title: Comparison of volume and diameter measurement in assessing small abdominal aortic aneurysm expansion examined using computed tomographic angiography.
abstract: OBJECTIVE
  First we aimed to assess the reproducibility of a computer tomography angiography (CTA) based technique for measuring infra-renal aortic volume and diameter. Second we sought to investigate whether changes in aortic volume and diameter were similar during follow-up.
  
  
  METHODS
  A prospective series of 57 patients, with aortic diameter initially measuring between 25 and 55 mm, were assessed with 2 CTAs a median of 14 months apart. Aortic volume and maximum diameter (both axial and orthogonal) were measured by a semi-automated workstation protocol based on previously defined techniques. Intra- and inter-observer reproducibility were assessed by repeat assessment of the initial CTA images of the first 33 patients included in the study, in order to estimate the 95% limits of agreements. Changes in aortic dimensions between the first and follow-up CTA, were defined for volume and diameter separately as changes greater than their respective 95% limits of agreement.
  
  
  RESULTS
  Reproducibility of aortic volume and diameter was excellent with an average coefficient of variation <4%. The median (inter-quartile range) increases in total volume, orthogonal and axial diameters were 4.9 cm(3) (0.01-14.18), 1.2mm (0.40-3.50) and 1.4mm (-0.15 to 3.55) respectively. Forty-two percent of patients who had increased aortic volume above the 95% limit of agreement did not display corresponding axial or orthogonal diameter changes.
  
  
  CONCLUSIONS
  Infra-renal total aortic volume, axial and orthogonal diameter can all be measured reproducibly from CTA. Aortic volume changes are not always reflected by similar changes in diameter and therefore provide complementary information when assessing AAA expansion over time.
authors.affiliation: The Vascular Biology Unit, James Cook University, Townsville, Queensland 4811, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Parr
authors.forename: Chanaka
authors.initials: C
authors.lastname: Jayaratne
authors.forename: Petra
authors.initials: P
authors.lastname: Buttner
authors.forename: Jonathan
authors.initials: J
authors.lastname: Golledge
mesh_terms: D000368:Aged; D000792:Angiography / Q000379:methods*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media; D005260:Female; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D008297:Male; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide