Diffusion Tensor Fiber Tractography for Arteriovenous Malformations: Quantitative Analyses to Evaluate the Corticospinal Tract and Optic Radiation
T. Okadaa,
Y. Mikia,
K. Kikutab,
N. Mikunib,
S. Urayamac,
Y. Fushimia,
A. Yamamotoa,
N. Moria,
H. Fukuyamac,
N. Hashimotob and
K. Togashia
a Departments of Diagnostic Imaging & Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan
b Neurosurgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
c Human Brain Research Center, Kyoto University, Kyoto, Japan
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Fig 1. A, ROI segmentation for corticospinal tract tractography. Polygonal ROIs are placed on transverse b = 0 images (TR/TE, 7000 ms/79 ms). The first "OR" ROI (blue) is placed at either side of the cerebral peduncle on the plane where the characteristic  shape of the central sulcus is at the center of cerebral hemisphere (top left). The second "AND" ROI (blue) is placed at the ipsilateral precentral gyrus (top right). Left and right ROI segmentations were separately performed. "NOT" ROIs (green) are placed on midline structures connecting right and left corticospinal tracts on sagittal reconstructed image (bottom left) and fibers projecting into ipsilateral cerebellar peduncle on coronal reconstructed image (bottom right). Examples of bilateral corticospinal tract overlaid on coronal reconstructed image are shown (bottom right).
B, ROI segmentation for optic radiation tractography. The 4 kinds of ROIs (white polygon) are placed on coronal or sagittal color-coded maps. Cross lines indicate the orthogonal planes. The first "OR" ROI is placed at either side of the occipital lobe, including the calcarine cortex on the coronal plane through the anterior edge of the occipital-parietal sulcus (top left). The second "AND" ROI is placed at the ipsilateral temporal stem, including the Meyer loop on the sagittal plane (top right). Temporal stem is identified as green, and the Meyer loop is identified as a small red area inside the temporal stem (red arrow). The third and fourth "NOT" ROIs are placed on the same coronal plane through the dorsal end of the Sylvian fissure (bottom left). Bilateral Meyer loops are indicated as red arrows. Occipital-frontal connections medial to the Meyer loop and fibers projecting to the temporal horn passing through lateral to the Meyer loop are removed using the "NOT" operation. Examples of bilateral optic radiation overlaid on transverse b = 0 images (TR/TE, 7000 ms/79 ms) are shown (bottom right).
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Fig 2. A, Corticospinal tract tractography. Patients were classified into 1 of 3 groups based on the distance between AVM nidus and tract and the presence of motor weakness. Three groups (A–C) are assigned from top row to bottom row. Left column displays transverse b = 0 images (TR/TE, 7000 ms/79 ms). Blue areas represent the voxel where fiber tracts penetrate the image. Middle column displays transverse maximum intensity projection (MIP) images of MR angiography. Red arrows indicate AVM nidus. Right column displays 3D reconstruction of fibers and MR angiography superimposed on b = 0 images. 3D reconstructions of AVM nidus (red) and hemorrhage (yellow) segmented from MR angiography were displayed by using shaded surface rendering. Patients in groups A and B are subjects without hemorrhage, and the group C patient is a subject with hemorrhage in this figure. In this group C patient, left corticospinal tract veers laterally, and projection fibers from the medial precentral gyrus are not visualized (green arrow).
B, Optic radiation tractography. Patients were classified into 1 of 3 groups based on the distance between AVM nidus and tract and the presence of visual field defect. Optic radiation tractography is represented in green, and imaging methods are the same as explained in A. The group B patient is the same as the group A patient presented in A. In this group C patient, left optic radiation was disrupted around the occipital pole.
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Fig 3. Results of statistical analysis with significant differences are demonstrated. Top row displays patients without intracranial hemorrhage, and bottom row displays patients with intracranial hemorrhage. Gray rhomboids indicate mean and its 95% confident intervals. Horizontal axes represent groups A–C, and vertical axes represent AIs. In patients without intracranial hemorrhage, AI of perinidal FA along corticospinal tract (left, P = .006) and optic radiation (middle, P = .01) and AI of optic radiation volume (right, P < .0001) differed significantly between groups. In patients with hemorrhage, AIs of perinidal FA (P = .04), tract volume (P = .01) of corticospinal tract, and AI of perinidal FA along optic radiation (P = .004) differed significantly between groups.
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