Latency and Echo-Time Dependence of the GRE-BOLD Signal in High-Resolution FMRI

Stefan Hetzer¹, Toralf Mildner¹, Thies H. Jochimsen¹, Karsten Mller¹, Torsten Schlumm¹, Harald E. Mller¹

The relation between amplitude and latency of the BOLD signal was studied at 3T by use of high-resolution fMRI employing a center-out EPI sequence that allowed a minimum TE of 2 ms. The measured relaxation rate change δR2* during visual stimulation, i. e. the slope of the linear fit of the TE dependence and the corresponding intercept were found to increase with the BOLD latency. The δR2* increase over the total range of the BOLD latency was between 40 and 70%. In general, δR2* increased with image resolution which points to an underestimation of δR2* in low-resolution fMRI studies.