Abstract
Magnetic resonance imaging (MRI) can potentially be used for non-invasive screening of patients with stable angina pectoris to identify probable obstructive coronary artery disease. MRI-based coronary blood flow quantification has to date only been performed in a 2D fashion, limiting its clinical applicability. In this study, we propose a framework for coronary blood flow quantification using accelerated 4D flow MRI with respiratory motion correction and compressed sensing image reconstruction. We investigate its feasibility and repeatability in healthy subjects at rest. Fourteen healthy subjects received 8 times-accelerated 4D flow MRI covering the left coronary artery (LCA) with an isotropic spatial resolution of 1.0 mm3. Respiratory motion correction was performed based on 1) lung-liver navigator signal, 2) real-time monitoring of foot-head motion of the liver and LCA by a separate acquisition, and 3) rigid image registration to correct for anterior-posterior motion. Time-averaged diastolic LCA flow was determined, as well as time-averaged diastolic maximal velocity (VMAX) and diastolic peak velocity (VPEAK). 2D flow MRI scans of the LCA were acquired for reference. Scan-rescan repeatability and agreement between 4D flow MRI and 2D flow MRI were assessed in terms of concordance correlation coefficient (CCC) and coefficient of variation (CV). The protocol resulted in good visibility of the LCA in 11 out of 14 subjects (six female, five male, aged 28 ± 4 years). The other 3 subjects were excluded from analysis. Time-averaged diastolic LCA flow measured by 4D flow MRI was 1.30 ± 0.39 ml/s and demonstrated good scan-rescan repeatability (CCC/CV = 0.79/20.4%). Time-averaged diastolic VMAX (17.2 ± 3.0 cm/s) and diastolic VPEAK (24.4 ± 6.5 cm/s) demonstrated moderate repeatability (CCC/CV = 0.52/19.0% and 0.68/23.0%, respectively). 4D flow- and 2D flow-based diastolic LCA flow agreed well (CCC/CV = 0.75/20.1%). Agreement between 4D flow MRI and 2D flow MRI was moderate for both diastolic VMAX and VPEAK (CCC/CV = 0.68/20.3% and 0.53/27.0%, respectively). In conclusion, the proposed framework of accelerated 4D flow MRI equipped with respiratory motion correction and compressed sensing image reconstruction enables repeatable diastolic LCA flow quantification that agrees well with 2D flow MRI.
Highlights
The clinical evaluation of obstructive coronary artery disease (CAD) relies on a combined approach of catheter-based coronary artery angiography (CAG) and physiological testing with for example fractional flow reserve (FFR) or instantaneous wavefree ratio
A 4D flow MRI acquisition was performed with an isotropic spatial resolution of 1.0 mm3, covering the left coronary artery (LCA) in a 30-mm thick transversal slab
This acquisition was directly followed by a 2D flow MRI acquisition planned perpendicular to the LCA, with a spatial resolution of 1.0 × 1.0 mm2 and 6.0 mm slice thickness
Summary
The clinical evaluation of obstructive coronary artery disease (CAD) relies on a combined approach of catheter-based coronary artery angiography (CAG) and physiological testing with for example fractional flow reserve (FFR) or instantaneous wavefree ratio (iFR). MRI is a non-invasive, non-ionizing imaging technique that can reliably provide prognostic information in patients with CAD using stress-induced perfusion imaging (Motwani et al, 2018). MRI provides detailed anatomical information (Albrecht et al, 2018; Bustin et al, 2019; Roy et al, 2021) and can measure coronary flow (Hofman et al, 1996; Davis et al, 1997; Marcus et al, 1999; Johnson et al, 2008; Zhu et al, 2021), potentially enabling assessment of the coronary flow reserve (CFR). The potential of MRI to concurrently assess coronary anatomy, CFR and myocardial perfusion makes it a potential screening modality for accurate selection and planning of patients with SAP for percutaneous coronary intervention (PCI)
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