J Korean Soc Magn Reson Med.  2006 Jun;10(1):1-7.

Anisotropy Measurement and Fiber Tracking of the White Matter by Using Diffusion Tensor MR Imaging: Influence of the Number of Diffusion-Sensitizing Gradient Direction

• Jun WS
• Kim JH
• Hong SW
• Lee JS
• Kim SH

Abstract

PURPOSE: Recent development of diffusion tensor imaging enables the evaluation of the microstructural characteristics of the brain white matter. However, optimal imaging parameters for diffusion tensor imaging, particularly concerning the number of diffusion gradient direction, have not been studied thoroughly yet. The purpose of this study was to evaluate the influence of the number of diffusion gradient direction on the fiber tracking of the white matter.
MATERIALS AND METHODS
13 healthy volunteers (ten men and three women, mean age 30 years, age range 23-37 years) were included in this study. Diffusion tensor imaging was performed with different numbers of diffusion gradient direction as 6, 15, and 32, keeping the other imaging parameters constant. The imaging field ranged from 1 cm below the pons to 2-3 cm above the lateral ventricle, parallel to the anterior commissure-posterior commissure line. FA (fractional anisotropy) maps were created via image post-processing, and then FA and its standard deviation were calculated in the genu and the splenium of the corpus callosum on each of FA maps. Fiber tracking of the corticospinal tract in the brain was performed and the number of the reconstructed fibers of the tract was measured. FA, standard deviation of FA and the number of the reconstructed fibers were compared statistically between the different diffusion gradient directions.
RESULTS
FA is not statistically significantly different between the different diffusion gradient directions. By increasing the number of diffusion gradient direction, standard deviation of FA decreased significantly, and the number of the reconstructed fibers increased significantly.
CONCLUSION
The higher number of diffusion gradient direction provided better quality of fiber tracking.

Keyword

MRI; diffusion tenor MRI; fiber tracking; tractography

MeSH Terms

Anisotropy*
Brain
Corpus Callosum
Diffusion Tensor Imaging
Diffusion*
Female
Healthy Volunteers
Humans
Lateral Ventricles
Magnetic Resonance Imaging*
Male
Pons
Pyramidal Tracts