Artificial Intelligence Program, Cedars-Sinai Medical Center, Los Angeles, CA; Department of Medicine, UCLA School of Medicine, Los Angeles, CA.
Department of Medicine, UCLA School of Medicine, Los Angeles, CA; Cardiac Imaging, Cedars-Sinai Medical Center, Los Angeles, CA.
Semin Nucl Med. 2014 Jul;44(4):232-51. doi: 10.1053/j.semnuclmed.2014.04.003.
Nuclear cardiology instrumentation has evolved significantly in the recent years. Concerns about radiation dose and long acquisition times have propelled developments of dedicated high-efficiency cardiac SPECT scanners. Novel collimator designs, such as multipinhole or locally focusing collimators arranged in geometries that are optimized for cardiac imaging, have been implemented to enhance photon-detection sensitivity. Some of these new SPECT scanners use solid-state photon detectors instead of photomultipliers to improve image quality and to reduce the scanner footprint. These new SPECT devices allow dramatic up to 7-fold reduction in acquisition times or similar reduction in radiation dose. In addition, new hardware for photon attenuation correction allowing ultralow radiation doses has been offered by some vendors. To mitigate photon attenuation artifacts for the new SPECT scanners not equipped with attenuation correction hardware, 2-position (upright-supine or prone-supine) imaging has been proposed. PET hardware developments have been primarily driven by the requirements of oncologic imaging, but cardiac imaging can benefit from improved PET image quality and improved sensitivity of 3D systems. The time-of-flight reconstruction combined with resolution recovery techniques is now implemented by all major PET vendors. These new methods improve image contrast and image resolution and reduce image noise. High-sensitivity 3D PET without interplane septa allows reduced radiation dose for cardiac perfusion imaging. Simultaneous PET/MR hybrid system has been developed. Solid-state PET detectors with avalanche photodiodes or digital silicon photomultipliers have been introduced, and they offer improved imaging characteristics and reduced sensitivity to electromagnetic MR fields. Higher maximum count rate of the new PET detectors allows routine first-pass Rb-82 imaging, with 3D PET acquisition enabling clinical utilization of dynamic imaging with myocardial flow measurements for this tracer. The availability of high-end CT component in most PET/CT configurations enables hybrid multimodality cardiac imaging protocols with calcium scoring or CT angiography or both.
核医学仪器在近年来得到了显著发展。由于对辐射剂量和较长采集时间的担忧，专用高效心脏 SPECT 扫描仪得到了发展。新型准直器设计，如多针孔或局部聚焦准直器，采用优化心脏成像的几何形状排列，提高了光子探测灵敏度。其中一些新型 SPECT 扫描仪使用固态光子探测器代替光电倍增管，以提高图像质量并减小扫描仪的占地面积。这些新型 SPECT 设备允许采集时间减少 7 倍，或类似地减少辐射剂量。此外，一些供应商提供了用于光子衰减校正的新硬件，允许进行超低辐射剂量校正。为了减轻未配备衰减校正硬件的新型 SPECT 扫描仪中的光子衰减伪影，提出了 2 个位置（直立-仰卧或俯卧-仰卧）成像。PET 硬件的发展主要是由肿瘤成像的要求驱动的，但心脏成像可以受益于改进的 PET 图像质量和 3D 系统的灵敏度提高。飞行时间重建与分辨率恢复技术的结合现在由所有主要 PET 供应商实施。这些新方法提高了图像对比度和图像分辨率，并降低了图像噪声。无层间隔板的高灵敏度 3D PET 允许减少心脏灌注成像的辐射剂量。同时开发了 PET/MR 混合系统。采用雪崩光电二极管或数字硅光电倍增管的固态 PET 探测器已经问世，它们提供了改进的成像特性和对电磁 MR 场的敏感性降低。新型 PET 探测器的最大计数率提高，允许常规进行 Rb-82 首过成像，3D PET 采集能够使心肌血流测量的动态成像得到临床应用。大多数 PET/CT 配置中都具有高端 CT 组件，这使得能够进行具有钙评分或 CT 血管造影或两者结合的混合多模态心脏成像方案。
