Quantitative comparison of functional contrast from BOLD-weighted spin-echo and gradient-echo echoplanar imaging at 1.5 Tesla and (H2OPET)-O-15 in the whole brain

Spin-echo and gradient-echo echoplanar functional magnetic resonance imagin g (fMRI) studies at 1.5 Tesla (T) were used to obtain blood oxygenation lev el-dependent (BOLD) contrast images of the whole brain in seven strongly ri ght-handed women during execution of a complex motor task. Five subjects un derwent subsequent (H2O)-O-15 positron emission tomography (PET) studies wh ile performing the same task. Group-averaged results for changes in the MRI relaxation rates R-2* and R-2 at 1.5T in response to neuronal activation i n nine cortical, subcortical, and cerebellar motor regions are reported. Re sults for each method are grouped according to tissue type-cerebral cortex (precentral gyrus and supplementary motor area), subcortical regions (thala mus and putamen), and cerebellar cortex (superior lobule). The observed cha nges in R,* from activation-induced oxygenation changes were more variable across brain regions with different tissue characteristics than observed ch anges in R-2. The ratio of Delta R-2* to Delta R-2 was 3.3 +/- 0.9 for cere bral cortex and 2.0 +/- 0.6 for subcortical tissue. Delta R-2* Delta R-2, a nd relative blood flow changes were Delta R-2* = -0.201 +/- 0.040 s(-1). De lta R-2 = -0.064 +/- 0.011 s(-1), and Delta f/f = 16.7 +/- 0.8% in the cere bral cortex; Delta R-2* = -0.100 +/- 0.026 s(-1), Delta R-2 -0.049 +/- 0.00 9 s(-1), and Delta f/f = 9.4 +/- 0.7% in the subcortical regions; and Delta R-2* = -0.215 +/- 0.093 s(-1), Delta R-2 = -0.0;69 +/- 0.012 s(-1), and De lta f/f = 16.2 +/- 1.2% in the cerebellar cortex.