Abstract
PURPOSE: Design a b-value, first-order motion moment (M(1)), and echo time (TE)-optimized data acquisition for simultaneous intravoxel incoherent motion (IVIM) and R(2) quantification in the liver. METHODS: The b-M(1)-optimized (i.e., single TE) and b-M(1)-TE-optimized (i.e., multi-TE) IVIM acquisitions were determined using Cramer-Rao lower-bound optimization. Eleven healthy volunteers underwent MRI of the liver where each optimized acquisition was acquired twice (test-retest). For each data set, IVIM estimates (diffusion coefficient [D], perfusion signal fractions [f(1) and f(2)], blood velocity standard deviations [SDs] [V(b1) and V(b2)], and/or relaxation rates of tissue and blood [R(2t) and R(2b)]) were obtained in the right and left liver lobes within distinct spatial locations associated with slow (f(1) and V(b1)) and fast (f(2) and V(b2)) microvascular flow. Six R(2)-correction methods using combinations of estimated and/or fixed values of R(2t) and R(2b) were performed. Test-retest repeatability and interlobar agreement were evaluated using coefficients of variation (CVs) and relative mean differences (rMDs). RESULTS: The b-M(1)-TE-optimized acquisition demonstrated acceptable to excellent right-lobe test-retest repeatability (CV = 4.58%, 8.94%, 8.62%, 27.5%, 18.8%, 2.85%, and 17.7% for D, V(b1), V(b2), f(1), f(2), R(2t), and R(2b), respectively) and interlobar agreement (|rMD| = 8.82%, 1.84%, 8.72%, 3.08%, and 0.20% for D, V(b1), V(b2), R(2t), and R(2b), respectively), except for interlobar agreement of f(1) and f(2) (rMD ≥ 37.7%). For the b-M(1)-optimized acquisition, R(2) correction of f(1) and f(2) provided similar estimates as the b-M(1)-TE-optimized acquisition (|MD| ≤ 1.98%). CONCLUSION: The b-M(1)-TE-optimized IVIM acquisition enabled simultaneous and repeatable IVIM and R(2) quantification in the liver. For single-TE IVIM data, R(2) correction of f estimates using fixed values of R(2t) and R(2b) may be acceptable.