Background R2* correction for χ-separation (chi-separation)

Motivation: An advanced quantitative susceptibility mapping (QSM) technique, χ-separation, requires tissue field map and R2* to separate paramagnetic and diamagnetic components. As the background field is removed to acquire the tissue field map, the background R2* needs to be removed to accurately estimate paramagnetic and diamagnetic susceptibility maps. Goal(s): Investigate the effect of background R2* correction on χ-separation. Approach: The effect of background R2* correction on χ-separation was tested by varying the background R2* with multiple head orientations and k-space filtering. Results: Background R2* correction successfully reduced overestimation in χ-separation maps in different head orientations and low-pass filtering levels. Impact: Background R2* correction enables consistent χ-separation across different head orientations and k-space filtering.