title: Acoustic schwannomas: awareness of radiologic error will reduce unnecessary treatment.
abstract: OBJECTIVE
  To measure the intra- and interobserver error in size estimation of acoustic schwannomas from magnetic resonance imaging (MRI) scans by experienced radiologists to determine whether small amounts of tumor growth that may affect management (2 mm) could be reliably measured in clinical practice.
  
  
  METHODS
  Duplicated, blinded size estimation of acoustic neuromas (according to American Academy of Otolaryngology-Head and Neck Surgery guidelines, 1995) from MRI scans of patients with acoustic neuromas.
  
  
  METHODS
  Tertiary referral teaching hospital and DGH.
  
  
  METHODS
  Four radiologists (including 2 dedicated neuroradiologists) measuring positive MRI scans of 26 patients with an acoustic neuroma.
  
  
  METHODS
  Intraradiologist and inter-radiologist repeatability coefficients in millimeters for the maximal tumor diameter in the anteroposterior (AP) axis, medial-longitudinal (ML) axis, and the square-root of the product of these two measurements. Repeatability coefficients give the 95% range within which the differences in repeated measurements lie.
  
  
  RESULTS
  The intraradiologist repeatability for AP and ML measurements ranged from 1.51 to 6.03 mm and 2.01 to 3.83 mm, respectively. The repeatability of the square-root of the product ranged from 1.43 to 4.94 mm. The inter-radiologist repeatability was 6.48 mm and 7.46 mm for the AP and ML measurements, respectively, giving a repeatability of 3.65 mm for the square-root of the product.
  
  
  CONCLUSIONS
  The study indicates that, in routine clinical practice, differences in tumor size of the order of 2 mm cannot be reliably measured, even by the same radiologist. Thus, reported growth of acoustic tumors should be interpreted with caution, especially if this is the criterion for recommending treatment.
authors.affiliation: Department of Otolaryngology, Queen's Medical Center NHS Trust, University Hospital, Nottingham, UK.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Marshall
authors.forename: Victoria M F
authors.initials: VM
authors.lastname: Owen
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Nikolopoulos
authors.forename: Gerard M
authors.initials: GM
authors.lastname: O'Donoghue
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging; D009464:Neuroma, Acoustic / Q000175:diagnosis*; D015588:Observer Variation; D015203:Reproducibility of Results; D016037:Single-Blind Method; D019564:Unnecessary Procedures