title: Measurement of ventricular size: reliability of the frontal and occipital horn ratio compared to subjective assessment.
abstract: BACKGROUND
  The frontal and occipital horn ration (FOR) has recently been described as a simple, linear measurement of ventricular size that correlates very well with ventricular volume. This study further characterizes the measurement properties of the FOR by investigating its interobserver reliability and comparing it to a subjective assessment of ventricular size.
  
  
  METHODS
  Axial images (CT and MR) of children with hydrocephalus taken before and after third ventriculostomy were reviewed by 4 independent observers. Two observers were blinded to patient identity and clinical status and 2 observers were nonblinded. Each observer independently recorded linear measurements from which the FOR was calculated for each image. Each reviewer also made a separate subjective assessment of the degree of hydrocephalus on a 9-point adjectival scale. Reliability was calculated using a repeated-measures analysis of variance (ANOVA) and an intraclass correlation coefficient (ICC) with random image and observer effects.
  
  
  RESULTS
  There were 120 separate observations (4 observers, 30 images). The FOR ranged from 0.33 to 0.75 (mean 0.55, standard deviation 0.11). The reliability coefficient was 0.93 (95% confidence interval, CI 0.80-0.97) between the 2 blinded observers and 0.98 (95% CI, 0.95-0.99) between the 2 nonblinded observer. The overall interobserver reliability for all 4 observers was 0.95 (95% CI 0.92-0.98). The mean FOR for each observer was very similar, regardless of the observer's blinding status. However, the reliability of the observers' subjective assessment of the hydrocephalus was much lower (ICC = 0.77, 95% CI 0. 60-0.88).
  
  
  CONCLUSIONS
  The FOR demonstrates excellent interobserver reliability (>0.9) and was superior to subjective assessments of hydrocephalus. In this study, excellent reliability was maintained regardless of the blinding status of the observers. This further demonstrates the properties of the FOR as a simple and reproducible measure of ventricular size. It is suitable for use in clinical studies, possibly even in situations in which observer blinding is not possible.
authors.affiliation: Divisions of Neurosurgery and Neuroradiology, Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors.forename: A V
authors.initials: AV
authors.lastname: Kulkarni
authors.forename: J M
authors.initials: JM
authors.lastname: Drake
authors.forename: D C
authors.initials: DC
authors.lastname: Armstrong
authors.forename: P B
authors.initials: PB
authors.lastname: Dirks
mesh_terms: D002552:Cerebral Ventricles / Q000033:anatomy & histology*; D002648:Child; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D012016:Reference Values; D014057:Tomography, X-Ray Computed