1Medical Biophysics, University of Toronto, Toronto, ON, Canada, 2Roman Research Institute, Toronto, ON, Canada
The optimal echo time (TE) for spin-echo EPI
(SE-EPI) BOLD is assumed to be near the tissue T2 (65–100ms at 3 T), but this
was never experimentally tested. In this study, we use a hypercapnia paradigm with
SE-EPI at different TEs to identify the TE that maximizes BOLD detection at 3
T. Based on the normalized percent change in BOLD signal (∆BOLD%/mmHg), BOLD contrast-to-noise
ratio (CNR/mmHg) and temporal signal-to-noise ratio (tSNR), we concluded that
the optimal SE-EPI TE may be much shorter than the tissue T2, and the optimal
TE at 3 T is near 50ms.