Feasibility of Golden Angle Spiral Real-Time Phase Contrast MRI at 0.55T: A Single-Center Prospective Study

<b>Background</b>: Real-time phase-contrast magnetic resonance (RT-PCMR) imaging allows free-breathing assessment of blood flow across cardiac valves and vessels. However, the feasibility of free-breathing RT-PCMR on a mid-field (0.55T) MRI system has yet to be established. <b>Aim:</b> The primary objective of this study was to implement a RT-PCMR sequence using a dual-density golden-angle spiral readout with SENSE-based compressed sensing (CS) reconstruction on a 0.55T MRI system. The secondary objective was to evaluate the feasibility of this approach in an adult cohort comprising healthy volunteers and patients with cardiovascular disease. <b>Materials and Methods:</b> Data from 33 participants were included in the flow quantification analysis (healthy volunteers: <i>n</i> = 17, 9 females, mean age 30.4 ± 14.6 years; patients: <i>n</i> = 16, 11 females, mean age 45.9 ± 17.4 years), with breath-held (BH) segmented Cartesian PCMR used as the reference standard. <b>Results:</b> In volunteers, RT-PCMR showed good agreement for net flow, peak flow rate, and pulmonary-systemic flow ratio (Qp/Qs), without significant bias (<i>p</i> > 0.05) and slightly underestimated peak velocity [7.9% in the aorta and 8.6% in the main pulmonary artery (MPA)]. In patients, RT-PCMR slightly underestimated peak flow rate (aorta, 6.2%; MPA; 4.6%) and peak velocity (aorta,12.7%; MPA, 10.4%). A sub-analysis of six patients scanned at both 0.55T and 3T showed close agreement between field strengths. <b>Conclusions:</b> These results demonstrate the feasibility of our RT-PCMR sequence on a commercial 0.55T system.