Simultaneous 13N-Ammonia and gadolinium first-pass myocardial perfusion with quantitative hybrid PET-MR imaging: a phantom and clinical feasibility study

Muhummad Sohaib Nazir,Tobias Schaeffter,Hui Xue,Jim O’Doherty,Sébastien Roujol,Reza Razavi,Amedeo Chiribiri,Paul Marsden,Eliana Reyes,Sven Plein,Peter Kellman,Xenios Milidonis,Radhouene Neji,Sally F Barrington,Tevfik F Ismail,Sarah-May Gould

doi:10.1186/s41824-019-0062-6

Abstract

BackgroundPositron emission tomography (PET) is the non-invasive reference standard for myocardial blood flow (MBF) quantification. Hybrid PET-MR allows simultaneous PET and cardiac magnetic resonance (CMR) acquisition under identical experimental and physiological conditions. This study aimed to determine feasibility of simultaneous 13N-Ammonia PET and dynamic contrast-enhanced CMR MBF quantification in phantoms and healthy volunteers.MethodsImages were acquired using a 3T hybrid PET-MR scanner. Phantom study: MBF was simulated at different physiological perfusion rates and a protocol for simultaneous PET-MR perfusion imaging was developed. Volunteer study: five healthy volunteers underwent adenosine stress. 13N-Ammonia and gadolinium were administered simultaneously. PET list mode data was reconstructed using ordered subset expectation maximisation. CMR MBF was quantified using Fermi function-constrained deconvolution of arterial input function and myocardial signal. PET MBF was obtained using a one-tissue compartment model and image-derived input function.ResultsPhantom study: PET and CMR MBF measurements demonstrated high repeatability with intraclass coefficients 0.98 and 0.99, respectively. There was high correlation between PET and CMR MBF (r = 0.98, p < 0.001) and good agreement (bias − 0.85 mL/g/min; 95% limits of agreement 0.29 to − 1.98). Volunteer study: Mean global stress MBF for CMR and PET were 2.58 ± 0.11 and 2.60 ± 0.47 mL/g/min respectively. On a per territory basis, there was moderate correlation (r = 0.63, p = 0.03) and agreement (bias − 0.34 mL/g/min; 95% limits of agreement 0.49 to − 1.18).ConclusionSimultaneous MBF quantification using hybrid PET-MR imaging is feasible with high test repeatability and good to moderate agreement between PET and CMR. Future studies in coronary artery disease patients may allow cross-validation of techniques.

Highlights

Positron emission tomography (PET) is the non-invasive reference standard for myocardial blood flow (MBF) quantification
Intrasubject biological variation between PET and MR measurements can be avoided by performing simultaneous PET and cardiac magnetic resonance (CMR) imaging that provides an opportunity to ascertain the intrinsic magnitude of differences in MBF measurements without physiological variation (Nazir et al 2018)
CMR MBF measurements were highly repeatable with intraclass coefficients of 0.99

Summary

Introduction

Positron emission tomography (PET) is the non-invasive reference standard for myocardial blood flow (MBF) quantification. Positron emission tomography (PET) is considered the non-invasive reference standard for the quantification of absolute myocardial blood flow (MBF) (Bratis et al 2013). The interstudy variation for stress MBF has been reported to be 19% with PET (Kitkungvan et al 2017) and 12–40% with CMR (Brown et al 2018; Larghat et al 2013). It is unknown how much variation relates to intrinsic differences in modelling, imaging and tracer kinetics or due to biological variation. Intrasubject biological variation between PET and MR measurements can be avoided by performing simultaneous PET and CMR imaging that provides an opportunity to ascertain the intrinsic magnitude of differences in MBF measurements without physiological variation (Nazir et al 2018)

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