title: Variation in maximum diameter measurements of descending thoracic aortic aneurysms using unformatted planes versus images corrected to aortic centerline.
abstract: OBJECTIVE
  Evaluation of variation in descending thoracic aortic aneurysm (dTAA) diameters measured on CT scans in different planes and by different observers and the potential impact on treatment decisions.
  
  
  METHODS
  CT angiography of dTAA (N = 20) were assessed by three specialists, with measurements repeated after 1 month. Calliper measurements of maximum external diameters were made on unformatted images and perpendicular to the aneurysm centerline after image processing (corrected). Repeatability was assessed using Bland-Altman plots.
  
  
  RESULTS
  Maximum corrected diameter measurements were smaller than axial measurements (66.3 ± 7.9 mm vs. 74.9 ± 20.9 mm, p < .001). Both intraobserver and interobserver variation were less for corrected than for axial measurements (mean intraobserver differences 5.0 ± 3.8 mm vs. 11.8 ± 9.3 mm, p < .001; mean interobserver differences 2.8 ± 2.5 mm versus 10.4 ± 14.0 mm, p < .001) and interobserver variation increased with aneurysm diameter for maximum axial but not corrected measurements. Using corrected rather than axial measurements could have changed treatment decisions in two patients (10%) using a treatment threshold diameter of 55 mm and 10 patients (50%) using a threshold of 65 mm.
  
  
  CONCLUSIONS
  Corrected diameters were smaller than axial diameters, could be measured with higher repeatability, and were subject to less interobserver variability. Using corrected versus axial measurements would have changed management decisions in up to half of the cases in this study.
authors.affiliation: Department of Surgery and Cancer, Imperial College, London, UK; Imperial Vascular Unit, Imperial College Healthcare NHS Trust, London, UK. Electronic address: N.Rudarakanchana@imperial.ac.uk.
authors.forename: N
authors.initials: N
authors.lastname: Rudarakanchana
authors.affiliation: Department of Surgery and Cancer, Imperial College, London, UK; Imperial Vascular Unit, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: C D
authors.initials: CD
authors.lastname: Bicknell
authors.affiliation: Department of Surgery and Cancer, Imperial College, London, UK; Imperial Vascular Unit, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: N J
authors.initials: NJ
authors.lastname: Cheshire
authors.affiliation: Department of Interventional Radiology, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Burfitt
authors.affiliation: Department of Interventional Radiology, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Chapman
authors.affiliation: Department of Surgery and Cancer, Imperial College, London, UK; Department of Interventional Radiology, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Hamady
authors.affiliation: Department of Surgery and Cancer, Imperial College, London, UK.
authors.forename: J T
authors.initials: JT
authors.lastname: Powell
mesh_terms: D000704:Analysis of Variance; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging* / Q000628:therapy; D001027:Aortography / Q000379:methods*; D006801:Humans; D061330:Multidetector Computed Tomography; D015588:Observer Variation; D011237:Predictive Value of Tests; D011379:Prognosis; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results
keywords: CT scan; Dimensional measurement accuracy; Endovascular procedure; Thoracic aortic aneurysm