Spatial correspondence of spinal cord white matter tracts using diffusion tensor imaging, fibre tractography, and atlas-based segmentation

Stewart McLachlin [1] & Jason Leung [2] & Vignesh Sivan [2] & Pierre-Olivier Quirion [3] & Phoenix Wilkie [2] & Julien Cohen-Adad [3] &
Cari Marisa Whyne [2,4] & Michael Raymond Hardisty [2,4]

Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, E7 3424,
Waterloo, Ontario N2L 3G1, Canada
Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave, S621, Toronto, Ontario M4N 3M5,
Canada
Department of Electrical Engineering, Polytechnique Montreal,
Ecole Polytechnique, Pavillon Lassonde, 2700 Ch de la Tour, L-5610, Montréal, Quebec H3T 1N8, Canada
Department of Surgery, University of Toronto, 2075 Bayview Ave, S621, Toronto, Ontario M4N 3M5, Canada

Globe

mclachlin-et-al-2021.pdf

Abstract

Introduction:

Neuroimaging provides great utility in complex spinal surgeries, particularly when anatomical geometry is distorted by pathology (tumour, degeneration, etc.). Spinal cord MRI diffusion tractography can be used to generate streamlines; however, it is unclear how well they correspond with white matter tract locations along the cord microstructure. The goal of this work was to evaluate the spatial correspondence of DTI tractography with anatomical MRI in healthy anatomy (where anatomical locations can be well defined in T1-weighted images).

Methods:

Tenhealthyvolunteerswerescannedona 3Tsystem.T1-weighted (1×1×1mm)anddiffusion-weightedimages(EPI readout, 2 × 2 × 2 mm, 30 gradient directions) were acquired and subsequently registered (Spinal Cord Toolbox (SCT)). Atlas based (SCT)anatomiclabelmapsoftheleftand right lateral corticospinal tracts were identified for each vertebral region (C2–C6) from T1 images. Tractography streamlines were generated with a customized approach, enabling seeding of specific spinal tract regions corresponding to individual vertebral levels. Spatial correspondence of generated fibre streamlines with anatomic tract segmentations was compared in unseeded regions of interest (ROIs).

Results:

Spatial correspondence of the lateral corticospinal tract streamlines was good over a single vertebral ROI (Dice’s similarity coefficient (DSC) = 0.75 ± 0.08, Hausdorff distance = 1.08 ± 0.17 mm). Over larger ROI, fair agreement between tractography and anatomical labels was achieved (two levels: DSC = 0.67 ± 0.13, three levels: DSC = 0.52 ± 0.19).

Conclusion:

DTItractography producedgoodspatial correspondencewith anatomic white matter tracts, superior to the agreement between multiple manual tract segmentations (DSC ~ 0.5). This supports further development of spinal cord tractography for computer-assisted neurosurgery.