Department of Nuclear Medicine, Scientific Institute San Raffaele, Segrate, Milan, Italy.
Semin Nucl Med. 2012 Sep;42(5):289-307. doi: 10.1053/j.semnuclmed.2012.04.001.
Hybrid positron emission tomography (PET)/computed tomography (CT) scanners combine, in a unique gantry, 2 of the most important diagnostic imaging systems, a CT and a PET tomograph, enabling anatomical (CT) and functional (PET) studies to be performed in a single study session. Furthermore, as the 2 scanners use the same spatial coordinate system, the reconstructed CT and PET images are spatially co-registered, allowing an accurate localization of the functional signal over the corresponding anatomical structure. This peculiarity of the hybrid PET/CT system results in improved tumor characterization for oncological applications, and more recently, it was found to be also useful for target volume definition (TVD) and treatment planning in radiotherapy (RT) applications. In fact, the use of combined PET/CT information has been shown to improve the RT treatment plan when compared with that obtained by a CT alone. A limiting factor to the accuracy of TVD by PET/CT is organ and tumor motion, which is mainly due to patient respiration. In fact, respiratory motion has a degrading effect on PET/CT image quality, and this is also critical for TVD, as it can lead to possible tumor missing or undertreatment. Thus, the management of respiratory motion is becoming an increasingly essential component in RT treatment planning; indeed, it has been recognized that the use of personalized motion information can improve TVD and, consequently, permit increased tumor dosage while sparing surrounding healthy tissues and organs at risk. This review describes the methods used for motion management in PET/CT for radiation treatment planning. The article covers the following: (1) problems caused by organ and lesion motion owing to respiration, and the artifacts generated on CT, PET, and PET/CT images; (2) data acquisition and processing techniques used to manage respiratory motion in PET/CT studies; and (3) the use of personalized motion information for TVD and radiation treatment planning.
正电子发射断层扫描（PET）/计算机断层扫描（CT）混合扫描仪在一个独特的龙门架中结合了两种最重要的诊断成像系统，即 CT 和 PET 体层扫描仪，使解剖学（CT）和功能（PET）研究能够在单次研究中进行。此外，由于这两种扫描仪使用相同的空间坐标系，重建的 CT 和 PET 图像在空间上是配准的，允许在相应的解剖结构上对功能信号进行准确的定位。这种混合 PET/CT 系统的独特性导致了肿瘤特征的改善，特别是在肿瘤学应用中，最近发现它在放射治疗（RT）应用中的靶区定义（TVD）和治疗计划中也很有用。事实上，与单独使用 CT 相比，联合使用 PET/CT 信息可以改善 RT 治疗计划。影响 PET/CT 靶区定义准确性的一个限制因素是器官和肿瘤运动，这主要是由于患者呼吸引起的。事实上，呼吸运动对 PET/CT 图像质量有降低作用，这对 TVD 也很关键，因为它可能导致肿瘤漏诊或治疗不足。因此，管理呼吸运动正在成为 RT 治疗计划中越来越重要的组成部分；事实上，人们已经认识到，使用个性化的运动信息可以改善 TVD，从而在保护周围健康组织和器官的同时增加肿瘤剂量。本文综述了用于 PET/CT 放射治疗计划的运动管理方法。本文涵盖以下内容：（1）呼吸引起的器官和病变运动以及 CT、PET 和 PET/CT 图像上产生的伪影所引起的问题；（2）用于管理 PET/CT 研究中呼吸运动的数据采集和处理技术；（3）个性化运动信息在 TVD 和放射治疗计划中的应用。
