title: Time-resolved CT angiography in aortic dissection.
abstract: OBJECTIVE
  We performed this study to assess feasibility and additional diagnostic value of time-resolved CT angiography of the entire aorta in patients with aortic dissection.
  
  
  METHODS
  14 consecutive patients with known or suspected aortic dissection (aged 60±9 years) referred for aortic CT angiography were scanned on a dual-source CT scanner (Somatom Definition Flash; Siemens, Forchheim, Germany) using a shuttle mode for multiphasic image acquisition (range 48 cm, time resolution 6s, 6 phases, 100 kV, 110 mAs/rot). Effective radiation doses were calculated from recorded dose length products. For all phases, CT densities were measured in the aortic lumen and renal parenchyma. From the multiphasic data, 3 phases corresponding to a triphasic standard CT protocol, served as a reference and were compared against findings from the time-resolved datasets.
  
  
  RESULTS
  Mean effective radiation dose was 27.7±3.5 mSv. CT density of the true lumen peaked at 355±53 HU. Compared to the simulated triphasic protocol, time-resolved CT angiography added diagnostic information regarding a number of important findings: the enhancement delay between true and false lumen (n=14); the degree of membrane oscillation (n=14); the perfusion delay in arteries originating from the false lumen (n=9). Other additional information included true lumen collapse (n=4), quantitative assessment of renal perfusion asymmetry (n=2), and dynamic occlusion of aortic branches (n=2). In 3/14 patients (21%), these additional findings of the multiphasic protocol altered patient management.
  
  
  CONCLUSIONS
  Multiphasic, time-resolved CT angiography covering the entire aorta is feasible at a reasonable effective radiation dose and adds significant diagnostic information with therapeutic consequences in patients with aortic dissection.
authors.affiliation: Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany. felix.meinel@med.uni-muenchen.de
authors.forename: Felix G
authors.initials: FG
authors.lastname: Meinel
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.forename: Rolf
authors.initials: R
authors.lastname: Weidenhagen
authors.forename: Katharina
authors.initials: K
authors.lastname: Hellbach
authors.forename: Andreas
authors.initials: A
authors.lastname: Helck
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
mesh_terms: D000465:Algorithms; D000784:Aortic Dissection / Q000000981:diagnostic imaging*; D000792:Angiography / Q000379:methods*; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging*; D001027:Aortography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*