Functional MR Imaging of Cerbral Motor Cortex: Comparison between Conventional Gradient Echo and EPI Techniques

ABSTRACT

PURPOSE: To evaluate the differences of functional imaging patterns between conventional spoiled gradient echo(SPGR) and echo planar imaging(EPI) methods in cerebral motor cortex activation. MATERIALS AND METHODS: Functional MR imaging of cerebral motor cortex activation was examined on a 1.5T MR unit with SPGR (TR/TE/flip angle=50ms/40ms/30degree, FOV=300mm, matrix size=256x256, slice thickness=5mm) and an interleaved single shot gradient echo EPI (TR/TE/flip angle=3000ms/40ms/90 degree, FOV=300mm, matrix size=128x128, slice thickness=5mm) techniques in five male healthy volunteers. A total of 160 imaging in one slice and 960 images in 6 slices were obtained with SPGR and EPI, respectively. A right finger movement was accomplished with a paradigm of an 8 activation/ 8 rest periods. The cross-correlation was used for a statistical mapping algorithm. We evaluated any differences of the time series and the signal intensity changes between the rest and activation periods obtained with two techniques. Also, the locations and areas of the activation sites were compared between two techniques. RESULTS: The acivation sites in the motor cortex were accurately localized with both methods. In the signal intensity changes between the rest and activation periods at the activation regions, no significant differences were found between EPI and SPGR. Signal to noise ratio (SNR) of the time series data was higher in EPI than in SPGR by two folds. Also, larger pixels distributed over small p-values at the activation sites in EPI. CONCLUSIONS: Good quality functional MR imaging of the cerebral motor cortex activation could be obtained with both SPGR and EPI. However, EPI os preferable because it provides more precise information on hemodynamics related to neural activities than SPGR due to high sensitivity.