New SPECT and PET Radiopharmaceuticals for Imaging Cardiovascular Disease

Table 9

SPECT Radiotracers for Imaging Autonomic Dysfunction in Heart Failure.

^123I-Meta-Iodobenzyl Guanidine (^123I-MIBG); (i) ^123I-MIBG targets presynaptic sympathetic neurons; (ii) differs from physiological norepinephrine in three key ways (Figure 11): (1) does not interact with post-synaptic 𝛼- or 𝛽-adrenergic receptors; (2) does not undergo post-synaptic catechol-O-methyl transferase; (COMT) metabolism into normetanephrine (NMN); (3) does not interact with α2c presynaptic receptors that regulate norepinephrine; release; (iii) conversely ^123I-MIBG does mimic norepinephrine in its escape from the synaptic cleft into the blood pool