title: Semi-automatic software increases CT measurement accuracy but not response classification of colorectal liver metastases after chemotherapy.
abstract: OBJECTIVE
  This study evaluates intra- and interobserver variability of automatic diameter and volume measurements of colorectal liver metastases (CRLM) before and after chemotherapy and its influence on response classification.
  
  
  METHODS
  Pre-and post-chemotherapy CT-scans of 33 patients with 138 CRLM were evaluated. Two observers measured all metastases three times on pre-and post-chemotherapy CT-scans, using three different techniques: manual diameter (MD), automatic diameter (AD) and automatic volume (AV). RECIST 1.0 criteria were used to define response classification. For each technique, we assessed intra- and interobserver reliability by determining the intraclass correlation coefficient (α-level 0.05). Intra-observer agreement was estimated by the variance coefficient (%). For inter-observer agreement the relative measurement error (%) was calculated using Bland-Altman analysis. In addition, we compared agreement in response classification by calculating kappa-scores (κ) and estimating proportions of discordance between methods (%).
  
  
  RESULTS
  Intra-observer variability was 6.05%, 4.28% and 12.72% for MD, AD and AV, respectively. Inter-observer variability was 4.23%, 2.02% and 14.86% for MD, AD and AV, respectively. Chemotherapy marginally affected these estimates. Agreement in response classification did not improve using AD or AV (MD κ=0.653, AD κ=0.548, AV κ=0.548) and substantial discordance between observers was observed with all three methods (MD 17.8%, AD 22.2%, AV 22.2%).
  
  
  CONCLUSIONS
  Semi-automatic software allows repeatable and reproducible measurement of both diameter and volume measurements of CRLM, but does not reduce variability in response classification.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. c.s.vankessel@umcutrecht.nl
authors.forename: Charlotte S
authors.initials: CS
authors.lastname: van Kessel
authors.forename: Maarten S
authors.initials: MS
authors.lastname: van Leeuwen
authors.forename: Petronella O
authors.initials: PO
authors.lastname: Witteveen
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Kwee
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
authors.forename: Richard
authors.initials: R
authors.lastname: van Hillegersberg
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000556:secondary; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods; D010363:Pattern Recognition, Automated / Q000379:methods*; D011379:Prognosis; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents