Three-dimensional functional MRI with parallel acceleration: balanced SSFP versus PRESTO

To compare the sensitivity and specificity of three-dimensional (3D) principles of echo shifting using a train of observations (PRESTO) and passband balanced steady-state free precession (SSFP) functional MRI (fMRI) sequences combined with integrated parallel acquisition techniques (iPAT) at 3 Tesla (T).

The 3D fMRI was performed using PRESTO and passband balanced SSFP with 3 mm and 1.9 mm isotropic voxels combined with iPAT, while volunteers underwent visual stimulation. From whole-brain activation maps and predefined regions of interest in the visual cortex, Z-score distributions, percentage of fMRI signal change, and the fMRI signals' temporal profile were compared between the sequences for the two spatial resolutions to estimate sensitivity and specificity.

For PRESTO, the Z-score distributions had higher mean and maximum Z-values for both resolutions than for SSFP, and the activated voxels were located to the visual cortex with high sensitivity. For SSFP, the activation was more scattered, and voxels with the highest sensitivity were found in the draining veins. The good functional contrast in PRESTO allowed for separation of voxels with early (<5 s) and late (>5 s) signal change; thus, the signal from larger draining veins could be removed. The ensuing PRESTO activation maps represent the early fMRI signal, probably more closely related to neuronal activity.

The 3D fMRI PRESTO sequence demonstrated better sensitivity and specificity than SSFP.