Three-dimensional spiral technique for high-resolution functional MRI

For high-resolution functional MRI (fMRI) studies, signal-to-noise ratio (SNR) plays an important role. Any method that results in an improvement in SNR will be able to improve the quality of activation maps. Three-dimensional (3D) acquisition methods in general can provide higher SNR than that of 2D methods due to volume excitation. To demonstrate the superiority of 3D methods for high-resolution fMRI scans, a comparison study between 3D and 2D spiral methods was performed using a contrast-reversing checkerboard visual stimulus. A 3-inch surface coil was used to limit the in-plane FOV to 14 cm x 14 cm so that 32 1-mm slices with an in-plane voxel size of 1.1 mm x 1.1 mm could be acquired within 5.76 seconds. Results showed that average numbers of activated voxels were 407 and 841 for 2D and 3D methods, respectively (P < 0.01). Therefore, the 3D technique may be a useful alternative to the conventional 2D method for high resolution fMRI studies.