Prone position acquisition is more effective than changing reconstruction method for regional myocardial 123I metaiodobenzylguanidine (MIBG) SPECT uptake

Objectives 123I metaiodobenzylguanidine (MIBG) has been applied for estimating cardiac sympathetic nervous innervation in heart failure and arrhythmogenic heart disease. However, MIBG SPECT has heterogeneous distribution mainly due to high physiological MIBG uptakes in liver. Prone position acquisition and ordered subset expectation maximization method (OSEM) reconstruction might effective for myocardial MIBG uptake, with separation from high liver uptake similarly to myocardial perfusion SPECT. However, this possibility has not been tested. The purpose of this study was to investigate which approach is effective to improve MIBG image uptake. We also compared MIBG images to high quality 11C hydroxyephedrine (HED) PET/CT as standard.

Methods Ten healthy volunteers (age 37±10y, body mass index 22±2) underwent prone and supine 123I MIBG and 11C HED PET. Relative regional tracer uptake was estimated in early MIBG and HED PET. MIBG images were reconstructed using filtered back projection (FBP) and OSEM. MIBG imaging and 11C HED PET images were divided into 17 segments, and were grouped 4 regions including anterior, inferior, septum, and lateral wall. In each region, inferior/anterior ratio was calculated.

Results In standard supine position, there was no significant differences in inferior/anterior ratio between FBP and OSEM reconstruction (83.8±5.7% vs 85.0±8.0, P=0.72). Prone MIBG SPECT showed significantly higher inferior/anterior uptake ratio compared to supine imaging (92.2±7.2% vs 83.8±5.7%, P<0.001). However, iHED PET still showed higher uptake ratio compared to prone MIBG (103.9±8.0% vs. 92.2±7.2%, P<0.001).

Conclusions Changing reconstruction from FBP to OSEM did not improve inferior MIBG uptake. In contrast, prone 123I MIBG SPECT improved inferior uptake compared to supine data acquisition. Therefore, prone data acquisition might be more effective approach to evaluate regional abnormalities of 123I MIBG SPECT images.