Introduction

Emerging time-resolved, 4D-flow MRI sequences for assessing blood flow to the liver provides simultaneous and spatially coregistered anatomical and hemodynamic information of all vessels within the imaging volume[1-2].Meal challenges are standard clinical procedures applied in imaging modalities such as ultrasound and MRI to induce physiological hyperemia [3]. The purpose of this study was tomonitor the flow changes in the portal system through a meal challenge in healthy volunteers with 4D flow MRI to investigate the feasibility of non-invasively quantifying the hemodynamic changes in pathological conditions.

Purpose

This study monitors the flow changes in the portal system through a meal challenge in healthy volunteers with 4D flow MRI to investigate the feasibility of non-invasively quantifying the hemodynamics changes in pathological conditions.

Methods

Ten healthy subjects were prospectively enrolled for MRI examination at 3.0 T (Ingenia CX, Philips Healthcare, the Netherlands) with a 16-channel abdominal array coil. The MR protocol included a 2D quantitative flow sequence (axial, TR/TE = 4.4/2.7 ms, FOV = 200×200 mm2, resolution = 1.5×1.5×8 mm3, PC direction = RL, PC velocity = 200 cm/s, scan time = 13 s) to measure the flow velocity in the portal vein as a reference for velocity encodings (VENC) and a 4Dflow sequence with compressed sensing (CS) acceleration (axial, TR/TE = 5.0/3.2 ms, FOV = 300×350 mm2, resolution = 2.5×2.5×2.5 mm3, PC direction = RL-AP-FH, CS =8, scan time = 370 s) for hemodynamic quantification. VENC was set to 30 cm/s for the 4D flow sequence to slightly surpass the measured velocity and avoid phase wrapping. The acquired images were processed in CVI42 (Canada Circle Cardiovascular Imaging）by a single radiologist to obtain a 3D angiogram (Figure 1). The measurement planes were put at the middle of the portal vein (PV), superior mesenteric vein (SMV), and splenic vein (SV) trunk. Flow velocity (cm/s)and volume (ml/cardiac cycle) measurements were performed blinded to subject status (fasting/meal).The intra-class correlation coefficients (ICC) was used to check the consistency of the data measured by the two observers. The flow velocity and volume for each vessel were compared before and after the meal using paired t test.

Results

The consistency of the data obtained by the two observers were good (Table 1), ICC value > 0. 75. After meal, significant increased blood flow velocity and volume were observed in PV and SMV and significantly decreased blood flow was observed in SV (P＜0.05) (Table 2).

Discussion and Conclusions

We have non-invasively measured the increase of flow velocity and volume in both PV and SMV and a decrease in SV after the meal uptake in all the healthy volunteers using 4D-flow MRI, indicating this technique a sensitive tool for the quantification of portal system flow changes [3]. A varying range of complicated abdominal and whole-body conditions may involve changes in portal system flow, such as hepatic encephalopathy and hypersplenism, for which 4D-flow MRI can help to provide both diagnosis and therapy monitoring information.

Acknowledgements

No acknowledgement found.