Christina Triantafyllou1,2, Boris Keil2,
Jonathan R. Polimeni2,
1MIT, Athinoula A. Martinos Imaging Center, McGovern Institute for Brain Research, Cambridge, MA, United States; 2A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States; 3Harvard-MIT Division of Health Sciences & Technology, Cambridge, MA, United States
Sensitivity in BOLD fMRI is characterized by the time-series SNR (tSNR), which contains fluctuations from thermal (σ0) and physiological (σp) noise sources. The relationship between tSNR and the image SNR (SNR0)often fit to a model where σp is proportional to signal. Our findings demonstrate that the relationship between tSNR and SNR0 is well described by this for small count of channels, however for higher field strengths and multiple channel arrays, a modified model with an additional constant term in σp (which does not scale with signal strength) produces a significantly better fit to both SE and GrE data.