Division of Radiology, Department of Medical Technology, Kyushu University Hospital, 3-1-1, Maidashi Higashi-Ku, Fukuoka, 812-8582, Japan.
Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, 3-1-1 Tsushima-Naka, Kita-Ku, Okayama, 700-8530, Japan.
Radiol Phys Technol. 2023 Dec;16(4):497-505. doi: 10.1007/s12194-023-00737-y. Epub 2023 Sep 15.
This study evaluated the validity of internal target volumes (ITVs) defined by three- (3DCT) and four-dimensional computed tomography (4DCT), and subsequently compared them with actual movements during treatment. Five patients with upper lobe lung tumors were treated with stereotactic body radiotherapy (SBRT) at 48 Gy in four fractions. Planning 3DCT images were acquired with peak-exhale and peak-inhale breath-holds, and 4DCT images were acquired in the cine mode under free breathing. Cine images were acquired using an electronic portal imaging device during irradiation. Tumor coverage was evaluated based on the manner in which the peak-to-peak breathing amplitude on the planning CT covered the range of tumor motion (± 3 SD) during irradiation in the left-right, anteroposterior, and cranio-caudal (CC) directions. The mean tumor coverage of the 4DCT-based ITV was better than that of the 3DCT-based ITV in the CC direction. The internal margin should be considered when setting the irradiation field for 4DCT. The proposed 4DCT-based ITV can be used as an efficient approach in free-breathing SBRT for upper-lobe tumors of the lung because its coverage is superior to that of 3DCT.
本研究评估了三维 CT（3DCT）和四维 CT（4DCT）定义的内部靶区（ITV）的有效性，并随后将其与治疗期间的实际运动进行了比较。五例上叶肺癌患者接受立体定向体部放疗（SBRT），48Gy 分 4 次。采用峰值呼气和峰值吸气屏气采集计划 3DCT 图像，并在自由呼吸下采用电影模式采集 4DCT 图像。在照射过程中使用电子射野影像装置采集电影图像。基于计划 CT 上的峰峰呼吸幅度覆盖照射过程中肿瘤运动范围（±3 SD）的方式评估肿瘤覆盖，方向为左右、前后和头尾（CC）。4DCT 基于 ITV 的肿瘤平均覆盖范围优于 3DCT 基于 ITV 的覆盖范围。在设置 4DCT 照射野时应考虑内部边界。对于肺部上叶肿瘤的自由呼吸 SBRT，建议使用基于 4DCT 的 ITV，因为它的覆盖范围优于 3DCT。
