Accuracy and precision of R2* and fat-specific R1 from multiparametric relaxation mapping in fat-water mixtures

Motivation: Grouping water- and fat-specific (R2*w and R2*f) into a single parameter (R2*observed) is a common assumption in MRI. However, the current literature does not address how this assumption affects the joint mapping of R1f and R2*. Goal(s): To evaluate the precision and accuracy of R1f and R2*, under the assumptions of single- or dual-R2*. Approach: Accuracy and precision of R2*observed, R2*w, R2*f, and R1f estimates from Fat DESPOT were studied under both assumptions in simulations and phantom experiments. Results: R2*observed was equivalent to R2*w and R2*f for high and low PDFF, respectively; and R1f was not affected by R2*-based assumptions. Impact: We determined that the single-R2* assumption has negligible effects on R1f precision and accuracy while enabling robust and precise estimation of R2*observed. Thus, the single-R2* assumption is a preferable alternative to the dual-R2* assumption.