Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450000, People's Republic of China.
Department of Radiation Oncology, University of California, San Francisco, CA, USA.
Radiat Oncol. 2020 Nov 7;15(1):257. doi: 10.1186/s13014-020-01698-x.
To assess the effects of various treatment planning parameters to identify the optimal gap distance for precise two-segment total body irradiation (TBI) using helical tomotherapy (HT) with fixed jaw mode.
Data of a treatment plan for 8 acute leukemia patients (height range: 109-130 cm) were analyzed. All patients underwent total-body computed tomography (CT) with 5-mm slice thickness. A lead wire, placed at 10 cm above the patella, was used to mark the boundary between the two segments. Target volumes and organs at risk were delineated using a Varian Eclipse 10.0 physician's workstation. Different distances between the lead wire and the boundary of the two targets were used. CT images were transferred to the HT workstation to design the treatment plans, by adjusting parameters, including the field width (FW; 2.5 cm, and 5 cm), pitch (0.287 and 0.430), modulation factor (1.8). The plans were superimposed to analyze the dose distributions in the overlap region when varying target gap distances, FWs, pitches to determine the optimal combinations.
The pitch did not affect the dose distribution in the overlap region. The dose distribution in the overlap region was mostly homogeneous when the target gap distance was equal to the FW. Increased FW diminished the effect of the target gap distance on the heterogeneous index of the overlap region.
In two-segment TBI treatments by HT with Helix mode, a gap distance equal to the FW may achieve optimal dose distribution in the overlap region.
评估各种治疗计划参数的效果，以确定使用螺旋断层放疗（HT）的固定机架模式进行精确的两段式全身照射（TBI）的最佳间隔距离。
分析了 8 例急性白血病患者（身高范围：109-130cm）的治疗计划数据。所有患者均接受了总身体计算机断层扫描（CT），层厚为 5mm。在髌骨上方 10cm 处放置一根导丝，用于标记两段之间的边界。使用瓦里安 Eclipse 10.0 医生工作站勾画靶区和危及器官。使用不同的导丝与两个靶区边界之间的距离。将 CT 图像传输到 HT 工作站，通过调整参数来设计治疗计划，包括射野宽度（FW；2.5cm 和 5cm）、螺距（0.287 和 0.430）、调制因子（1.8）。当改变靶区间隔距离、FW 和螺距以确定最佳组合时，叠加计划以分析重叠区域的剂量分布。
螺距不会影响重叠区域的剂量分布。当靶区间隔距离等于 FW 时，重叠区域的剂量分布基本均匀。增加 FW 会降低靶区间隔距离对重叠区域不均匀指数的影响。
在使用 Helix 模式的 HT 进行两段式 TBI 治疗时，间隔距离等于 FW 可能会在重叠区域实现最佳的剂量分布。
