一种“虚拟”图像引导替代方案的剂量学评估，用于明确的 6 自由度机器人床校正。

Dosimetric evaluation of a "virtual" image-guidance alternative to explicit 6 degree of freedom robotic couch correction.

机构信息

Department of Radiation Oncology, University of Utah, Salt Lake City, Utah.

Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah.

出版信息

Pract Radiat Oncol. 2012 Apr-Jun;2(2):122-37. doi: 10.1016/j.prro.2011.07.005. Epub 2011 Sep 25.

DOI:10.1016/j.prro.2011.07.005

PMID:24674088

Abstract

PURPOSE

Clinical evaluation of a "virtual" methodology for providing 6 degrees of freedom (6DOF) patient set-up corrections and comparison to corrections facilitated by a 6DOF robotic couch.

METHODS

A total of 55 weekly in-room image-guidance computed tomographic (CT) scans were acquired using a CT-on-rails for 11 pelvic and head and neck cancer patients treated at our facility. Fusion of the CT-of-the-day to the simulation CT allowed prototype virtual 6DOF correction software to calculate the translations, single couch yaw, and beam-specific gantry and collimator rotations necessary to effectively reproduce the same corrections as a 6DOF robotic couch. These corrections were then used to modify the original treatment plan beam geometry and this modified plan geometry was applied to the CT-of-the-day to evaluate the dosimetric effects of the virtual correction method. This virtual correction dosimetry was compared with calculated geometric and dosimetric results for an explicit 6DOF robotic couch correction methodology.

RESULTS

A (2%, 2mm) gamma analysis comparing dose distributions created using the virtual corrections to those from explicit corrections showed that an average of 95.1% of all points had a gamma of 1 or less, with a standard deviation of 3.4%. For a total of 470 dosimetric metrics (ie, maximum and mean dose statistics for all relevant structures) compared for all 55 image-guidance sessions, the average dose difference for these metrics between the plans employing the virtual corrections and the explicit corrections was -0.12% with a standard deviation of 0.82%; 97.9% of all metrics were within 2%.

CONCLUSIONS

Results showed that the virtual corrections yielded dosimetric distributions that were essentially equivalent to those obtained when 6DOF robotic corrections were used, and that always outperformed the most commonly employed clinical approach of 3 translations only. This suggests that for the patient datasets studied here, highly effective image-guidance corrections can be made without the use of a robotic couch.

摘要

目的

临床评估一种提供 6 自由度（6DOF）患者摆位校正的“虚拟”方法，并将其与 6DOF 机器人治疗床辅助校正进行比较。

方法

对在我院治疗的 11 例骨盆和头颈部癌症患者，每周在治疗室内进行一次 CT-on-rails 采集共 55 次图像引导的 CT 扫描。将当天的 CT 与模拟 CT 融合，使原型虚拟 6DOF 校正软件能够计算出平移、单个治疗床偏航以及束特定的旋转台和准直器旋转，以有效再现与 6DOF 机器人治疗床相同的校正。然后，这些校正用于修改原始治疗计划束几何形状，并将修改后的计划几何形状应用于当天的 CT，以评估虚拟校正方法的剂量学效应。将这种虚拟校正剂量学与明确的 6DOF 机器人治疗床校正方法的计算几何和剂量学结果进行比较。

结果

通过比较使用虚拟校正和显式校正创建的剂量分布，（2%，2mm）伽玛分析显示，所有点中平均有 95.1%的点伽玛值为 1 或更小，标准差为 3.4%。对于总共 470 个剂量学指标（即所有相关结构的最大和平均剂量统计）在所有 55 次图像引导治疗期间进行比较，使用虚拟校正和显式校正的计划之间这些指标的平均剂量差异为-0.12%，标准差为 0.82%；97.9%的所有指标都在 2%以内。