title: Aortic Curvature Instead of Angulation Allows Improved Estimation of the True Aorto-iliac Trajectory.
abstract: OBJECTIVE
  Supra- and infrarenal aortic neck angulation have been associated with complications after endovascular aortic aneurysm repair. However, a uniform angulation measurement method is lacking and the concept of angulation suggests a triangular oversimplification of the aortic anatomy. (Semi-)automated calculation of curvature along the center luminal line describes the actual trajectory of the aorta. This study proposes a methodology for calculating aortic (neck) curvature and suggests an additional method based on available tools in current workstations: curvature by digital calipers (CDC).
  
  
  METHODS
  Proprietary custom software was developed for automatic calculation of the severity and location of the largest supra- and infrarenal curvature over the center luminal line. Twenty-four patients with severe supra- or infrarenal angulations (≥45°) and 11 patients with small to moderate angulations (<45°) were included. Both CDC and angulation were measured by two independent observers on the pre- and postoperative computed tomographic angiography scans. The relationships between actual curvature and CDC and angulation were visualized and tested with Pearson's correlation coefficient. The CDC was also fully automatically calculated with proprietary custom software. The difference between manual and automatic determination of CDC was tested with a paired Student t test. A p-value was considered significant when two-tailed α < .05.
  
  
  RESULTS
  The correlation between actual curvature and manual CDC is strong (.586-.962) and even stronger for automatic CDC (.865-.961). The correlation between actual curvature and angulation is much lower (.410-.737). Flow direction angulation values overestimate CDC measurements by 60%, with larger variance. No significant difference was found in automatically calculated CDC values and manually measured CDC values.
  
  
  CONCLUSIONS
  Curvature calculation of the aortic neck improves determination of the true aortic trajectory. Automatic calculation of the actual curvature is preferable, but measurement or calculation of the curvature by digital calipers is a valid alternative if actual curvature is not at hand.
authors.affiliation: Technical Medicine, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands; Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands. Electronic address: richte.schuurmann@gmail.com.
authors.forename: R C L
authors.initials: RC
authors.lastname: Schuurmann
authors.affiliation: Technical Medicine, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Kuster
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: C H
authors.initials: CH
authors.lastname: Slump
authors.affiliation: Department of Vascular Surgery, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Vahl
authors.affiliation: Department of Radiology, St. Antonius Hospital, Nieuwegein, The Netherlands.
authors.forename: D A F
authors.initials: DA
authors.lastname: van den Heuvel
authors.affiliation: Syntactx, World Trade Center, New York, NY, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ouriel
authors.affiliation: Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands.
authors.forename: J-P P M
authors.initials: JP
authors.lastname: de Vries
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery; D001027:Aortography / Q000379:methods*; D001331:Automation; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation; D057510:Endovascular Procedures / Q000295:instrumentation; D005260:Female; D006801:Humans; D007083:Iliac Artery / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012984:Software; D015607:Stents; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: Abdominal aortic aneurysm; Computing methodologies; Endovascular procedures; Stents