Sun Jiayao, Zhang Lijia, Wang Weiwei, Kong Lin, Guan Xiyin, Dong Sixue, You Dan, Shen Zhuangming, Sheng Yinxiangzi
Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai, China.
Shanghai Key Laboratory of Radiation Oncology, Shanghai, China.
Med Phys. 2025 Jul;52(7):e17824. doi: 10.1002/mp.17824. Epub 2025 Apr 11.
Carbon-ion rotating gantries use is limited by its large size, weight, and high cost. Gantry-free modality enables the reduction of the overall size, weight, and cost. Among them, upright treatment, which utilizes fixed ion beamlines, in combination with a treatment chair capable of 360° rotation and adjustable pitch angle (enabling non-coplanar beam delivery), provides a wider range of beam entry angles compared to conventional couch-based setups and has already been applied in particle radiotherapy for head and neck cancer patients.
In this study, we analyzed clinical data from the Shanghai Proton and Heavy Ion Center (SPHIC) to quantify residual setup errors across various regions of interest (ROIs) for both upright and supine treatments.
A total of 402 treatment fractions from 28 patients (median 5 fractions, range: 5-16 fractions per posture per patient) were enrolled in this study. All these patients were immobilized and scanned in supine posture and received both supine and upright radiotherapy. Three rectangular-shaped ROIs were delineated based on bone structures, encompassing the mandible, orbit, and neck vertebrae C1-C3. Box-based registration, focusing solely on the anatomical structures within the specific ROIs was performed to subtract the correction vector used in treatment, thereby obtaining the residual setup error for each ROI. Margins for each ROIs were calculated.
For both postures, the median values of residual setup error for all translational directions were less than 1 mm. The median values did not exceed 0.2 degrees for rotational errors. More than 78% of the fractions for upright treatment fell within the 1 mm/° threshold, while 94% were within the 2 mm/° threshold. In contrast, for supine treatment, over 61% fell within the 1 mm/° threshold, while 86% were within the 2 mm/° threshold. The maximum margin was 3.3 mm in the AP direction of the C1-C3 region for the supine posture.
Upright treatments demonstrated comparable residual setup errors to supine treatments, with most errors falling within clinically acceptable thresholds. This study provides valuable clinical evidence for the continued development and implementation of upright radiotherapy.
碳离子旋转机架因其体积大、重量重和成本高而使用受限。无机架模式能够减小整体尺寸、重量和成本。其中，直立治疗利用固定离子束线，结合能够360°旋转和俯仰角可调（实现非共面射束输送）的治疗椅，与传统的基于治疗床的设置相比，提供了更宽的射束入射角范围，并且已经应用于头颈部癌患者的粒子放射治疗。
在本研究中，我们分析了上海质子重离子中心（SPHIC）的临床数据，以量化直立和仰卧治疗中各个感兴趣区域（ROI）的残余摆位误差。
本研究纳入了28例患者的402个治疗分次（中位数为5个分次，范围：每位患者每个姿势5 - 16个分次）。所有这些患者均以仰卧姿势固定并进行扫描，并接受了仰卧和直立放射治疗。基于骨骼结构划定了三个矩形ROI，涵盖下颌骨、眼眶和颈椎C1 - C3。进行仅关注特定ROI内解剖结构的基于盒体的配准，以减去治疗中使用的校正向量，从而获得每个ROI的残余摆位误差。计算每个ROI的边界。
对于两种姿势，所有平移方向的残余摆位误差中位数均小于1 mm。旋转误差中位数不超过0.2度。直立治疗中超过78%的分次落在1 mm/°阈值内，而94%在2 mm/°阈值内。相比之下，仰卧治疗中超过61%落在1 mm/°阈值内，而86%在2 mm/°阈值内。仰卧姿势下C1 - C3区域的前后方向最大边界为3.3 mm。
直立治疗显示出与仰卧治疗相当的残余摆位误差，大多数误差落在临床可接受的阈值内。本研究为直立放射治疗的持续发展和实施提供了有价值的临床证据。
