Bey Anissa, Ma Jiasen, Furutani Keith M, Herman Michael G, Johnson Jedediah E, Foote Robert L, Beltran Chris J
Department of Radiation Oncology, Mayo Clinic, Rochester, MN, USA.
Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL, USA.
Int J Part Ther. 2021 Sep 1;8(4):25-36. doi: 10.14338/IJPT-20-00040.1. eCollection 2022 Spring.
This article presents an in vivo imaging technique based on nuclear fragmentation of carbon ions in irradiated tissues for potential real-time monitoring of carbon-ion radiation therapy (CIRT) treatment delivery and quality assurance purposes in clinical settings.
A proof-of-concept imaging and monitoring system (IMS) was devised to implement the technique. Monte Carlo simulations were performed for a prospective pencil-beam scanning CIRT nozzle. The development IMS benchmark considered a 5×5-cm pixelated charged-particle detector stack positioned downstream from a target phantom and list-mode data acquisition. The abundance and production origins, that is, vertices, of the detected fragments were studied. Fragment trajectories were approximated by straight lines and a beam back-projection algorithm was built to reconstruct the vertices. The spatial distribution of the vertices was then used to determine plan relevant markers.
The IMS technique was applied for a simulated CIRT case, a primary brain tumor. Four treatment plan monitoring markers were conclusively recovered: a depth dose distribution correlated profile, ion beam range, treatment target boundaries, and the beam spot position. Promising millimeter-scale (3-mm, ≤10% uncertainty) beam range and submillimeter (≤0.6-mm precision for shifts <3 cm) beam spot position verification accuracies were obtained for typical therapeutic energies between 150 and 290 MeV/u.
This work demonstrated a viable online monitoring technique for CIRT treatment delivery. The method's strong advantage is that it requires few signal inputs (position and timing), which can be simultaneously acquired with readily available technology. Future investigations will probe the technique's applicability to motion-sensitive organ sites and patient tissue heterogeneities. In-beam measurements with candidate detector-acquisition systems are ultimately essential to validate the IMS benchmark performance and subsequent deployment in the clinic.
本文介绍一种基于受辐照组织中碳离子核碎裂的体内成像技术，用于在临床环境中对碳离子放射治疗（CIRT）的治疗实施和质量保证进行潜在的实时监测。
设计了一个概念验证成像与监测系统（IMS）来实施该技术。对一个前瞻性笔形束扫描CIRT喷嘴进行了蒙特卡罗模拟。开发的IMS基准考虑了一个位于靶体模下游的5×5厘米像素化带电粒子探测器堆栈以及列表模式数据采集。研究了检测到的碎片的丰度和产生源，即顶点。碎片轨迹用直线近似，并构建了一种束反向投影算法来重建顶点。然后利用顶点的空间分布来确定与计划相关的标记。
IMS技术应用于一个模拟的CIRT病例，即原发性脑肿瘤。最终恢复了四个治疗计划监测标记：深度剂量分布相关曲线、离子束射程、治疗靶区边界和束斑位置。对于150至290MeV/u之间的典型治疗能量，获得了有前景的毫米级（3毫米，不确定度≤10%）束射程和亚毫米级（对于<3厘米的位移，精度≤0.6毫米）束斑位置验证精度。
这项工作展示了一种用于CIRT治疗实施的可行在线监测技术。该方法的显著优势在于它需要很少的信号输入（位置和时间），这些可以通过现成的技术同时获取。未来的研究将探讨该技术对运动敏感器官部位和患者组织异质性的适用性。使用候选探测器采集系统进行束内测量对于验证IMS基准性能以及随后在临床中的应用至关重要。
