title: CT colonography: automated measurement of colonic polyps compared with manual techniques--human in vitro study.
abstract: OBJECTIVE
  To prospectively investigate the relative accuracy and reproducibility of manual and automated computer software measurements by using polyps of known size in a human colectomy specimen.
  
  
  METHODS
  Institutional review board approval was obtained for the study; written consent for use of the surgical specimen was obtained. A colectomy specimen containing 27 polyps from a 16-year-old male patient with familial adenomatous polyposis was insufflated, submerged in a container with solution, and scanned at four-section multi-detector row computed tomography (CT). A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were produced to aid CT-histologic measurement correlation. A novice (radiographic technician) and an experienced (radiologist) observer independently estimated polyp diameter with three methods: manual two-dimensional (2D) and manual three-dimensional (3D) measurement with software calipers and automated measurement with software (automatic). Data were analyzed with paired t tests and Bland-Altman limits of agreement.
  
  
  RESULTS
  Seven polyps (<or=6-mm diameter) could not be extracted by using the software; 20 polyps (5-15-mm diameter) remained for analysis. Automated measurement was not significantly different from histologic size for the experienced reader (mean difference, 0.63 mm; P=.06) or novice reader (mean difference, 0.58 mm; P=.12). With manual 2D measurement and manual 3D measurement, the experienced reader (1.21-mm mean difference, P<.001, and 0.68-mm mean difference, P=.03, respectively) and novice reader (1.54-mm mean difference, P<.001, and 0.84-mm mean difference, P=.002, respectively) significantly underestimated polyp size. Interobserver agreement was good and similar for all three methods (95% limits of agreement span, approximately 2.5 mm). Intraobserver agreement was related to reader experience, with differences of up to 2.5 mm within expected limits of agreement.
  
  
  CONCLUSIONS
  For polyps smaller than 1 cm, measurement differences of up to 2.5 mm are within the expected limits of inter- and intraobserver agreement for all measurement techniques. Automated and manual 3D polyp measurements are more accurate than manual 2D measurements.
authors.affiliation: Department of Imaging, University College Hospital, 2F Podium, 235 Euston Rd, London NW1 2BU, England. csytaylor@yahoo.co.uk
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Taylor
authors.forename: Andrew
authors.initials: A
authors.lastname: Slater
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: Lesley
authors.initials: L
authors.lastname: Honeyfield
authors.forename: Mary E
authors.initials: ME
authors.lastname: Roddie
authors.forename: Jamshid
authors.initials: J
authors.lastname: Demeshski
authors.forename: Hamdam
authors.initials: H
authors.lastname: Amin
authors.forename: David
authors.initials: D
authors.lastname: Burling
mesh_terms: D000293:Adolescent; D000465:Algorithms; D001185:Artificial Intelligence; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008297:Male; D015588:Observer Variation; D010363:Pattern Recognition, Automated / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity