title: Prediction of thoracic aortic aneurysm expansion: validation of formulae describing growth.
abstract: BACKGROUND
  The expansion rate of thoracic aortic aneurysms may be an important and clinically relevant index of the risk of rupture. The aims of this study were to assess the validity of three published exponential equations that predict expansion rate in a separate sample population, and to calculate an expansion rate formula for this cohort of patients.
  
  
  METHODS
  We studied 88 consecutive patients undergoing serial computed tomographic or magnetic resonance imaging scanning to monitor thoracic aortic aneurysm progression. In interval scans of at least 6 months, we measured minimum coronal aortic diameter at seven set levels and maximal diameter, yielding 780 segment-intervals.
  
  
  RESULTS
  The linear expansion rate (mean 2.6 mm/year) increased with incremental aortic diameter (aortic diameter < 40 mm: 2.0; 40-49 mm: 2.3; 50-59 mm: 3.6; > or = 60 mm: 5.6 mm/year; p < 0.01). Regression analysis showed close correlation between predicted and sample data, but there were significant differences between observed and expected measurements. The Yale formula underestimated growth by 0.8 mm, while Mt. Sinai and Osaka formulae overestimated actual change by 1.5 and 0.2 mm, respectively. The expansion rate derived from our population was: last diameter = initial diameter x e(0.00367 x time) (r = 0.617).
  
  
  CONCLUSIONS
  Although formulae derived from one thoracic aortic aneurysm sample population may not extrapolate exactly to others, there is close concordance of results for patient populations in three different continents.
authors.affiliation: Department of Radiology, Queen Elizabeth Hospital, and University of Birmingham, Edgbaston, United Kingdom.
authors.forename: I
authors.initials: I
authors.lastname: Shimada
authors.forename: S J
authors.initials: SJ
authors.lastname: Rooney
authors.forename: D
authors.initials: D
authors.lastname: Pagano
authors.forename: P A
authors.initials: PA
authors.lastname: Farneti
authors.forename: P
authors.initials: P
authors.lastname: Davies
authors.forename: P J
authors.initials: PJ
authors.lastname: Guest
authors.forename: R S
authors.initials: RS
authors.lastname: Bonser
mesh_terms: D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed