Department of Radiology, Kurume University Hospital, 67 Asahimachi, Kurume, Fukuoka, 830-0011, Japan.
Radiol Phys Technol. 2024 Mar;17(1):248-257. doi: 10.1007/s12194-023-00773-8. Epub 2024 Feb 9.
TomoTherapy involves image-guided radiation therapy (IGRT) using Mega-voltage CT (MVCT) for each treatment session. The acquired MVCT images can be utilized for the retrospective assessment of dose distribution. The TomoTherapy provides 18 distinct imaging conditions that can be selected based on a combination of algorithms, acquisition pitch, and slice interval. We investigated the accuracy of dose calculation and deformable image registration (DIR) depending on MVCT scan parameters and their effects on adaptive radiation therapy (ART). We acquired image values for density calibration tables (IVDTs) under 18 different MVCT conditions and compared them. The planning CT (pCT) was performed using a thoracic phantom, and an esophageal intensity-modulated radiation therapy (IMRT) plan was created. MVCT images of the thoracic phantom were acquired under each of the 18 conditions, and dose recalculation was performed. DIR was performed on the MVCT images acquired under each condition. The accuracy of DIR, depending on the MVCT scan parameters, was compared using the mean distance to agreement (MDA) and Dice similarity coefficient (DSC). The dose distribution calculated on the MVCT images was deformed using deformed vector fields (DVF). No significant differences were observed in the results of the 18 IVDTs. The esophageal IMRT plan also showed a small dose difference. Regarding verifying the DIR accuracy, the MDA increased, and the DSC decreased as the acquisition pitch and slice interval increased. The difference between the dose distributions after dose mapping was comparable to that before DIR. The MVCT scan parameters had little effect on ART.
TomoTherapy 采用图像引导放射治疗（IGRT），每次治疗都使用兆伏 CT（MVCT）。获取的 MVCT 图像可用于回顾性评估剂量分布。TomoTherapy 提供了 18 种不同的成像条件，可以根据算法、采集螺距和切片间隔的组合进行选择。我们研究了剂量计算和变形图像配准（DIR）的准确性，以及它们对自适应放射治疗（ART）的影响，取决于 MVCT 扫描参数。我们在 18 种不同的 MVCT 条件下获取了密度校准表（IVDT）的图像值，并进行了比较。在胸部体模上进行了计划 CT（pCT），并创建了食管强度调制放射治疗（IMRT）计划。在 18 种条件下分别采集了胸部体模的 MVCT 图像，并进行了剂量重新计算。在每种条件下采集的 MVCT 图像上进行了 DIR。使用平均差异（MDA）和骰子相似系数（DSC）比较了 DIR 准确性与 MVCT 扫描参数的关系。使用变形矢量场（DVF）对 MVCT 图像上计算的剂量分布进行变形。18 个 IVDT 的结果没有明显差异。食管 IMRT 计划也显示出较小的剂量差异。关于验证 DIR 准确性，随着采集螺距和切片间隔的增加，MDA 增加，DSC 降低。剂量映射后剂量分布的差异与 DIR 之前的差异相当。MVCT 扫描参数对 ART 的影响很小。
