在水模体…
Secondary radiation measurements for particle therapy applications: Charged secondaries produced by 4He and 12C ion beams in a PMMA target at large angle
Secondary radiation measurements for particle therapy applications: prompt photons produced by $^{4}$He, $^{12}$C and $^{16}$O ion beams in a PMMA target
Bragg-Curve Simulation of Carbon-Ion Beams for Particle-therapy Applications: a study with the GEANT4 toolkit
我们使用GEANT4 Monte Carlo MC Toolkit模拟碳离子束入射到水、组织和骨骼上，同时考虑到核碎裂反应。在增加初级射束的能量时，布拉格峰的位置转移到体模内部更深的位置。对于不同的材料，峰值位于沿束方向的较浅的深度处，并且随着电子密度NZ的增加而变得尖锐。随后，产生的深度剂量的布拉格曲线，然后基准与德国GSI的实验数据。计算结果与GSI实验数据具有较好的相关性，精度在0.02~0.08cm之间，为在重离子治疗计划中采用MC奠定了基础。Kolmogorov-Smirnov K-S检验从统计学的角度进一步确定了模拟数据与实验测量数据非常匹配。将入口处的二维等剂量线与峰值位置周围和超出峰值的尾部区域中的等剂量线进行比较，表明由于二次剂量，与水和组织相比，骨产生更多剂量。在水中，结果表明，每个碎片沉积的最大能量主要归因于次级碳离子，其次是次级硼和铍。此外，产生的质子数是最高的，从而对尾区的总剂量沉积做出最大贡献。最后分析了中子和光子的关联谱。平均中子能量值为16.29 MeV，次级γ射线为1.03 MeV。然而，中子剂量被认为是可以忽略不计的总剂量相比，由于其较长的范围。
AI-driven projection tomography with multicore fibre-optic cell rotation
Shanghai Artificial Intelligence Laboratory（上海人工智能实验室）；TU Dresden（德累斯顿工业大学）；Max Planck Institute for the Science of Light（马克斯·普朗克光科学研究所）；Max Planck-Zentrum für Physik und Medizin（马克斯·普朗克物理与医学中心）
