Background 4D Flow MRI is a quantitative imaging technique to evaluate blood flow patterns; however, it is unclear how compressed sensing (CS) acceleration would impact aortic hemodynamic quantification in type B aortic dissection (TBAD). Purpose To investigate CS‐accelerated 4D Flow MRI performance compared to GRAPP‐accelerated 4D Flow MRI (GRAPPA) to evaluate aortic hemodynamics in TBAD. Study Type Prospective. Population Twelve TBAD patients, two volunteers. Field Strength/Sequence 1.5T, 3D time‐resolved cine phase‐contrast gradient echo sequence. Assessment GRAPPA (acceleration factor [R] = 2) and two CS‐accelerated (R = 7.7 [CS7.7] and 10.2 [CS10.2]) 4D Flow MRI scans were acquired twice for interscan reproducibility assessment. Voxelwise kinetic energy (KE), peak velocity (PV), forward flow (FF), reverse flow (RF), and stasis were calculated. Plane‐based mid‐lumen flows were quantified. Imaging times were recorded. Tests Repeated measures analysis of variance, Pearson correlation coefficients (r), intraclass correlation coefficients (ICC). P < 0.05 indicated statistical significance. Results The KE and FF in true lumen (TL) and PV in false lumen (FL) did not show difference among three acquisition types (P = 0.818, 0.065, 0.284 respectively). The PV and stasis in TL were higher, KE, FF, and RF in FL were lower, and stasis was higher in GRAPPA compared to CS7.7 and CS10.2. The RF was lower in GRAPPA compared to CS10.2. The correlation coefficients were strong in TL (r = [0.781–0.986]), and low to strong in FL (r = [0.347–0.948]). The ICC levels demonstrated moderate to excellent interscan reproducibility (0.732–0.989). The FF and net flow in mid‐descending aorta TL were significantly different between CS7.7 and CS10.2. Conclusion CS‐accelerated 4D Flow MRI has potential for clinical utilization with shorter scan times in TBAD. Our results suggest similar hemodynamic trends between acceleration types, but CS‐acceleration impacts KE, FF, RF, and stasis more in FL. Evidence Level: 1 Technical Efficacy: Stage 2

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The aim of this study is to investigate the applicability of the dual-venc (DV) 4D flow magnetic resonance imaging (MRI) to quantify the complex flow patterns in type B aortic dissection (TBAD). One GRAPPA-accelerated single-venc (SV) and one compressed-sensing (CS) accelerated DV 4D flow MRI sequences are used to scan all subjects, including twelve chronic TBAD patients and two volunteers. The scans are performed twice for the reproducibility assessment of the scan protocols. Voxelwise quantitative flow parameters including kinetic energy (KE), peak velocity (PV), forward and reverse flows (FF, RF) and stasis are calculated. High-venc (HV) data from the DV acquisition are separately analyzed. The scan time reduction by the CS-accelerated DV 4D flow MRI acquisition is 46.4% compared with the SV acquisition. The DV velocity-to-noise ratio (VNR) is higher compared with HV (p = 0.000). No true lumen (TL) parameter shows a significant difference among the acquisition types (p > 0.05). The false lumen (FL) RF is higher in SV compared with the DV acquisition (p = 0.009). The KE is higher (p = 0.038) and stasis is lower (p = 0.01) in HV compared with SV acquisition. All FL parameters except stasis are higher and stasis is lower in HV compared with DV acquisition (p < 0.05). Positive Pearson correlations among the acquisition types in TL and high agreements between the two scans for all acquisition types are observed except HV RF in the FL, which demonstrates a moderate agreement. The CS-accelerated DV 4D flow MRI may have utility in the clinical daily routine with shortened scan times and improved velocity measurements while providing high VNR in TBAD. The observed hemodynamic flow trends are similar between GRAPPA-accelerated SV and CS-accelerated DV 4D flow MRI acquisitions; however, parameters are more impacted by CS-accelerated HV protocol in FL, which may be secondary to the CS regularization effects.

Background The hemispherical aortic annuloplasty reconstructive technology (HAART) is an internal geometric annuloplasty ring designed to restore a natural elliptical shape to the aortic annulus as part of aortic valve repair. We present four‐dimensional flow hemodynamic analysis before and after implementation of the HAART ring in patients undergoing ascending aortic replacement. Methods Aortic hemodynamics over the cardiac cycle were visualized using time‐resolved three‐dimensional pathlines. Velocity streamlines tangent to the time‐resolved velocity vector field were used to demonstrate instantaneous aortic hemodynamics. Peak velocities, forward and retrograde flow were calculated at nine planes placed along the midline of the thoracic aorta. Systolic wall shear stress and peak viscous energy loss over the cardiac cycle were calculated. Results HAART patients displayed similar or improved flow profiles after surgery when compared to a patient undergoing ascending aortic replacement alone. Conclusion There may be a trend towards improved flow dynamics in patients undergoing HAART ring implantation.

The hemispherical aortic annuloplasty reconstructive technology (HAART) is an internal geometric annuloplasty ring designed to restore a natural elliptical shape to the aortic annulus as part of aortic valve repair. We present 4D flow hemodynamic analysis before and after implementation of the HAART ring in patients undergoing ascending aortic replacement. HAART patients displayed similar or improved flow profiles when compared to a patient undergoing ascending aortic replacement alone.