title: Standardization and validation of a novel and simple method to assess lumbar dural sac size.
abstract: OBJECTIVE
  To develop and validate a simple, reproducible method to assess dural sac size using standard imaging technology.
  
  
  METHODS
  This study was institutional review board-approved. Two readers, blinded to the diagnoses, measured anterior-posterior (AP) and transverse (TR) dural sac diameter (DSD), and AP vertebral body diameter (VBD) of the lumbar vertebrae using MRI images from 53 control patients with pre-existing MRI examinations, 19 prospectively MRI-imaged healthy controls, and 24 patients with Marfan syndrome with prior MRI or CT lumbar spine imaging. Statistical analysis utilized linear and logistic regression, Pearson correlation, and receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  AP-DSD and TR-DSD measurements were reproducible between two readers (r = 0.91 and 0.87, respectively). DSD (L1-L5) was not different between male and female controls in the AP or TR plane (p = 0.43; p = 0.40, respectively), and did not vary by age (p = 0.62; p = 0.25) or height (p = 0.64; p = 0.32). AP-VBD was greater in males versus females (p = 1.5 × 10(-8)), resulting in a smaller dural sac ratio (DSR) (DSD/VBD) in males (p = 5.8 × 10(-6)). Marfan patients had larger AP-DSDs and TR-DSDs than controls (p = 5.9 × 10(-9); p = 6.5 × 10(-9), respectively). Compared to DSR, AP-DSD and TR-DSD better discriminate Marfan from control subjects based on area under the curve (AUC) values from unadjusted ROCs (AP-DSD p < 0.01; TR-DSD p = 0.04).
  
  
  CONCLUSIONS
  Individual vertebrae and L1-L5 (average) AP-DSD and TR-DSD measurements are simple, reliable, and reproducible for quantitating dural sac size without needing to control for gender, age, or height.
authors.affiliation: Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599, USA. Electronic address: Leighanne_Daniels@med.unc.edu.
authors.forename: M L A
authors.initials: ML
authors.lastname: Daniels
authors.affiliation: Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Lowe
authors.affiliation: Department of Biostatistics, UNC at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: P
authors.initials: P
authors.lastname: Roy
authors.affiliation: Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Patrone
authors.affiliation: Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Conyers
authors.affiliation: Department of Biostatistics, UNC at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Fine
authors.affiliation: Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Knowles
authors.affiliation: Department of Radiology, UNC School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Birchard
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001827:Body Height; D001835:Body Weight; D001837:Body Weights and Measures / Q000379:methods*; D004388:Dura Mater / Q000033:anatomy & histology* / Q000473:pathology*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000473:pathology*; D008161:Lumbosacral Region / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008382:Marfan Syndrome / Q000473:pathology*; D008875:Middle Aged; D015588:Observer Variation; D012015:Reference Standards; D015203:Reproducibility of Results; D055815:Young Adult