SPIN-ECHO AND GRADIENT-ECHO EPI OF HUMAN BRAIN ACTIVATION USING BOLD CONTRAST - A COMPARATIVE-STUDY AT 1.5 T

In this study, Blood Oxygenation Level Dependent (BOLD) contrast in the detection of human brain activation was compared between spin-echo and gradient-echo echo-planar sequences at 1.5 T. Time course series of spin-echo and gradient-echo images containing the primary motor cortex were collected during rest (no finger movement) and activation (finger movement). Each time course series was collected using a different TE. Resting and active state signal intensities at each TE were measured in identical regions in the motor cortex. From these data, resting and active state R(2) (1/T-2) and R(2)* (1/T-2*) values were obtained. Across four subjects, brain activation produced an average R(2) change of -0.16+/-0.02/s (+/-SE), and an average R(2)* change of -0.55+/-0.08/s. The average Delta R(2)*/Delta R(2) ratio was 3.52+/-0.56. The average gradient-echo/spin-echo ratio of activation-induced signal changes at the TE for maximal BOLD contrast for each sequence (TE approximate to T-2* and T-2) was calculated to be 1.87+/-0.40.