title: Disambiguating the optic nerve from the surrounding cerebrospinal fluid: Application to MS-related atrophy.
abstract: OBJECTIVE
  Our goal is to develop an accurate, automated tool to characterize the optic nerve (ON) and cerebrospinal fluid (CSF) to better understand ON changes in disease.
  
  
  METHODS
  Multi-atlas segmentation is used to localize the ON and sheath on T2-weighted MRI (0.6 mm(3) resolution). A sum of Gaussian distributions is fit to coronal slice-wise intensities to extract six descriptive parameters, and a regression forest is used to map the model space to radii. The model is validated for consistency using tenfold cross-validation and for accuracy using a high resolution (0.4 mm(2) reconstructed to 0.15 mm(2)) in vivo sequence. We evaluated this model on 6 controls and 6 patients with multiple sclerosis (MS) and a history of optic neuritis.
  
  
  RESULTS
  In simulation, the model was found to have an explanatory R-squared for both ON and sheath radii greater than 0.95. The accuracy of the method was within the measurement error on the highest possible in vivo resolution. Comparing healthy controls and patients with MS, significant structural differences were found near the ON head and the chiasm, and structural trends agreed with the literature.
  
  
  CONCLUSIONS
  This is a first demonstration that the ON can be exclusively, quantitatively measured and separated from the surrounding CSF using MRI.
authors.affiliation: Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Harrigan
authors.affiliation: Department of Computer Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Plassard
authors.affiliation: Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA.|Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Bryan
authors.affiliation: Biomedical Engineering, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Caires
authors.affiliation: Vanderbilt Eye Institute, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Mawn
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Dethrage
authors.affiliation: Department of Neurology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Siddharama
authors.initials: S
authors.lastname: Pawate
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Galloway
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.|Department of Radiology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Seth A
authors.initials: SA
authors.lastname: Smith
authors.affiliation: Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA.|Department of Computer Science, Vanderbilt University, Nashville, Tennessee, USA.|Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.|Department of Radiology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Bennett A
authors.initials: BA
authors.lastname: Landman
mesh_terms: D000328:Adult; D000465:Algorithms; D002555:Cerebrospinal Fluid / Q000166:cytology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015233:Models, Statistical; D009103:Multiple Sclerosis / Q000150:complications / Q000473:pathology*; D009896:Optic Atrophy / Q000209:etiology / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D055815:Young Adult
keywords: magnetic resonance imaging; multi-atlas; nonconvex optimization; optic nerve; segmentation