J Korean Soc Radiol.  2016 Aug;75(2):113-120. 10.3348/jksr.2015.73.6.113.

Diffusion Tensor Tractography of the Brainstem Pyramidal Tract: A Study on the Optimal Reduction Factor in Parallel Imaging

• Bae YJ
• Park JB
• Kim JH
• Choi BS
• Jung C

• KMID: 2344800
• DOI: http://doi.org/10.3348/jksr.2015.73.6.113

Abstract

PURPOSE
Parallel imaging mitigates susceptibility artifacts that can adversely affect diffusion tensor tractography (DTT) of the pons depending on the reduction (R) factor. We aimed to find the optimal R factor for DTT of the pons that would allow us to visualize the largest possible number of pyramidal tract fibers.
MATERIALS AND METHODS
Diffusion tensor imaging was performed on 10 healthy subjects at 3 Tesla based on single-shot echo-planar imaging using the following parameters: b value, 1000 s/mm²; gradient direction, 15; voxel size, 2 × 2 × 2 mm³; and R factors, 1, 2, 3, 4, and 5. DTT of the right and left pyramidal tracts in the pons was conducted in all subjects. Signal-to-noise ratio (SNR), image distortion, and the number of fibers in the tracts were compared across R factors.
RESULTS
SNR, image distortion, and fiber number were significantly different according to R factor. Maximal SNR was achieved with an R factor of 2. Image distortion was minimal with an R factor of 5. The number of visible fibers was greatest with an R factor of 3.
CONCLUSION
R factor 3 is optimal for DTT of the pontine pyramidal tract. A balanced consideration of SNR and image distortion, which do not have the same dependence on the R factor, is necessary for DTT of the pons.

MeSH Terms

Artifacts
Brain Stem*
Diffusion Tensor Imaging
Diffusion*
Echo-Planar Imaging
Healthy Volunteers
Magnetic Resonance Imaging
Pons
Pyramidal Tracts*
R Factors
Signal-To-Noise Ratio