Figure 3.

A comparison of the image quality acquired with true FISP and EPI pulse sequences in the absence of an ASL preparation. Scans were obtained by applying equivalent imaging parameters to one healthy subject in the same oblique-axial slice position parallel to the AC-PC line at the level of the basal ganglia. Each pulse sequence employed a segmented approach using a 256 × 256 image matrix corresponding to an in-plane resolution of 1 mm, and a single-shot approach using 256 × 256, 128 × 128, and 64 × 64 image matrices corresponding to in-plane resolutions of 1 mm, 2 mm, and 4 mm. A T2 weighted (T2W) structural scan was also acquired at same slice position and is shown on the left for anatomical reference. The top row (a₁–a₄) shows the results of the true FISP scans, the middle row (b₁–b₄) shows the results of the EPI scans implemented with an RL phase encoding scheme, and the bottom row (c₁–c₄) shows the results of the EPI scans implemented with an AP phase encoding scheme. It can be observed from this series that segmented true FISP significantly diminishes blurring found in the single-shot approach that obscures anatomical substructures found within deep gray matter. Segmented true FISP also does not display any of the magnetic field distortion artifacts that are evident with EPI. The amount of distortion can be significantly curtailed in EPI through the application of a segmented approach, but the effect still remains distinctly evident.