MR Diffusion Tensor Imaging and Fiber Tracking in Spinal Cord Compression
David Facona,
Augustin Ozannea,
Pierre Fillardd,
Jean-François Lepeintreb,
Caroline Tournoux-Faconc and
Denis Ducreuxa
a Department of Neuroradiology, C.H.U. de Bicêtre, Paris XI University, Le Kremlin-Bicêtre, France
b Department of Neurosurgery, C.H.U. de Bicêtre, Paris XI University, Le Kremlin-Bicêtre, France
c Department of Biostatistics, Institut Curie, Paris V University, Paris, France
d Department of Computer Science, University of North Carolina, Chapel Hill, NC
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FIG 1. A, MR imaging of a spinal cord compression due to a breast tumor metastasis in patient 1. Images are from C7–T10. Color-coded scale related to parameters values. Higher values are coded in red, medium values in green, and lower values in blue. T2-weighted imaging (first image) shows a high signal intensity (white arrow), ADC (second image) is slightly increased (blue-green areas; ADC = 1.1 10–3 mm2/s versus 0.84 10–3 mm2/s in normal cervicothoracic area) and FA (third image) is decreased (green areas; FA = 0.61 vs 0.75 in normal cervicothoracic area) after region of interest measurements. The region of interest in abnormal area was drawn by using the fiber tracking three-dimensional reconstruction.
B, MR imaging of a spinal cord compression due to a breast tumor metastasis with epidural involvement in patient 1. Fiber tracking over b0 image shows a mass-effect on fibers tracts. The region of interest (green area) was drawn over the maximal level of compression (blue arrow) and then automatically reported on the coregistered ADC and FA maps to measure ADC and FA values in the compression site.
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FIG 2. Time course from d1 to d30 of the averaged FA parameter estimated from the compression sites in 11 patients with abnormal FA values. FA values decreased from the 1st to the 21st days, then slightly increased, both related to the extracellular water diffusivity: restricted diffusivity in acute stage and increased diffusivity in chronic stage. Normal values range from 0.69 to 0.8.
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FIG 3. Fiber tracking performed on a volunteer’s cervical spinal cord. Sagittal (A), axial (B), and coronal (C) views show tracts reconstructed over the b0 sequence. Main white matter tracts are visible on axial (B) and coronal (C) views of the three-dimensional reconstructions: two individualized posterior lemniscal tracts (arrowheads), and posterolateral corticospinal tracts (arrows). Other tracts are visible, but have to be more correlated with known anatomy.
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FIG 4. Three-dimensional reconstructions are mapped over the b0 images. Fiber tracking performed on the spinal cord volunteer shows some pitfalls of the FT method due to magnetic susceptibility effect of the DTI MR image: "hole" effect, gap in three-dimensional reconstruction (blue arrows).
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