Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Switzerland.
Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Switzerland.
Radiother Oncol. 2017 Dec;125(3):445-452. doi: 10.1016/j.radonc.2017.08.035. Epub 2017 Sep 18.
Motion mitigation during prostate stereotactic body radiation therapy (SBRT) ensures optimal target coverage while reducing the risk of overdosage of nearby organs. The geometrical and dosimetrical performance of motion mitigation with the multileaf-collimator (MLC tracking) or the treatment couch (couch tracking) were compared.
For ten prostate patients, SBRT treatment plans with integrated boosts were prepared using volumetric modulated arc technique. For the geometrical evaluation, a lead sphere at the beam isocenter was moved according to five prostate motion curves (i) without mitigation, (ii) with MLC tracking or (iii) with couch tracking. During irradiation, MV images were taken and the over-/underexposed areas were evaluated. For the dosimetrical evaluation, the plans were applied to a dosimetric phantom. Dose distributions with and without mitigation were evaluated inside the target structure and organs at risk.
The median over-/underexposed area was reduced significantly from 2.02cm without mitigation to 1.00cm and 0.45cm with MLC and couch tracking. Closest dosimetrical agreement to the static references was achieved with couch tracking.
MLC and couch tracking at a conventional linear accelerator significantly improved the accuracy of prostate SBRT in the presence of motion, whereby couch tracking showed slightly better performance than MLC tracking.
在前列腺立体定向体放射治疗（SBRT）中减轻运动可确保最佳的靶区覆盖，同时降低邻近器官超剂量的风险。本文比较了多叶准直器（MLC 跟踪）或治疗床（床跟踪）的运动缓解的几何和剂量学性能。
对于 10 例前列腺患者，使用容积调制弧形技术准备了集成增敏的 SBRT 治疗计划。为了进行几何评估，将射束等中心的一个铅球按照 5 个前列腺运动曲线（i）无缓解，（ii）有 MLC 跟踪或（iii）有治疗床跟踪进行移动。在照射过程中，拍摄 MV 图像，并评估过/低估区域。对于剂量学评估，将计划应用于剂量学体模。评估了有和没有缓解时靶结构内部和危及器官的剂量分布。
无缓解时的过/低估面积中位数为 2.02cm，有 MLC 和治疗床跟踪时分别减少至 1.00cm 和 0.45cm。与静态参考相比，治疗床跟踪实现了最接近的剂量学一致性。
在存在运动的情况下，常规直线加速器上的 MLC 和治疗床跟踪显著提高了前列腺 SBRT 的准确性，其中治疗床跟踪的性能略优于 MLC 跟踪。
