Department of Radiation Medicine, Princess Margaret Hospital, University Health Network, Toronto, ON, Canada.
Int J Radiat Oncol Biol Phys. 2011 May 1;80(1):97-102. doi: 10.1016/j.ijrobp.2010.01.042.
To assess the movement of rectum, mesorectum, and rectal primary during a course of preoperative chemoradiotherapy.
Seventeen patients with Stage II or III rectal cancer had a planning CT scan with rectal contrast before commencement of preoperative chemoradiation. The scan was repeated during Weeks 1, 3, and 5 of chemoradiation. The rectal primary (gross tumor volume), rectum, mesorectum, and bladder were contoured on all four scans. An in-house biomechanical model-based deformable image registration technique, Morfeus, was used to measure the three-dimensional spatial change in these structures after bony alignment. The required planning target volume margin for this spatial change, after bone alignment, was also calculated.
Rectal contrast was found to introduce a systematic error in the position of all organs compared with the noncontrast state. The largest change in structures during radiotherapy was in the anterior and posterior directions for the mesorectum and rectum and in the superior and inferior directions for the gross tumor volume. The planning target volume margins required for internal movement for the mesorectum based on the three scans acquired during treatment are 4 mm right, 5 mm left, 7 mm anterior, and 6 mm posterior. For the rectum, values were 8 mm right, 8 mm left, 8 mm anterior, and 9 mm posterior. The greatest movement of the rectum occurred in the upper third.
Contrast is no longer used in CT simulation. Assuming bony alignment, a nonuniform margin of 8 mm anteriorly, 9 mm posteriorly, and 8 mm left and right is recommended.
评估直肠、直肠系膜和直肠原发肿瘤在术前放化疗过程中的运动情况。
17 例 II 期或 III 期直肠癌患者在术前放化疗前进行了直肠对比增强 CT 扫描。在放化疗的第 1、3 和 5 周重复扫描。在所有四次扫描中对直肠原发肿瘤（大体肿瘤体积）、直肠、直肠系膜和膀胱进行了轮廓勾画。使用 Morfeus 内部基于生物力学模型的变形图像配准技术测量这些结构在骨性配准后的三维空间变化。还计算了该空间变化后（骨性配准后）所需的计划靶区边界。
与非对比状态相比，直肠对比会导致所有器官的位置出现系统误差。在放疗过程中，结构变化最大的是直肠系膜和直肠的前后方向，以及大体肿瘤体积的上下方向。基于治疗期间获得的三次扫描，直肠系膜的内部运动所需的计划靶区边界为右侧 4 毫米、左侧 5 毫米、前侧 7 毫米和后侧 6 毫米。对于直肠，值为右侧 8 毫米、左侧 8 毫米、前侧 8 毫米和后侧 9 毫米。直肠的最大运动发生在上三分之一。
CT 模拟不再使用对比剂。假设骨性配准，建议采用非均匀边界，前后方向为 8 毫米，后前方向为 9 毫米，左右方向为 8 毫米。
