Prandial Effects on Intravoxel Incoherent Motion Quantification in the Liver

To evaluate the feasibility of detecting prandial (i.e., meal) induced changes in microvascular flow in the liver, including changes in the spatial distribution of flow velocities, using intravoxel incoherent motion (IVIM) MRI.

Thirteen (n = 13) healthy volunteers underwent two liver MR exams: one preprandial after fasting and one postprandial after ingesting nutrition shakes. IVIM data were acquired four times: twice preprandial to evaluate repeatability using coefficients of variation (CV) and twice postprandial to evaluate meal-induced changes relative to preprandial estimates. 4D flow MRI was acquired once pre- and postprandial to estimate portal venous flow rate, which was normalized by liver volume to evaluate correlations with IVIM. IVIM estimates of the diffusion coefficient (D), R₂-corrected perfusion signal fraction (F_c), blood velocity standard deviation (V_b), and spatial volumes associated with slow microvascular flow (Ω₁), fast microvascular flow (Ω₂), and major vessels (Ω₃) were determined.

Significantly (p ≤ 0.01) higher V_b and Ω₂ volume and lower Ω₁ volume were observed postprandial compared to preprandial. The magnitudes of the postprandial changes in V_b, Ω₁ volume, and Ω₂ volume (|median relative change| ≥ 10.2%, 48.4%, and 13.7%, respectively) were greater than the corresponding repeatability (CV = 5.19%, 21.3%, and 8.13%, respectively). Significant (p = 0.01) correlation between liver volume-normalized portal venous flow rate and V_b was observed.

The potential of IVIM to detect physiological (e.g., prandial-induced) changes in microvascular flow in the liver was demonstrated. IVIM data may need to be acquired in a fasting state to avoid confounding prandial effects on IVIM-derived microvascular flow estimates.