Parametric Hemodynamic 4D Flow MRI Maps for the Characterization of Chronic Thoracic Descending Aortic Dissection

Abstract

Background: Systematic evaluation of complex flow in the true lumen and false lumen (TL, FL) is needed to better understand which patients with chronic descending aortic dissection (DAD) are predisposed to complications. Purpose: To develop quantitative hemodynamic maps from 4D flow MRI for evaluating TL and FL flow characteristics. Study Type: Retrospective. Population: In all, 20 DAD patients (age = 60 AE 11 years; 12 male) (six medically managed type B AD [TBAD], 14 repaired type A AD [rTAAD] now with ascending aortic graft [AAo] or elephant trunk [ET1] repair) and 21 age-matched controls (age = 59 AE 10 years; 13 male) were included. Field Strength/Sequence: 1.5T, 3T, 4D flow MRI. Assessment: 4D flow MRI was acquired in all subjects. Data analysis included 3D segmentation of TL and FL and voxelwise calculation of forward flow, reverse flow, flow stasis, and kinetic energy as quantitative hemodynamics maps. Statistical Tests: Analysis of variance (ANOVA) or Kruskal-Wallis tests were performed for comparing subject groups. Correlation and Bland-Altman analysis was performed for the interobserver study. Results: Patients with rTAAD presented with elevated TL reverse flow (AAo repair: P = 0.004, ET1: P = 0.018) and increased TL kinetic energy (AAo repair: P = 0.0002, ET1: P = 0.011) compared to controls. In addition, TL kinetic energy was increased vs. patients with TBAD (AAo repair: P = 0.021, ET1: P = 0.048). rTAAD was associated with higher FL kinetic energy and lower FL stasis compared to patients with TBAD (AAo repair: P = 0.002, ET1: P = 0.024 and AAo repair: P = 0.003, ET1: P = 0.048, respectively). Data Conclusion: Quantitative maps from 4D flow MRI demonstrated global and regional hemodynamic differences between DAD patients and controls. Patients with rTAAD vs. TBAD had significantly altered regional TL and FL hemodynamics. These findings indicate the potential of 4D flow MRI-derived hemodynamic maps to help better evaluate patients with DAD.

Highly accelerated aortic 4D flow MRI using compressed sensing: Performance at different acceleration factors in patients with aortic disease

“…When used in cardiovascular imaging, 4D flow MRI helps in the evaluation and characterization of various congenital 1‐4 and adult heart diseases, 5‐8 particularly several aortic diseases 9‐12 . The unique ability of 4D flow MRI to measure advanced metrics such as flow energetics and wall shear stress (WSS) has given newer insights into disease pathophysiology that could not be obtained through other existing imaging modalities 13‐17 . However, these benefits come at the expense of long scan times associated with multi‐dimensional imaging, hindering the adoption of 4D flow MRI into routine clinical imaging.…”

“…[9][10][11][12] The unique ability of 4D flow MRI to measure advanced metrics such as flow energetics and wall shear stress (WSS) has given newer insights into disease pathophysiology that could not be obtained through other existing imaging modalities. [13][14][15][16][17] However, these benefits come at the expense of long scan times associated with multi-dimensional imaging, hindering the adoption of 4D flow MRI into routine clinical imaging. In cardiothoracic applications, the scan times are further increased by the need for respiratory motion compensation, where typically a respiratory navigator follows the movement of the diaphragm, and only accepts data acquired in end-expiration.…”

Renin Angiotensin System Inhibitors Reduce Aortic Stiffness and Flow Reversal After a Cryptogenic Stroke

“…For generation of parametric reverse flow maps, voxelwise flow reversal was summed over the cardiac cycle and flow reversal fraction () was calculated according to methods previously described. 27,37,38 . Briefly, each voxel in the aortic volume was analyzed to determine the direction of forward flow (AAo to DAo) and reverse flow (DAo to AAo), as defined by the aortic centerline (Fig.…”

4D flow MRI after aortic replacement with frozen elephant trunk using thoraflex hybrid graft

“…It provides an opportunity to repair residual descending dissections through endovascular approaches into the existing stent‐graft, reducing the morbidity of another open operation. 4D flow MRI has been used to quantitatively characterize flow dynamics in chronic residual descending aortic dissections 2 . More studies are needed to define the clinical relevance of absolute 4D flow MRI parameter values but in select cases, the modality can provide information to help guide clinical care.…”