Automatic Spinal Cord Gray Matter Quantification: A Novel Approach

C. Tsagkas; A. Horvath; A. Altermatt; S. Pezold; M. Weigel; T. Haas; M. Amann; L. Kappos; T. Sprenger; O. Bieri; P. Cattin; K. Parmar

doi:10.3174/ajnr.A6157

Abstract

BACKGROUND AND PURPOSE: Currently, accurate and reproducible spinal cord GM segmentation remains challenging and a noninvasive broadly accepted reference standard for spinal cord GM measurements is still a matter of ongoing discussion. Our aim was to assess the reproducibility and accuracy of cervical spinal cord GM and WM cross-sectional area measurements using averaged magnetization inversion recovery acquisitions images and a fully-automatic postprocessing segmentation algorithm.

MATERIALS AND METHODS: The cervical spinal cord of 24 healthy subjects (14 women; mean age, 40 ± 11 years) was scanned in a test-retest fashion on a 3T MR imaging system. Twelve axial averaged magnetization inversion recovery acquisitions slices were acquired over a 48-mm cord segment. GM and WM were both manually segmented by 2 experienced readers and compared with an automatic variational segmentation algorithm with a shape prior modified for 3D data with a slice similarity prior. Precision and accuracy of the automatic method were evaluated using coefficients of variation and Dice similarity coefficients.

RESULTS: The mean GM area was 17.20 ± 2.28 mm² and the mean WM area was 72.71 ± 7.55 mm² using the automatic method. Reproducibility was high for both methods, while being better for the automatic approach (all mean automatic coefficients of variation, ≤4.77%; all differences, P < .001). The accuracy of the automatic method compared with the manual reference standard was excellent (mean Dice similarity coefficients: 0.86 ± 0.04 for GM and 0.90 ± 0.03 for WM). The automatic approach demonstrated similar coefficients of variation between intra- and intersession reproducibility as well as among all acquired spinal cord slices.

CONCLUSIONS: Our novel approach including the averaged magnetization inversion recovery acquisitions sequence and a fully-automated postprocessing segmentation algorithm demonstrated an accurate and reproducible spinal cord GM and WM segmentation. This pipeline is promising for both the exploration of longitudinal structural GM changes and application in clinical settings in disorders affecting the spinal cord.

ABBREVIATIONS:

AMIRA: averaged magnetization inversion recovery acquisitions
CV: coefficient of variation
DSC: Dice similarity coefficient
HD: Hausdorff distance
SC: spinal cord

Footnotes

C. Tsagkas and A. Horvath contributed equally as first authors.
Disclosures: Charidimos Tsagkas—RELATED: Grant: Swiss National Science Foundation (grant No. 320030_156860) and the Foundation for Sponsorship of Gastroenterological and General Clinical Research as well as of Medical Imaging (application ID 02/2015); UNRELATED: Grants/Grants Pending: University of Basel, Forschungsfonds für exzellente Nachwuchsforschende, pending. Antal Horvath—RELATED: Support for Travel to Meetings for the Study or Other Purposes: Swiss National Science Foundation.* Simon Pezold—UNRELATED: Grants/Grants Pending: Novartis Research Foundation.* Matthias Weigel—RELATED: Grant: Swiss National Science Foundation, Comments: grant No. 320030_156860, Method Development for MRI of Spinal Cord*; UNRELATED: Employment: Department of Biomedical Engineering, University of Basel, Switzerland, Comments: postdocterate; Patents (Planned, Pending or Issued): University Hospital Freiburg, Freiburg, Germany, Comments: patent for Optical Motion Correction, neither relevant nor used in the present work; Travel/Accommodations/Meeting Expenses Unrelated to Activities Listed: International Society for Magnetic Resonance in Medicine, European Society for Magnetic Resonance in Medicine and Biology, MR Compact, Comments: travel reimbursement and accommodation for invited, scientific talks about MRI physics. Ludwig Kappos—UNRELATED: Board Membership: Actelion, Almirall, Bayer AG, Biogen, Celgene/Receptos, df-mp, Excemed, Genzyme, Japan Tobacco, Merck, Minoryx, Mitsubishi Tanabe Pharma, Novartis, Roche, Sanofi-Aventis, Santhera, Teva Pharmaceutical Industries, Vianex*; Consultancy: Actelion, Almirall, Bayer AG, Biogen, Celgene/Receptos, df-mp, Excemed, Genzyme, Japan Tobacco, Merck, Minoryx, Mitsubishi Tanabe Pharma, Novartis, Roche, Sanofi-Aventis, Santhera, Teva Pharmaceutical Industries, Vianex*; Grants/Grants Pending: Bayer AG, Biogen, Novartis, Roche, the Swiss MS Society, the Swiss National Research Foundation*; Payment for Lectures Including Service on Speakers Bureaus: Allergan, Almirall, Baxalta, Bayer AG, Biogen, CSL Behring, Desitin, Excemed, Genzyme, Merck, Novartis, Pfizer, Roche, Sanofi-Aventis, Teva Pharmaceutical Industries*; Payment for Development of Educational Presentations: Allergan, Almirall, Baxalta, Bayer AG, Biogen, CSL Behring, Desitin, Excemed, Genzyme, Merck, Novartis, Pfizer, Roche, Sanofi-Aventis, Teva Pharmaceutical Industries.* Till Sprenger—RELATED: Grant: Swiss National Science Foundation*; UNRELATED: Consultancy: Actelion, ATI, Biogen, Desitin, electroCore, Sanofi Genzyme, Novartis, and Mitsubishi Tanabe Pharma Europe*; Grants/Grants Pending: EFIC-Grünenthal, Novartis Switzerland, the Swiss Multiple Sclerosis Society*; Payment for Lectures Including Service on Speakers Bureaus: Sanofi Genzyme, Biogen, Novartis, Teva Pharmaceutical Industries.* Oliver Bieri—RELATED: Grant: Swiss National Science Foundation*; UNRELATED: Grants/Grants Pending: Swiss National Science Foundation.* Katrin Parmar—RELATED: Grant: Swiss National Science Foundation*; UNRELATED: Grants/Grants Pending: Baasch Medicus Foundation; Payment for Lectures Including Service on Speakers Bureaus: Excemed, Novartis Switzerland*; Travel/Accommodations/Meeting Expenses Unrelated to Activities Listed: Novartis Switzerland. *Money paid to the institution.
This work was supported by the Swiss National Science Foundation (grant No. 320030_156860) and the Foundation for Sponsorship of Gastroenterological and General Clinical Research as well as of Medical Imaging (application ID 02/2015).