Purpose. This study explored a novel technique to improve the MV imaging based fiducial visibility for a cohort of prostate radiotherapy patients, without compromising the original treatment plan. The study also compared these results to visibility using single MLC control points, as well as short arcs. Methods. Geometric data from 68 prostate radiotherapy treatments, each with implanted gold fiducials, was retrospectively analysed. Fiducials were contoured for each patient, and conventional and SBRT treatment plans were generated using a VMAT technique. Using an in-house script, fiducial contours were projected onto the VMAT MLC control points. Resulting data was assessed to determine whether the fiducial contours were theoretically visible for single MLC control points and groups of MLC control points (short arcs), both being surrogates for intra-fraction MV imaging. Using this data, a theoretical quadrant technique was investigated that assessed the region surrounding each fiducial to determine if visualisation would theoretically improve. Results. Using a conventional treatment type, mean fiducial visibility for single MLC control points across the patient cohort ranged from 2.5% up to 17.8%. For SBRT, fiducial visibility ranged from 1.8% up to 19.7%. For short arcs, fiducial visibility for conventional treatment types ranged from 5.9% up to 20.7%. For SBRT, fiducial visibility ranged from 4.6% up to 23.1%. When the novel fiducial quadrant technique was used, theoretical visibility improved two-fold, from 22.7% up to 52.5% and from 24.7% up to 55.3% for conventional and SBRT treatment types respectively. Conclusions. Fiducial visibility was assessed for a cohort of VMAT prostate patients. Using the novel quadrant technique, it was demonstrated that theoretical visualisation and localisation of the implanted fiducials could be improved two-fold, without sacrificing treatment plan quality.

目的。本研究探索了一种新技术，可以在不影响原始治疗计划的情况下，提高一组前列腺放疗患者基于 MV 成像的基准可见性。该研究还将这些结果与使用单个 MLC 控制点以及短弧的可见性进行了比较。方法. 对来自 68 次前列腺放射治疗的几何数据进行了回顾性分析，每次治疗均植入了金基准。为每位患者绘制基准轮廓，并使用 VMAT 技术生成常规和 SBRT 治疗计划。使用内部脚本，将基准轮廓投影到 VMAT MLC 控制点上。评估结果数据以确定基准轮廓在理论上是否对于单个 MLC 控制点和 MLC 控制点组（短弧）可见，两者都是分次内 MV 成像的替代物。使用此数据，研究了一种理论象限技术，该技术评估了每个基准点周围的区域，以确定可视化是否会在理论上得到改善。结果. 使用传统的治疗类型，整个患者队列中单个 MLC 控制点的平均基准可见度范围为 2.5% 至 17.8%。对于 SBRT，基准能见度从 1.8% 到 19.7% 不等。对于短弧，常规处理类型的基准能见度范围从 5.9% 到 20.7%。对于 SBRT，基准能见度范围从 4.6% 到 23.1%。当使用新的基准象限技术时，理论能见度提高了两倍，常规和 SBRT 治疗类型分别从 22.7% 提高到 52.5% 和从 24.7% 提高到 55.3%。结论. 评估了一组 VMAT 前列腺患者的基准​​可见性。使用新的象限技术，证明了在不牺牲治疗计划质量的情况下，植入基准的理论可视化和定位可以提高两倍。