Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Pract Radiat Oncol. 2011 Jul-Sep;1(3):152-5. doi: 10.1016/j.prro.2011.01.002. Epub 2011 May 6.
In computed tomography (CT)-guided radiation treatment planning, an accurate assessment of a patient's external contour is needed to determine the number of monitor units appropriate to treat a target volume to the prescribed dose. When obese patients are imaged, even using a large-bore CT scanner, lateral tissues frequently fall outside the field of view of the CT scanner, which makes it difficult to accurately calculate the dose needed for lateral or oblique treatment fields. We aimed to develop a technique to capture the external contour of patients in whom traditional simulation techniques would fail to capture part of the anatomy.
The following technique was used in multiple patients. The patient was centered on the CT couch, and an isocenter was placed. The initial scan was obtained with the isocenter at the central position on the table. Two subsequent scans were obtained with the patient first shifted right on the table and then shifted left. The 3 CT scans were fused using a CT-CT cross-correlation algorithm. The accuracy of the scans was reviewed manually. Using the fused scans, lateral tissues were contoured on the primary scan and assigned a density of 1 g/cm(3).
With this technique, each patient's entire body contour was available on a single fused scan. The availability of the entire body contour on the scan allowed for treatment planning with a 360-degree freedom for external beam placement.
This novel approach of fusing multiple CT scans allows for the external anatomy of obese patients to be completely captured. The increase in available beam angles made possible by this approach can optimize external beam treatment planning, including planning for intensity-modulated radiation therapy.
在计算机断层扫描（CT）引导的放射治疗计划中，需要准确评估患者的外部轮廓，以确定治疗靶体积至规定剂量所需的监测单位数量。当肥胖患者进行成像时，即使使用大孔径 CT 扫描仪，侧面组织也经常超出 CT 扫描仪的视野，这使得难以准确计算侧面或斜角治疗场所需的剂量。我们旨在开发一种技术，以捕获传统模拟技术无法捕获部分解剖结构的患者的外部轮廓。
在多个患者中使用了以下技术。将患者置于 CT 检查台上，并放置等中心点。首先在等中心点位于桌子中央位置时获取初始扫描。然后让患者先在桌子上向右移动，然后再向左移动，分别进行两次后续扫描。使用 CT-CT 交叉相关算法融合这 3 次 CT 扫描。手动审查扫描的准确性。使用融合扫描，在主扫描上对侧面组织进行轮廓，并将其密度分配为 1 g/cm(3)。
通过该技术，每位患者的整个身体轮廓都可在单个融合扫描中获得。扫描中整个身体轮廓的可用性允许进行 360 度自由的外部束放置的治疗计划。
这种融合多个 CT 扫描的新方法可以完全捕获肥胖患者的外部解剖结构。这种方法增加了可用光束角度，可以优化外部束治疗计划，包括调强放射治疗计划。
