Marta Bianciardi1, Masaki Fukunaga1, Peter van Gelderen1, Jacco A. de Zwart1, Jeff H. Duyn1
1Advanced MRI Section, LFMI/NINDS/NIH,
To exploit the increased BOLD-contrast available at 7T for fMRI-studies, it is crucial to identify the various noise-sources and their origin. We determined the contribution of non-thermal noise to fluctuations in BOLD-weighted-, T2*- and S0-signals in the visual cortex at 7T during rest. The following noise-sources were considered: low-frequency-drifts, effects related to the phase of physiological cycles and to changes in physiological rates, thermal-noise, and other sources, tentatively attributed to spontaneous-activity. Our findings show that low-frequency-drifts have a physiological-contribution, and that spontaneous-activity has an echo-time dependence. Effects related to physiological-cycles and their rates contributed both to T2*- and to S0-images.