Chen George T Y, Kung Jong H, Rietzel Eike
Department of Radiation Oncology, Massachusetts General Hospital, Boston, Mass. , USA.
Front Radiat Ther Oncol. 2007;40:59-71. doi: 10.1159/000106028.
Four-dimensional CT acquisition is commercially available, and provides important information on the shape and trajectory of the tumor and normal tissues. The primary advantage of four-dimensional imaging over light breathing helical scans is the reduction of motion artifacts during scanning that can significantly alter tumor appearance. Segmentation, image registration, visualization are new challenges associated with four-dimensional data sets because of the overwhelming increase in the number of images. Four-dimensional dose calculations, while currently laborious, provide insights into dose perturbations due to organ motion. Imaging before treatment (image guidance) improves accuracy of radiation delivery, and recording transmission images can provide a means of verifying gated delivery.
四维CT采集在商业上是可行的，并且能提供有关肿瘤和正常组织的形状及轨迹的重要信息。与浅呼吸螺旋扫描相比，四维成像的主要优势在于减少扫描过程中的运动伪影，而这种伪影会显著改变肿瘤的外观。由于图像数量的大幅增加，分割、图像配准、可视化成为与四维数据集相关的新挑战。四维剂量计算虽然目前很繁琐，但能深入了解器官运动引起的剂量扰动。治疗前成像（图像引导）可提高放射治疗的准确性，记录透射图像能提供一种验证门控放射治疗的方法。
