Regional and state-dependent properties of M for high-field calibrated fMRI in rat brain
Christina Y. Shu 1 , Daniel Coman 2 , Basavaraju G. Sanganahalli 2 , Helen Wang 2 , Christoph Juchem 2 , Peter Herman 2 , and Fahmeed Hyder 1,2
Biomedical Engineering, Yale University, New
Haven, CT, United States,
Radiology, Yale University, CT, United States
In calibrated fMRI the BOLD signal range from
deoxyhemoglobin to oxyhemoglobin is reflected by M.
Since blood oxygenation changes are captured with
relaxation rates by gradient echo (R2*) and spin echo
(R2), M is echo time multiplied by R2 (i.e., R2*- R2).
Because it is unclear if the M range reported in
calibrated fMRI studies is due to regional/state
differences, we tested M estimated from R2 in rat
brain. Homogenous M values were found in the cortex
regardless of the brain state. These results suggest
that a direct R2 mapping method may provide more
accurate M values for calibrated fMRI.
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