Comparison of treatment planning approaches for spatially fractionated irradiation of deep tumors
Comparison of treatment planning approaches for spatially fractionated irradiation of deep tumors
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DOI：
10.1002/acm2.12617
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发表时间：
2019-06-01
影响因子：
2.1
通讯作者：
Meyer, Jeffrey
中科院分区：
文献类型：
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作者：
Sheikh, Khadija;Hrinivich, William T.;Meyer, Jeffrey
目的比较三维适形放射治疗(3DCRT)、体积调制弧形放射治疗(VMAT)和断层放射治疗(TomoTreatment)三种放射治疗方法对深部肿瘤靶区空间分割放射治疗的剂量学和传输时间。方法建立2个虚拟网格模型，由7个直径为1 cm的“靶柱”沿肿瘤纵向排列成蜂窝状，模拟传统的网格模型，中心距2 cm(网格2 cm)，中心距3 cm(网格3 cm)，均包含在一个较大的圆柱体中(网格2 cm，网格3 cm，直径分别为8 cm和10 cm)。在单个患者中，在大体肿瘤体积(GTV)内创建了一个网格(3厘米)结构。断层治疗、VMAT(6 MV+6 MV-平坦化-无滤光片)和多叶准直器节段3DCRT(6 MV)计划使用商业软件创建。创建两个放射治疗计划，视野宽度(TOMO2.5 cm)2.5 cm和(TOMO5 Cm)5 cm。所有计划的处方都被设定为在一小部分时间内向网格目标提供平均剂量为15GY的辐射。得到了栅格靶的平均剂量和栅格靶内剂量分布的非均匀分布(峰谷剂量比和峰边剂量比)。测定照射剂量为7.5Gy时正常组织的体积。结果3DCRT、VMAT、TOMO5 cm和TOMO2.5 cm计划的网格(2 Cm)/网格(3 Cm)/患者的峰谷比分别为2.1/2.3/2.8、1.7/1.5/2.8、1.7/1.9/2.4和1.8/2.0/2.8。网格(2 Cm)/网格(3 Cm)/患者的峰边比分别为2.8/3.2/5.4、2.1/1.8/5.4、2.0/2.2/3.9、2.1/2.7/5.2；3DCRT、VMAT、TOMO5 cm和TOMO2.5 cm平面的峰边比分别为2.8/3.2/5.4、2.1/2.2/3.9、2.1/2.7/5.2。TOMO2.5 cm平面内正常组织体积最小(网格2 cm/网格3 cm/患者=54 cm(3)/19 cm(3)/10 cm(3))。VMAT计划的交付时间最短(网格(2 Cm)/网格(3 Cm)/患者=17分钟/8分钟/9分钟)。结论我们的结果首次提供了初步证据，比较了调强放射治疗-网格方法在靶区内导致高剂量“孤岛”的效果，模拟了传统网格块所达到的效果，但没有靶区外的高剂量“尾部”区域。这些方法在实现高峰边比的能力上略有不同，在交付时间上也有所不同。
Purpose The purpose of this work was to compare the dosimetry and delivery times of 3D-conformal (3DCRT)-, volumetric modulated arc therapy (VMAT)-, and tomotherapy-based approaches for spatially fractionated radiation therapy for deep tumor targets. Methods Two virtual GRID phantoms were created consisting of 7 "target" cylinders (1-cm diameter) aligned longitudinally along the tumor in a honey-comb pattern, mimicking a conventional GRID block, with 2-cm center-to-center spacing (GRID(2 cm)) and 3-cm center-to-center spacing (GRID(3 cm)), all contained within a larger cylinder (8 and 10 cm in diameter for the GRID(2 cm) and GRID(3 cm), respectively). In a single patient, a GRID(3 cm) structure was created within the gross tumor volume (GTV). Tomotherapy, VMAT (6 MV + 6 MV-flattening-filter-free) and multi-leaf collimator segment 3DCRT (6 MV) plans were created using commercially available software. Two tomotherapy plans were created with field widths (TOMO2.5 cm) 2.5 cm and (TOMO5 cm) 5 cm. Prescriptions for all plans were set to deliver a mean dose of 15 Gy to the GRID targets in one fraction. The mean dose to the GRID target and the heterogeneity of the dose distribution (peak-to-valley and peak-to-edge dose ratios) inside the GRID target were obtained. The volume of normal tissue receiving 7.5 Gy was determined. Results The peak-to-valley ratios for GRID(2 cm)/GRID(3 cm)/Patient were 2.1/2.3/2.8, 1.7/1.5/2.8, 1.7/1.9/2.4, and 1.8/2.0/2.8 for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The peak-to-edge ratios for GRID(2 cm)/GRID(3 cm)/Patient were 2.8/3.2/5.4, 2.1/1.8/5.4, 2.0/2.2/3.9, 2.1/2.7/5.2 and for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The volume of normal tissue receiving 7.5 Gy was lowest in the TOMO2.5 cm plan (GRID(2 cm)/GRID(3 cm)/Patient = 54 cm(3)/19 cm(3)/10 cm(3)). The VMAT plans had the lowest delivery times (GRID(2 cm)/GRID(3 cm)/Patient = 17 min/8 min/9 min). Conclusion Our results present, for the first time, preliminary evidence comparing IMRT-GRID approaches which result in high-dose "islands" within a target, mimicking what is achieved with a conventional GRID block but without high-dose "tail" regions outside of the target. These approaches differ modestly in their ability to achieve high peak-to-edge ratios and also differ in delivery times.