A comparative fMRI study: T-2*-weighted imaging versus R-2* mapping

Functional magnetic resonance imaging experiments were performed in human m otor cortex at 1.5 T by sampling two successive gradient recalled echo imag es in a single shot. Several aspects of brain mapping methods based on T-2* -weighted imaging and R-2* mapping were quantitatively compared. These incl ude the detected activation volume, functional contrast (FC), signal-to-noi se ratio (SNR), and contrast-to-noise ratio (CNR). Studies based on the R-2 * mapping method have the following potential advantages: maximum functiona l contrast, less dependent on TE; and reduced inflow effects. R-2* mapping produced the highest functional contrast, but not the largest activation vo lume due to the reduced signal-to-noise ratio and inflow effects. The sensi tivity for activation detection is significantly correlated with the contra st-to-noise ratio, which is determined by both the SNR and FC. Copyright (C ) 2001 John Wiley & Sons, Ltd.