title: Nasopharyngeal carcinoma volume measurements determined with computed tomography: study of intraobserver and interobserver variability.
abstract: OBJECTIVE
  To investigate the intraobserver and interobserver variability of computed tomography-based volume measurements of nasopharyngeal carcinoma.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Tertiary care centre.
  
  
  METHODS
  The primary tumour volume of 13 nasopharyngeal carcinomas was repeatedly measured by two trained observers independently in two different sessions, using the summation of area technique.
  
  
  METHODS
  Mean tumour volume and its standard deviation were calculated for each tumour. Statistical analysis was done with multivariate analysis, linear regression, and a two-way analysis of variance (ANOVA) random effects model.
  
  
  RESULTS
  The coefficient of variation was less than 20% in 11 volume measurements, but a large discrepancy between observers was noted in two tumours with involvement of the paranasal sinuses. A good linear correlation was found between mean tumour volume and its standard deviation: standard deviation = 0.26 volume - 2.48 (r = .80). When the two tumours with a large coefficient of variation were excluded, the two-way ANOVA random effects model revealed that both the interobserver (p = .83) and the intraobserver (p = .90) effect are not statistically significant; interobserver variability was the major component of total variability (71.0%).
  
  
  CONCLUSIONS
  Total variability in the computed tomography-based measurement of nasopharyngeal carcinoma volume is small by having the measurements done by a trained observer, except in tumours with involvement of the paranasal sinuses.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, National Yang-Ming University, Taiwan.
authors.forename: Cheng-Chuan
authors.initials: CC
authors.lastname: Chang
authors.forename: Mu-Kuan
authors.initials: MK
authors.lastname: Chen
authors.forename: Hwa-Koon
authors.initials: HK
authors.lastname: Wu
authors.forename: Mu-Tai
authors.initials: MT
authors.lastname: Liu
mesh_terms: D000704:Analysis of Variance; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D002983:Clinical Competence / Q000706:statistics & numerical data; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D009367:Neoplasm Staging; D015588:Observer Variation; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*