title: Pulmonary metastases: effect of CT section thickness on measurement--initial experience.
abstract: OBJECTIVE
  To assess the effect of commonly used computed tomographic (CT) section thicknesses on metastatic tumor measurements calculated with unidimensional, bidimensional, area, and volumetric methods.
  
  
  METHODS
  Analysis and data collection were approved by the Institutional Review Board, with waived informed patient consent. Forty-two pulmonary metastases in 10 patients (three men and seven women; age range, 43-83 years; mean age, 65.4 years) were analyzed on CT scans obtained with 3.75-, 5.0-, and 7.5-mm section thicknesses. The lesions were automatically delineated by using a three-dimensional multicriteria segmentation algorithm. Unidimensional (the largest diameter), bidimensional (the product of the two maximal perpendicular diameters), maximal cross-sectional area, and volumetric measurements were automatically obtained for each pulmonary lesion on each section thickness. Means and variances were calculated, and the differences across the three section thicknesses for each of the four measurements were studied by using linear mixed-effects models. The Levene test was used to study the equality of variances.
  
  
  RESULTS
  Differences in the means for unidimensional, bidimensional, and area measurements were significant between a section thickness of 3.75 and 5.0 mm (unidimensional, P=.05; bidimensional, P=.05; area, P=.01) and 3.75 and 7.5 mm (unidimensional, P=.06; bidimensional, P=.03; area, P=.02), but not 5.0 and 7.5 mm. There was a significant difference in volumetric measurement as section thickness decreased from 7.5 to 5.0 mm (P <.001) and from 7.5 to 3.75 mm (P <.001). Although there was a slight trend for differences in the variances across section thickness for each measurement, none of the differences were significant.
  
  
  CONCLUSIONS
  Volumetric tumor measurements change with a reduction in section thickness from 7.5 to 5.0 and 3.75 mm. For unidimensional measurement, no change was found when thickness decreased from 7.5 to 5.0 mm.
authors.affiliation: Department of Radiology and Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021, USA. zhaob@mskcc.org
authors.forename: Binsheng
authors.initials: B
authors.lastname: Zhao
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Schwartz
authors.forename: Chaya S
authors.initials: CS
authors.lastname: Moskowitz
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Ginsberg
authors.forename: Cathleen A
authors.initials: CA
authors.lastname: Cooper
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.forename: John P
authors.initials: JP
authors.lastname: Kalaigian
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D016014:Linear Models; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods*