Haqqi Firyal Dhiyaul, Sudarmaji Arief, Wibowo Wahyu Edy, Nasution Nuruddin, Handoko Handoko, Fauzia Annisa Rahma, Qudsi Jihadil, Pawiro Supriyanto Ardjo
Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, West Java, Indonesia.
Department of Radiation Oncology, Faculty of Medicine, Universitas Indonesia, dr. Cipto Mangunkusumo General Hospital, Jakarta, Indonesia.
Rep Pract Oncol Radiother. 2022 May 19;27(2):360-370. doi: 10.5603/RPOR.a2022.0029. eCollection 2022.
This study aimed to evaluate the target volume and dose accuracy in intrafraction cases using 4-dimensional imaging modalities and an in-house dynamic thorax phantom. Intrafraction motion can create errors in the definition of target volumes, which can significantly affect the accuracy of radiation delivery. Motion management using 4-dimensional modalities is required to reduce the risk.
Two variations in both breathing amplitude and target size were applied in this study. From these variations, internal target volume (ITVs) contoured in 10 phases of 4D-CT (ITV), average intensity projection (AIP), and mid-ventilation (Mid-V) images were reconstructed from all 4D-CT datasets as reference images. Free-breathing (FB), augmentation free-breathing (Aug-FB), and static images were also acquired using the 3D-CT protocol for comparisons. In dose evaluations, the 4D-CBCT modality was applied before irradiation to obtain position correction. Then, the dose was evaluated with Gafchromic film EBT3.
The ITV, AIP, and Mid-V provide GTVs that match the static GTV. The AIP and Mid-V reference images allowed reductions in ITVs and PTVs without reducing the range of target movement areas compared to FB and Aug-FB images with varying percentages in the range of 29.17% to 48.70%. In the dose evaluation, the largest discrepancies between the measured and planned doses were 10.39% for the FB images and 9.21% for the Aug-FB images.
The 4D-CT modality can enable accurate definition of the target volume and reduce the PTV. Furthermore, 4D-CBCT provides localization images during registration to facilitate position correction and accurate dose delivery.
本研究旨在使用四维成像模态和内部动态胸部体模评估分次治疗过程中靶区体积和剂量准确性。分次治疗过程中的运动可导致靶区体积定义出现误差，这会显著影响放疗的准确性。需要采用四维模态进行运动管理以降低风险。
本研究应用了呼吸幅度和靶区大小的两种变化。基于这些变化，从所有四维CT数据集中重建在四维CT的10个时相（ITV）、平均强度投影（AIP）和中期通气（Mid-V）图像上勾勒出的内部靶区体积（ITV），作为参考图像。还使用三维CT协议采集了自由呼吸（FB）、增强自由呼吸（Aug-FB）和静态图像用于比较。在剂量评估中，照射前应用四维CBCT模态以获得位置校正。然后，使用Gafchromic EBT3胶片评估剂量。
ITV、AIP和Mid-V提供的大体靶区（GTV）与静态GTV匹配。与FB和Aug-FB图像相比，AIP和Mid-V参考图像可减少ITV和计划靶区（PTV），且不减小靶区运动范围，减少百分比在29.17%至48.70%范围内。在剂量评估中，FB图像测量剂量与计划剂量之间的最大差异为10.39%，Aug-FB图像为9.21%。
四维CT模态能够准确界定靶区体积并减小PTV。此外，四维CBCT在配准过程中提供定位图像，便于位置校正和精确的剂量投送。
