Johannes Gregori1, Norbert Schuff1,2, Matthias Gnther3
1Radiology & Biomedical Imaging, University of San Francisco, San Francisco, CA, USA; 2VA Medical Center , Center for Imaging of Neurodegenerate Diseases, CIND, San Francisco; 3Neurology, University Hospital Mannheim, University of Heidelberg, Heidelberg, Germany
Quantification of local T2*, which is used in fMRI as a surrogate for neuronal activity, can be difficult because static (R2) and irreversible (R2) effects contribute to the decay. In this work, we developed a 3D mapping scheme based on GRASE, in which two spiral-out planar readouts per k-space partition are used to acquire a spin echo (governed by R2) and a time-shifted gradient echo (governed by R2) on the ascending slope of the corresponding spin echo. From a combination of R2 and R2, local T2* variations can be quantified. Measurements were also performed in conjunction with arterial spin labeling allowing to selectively measure T2* of labeled water.