发表机构
Department of Radiation Oncology, Mayo Clinic（梅奥诊所放射肿瘤科）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对美国首个碳离子治疗设施的运动剂量模拟难题，提出含真实轨迹、时变强度及波动模型的方法，经TOPAS验证可准确建模，为临床CIRT的MC剂量计算提供实用框架。
AI 中文摘要
碳离子放射治疗（CIRT）相较于传统光子疗法具有更高的生物学效应，原因在于其高线性能量转移特性，且能诱导复杂的DNA损伤。梅奥诊所佛罗里达分院正在开发美国首个CIRT设施，采用基于同步加速器的剂量驱动连续扫描（DDCS）系统。尽管DDCS通过在点扫描转换期间保持束流开启提升了递送效率，但也带来了准确模拟束流运动期间递送剂量（即运动剂量）的挑战，这一问题在当前治疗计划系统中尚未得到充分解决。本研究提出一种用于准确模拟运动剂量的方法，以支持蒙特卡罗（MC）剂量计算。该方法对真实束流轨迹进行建模，包括由X和Y方向不同扫描速度导致的特征性“曲棍球棒”运动，并考虑具有线性上升行为的时间依赖束流强度。束流路径被划分为多个小段，每段由一个运动源表示，其位置、强度和监测单元均通过解析确定。此外，还采用基于测量的随机模型纳入束流强度波动。针对水模体中430 MeV/u碳离子束的TOPAS模拟验证显示，该方法对运动剂量及由此产生的剂量分布的建模准确，为临床CIRT中的基于MC的剂量计算提供了实用框架。
英文摘要
Carbon ion radiotherapy (CIRT) provides greater biological effectiveness than conventional photon therapy because of its high linear energy transfer and its ability to induce complex DNA damage. Mayo Clinic Florida is developing the first CIRT facility in the United States, using a synchrotron-based system with dose-driven continuous scanning (DDCS). Although DDCS improves delivery efficiency by keeping the beam on during spot transitions, it also creates the challenge of accurately modeling the dose delivered during beam motion (move dose), which is not fully addressed in current treatment planning systems. In this work, we present a method for accurate simulation of move dose to support Monte Carlo (MC) dose calculations. The method models realistic beam trajectories, including the characteristic hockey stick motion caused by different scanning speeds in the X and Y directions, and accounts for time-dependent beam intensity with linear ramp-up behavior. The beam path is divided into small segments, each represented by a move source with analytically determined position, intensity, and monitor units. Beam intensity fluctuations are also included using a stochastic model based on measurements. Validation using TOPAS simulations for a 430 MeV/u carbon ion beam in a water phantom showed accurate modeling of move dose and the resulting dose distributions. This method provides a practical framework for MC-based dose calculation in clinical CIRT.
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