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Balanced steady-state free precession (bSSFP) MRI sequences provide images with a high signal-to-noise ratio and T2/T1 contrast1. Phase-cycled (PC) bSSFP, which refers to multiple acquisitions with different linear phase increments of the radiofrequency (RF) pulse, can be used for artifact removal and quantitative parametric mapping. For this application, the signal phase is an indispensable source of information. In contrast to early publications, contradictory mathematical descriptions of the PC-bSSFP signal model have been reported. While the magnitude is typically well described, the signal phase is often not directly derived from the Bloch equations, leading to inaccurate signal descriptions. This is particularly relevant for multi-compartment systems where bSSFP profile asymmetries can be observed. This letter emphasizes the importance of accurate phase definitions to describe the bSSFP profile, by providing an intuitive derivation and an experimental validation using single and two-compartment phantoms., Comment: Submitted to Magn. Reson. Med

Objectives: Paravalvular leakage (PVL) and eccentric aortic regurgitation remain a major clinical concern in patients receiving transcatheter aortic valve replacement (TAVR), and regurgitant volume remains the main readout parameter in clinical assessment. In this work we investigate the effect of jet origin and trajectory of mild aortic regurgitation on left ventricular hemodynamics in a porcine model. Methods: A pig model of mild aortic regurgitation/PVL was established by transcatheter piercing and dilating the non-coronary (NCC) or right coronary cusp (RCC) of the aortic valve close to the valve annulus. The interaction between regurgitant blood and LV hemodynamics was assessed by 4D flow cardiovascular MRI. Results: Six RCC, six NCC, and two control animals were included in the study and with one dropout in the NCC group, the success rate of model creation was 93%. Regurgitant jets originating from NCC were directed along the ventricular side of the anterior mitral leaflet and integrated well into the diastolic vortex forming in the left ventricular outflow tract. However, jets from the RCC were orientated along the septum colliding with flow within the vortex, and progressing down to the apex. As a consequence, the presence as well as the area of the vortex was reduced at the site of impact compared to the NCC group. Impairment of vortex formation was localized to the area of impact and not the entire vortex ring. Blood from the NCC jet was largely ejected during the following systole, whereas ejection of large portion of RCC blood was protracted. Conclusions: Even for mild regurgitation, origin and trajectory of the regurgitant jet does cause a different effect on LV hemodynamics. Septaly oriented jets originating from RCC collide with the diastolic vortex, reduce its size, and reach the apical region of the left ventricle where blood resides extendedly. Hence, RCC jets display hemodynamic features which may have a potential negative impact on the long-term burden to the heart., Frontiers in Cardiovascular Medicine, 8, ISSN:2297-055X