SPECT vs. PET in cardiac innervation imaging: clash of the titans

Abstract

PurposeWe aim to provide an overview of the conventional single photon emission computed tomography (SPECT) and emerging positron emission tomography (PET) catecholamine analogue tracers for assessing myocardial nerve integrity, in particular focusing on 18F-labeled tracers.ResultsIncreasingly, the cardiac sympathetic nervous system (SNS) is being studied by non-invasive molecular imaging approaches. Forming the backbone of myocardial SNS imaging, the norepinephrine (NE) transporter at the sympathetic nerve terminal plays a crucial role for visualizing denervated myocardium: in particular, the single-photon-emitting NE analogue 123I-meta-Iodobenzylguanidine (123I-mIBG) has demonstrated favorable results in the identification of patients at a high risk for cardiac death. However, cardiac neuronal PET agents offer several advantages including improved spatio-temporal resolution and intrinsic quantifiability. Compared to their 11C-labeled counterparts with a short half-life (20.4 min), novel 18F-labeled PET imaging agents to assess myocardial nerve integrity have the potential to revolutionize the field of SNS molecular imaging. The longer half-life of 18F (109.8 min) allows for more flexibility in the study design and delivery from central cyclotron facilities to smaller hospitals may lead to further cost reduction. A great deal of progress has been made by the first in-human studies of such 18F-labeled SNS imaging agents. Moreover, dedicated animal platforms open avenues for further insights into the handling of radiolabeled catecholamine analogues at the sympathetic nerve terminal.Conclusions18F-labeled imaging agents demonstrate key properties for mapping cardiac sympathetic nerve integrity and might outperform current SPECT-based or 11C-labeled tracers in the long run.

Initial Evaluation of AF78: a Rationally Designed Fluorine-18-Labelled PET Radiotracer Targeting Norepinephrine Transporter

“…In recent years, the development of positron emission tomography (PET) technology has increasingly been explored for cardiac and other applications due to its higher spatial and temporal resolution compared to single photon emission computed tomography (SPECT) [1]. This allows for a broader range of potential functional and kinetic analyses [2].…”

I-123-MIBG cardiac innervation imaging in patients with atrial fibrillation

“…20 The natural alternative for MIBG-CZT-SPECT-CT technique could be PET-CT. Taking into account its high sensitivity, spatial resolution, existing advanced software for reconstruction and fusion, proved ability to image small uptake areas within heart (for example, for identification of high-risk atherosclerotic plaques in coronary arteries 21 ), and advanced development of new F-18 labeled tracers of cardiac innervation, 22 PET-CT has a high potential to apply to atrial diagnostics.…”

Cardiac innervation imaging as a risk stratification tool for potential device therapy candidates

“…Taken together, those cardiac nerve imaging agents may allow for a precise assessment of sympathetic neurotransmission in the failing heart. 5,6 As a a scintigraphic approach, 123 I-metaiodobenzylguanidine ( 123 I-mIBG) has been recently Food and Drug Administration approved and is extensively used in clinical practice. [7][8][9] However, in recent years, the field is expanding, in particular as cardiac neuronal PET imaging agents may offer an even more thorough evaluation of cardiac nerve integrity, mainly due an increased spatio-temporal resolution and the capability of quantification.…”

“…Notably, introduction of novel 18 F SNS imaging agents, such as 18 F-LMI1195, may overcome these limitations: the long physical halflife of 110 min allows for the use of delivery systems from central cyclotron facilities or even distribution by commercial vendors, which has proven to be cost-effective for the most commonly used imaging agent in nuclear oncology, 2-deoxy-2-18 F-fluoro-D-glucose. 5 However, if such cardiac nerve SPECT/PET probes should be one day become routinely available in the clinic to identify patients at highest risk for cardiac events, a precise understanding of the exact catecholamine radiotracer handling of such ''false neurotransmitters'' at the nerve terminal is indispensable. Thus, efforts in recent years aimed to provide deeper insights of cardiac retention kinetics on a subcellular level, which may be fundamental for a proper interpretation of imaging results.…”

“…14,15 Such a malfunction is in contradistinction to 65% of the patients, which will never have an appropriate ICD discharge. 5,16,17 Spearheaded by Scrima et al in a multicentric setting, 81 patients suffering from either ischemic or non-ischemic cardiomyopathy and a LVEF B 35% were enrolled. None of the included patients had any previous history of malignant ventricular arrhythmias.…”