Liver has a unique hemodynamic system which is neither fully recognized nor understood. Shear stresses to the liver and its vessels have been reported to play important roles to keep liver function and control its regeneration.

Non-contrast MRA using four-dimensional phase-contrast magnetic resonance angiography (4D-PCA) technique becomes clinically available and hemodynamic assessments using its cine data is reportedly useful for evaluations of cerebral and aortic aneurysms.

We applied these techniques to hemodynamic assessments of whole liver vessels.

Our purpose was to assess hepatic vasculatures and hemodynamics using 4D-PCA and detailed hemodynamic analysis technique including wall shear stress parameters to vessel walls.

Patients & MRI Techniques

19 patients (9 men, 8 women, mean 64.2 years old), who were suspected to have hepato-biliary-pancreatic malignancy and underwent 3T-MRI, were enrolled. 4D-PCA were obtained (dSTorso, TR/TE/FA:4.1/2.4/10, matrix:240x191 (ZIP256x256), FOV:400mm, thk:120mm, slice number:60, voxel:1.6x1.6x2.0mm, NEX:1, PI:3.0 (RL), 10aqs/cardiac cycle, scan time:6-10min, pulse gating). 4D-PCA was obtained before and after Gd-EOB-DTPA administration in 8 patients, and obtained with VENCs of 30 and 80 cm/s in other 11.

Visual Assessments

Visualizations of abdominal aorta, celiac, common and proper hepatic, superior mesenteric, splenic arteries, main, right, left portal, superior mesenteric, splenic, hepatic veins, and inferior vena cava, were scored using a 5-point scale (1:poor, 5:excellent), and were compared between pre- and post-contrast and the two VENCs.

Hemodynamic Assessments

Using cine data obtained with 4D-PCA, hemodynamic assessments of each vessel were performed on a software (FLOVA, R'Tech). Blood flow and velocity in vessel, and shear stresses to vessel wall such as wall shear stress (WSS), oscillatory shear gradient (OSI), spatial WSS gradient (SWSSG), gradient oscillatory number (GON) were measured.

Visual Assessments

Visualization scores were more than 4 except for hepatic arteries and improved after EOB administration.

Scores were higher with 30 cm/s than 80 in proper hepatic artery and all the veins.

Hemodynamic Assessments

Hemodynamic assessment required approximately 1 hour for each patient and could be done in all the vessels except for proper hepatic arteries with diameters <4mm.

The results are shown in Table 1.

In 4D-PCA, vessel visualizations were improved after Gd-EOB-DTPA. The results were similar to the previous reports using other Gd and SPIO contrast agents.

4D-PCA can be clinically used as a non-contrast angiography. Further improvement of visualization is required for tiny abdominal vessels.

Hemodynamic assessments for each hepatic vessel could be done in short time. However, optimal assessment scheme is still unknown.

4D-PCA can be clinically used as a non-contrast angiography. Cine data enables detailed hemodynamic assessment for each hepatic vessel.