title: Continuous measurement of aortic dimensions in Turner syndrome: a cardiovascular magnetic resonance study.
abstract: BACKGROUND
  Severity of thoracic aortic disease in Turner syndrome (TS) patients is currently described through measures of aorta size and geometry at discrete locations. The objective of this study is to develop an improved measurement tool that quantifies changes in size and geometry over time, continuously along the length of the thoracic aorta.
  
  
  METHODS
  Cardiovascular magnetic resonance (CMR) scans for 15 TS patients [41 ± 9 years (mean age ± standard deviation (SD))] were acquired over a 10-year period and compared with ten healthy gender and age-matched controls. Three-dimensional aortic geometries were reconstructed, smoothed and clipped, which was followed by identification of centerlines and planes normal to the centerlines. Geometric variables, including maximum diameter and cross-sectional area, were evaluated continuously along the thoracic aorta. Distance maps were computed for TS and compared to the corresponding maps for controls, to highlight any asymmetry and dimensional differences between diseased and normal aortae. Furthermore, a registration scheme was proposed to estimate localized changes in aorta geometry between visits. The estimated maximum diameter from the continuous method was then compared with corresponding manual measurements at 7 discrete locations for each visit and for changes between visits.
  
  
  RESULTS
  Manual measures at the seven positions and the corresponding continuous measurements of maximum diameter for all visits considered, correlated highly (R-value = 0.77, P < 0.01). There was good agreement between manual and continuous measurement methods for visit-to-visit changes in maximum diameter. The continuous method was less sensitive to inter-user variability [0.2 ± 2.3 mm (mean difference in diameters ± SD)] and choice of smoothing software [0.3 ± 1.3 mm]. Aortic diameters were larger in TS than controls in the ascending [TS: 13.4 ± 2.1 mm (mean distance ± SD), Controls: 12.6 ± 1 mm] and descending [TS: 10.2 ± 1.3 mm (mean distance ± SD), Controls: 9.5 ± 0.9 mm] thoracic aorta as observed from the distance maps.
  
  
  CONCLUSIONS
  An automated methodology is presented that enables rapid and precise three-dimensional measurement of thoracic aortic geometry, which can serve as an improved tool to define disease severity and monitor disease progression.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier - NCT01678274 . Registered - 08.30.2012.
authors.affiliation: Department of Aerospace Engineering and Engineering Mechanics, CEAS, University of Cincinnati, Cincinnati, OH, USA.
authors.forename: Dhananjay Radhakrishnan
authors.initials: DR
authors.lastname: Subramaniam
authors.affiliation: Department of Aerospace Engineering and Engineering Mechanics, CEAS, University of Cincinnati, Cincinnati, OH, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Stoddard
authors.affiliation: Cardio-respiratory Unit, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK.
authors.forename: Kristian H
authors.initials: KH
authors.lastname: Mortensen
authors.affiliation: Institute for Clinical Medicine, Aarhus University, Aarhus N, Denmark.
authors.forename: Steffen
authors.initials: S
authors.lastname: Ringgaard
authors.affiliation: Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Trolle
authors.affiliation: Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus C, Denmark.|Department of Molecular Medicine, Aarhus University Hospital, Aarhus N, Denmark.
authors.forename: Claus H
authors.initials: CH
authors.lastname: Gravholt
authors.affiliation: Department of Aerospace Engineering and Engineering Mechanics, CEAS, University of Cincinnati, Cincinnati, OH, USA.|UC Department of Otolaryngology, Head and Neck Surgery, Cincinnati, OH, USA.
authors.forename: Ephraim J
authors.initials: EJ
authors.lastname: Gutmark
authors.affiliation: Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors.forename: Goutham
authors.initials: G
authors.lastname: Mylavarapu
authors.affiliation: Division of Endocrinology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA.
authors.forename: Philippe F
authors.initials: PF
authors.lastname: Backeljauw
authors.affiliation: Division of Endocrinology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA. iris.little@cchmc.org.
authors.forename: Iris
authors.initials: I
authors.lastname: Gutmark-Little
mesh_terms: D000328:Adult; D000784:Aortic Dissection / Q000000981:diagnostic imaging* / Q000209:etiology; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging* / Q000209:etiology; D001331:Automation; D016022:Case-Control Studies; D004108:Dilatation, Pathologic; D018450:Disease Progression; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors; D014424:Turner Syndrome / Q000150:complications* / Q000175:diagnosis; D051598:Whole Body Imaging
keywords: Aorta; Cardiovascular magnetic resonance; Centerlines; Continuous measures; Euclidean distance; Iterative closest point; Maximum diameter; Turner syndrome