Four‐dimensional velocity mapping of the hepatic and splanchnic vasculature with radial sampling at 3 tesla: A feasibility study in portal hypertension

Abstract

Purpose: To demonstrate the feasibility of PC‐VIPR (Phase Contrast Vastly undersampled Imaging with Projection Reconstruction) for the depiction and hemodynamic analysis of hepatic and splanchnic vessels in patients with portal hypertension. Materials and Methods: Twenty‐four cirrhotic patients (55.9 ± 10.4years) were scanned using 5‐point PC‐VIPR for high spatial resolution imaging with large volume coverage at 3 Tesla (T) using a 32‐channel body coil. Vessel segmentation and hemodynamic visualization included color‐coded three‐dimensional (3D) streamlines and particle traces. Segmentation quality was compared with contrast‐enhanced multi‐phase liver imaging. Flow pattern analysis was performed in consensus of three readers. The MELD score was calculated to estimate disease severity and was correlated to image quality. Results: Good to excellent visualization quality was achieved in 23/24 cases. All arterial vessels and 144/168 vessels of the portal venous (PV) circulation were unambiguously identified. No correlation with the MELD score was found. Eight of 148 vessels of the PV circulation demonstrated reverse (hepatofugal) flow. Hepatofugal flow in small tributaries to PV flow were present in three cases despite hepatopetal flow in the PV. Conclusion: This feasibility study demonstrates the feasibility of PC‐VIPR for simultaneous morphological and hemodynamic assessment of the hepatic and splanchnic vasculature in cirrhosis and portal hypertension. Future studies with quantitative analyses are warranted. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

MR-based Measurements of Portal Vein Flow and Liver Stiffness for Predicting Gastroesophageal Varices

“…Recently developed time-resolved 3-or 4-dimensional PC-MRI may soon resolve this problem. [34][35][36] The retrospective design also limited our study. We expect a prospective study with longitudinal observations would strengthen the conclusions of our study.…”

In vivo validation of 4D flow MRI for assessing the hemodynamics of portal hypertension

“…This approach also avoids the need to acquire numerous double oblique planes needed for 2D phase contrast MRI methods. Volumetric velocity mapping has shown to be well suited for the liver and abdomen vasculature where one comprehensive acquisition is followed by post-processing and flow measurements in specific vessels (31).…”

“…Further, a single velocity encoding (venc) setting limited evaluation of flow to the portal and splanchnic venous vasculature. Recent work by Frydrychowicz et al demonstrated feasibility of qualitative flow visualization with high spatial resolution and large volumetric coverage using 3D radial undersampling strategies (31). However, as with other accelerated imaging strategies, there is potential for inaccuracies in flow measurements, which have not been assessed for hepatic flow.…”

Impaired regulation of portal venous flow in response to a meal challenge as quantified by 4D flow MRI

“…Early studies using Cartesian-based 4D flow approaches for the analysis of the portal vein have shown promising results (27)(28)(29)(30). Similarly, recent studies have validated the use of 3D radially undersampled in 4D flow MRI for visualization and quantification in the abdominal circulation, with very high spatial resolution and large volumetric coverage with an approach termed PV VIPR (Phase Contrast Vastly Undersampled Projection Reconstruction) (25,26). Coupled with 5-point velocity encoding (31) this approach allows for quantifying a wide range of flow velocities, which is particularly advantageous for evaluating the arterial, portal venous and hepatic venous circulation (26).…”

“…Emerging time-resolved, three-dimensional (3D), three-directional flow-sensitive MRI ("4D flow MRI") sequences for assessing blood flow to the liver provides simultaneous and spatially co-registered anatomical and hemodynamic information of all vessels within the imaging volume (25)(26)(27)(28)(29)(30). However, assessment of liver hemodynamics using standard 4D flow MRI sequences is challenging due to the need for (a) large volumetric coverage, (b) high spatial resolution, (c) sensitivity to a large spectrum of flow velocities, (d) need for respiratory gating and (e) need for short scan times.…”