Ramesh Pavitra, Liu Hengjie, Gu Wenbo, Sheng Ke
Physics and Biology in Medicine interdepartmental program, University of California Los Angeles, Los Angeles, CA 90025 USA.
Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104 USA.
IEEE Trans Radiat Plasma Med Sci. 2022 Mar;6(3):288-293. doi: 10.1109/trpms.2021.3092296. Epub 2021 Jun 25.
A major obstacle for the adoption of heavy ion therapy is the cost and technical difficulties to construct and maintain a rotational gantry. Many heavy ion treatment facilities instead choose to construct fixed beamlines as a compromise, which we propose to mitigate with optimized treatment couch angle. We formulate the integrated beam orientation and scanning spot optimization problem as a quadratic cost function with a group sparsity regularization term. The optimization problem is efficiently solved using fast iterative shrinkage-thresholding algorithm (FISTA). To test the method, we created the fixed beamline plans with couch rotation (FBCR) and without couch rotation (FB) for intensity modulated carbon-ion therapy (IMCT) and compared with the ideal scenario where both the couch and gantry have 360 degrees of freedom (GCR). FB, FBCR, and GCR IMCT plans were compared for ten pancreas cases. The FBCR plans show comparable PTV coverage and OAR doses for each pancreas case. In conclusion, the dosimetric limitation of fixed beams in heavy ion radiotherapy may be largely mitigated with integrated beam orientation optimization of the couch rotation.
重离子治疗应用的一个主要障碍是建造和维护旋转机架的成本及技术难度。许多重离子治疗设施转而选择建造固定束线作为折衷方案，我们建议通过优化治疗床角度来缓解这一问题。我们将综合束流方向和扫描点优化问题表述为一个带有组稀疏正则化项的二次成本函数。使用快速迭代收缩阈值算法（FISTA）有效地解决了该优化问题。为了测试该方法，我们针对调强碳离子治疗（IMCT）创建了带有治疗床旋转（FBCR）和不带有治疗床旋转（FB）的固定束线计划，并与治疗床和机架均具有360度自由度的理想方案（GCR）进行比较。对十例胰腺病例的FB、FBCR和GCR IMCT计划进行了比较。FBCR计划在每个胰腺病例中显示出相当的靶区适形度和危及器官剂量。总之，通过治疗床旋转的综合束流方向优化，可在很大程度上缓解重离子放射治疗中固定束线的剂量学限制。
