Xiao-Hong Zhu1, Wei Chen1
1CMRR, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, United States
In Vivo 31P MRS is useful for studying the brain high-energy phosphate metabolism and ATP energy, and its low intrinsic sensitivity can be partially overcome at high/ultrahigh field. One key benefit of the high field in addition to the sensitivity gain is the improvement in spectral resolution. However, the field dependence of 31P resonance linewidth or T2* is determined by two relaxation mechanisms: dipole-dipole and chemical shift anisotropy (CSA). The later will accelerate the linewidth broadening at higher field following B02 relation. To address this concern, we quantitatively investigated the field dependence of PCr, α-ATP and γ-ATP linewidths based on the 31P MRS data of human and cat brains covering B0 from 1.5T to 16.4T. The overall results indicate large improvements in spectral resolution towards higher fields; they dont support the notion that CSA could become the dominate T2* relaxation mechanism at high/ultrahigh field.