Optimising Functional Quantitative Susceptibility Mapping (fQSM): The Effect of Multiband Acceleration and Absolute vs. Signed QSM

Motivation: fQSM has emerged as a complementary technique to fMRI but the effect of multiband acceleration factors is unknown. Some studies have used absolute QSM input but no systematic comparison has been performed. Goal(s): To investigate the impact of multiband factors on task-based fQSM activations and the effect of analysing absolute versus signed QSM. Approach: We compared fQSM with a visual stimulus for multiband factors 3 and 4, and for signed and absolute QSM inputs. Results: Increasing multiband factors reduced cluster sizes and activation t-scores in fQSM likely due to greater g-factor noise. Absolute QSM yielded fewer, larger activation clusters than signed QSM. Impact: fQSM activations decreased with increasing multiband acceleration, highlighting a tradeoff between multiband acceleration and fQSM sensitivity. Using absolute versus signed QSM for fQSM may result in loss of information. These factors must be carefully considered for optimal future fQSM studies.