Investigation of 4D dose in volumetric modulated arc therapy-based stereotactic body radiation therapy: does fractional dose or number of arcs matter?
Investigation of 4D dose in volumetric modulated arc therapy-based stereotactic body radiation therapy: does fractional dose or number of arcs matter?
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DOI：
10.1093/jrr/rrz103
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发表时间：
2020-03-01
影响因子：
2
通讯作者：
Mizowaki, Takashi
中科院分区：
文献类型：
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作者：
Shintani, Takashi;Nakamura, Mitsuhiro;Mizowaki, Takashi
本研究的目的是评估当使用体积调制式弧形治疗（VMAT）治疗具有大呼吸运动的肺肿瘤时，剂量分数和弧形数量对相互作用效应的影响。为10例肺癌病例创建了3（4、7.5或12.5戈伊分次剂量）× 2（弧数，1或2）VMAT计划。中位三维肿瘤运动为17.9 mm（范围：8.2- 27.2 mm）。通过使用时间分配的VMAT弧计算每个呼吸相位计算机断层扫描（CT）扫描的剂量，生成10个相位特定子计划。我们进行了时间分配的VMAT弧使用的呼吸信息，从红外标记放置在CT模拟过程中的患者的晶状体。使用基于轮廓的可变形图像配准将每个相位特异性剂量分布变形到呼气相位CT扫描上，并通过剂量累积创建4D计划。将每个4D计划的总肿瘤体积剂量（4D GTV剂量）与原始计划的内部靶体积剂量（3D ITV剂量）进行比较。接近最小4D GTV剂量（D-99%）高于接近最小3D内部靶体积（ITV）剂量，而接近最大4D GTV剂量（D-1%）低于接近最大3D ITV剂量。然而，差异可忽略不计，因此4D GTV剂量与3D ITV剂量对应良好，无论分数剂量和弧数如何。因此，在基于VMAT的立体定向体部放射治疗具有大呼吸运动的肺肿瘤时，相互作用效应可以忽略不计。
The aim of this study was to assess the impact of fractional dose and the number of arcs on interplay effects when volumetric modulated arc therapy (VMAT) is used to treat lung tumors with large respiratory motions. A three (fractional dose of 4, 7.5 or 12.5 Gy) by two (number of arcs, one or two) VMAT plan was created for 10 lung cancer cases. The median 3D tumor motion was 17.9 mm (range: 8.2-27.2mm). Ten phase-specific subplans were generated by calculating the dose on each respiratory phase computed tomography (CT) scan using temporally assigned VMAT arcs. We performed temporal assignment of VMAT arcs using respiratory information obtained from infrared markers placed on the abdomens of the patients during CT simulations. Each phase-specific dose distribution was deformed onto exhale phase CT scans using contour-based deformable image registration, and a 4D plan was created by dose accumulation. The gross tumor volume dose of each 4D plan (4D GTV dose) was compared with the internal target volume dose of the original plan (3D ITV dose). The near-minimum 4D GTV dose (D-99%) was higher than the near-minimum 3D internal target volume (ITV) dose, whereas the near-maximum 4D GTV dose (D-l%) was lower than the near-maximum 3D ITV dose. However, the difference was negligible, and thus the 4D GTV dose corresponded well with the 3D ITV dose, regardless of the fractional dose and number of arcs. Therefore, interplay effects were negligible in VMAT-based stereotactic body radiation therapy for lung tumors with large respiratory motions.