Reference values for 4D flow magnetic resonance imaging of the portal venous system

The purpose of this work was to establish normal reference values for 4D flow MRI-derived flow, velocity, and vessel diameters, and to define characteristic flow patterns in the portal venous system of healthy adult subjects.

For this retrospective study, we screened all available 4D flow MRI exams of the upper abdomen in healthy adults acquired at our institution between 2012 and 2022 at either 1.5 T or 3.0 T MRI after ≥ 5 h fasting. Flow, velocity, and effective diameter were quantified in the 8 planes in the portal venous system (splenic vein, superior mesenteric vein, main, right, and left portal veins). Vessel delineation was manually adjusted over time. Reference ranges for were defined as the mean ± 2 standard deviations. Three readers noted helical and vortical flow on time-resolved pathline visualizations. Conservation of mass flow analysis was performed for quality assurance.

We included 44 healthy subjects (26 female, 18-74 years) in the analysis. We report reference values for mean and peak flow, mean velocity, and vessel diameter in the healthy portal vein using 4D flow MRI. Normal flow patterns in the portal vein included faint helical (66%) or linear flow (34%). Conservation of mass analysis demonstrated a relative error of 1.1 ± 4.6% standard deviation (SD) at the splenomesenteric confluence and - 1.4 ± 4.1% SD at the portal bifurcation.

We have reported normal hemodynamic values that are necessary baseline data for emerging clinical applications of 4D flow MRI in the portal venous system. Results are consistent with previously published values from smaller cohorts.