Importance of reference in QSM and a new differential ROI reference method

Abstract

In this study, we developed a computer simulation to demonstrate the importance of reference in QSM. The results show that QSM values were not only dependent on the brain slab width but also dependent on brain mask size. Furthermore, when the background removal was not perfect, this difference was more dependent on this condition. Only when the data are referenced using a neighboring region, the QSM results provide correct susceptibility difference values regardless of these conditions. Also, we demonstrate this new approach for a Parkinsons disease (PD) patient study. In contrast to the previous QSM study, the use of differential ROI reference avoids the assumption of equal susceptibility in the reference between groups in group comparison and directly reports the susceptibility difference between two ROIs, no longer allowing ambiguity in interpretation.