Peak flow velocities in the ascending aorta—real-time phasecontrast magnetic resonance imaging vs. cine magnetic resonance imaging and echocardiography

This prospective study of eight healthy volunteers evaluates peak flow velocities (PFV) in the ascending aorta using real-time phase-contrast magnetic resonance imaging (MRI) in comparison to cine phase-contrast MRI and echocardiography. Flow measurements by echocardiography and cine phase-contrast MRI with breath-holding were performed according to clinical standards. Real-time phase-contrast MRI at 40 ms temporal resolution and 1.3 mm in-plane resolution was based on highly undersampled radial fast low-angle shot (FLASH) sequences with image reconstruction by regularized nonlinear inversion (NLINV). Evaluations focused on the determination of PFV. Linear regressions and Bland-Altman plots were used for comparisons of methods. When averaged across subjects, real-time phase-contrast MRI resulted in PFV of 120±20 cm s⁻¹ (mean ± SD) in comparison to 122±16 cm s⁻¹ for cine MRI and 124±20 cm s⁻¹ for echocardiography. The maximum deviations between real-time phase-contrast MRI and echocardiography ranged from –20 to +14 cm s⁻¹ (cine MRI: –10 to +12 cm s⁻¹). Thus, in general, real-time phase-contrast MRI of cardiac outflow revealed quantitative agreement with cine MRI and echocardiography. The advantages of real-time MRI are measurements during free breathing and access to individual cardiac cycles.