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AJNR - American Journal of Neuroradiology

Published ahead of print on October 18, 2007
doi: 10.3174/ajnr.A0742

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American Journal of Neuroradiology 29:146-150, January 2008
© 2008 American Society of Neuroradiology

BRAIN

Preliminary Experience with Visualization of Intracortical Fibers by Focused High-Resolution Diffusion Tensor Imaging

T. Jaermann^a,b, N. De Zanche^a, P. Staempfli^a,b, K.P. Pruessmann^a, A. Valavanis^b, P. Boesiger^a and S.S. Kollias^b

^a Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
^b Institute of Neuroradiology, University Hospital Zurich, Zurich, Switzerland

Please address correspondence to Prof Dr S.S. Kollias, Institute of Neuroradiology, University Hospital Zurich, CH-8091 Zurich, Switzerland; e-mail: spyros.kollias{at}usz.ch

BACKGROUND AND PURPOSE: The inherent low anisotropy of gray matter and the lack of adequate imaging sensitivity and resolution has, so far, impeded depiction of axonal fibers to their intracortical origin or termination. We tested the hypothesis that an experimental approach with high-resolution diffusion tensor imaging (DTI) provides anisotropic data for fiber tractography with sufficient sensitivity to visualize in vivo the fine distribution of white matter bundles at the intracortical level.

MATERIALS AND METHODS: We conducted phantom measurements of signal-to-noise ratio (SNR) and obtained diffusion tensor maps of the occipital lobe in 6 healthy volunteers using a dedicated miniature phased array detector at 3T. We reconstructed virtual fibers using a standard tracking algorithm.

RESULTS: The coil array provided a SNR of 8.0 times higher at the head surface compared with a standard quadrature whole head coil. Diffusion tensor maps could be obtained with an in-plane resolution of 0.58 x 0.58 mm². The axonal trajectories reconstructed from the diffusion data penetrate into the cortical ribbon perpendicular to the pial surface. This is the expected pattern for the terminations of thalamocortical afferent fibers to the middle layers of the occipital cortex and is consistent with the known microstructural organization of the mammalian cerebral cortex.

CONCLUSION: High-resolution DTI reveals intracortical anisotropy with a distinct parallel geometrical order, perpendicular to the pial surface, consistent with structures that may be identified as the terminal afferents in cortical gray matter.