Anatomic Dissection Tractography: A New Method for Precise MR Localization of White Matter Tracts
E. Leon Kiera,
Lawrence H. Staiba,c,d,
Lawrence M. Davisa and
Richard A. Bronena,b
a Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT
b Department of Neurosurgery, Yale University School of Medicine, New Haven, CT
c Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT
d Department of Electrical Engineering, Yale University School of Medicine, New Haven, CT
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FIG 1. Flowchart summarizes the stages of dissection tractography, which involves two methods: MR-assisted dissection and depiction of dissected tracts on MR images. In the first stage, MR imaging during the initial dissection helps prevent damage to the tracts under scrutiny. In the second stage, coregistration of 3D MR images of the specimen before and after the completion of dissection allows for the coregistration of a traced, dissected tract and the intact specimen. This in turn allows the creation of cross-sectional MR images with the traced white matter tract superimposed (Fig 4).
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FIG 2. Photographs of the lateral surface of a cerebral hemisphere show stages in the dissection of the temporal lobe.
A, Initially, the white matter of the anterior part of superior temporal gyrus (small arrow) and temporal lobe pole (large arrow) was isolated by progressive removal of the gray matter.
B, With further dissection, the white matter of the anterior segment of the middle temporal gyrus (arrows) was isolated by progressive removal of the gray matter.
C, To visualize the insular gyri (small white arrows) covered by the middle cerebral artery (arrowhead) and its insular branches, the white matter of the anterior segment of the superior temporal gyrus was completely removed by dissection. A portion of the white matter of the middle temporal gyrus (black arrows) was also removed by dissection. The inferior temporal gyrus (large white arrow) was left intact.
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FIG 3. Method used to identify the location of the dissected surface of the uncinate fasciculus on reformatted cross-sectional MR images.
A, Photograph of the lateral surface of the dissected brain specimen. Branches of the middle cerebral artery have been dissected away, leaving the horizontal segment (M1) of the middle cerebral artery as a landmark (arrowhead). The lower part of the cortex of the insular gyri (white arrows) and the posterior orbital gyrus (black arrow) have also been removed by dissection. A segment of the surface of the uncinate fasciculus (transparent red) is visible and courses from the temporal lobe into the white matter of the insula. It passes anteriorly around the middle cerebral artery and into the posterior orbital gyrus. To demonstrate the underlying dissected uncinate fasciculus, we used a 10% transparent red that results in a pink appearance.
B, 3D MR rendering of the dissected specimen in A demonstrates the accurate surface anatomy that can be depicted in this way. A segment of the surface of the uncinate fasciculus is color coded transparent red. The middle cerebral artery (arrowhead), the cortex of the insular gyri (white arrows), and the posterior orbital gyrus (black arrow) can be identified.
C and D, Coronal (C) and axial (D) reformatted cross-sectional MR images show the location of the dissected segment of the surface of the uncinate fasciculus (arrows). These cross-sectional images were generated at a level indicated by a cursor (X) placed on the surface of the uncinate fasciculus on the 3D MR rendering in B. The position of the cursor on the cross-sectional images indicates the surface of the uncinate fasciculus. Coregistration of the cursor permitted comparison of localization on the dissected surface with corresponding coronal and axial MR images.
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FIG 4. Method for MR localization of the dissected surface of the uncinate fasciculus on a 3D MR rendering and on multiplanar reformatted MR images of the specimen before dissection.
A, 3D MR rendering shows the undissected lateral surface of the brain.
B, 3D MR rendering shows the dissected lateral surface of the brain.
C, 3D MR rendering with the surface of the dissected segment of the uncinate fasciculus traced and color-coded red.
D, Coronal reformatted cross-sectional MR image of the dissected specimen in C shows the location of the dissected segment of the surface of the uncinate fasciculus in red.
E, Coronal reformatted cross-sectional MR image of the coregistered undissected specimen shows the color-coded tracing from D. This resulted in the identification of the precise MR location of the tract on the multiplanar reformatted images of the undissected specimen.
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