A comparative fMRI study: T2*‐weighted imaging versus R2*mapping

Functional magnetic resonance imaging experiments were performed in human motor cortex at 1.5 T by sampling two successive gradient recalled echo images in a single shot. Several aspects of brain mapping methods based on T2*‐weighted imaging and R2*mapping were quantitatively compared. These include the detected activation volume, functional contrast (FC), signal‐to‐noise ratio (SNR), and contrast‐to‐noise ratio (CNR). Studies based on the R2*mapping method have the following potential advantages: maximum functional contrast, less dependent on TE; and reduced inflow effects. R2*mapping produced the highest functional contrast, but not the largest activation volume due to the reduced signal‐to‐noise ratio and inflow effects. The sensitivity for activation detection is significantly correlated with the contrast‐to‐noise ratio, which is determined by both the SNR and FC. Copyright © 2001 John Wiley & Sons, Ltd.Abbreviations used:BOLDblood oxygen level dependentCNRcontrast‐to‐noise ratioFCfunctional contrastFFTfast fourier transformationGREgradient recalled echoROIregion of interestSNRSignal‐to‐noise ratioTEecho time.