The norepinephrine transporter (NET) is a major target for the evaluation of the cardiac sympathetic nerve system in patients with heart failure and Parkinson's disease. It is also used in the therapeutic applications against certain types of neuroendocrine tumors, as exemplified by the clinically used 123/131I-MIBG as theranostic single-photon emission computed tomography (SPECT) agent. With the development of more advanced positron emission tomography (PET) technology, more radiotracers targeting NET have been reported, with superior temporal and spatial resolutions, along with the possibility of functional and kinetic analysis. More recently, fluorine-18-labelled NET tracers have drawn increasing attentions from researchers, due to their longer radiological half-life relative to carbon-11 (110 min vs. 20 min), reduced dependence on on-site cyclotrons, and flexibility in the design of novel tracer structures. In the heart, certain NET tracers provide integral diagnostic information on sympathetic innervation and the nerve status. In the central nervous system, such radiotracers can reveal NET distribution and density in pathological conditions. Most radiotracers targeting cardiac NET-function for the cardiac application consistent of derivatives of either norepinephrine or MIBG with its benzylguanidine core structure, e.g. 11C-HED and 18F-LMI1195. In contrast, all NET tracers used in central nervous system applications are derived from clinically used antidepressants. Lastly, possible applications of NET as selective tracers over organic cation transporters (OCTs) in the kidneys and other organs controlled by sympathetic nervous system will also be discussed.

中文翻译：

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靶向去甲肾上腺素转运蛋白的放射性示踪剂的最新进展：结构发展和放射性标记改进。

去甲肾上腺素转运蛋白 (NET) 是评估心力衰竭和帕金森病患者心脏交感神经系统的主要目标。它还用于治疗某些类型的神经内分泌肿瘤，例如临床使用的 123/131I-MIBG 作为治疗诊断单光子发射计算机断层扫描 (SPECT) 试剂。随着更先进的正电子发射断层扫描 (PET) 技术的发展，已经报道了更多针对 NET 的放射性示踪剂，具有卓越的时间和空间分辨率，以及功能和动力学分析的可能性。最近，氟 18 标记的 NET 示踪剂引起了研究人员越来越多的关注，因为它们的放射半衰期相对于碳 11（110 分钟与 20 分钟）更长，减少对现场回旋加速器的依赖，以及设计新型示踪剂结构的灵活性。在心脏中，某些 NET 示踪剂提供有关交感神经支配和神经状态的完整诊断信息。在中枢神经系统中，这种放射性示踪剂可以揭示病理条件下的 NET 分布和密度。大多数针对心脏 NET 功能的放射性示踪剂与具有苄基胍核心结构的去甲肾上腺素或 MIBG 衍生物一致，例如 11C-HED 和 18F-LMI1195。相比之下，中枢神经系统应用中使用的所有 NET 示踪剂均来自临床使用的抗抑郁药。最后，