Three-dimensional spiral fMRI technique: a comparison with 2D spiral acquisition.

A comparison study was performed of 3D and 2D spiral k-space fMRI techniques using BOLD contrast with a 4.25-min finger-tapping task paradigm. The 3D sequence uses the conventional 2D spiral technique in conjunction with Fourier phase encoding in the slice select direction. Characteristics that were compared included image appearances, signal-to-noise ratio (SNR), fluctuation noise, functional contrast-to-noise ratio (fCNR), detected activation areas, inflow effect, and large vessel involvement. The results showed that, with constant total scan time, the 3D spiral acquisition has higher SNR and fCNR despite its slightly higher fluctuation noise. The capability for thin-slice incoherent averaging is a further advantage of 3D over 2D. With these advantages as well as its intrinsic ability for contiguous slices and image reformatting, the 3D spiral fMRI technique may be superior to its 2D counterpart.