Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital (MGH), 55 Fruit Street, Boston, MA 02114, USA.
Technol Cancer Res Treat. 2014 Feb;13(1):69-76. doi: 10.7785/tcrt.2012.500357. Epub 2013 Jun 24.
This study investigate the use of ion radiography as a tool for patient set-up and tumor tracking capabilities for image guided particle therapy (IGPT) using Monte Carlo simulations. One pediatric, two lung and one liver cancer patients were considered in this study. For each patient, 230 and 330 MeV proton, and 500 MeV/nucleon carbon ion pencil beams were simulated through their computed tomography (CT) data set using GEANT4.9.0. Energy, position and direction cosines of each particle were recorded in front and behind the patient. Ion radiographs were subsequently reconstructed using a dedicated in-house software. The image quality was assessed by evaluating the contrast-to-noise ratio of the tumor and its surrounding tissue. In the lung and liver cases, each CT phase of the breathing cycle was treated individually and dynamic sequences were later produced to appreciate tumor motion. Reconstructed radiographs show high spatial resolution. This allows for excellent imaging capabilities in pediatric patients, comparable to X-ray imaging at a fraction of the imaging dose. There is clear visualization of the tumor edges in the lung due to the great contrast-to-noise ratio between the tumor and its surrounding tissues; tumor motion is observed and comparable to 4D CT data thus allowing for on-line tumor tracking during ion radiotherapy. Conversely, tumor edge detection is difficult in liver, and fiducial markers are required to attempt indirect tumor tracking for IGPT. Ion radiographs with high spatial resolution can be generated using the PR-creator software resulting in pediatric patient set-up capabilities at a fraction of the current imaging dose, as well as the capacity to track moving targets in order to achieve IGPT.
本研究使用蒙特卡罗模拟，调查了离子射线照相术作为一种工具，用于图像引导粒子治疗（IGPT）中的患者设置和肿瘤跟踪能力。本研究考虑了一名儿科、两名肺癌和一名肝癌患者。对于每位患者，使用 GEANT4.9.0 通过其计算机断层扫描（CT）数据集模拟了 230 和 330 MeV 质子以及 500 MeV/核子碳离子笔形束。记录了每个粒子在患者前后的能量、位置和方向余弦。随后使用专用的内部软件重建离子射线照片。通过评估肿瘤及其周围组织的对比度噪声比来评估图像质量。在肺部和肝脏病例中，分别对呼吸周期的每个 CT 相位进行单独处理，然后生成动态序列以了解肿瘤运动。重建的射线照片具有高空间分辨率。这使得在儿科患者中具有出色的成像能力，可以与 X 射线成像相媲美，而成像剂量仅为其一小部分。由于肿瘤与其周围组织之间的对比度噪声比很高，因此在肺部可以清晰地看到肿瘤边缘；观察到肿瘤运动，与 4D CT 数据相当，从而允许在离子放射治疗期间进行在线肿瘤跟踪。相反，在肝脏中很难检测到肿瘤边缘，需要使用基准标记来尝试进行 IGPT 的间接肿瘤跟踪。使用 PR-creator 软件可以生成具有高空间分辨率的离子射线照片，从而以当前成像剂量的一小部分实现儿科患者设置能力，以及跟踪移动目标的能力，以实现 IGPT。
