Reproducibility of intravoxel incoherent motion quantification in the liver across field strengths and gradient...

To evaluate reproducibility and interlobar agreement of intravoxel incoherent motion (IVIM) quantification in the liver across field strengths and MR scanners with different gradient hardware.

Cramer-Rao lower bound optimization was performed to determine optimized monopolar and motion-robust 2D (b-value and first-order motion moment [M₁]) IVIM-DWI acquisitions. Eleven healthy volunteers underwent diffusion MRI of the liver, where each optimized acquisition was obtained five times across three MRI scanners. For each data set, IVIM estimates (diffusion coefficient (D), pseudo-diffusion coefficients ( $d_1^{*}$ and $d_2^{*}$ ), blood velocity SDs (V_b1 and V_b2), and perfusion fractions [f₁ and f₂]) were obtained in the right and left liver lobes using two signal models (pseudo-diffusion and M₁-dependent physical) with and without T₂ correction (f_c1 and f_c2) and three fitting techniques (tri-exponential region of interest-based full and segmented fitting and blood velocity SD distribution fitting). Reproducibility and interlobar agreement were compared across methods using within-subject and pairwise coefficients of variation (CV_w and CV_p), paired sample t-tests, and Bland-Altman analysis.

Using a combination of motion-robust 2D (b-M₁) data acquisition, M₁-dependent physical signal modeling with T₂ correction, and blood velocity SD distribution fitting, multiscanner reproducibility with median CV_w = 5.09%, 11.3%, 9.20%, 14.2%, and 12.6% for D, V_b1, V_b2, f_c1, and f_c2, respectively, and interlobar agreement with CV_p = 8.14%, 11.9%, 8.50%, 49.9%, and 42.0%, respectively, was achieved.

Recently proposed advanced IVIM acquisition, signal modeling, and fitting techniques may facilitate reproducible IVIM quantification in the liver, as needed for establishment of IVIM-based quantitative biomarkers for detection, staging, and treatment monitoring of diseases.