Detection and Hemodynamic Evaluation of Flap Fenestrations in Type B Aortic Dissection with 4D Flow MRI: Comparison with Conventional MRI and CT Angiography

Abstract

Purpose: The purpose of this study was to compare dissection flap fenestration visualization between 4D flow MRI, clinical MRI/MRA, and clinical CTA studies and describe the presence of hemodynamically active fenestration flow using 4D flow. Materials and Methods: Nineteen patients with type B dissection (age: 57±5 years) who had undergone standard of-care MRI/MRA of the chest including 4D flow MRI were retrospectively identified. Fourteen of the 19 patients also had CTA performed within 2 years of the MRI/MRA study with no interval surgery. Image review was performed independently by two radiologists. The number of fenestrations (including entry and exit tears), location, and flow directionality were recorded. Differences in the rate of detection between techniques was assessed using a Wilcoxon signed rank test. Results: 4D flow detected more fenestrations relative to MRI/MRA [rev 1: +3 (10%), rev 2: +5 (20%)]. There were similar numbers of fenestrations detected by 4D flow relative to CTA [rev 1: +1 (4%), rev 2: −3 (−12%)]. MRI/MRA detected fewer fenestration relative to CTA in this cohort [rev 1: −6 (−24%), rev 2: −5 (−19%)]. No differences were significant. Combining 4D flow and MRI/MRA resulted in additional fenestration detection. Most fenestrations demonstrated biphasic flow over the cardiac cycle (flow entering false lumen in systole and exiting during diastole, rev 1:18/33, rev 2: 16/30). Conclusions: 4D flow MRI can detect small flap fenestration in type B dissection patients while providing additional information about flow through fenestrations throughout the cardiac cycle relative to CTA and conventional MRI.

False lumen pressure estimation in type B aortic dissection using 4D flow cardiovascular magnetic resonance: comparisons with aortic growth

“…Time-resolved three-dimensional phase-contrast cardiovacular magnetic resonance (4D Flow CMR) is a non-invasive technique that provides volumetric assessment of blood flow, and has been extensively applied to study aortic hemodynamics [ 18 – 23 ]. Recent 4D Flow CMR studies have also proposed ways of estimating FL pressurization and to predict growth in TBAD [ 18 – 20 , 24 ].…”

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

“…4D flow magnetic resonance imaging (MRI) (ie, 3D time‐resolved phase contrast MRI with 3‐directional velocity encoding) is uniquely poised to evaluate complex flow patterns in DAD because of the ability to measure 1) blood flow in all three main directional components, and 2) volumetric coverage to allow for quantitative analysis of the entire aorta. This technique has detected flow alterations in aortic dissection related to aortic dilatation (visualization of helical flow and distal dominant entry tears, quantification of flow velocity in the FL), found substantially higher flow in the TL with FL thrombus, and has been used to identify small dissection flap fenestrations . Previous studies are promising, but were limited by either the utilization of qualitative assessment of flow patterns or localized quantification of hemodynamic metrics, and thus the systematic parameter mapping of flow in the TL and FL is needed .…”

Updates on Indications for TEVAR in Type B Aortic Dissection

“…4). 51,52 Imaging platforms that allow for multiplanar reconstructions and center-line sizing have made planning and sizing considerations for TEVAR easier. Patients should be continued on anti-impulse therapy as an outpatient.…”

“…4D Flow MRI demonstrating type B dissection with entry tear and flow into false lumen. Reproduced with permission from Allen et al 52 CEMRA, contrast-enhanced magnetic resonance angiography; 4D, 4-dimensional; MIP, maximum intensity projection; MRI, magnetic resonance imaging.…”