title: Noninvasive quantification of tumor volume in preclinical liver metastasis models using contrast-enhanced x-ray computed tomography.
abstract: OBJECTIVE
  To determine a timepoint after contrast injection that yields equal liver parenchymal and vascular enhancement in micro-computed tomography images. To evaluate the utility of images acquired during this time period for the noninvasive measurement of liver-tumor volume.
  
  
  METHODS
  The imaging timepoint was determined by quantifying the enhancement kinetics of Fenestra VC (0.015 mL/g) in NIH III mice. In respiratory-gated images of tumor bearing mice, the ability to measure tumor volume was evaluated with a measurement variability study, and by comparing in vivo and histologically measured tumor volume.
  
  
  RESULTS
  Eight hours after contrast injection the liver parenchyma and vasculature were equally enhanced allowing for clear delineation of the unenhanced tumors. The smallest tumor detected in this study was 1.1 mm in diameter. The coefficient of variation for tumor-volume measurement ranged from 3.6% to 12.9% and from 6.3% to 25.8% for intra and interobserver variability, respectively. In vivo and histologic tumor-volume measurements were closely correlated (r = 0.98, P < 0.0001).
  
  
  CONCLUSIONS
  Imaging at a time period of equal liver parenchyma and vascular enhancement after contrast injection allows for clear delineation of liver-tumor borders, thereby enabling quantitative tumor-volume monitoring.
authors.affiliation: Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Graham
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Ford
authors.forename: Lisa T
authors.initials: LT
authors.lastname: MacKenzie
authors.forename: Carl O
authors.initials: CO
authors.lastname: Postenka
authors.forename: Alan C
authors.initials: AC
authors.lastname: Groom
authors.forename: Ian C
authors.initials: IC
authors.lastname: MacDonald
authors.forename: David W
authors.initials: DW
authors.lastname: Holdsworth
authors.forename: Maria
authors.initials: M
authors.lastname: Drangova
authors.forename: Ann F
authors.initials: AF
authors.lastname: Chambers
mesh_terms: D000818:Animals; D003287:Contrast Media; D005260:Female; D007091:Image Processing, Computer-Assisted; D007479:Iopamidol; D008099:Liver / Q000473:pathology*; D008107:Liver Diseases / Q000175:diagnosis / Q000473:pathology; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000473:pathology; D051379:Mice; D008954:Models, Biological; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D003287:Contrast Media; D007479:Iopamidol