title: Assessing the effect of CT slice interval on unidimensional, bidimensional and volumetric measurements of solid tumours.
abstract: OBJECTIVE
  To study the magnitude of differences in tumour unidimensional (1D), bidimensional (2D) and volumetric (VOL) measurements determined from computed tomography (CT) images reconstructed at 5, 2.5 and 1.25 mm slice intervals.
  
  
  METHODS
  A total of 118 lesions in lung, liver and lymph nodes were selected from 30 patients enrolled in early phase clinical trials. Each CT scan was reconstructed at 5, 2.5 and 1.25 mm slice intervals during the image acquisition. Lesions were semi-automatically segmented on each interval image series and supervised by a radiologist. 1D, 2D and VOL were computed based on the final segmentation results. Average measurement differences across different slice intervals were obtained using linear mixed-effects analysis of variance models.
  
  
  RESULTS
  Lesion diameters ranged from 6.1 to 80.1 mm (median 18.4 mm). The largest difference was seen between 1.25 and 5 mm (mean difference of 7.6% for 1D [P < 0.0001], 13.1% for 2D [P < 0.0001], -5.7% for VOL [P = 0.0001]). Mean differences between 1.25 and 2.5 mm were all within ±3.5% (within ±6% confidence interval). For VOL, there was a larger average difference between measurements on different slice intervals for the smaller lesions (<10 mm) compared with the larger lesions.
  
  
  CONCLUSIONS
  Different slice intervals may give different 1D, 2D and VOL measurements. In clinical practice, it would be prudent to use the same slice interval for consecutive measurements.
authors.affiliation: Department of Radiology, Columbia University Medical Center, New York 10032, USA.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Tan
authors.forename: Pingzhen
authors.initials: P
authors.lastname: Guo
authors.forename: Helen
authors.initials: H
authors.lastname: Mann
authors.forename: Sarah Elizabeth
authors.initials: SE
authors.lastname: Marley
authors.forename: Marietta Louise
authors.initials: ML
authors.lastname: Juanita Scott
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Schwartz
authors.forename: Dana Cici
authors.initials: DC
authors.lastname: Ghiorghiu
authors.forename: Binsheng
authors.initials: B
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D000465:Algorithms; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011446:Prospective Studies; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*