Torres Espallardo I
Servicio de Medicina Nuclear-Área de Imagen Médica, Hospital Universitario y Politécnico La Fe, Valencia, España.
Radiologia. 2017 Sep-Oct;59(5):431-445. doi: 10.1016/j.rx.2016.10.010. Epub 2017 Jan 12.
Since it was first introduced, the main goal of PET/CT has been to provide both PET and CT images with high clinical quality and to present them to radiologists and specialists in nuclear medicine as a fused, perfectly aligned image. The use of fused PET and CT images quickly became routine in clinical practice, showing the great potential of these hybrid scanners. Thanks to this success, manufacturers have gone beyond considering CT as a mere attenuation corrector for PET, concentrating instead on design high performance PET and CT scanners with more interesting features. Since the first commercial PET/CT scanner became available in 2001, both the PET component and the CT component have improved immensely. In the case of PET, faster scintillation crystals with high stopping power such as LYSO crystals have enabled more sensitive devices to be built, making it possible to reduce the number of undesired coincidence events and to use time of flight (TOF) techniques. All these advances have improved lesion detection, especially in situations with very noisy backgrounds. Iterative reconstruction methods, together with the corrections carried out during the reconstruction and the use of the point-spread function, have improved image quality. In parallel, CT instrumentation has also improved significantly, and 64- and 128-row detectors have been incorporated into the most modern PET/CT scanners. This makes it possible to obtain high quality diagnostic anatomic images in a few seconds that both enable the correction of PET attenuation and provide information for diagnosis. Furthermore, nowadays nearly all PET/CT scanners have a system that modulates the dose of radiation that the patient is exposed to in the CT study in function of the region scanned. This article reviews the underlying physics of PET and CT imaging separately, describes the changes in the instrumentation and standard protocols in a combined PET/CT system, and finally points out the most important advances in this hybrid imaging modality.
自首次推出以来，PET/CT的主要目标一直是提供具有高临床质量的PET和CT图像，并将它们作为融合且完美对齐的图像呈现给放射科医生和核医学专家。融合的PET和CT图像的使用很快在临床实践中成为常规操作，显示出这些混合扫描仪的巨大潜力。由于这一成功，制造商不再仅仅将CT视为PET的单纯衰减校正器，而是专注于设计具有更有趣功能的高性能PET和CT扫描仪。自2001年第一台商用PET/CT扫描仪问世以来，PET组件和CT组件都有了巨大改进。就PET而言，具有高阻止本领的更快闪烁晶体，如LYSO晶体，使得能够制造出更灵敏的设备，从而有可能减少不需要的符合事件数量并使用飞行时间（TOF）技术。所有这些进展都改善了病变检测，特别是在背景噪声很大的情况下。迭代重建方法，连同重建过程中进行的校正以及点扩散函数的使用，都提高了图像质量。与此同时，CT仪器也有了显著改进，64排和128排探测器已被纳入最现代的PET/CT扫描仪中。这使得能够在几秒钟内获得高质量的诊断性解剖图像，既能够校正PET衰减，又能提供诊断信息。此外，如今几乎所有PET/CT扫描仪都有一个系统，该系统根据扫描区域调节患者在CT检查中所接受的辐射剂量。本文分别回顾了PET和CT成像的基础物理学，描述了组合式PET/CT系统中仪器设备和标准协议的变化，最后指出了这种混合成像模式的最重要进展。
