title: Acute aortic syndromes: a second look at dual-phase CT.
abstract: OBJECTIVE
  The purpose of this article is to assess the diagnostic performance of the unenhanced and contrast-enhanced phases separately in patients imaged with CT for suspected acute aortic syndromes.
  
  
  METHODS
  All adults (n = 2868) presenting to our emergency department from January 1, 2006, through August 1, 2010, who underwent unenhanced and contrast-enhanced CT of the chest and abdomen for suspected acute aortic syndrome were retrospectively identified. Forty-five patients with acute aortic syndrome and 45 healthy control subjects comprised the study population (55 women; mean age, 61 ± 16 years). Unenhanced followed by contrast-enhanced CT angiography (CTA) images were reviewed. Contrast-enhanced CTA examinations of case patients and control subjects with isolated intramural hematoma were reviewed. Radiation exposure was estimated by CT dose-length product.
  
  
  RESULTS
  Forty-five patients had one or more CT findings of acute aortic syndrome: aortic dissection (n = 32), intramural hematoma (n = 27), aortic rupture (n = 10), impending rupture (n = 4), and penetrating atherosclerotic ulcer (n = 2). Unenhanced CT was 89% (40/45) sensitive and 100% (45/45) specific for acute aortic syndrome. Unenhanced CT was 94% (17/18) and 71% (10/14) sensitive for type A and type B dissection, respectively (p = 0.142). Contrast-enhanced CTA was 100% (8/8) sensitive for isolated intramural hematoma. Mean radiation effective dose was 43 ± 20 mSv.
  
  
  CONCLUSIONS
  Unenhanced CT performed well in detection of acute aortic syndrome treated surgically, although its performance does not support its use in place of contrast-enhanced CTA. Unenhanced CT may be a reasonable first examination for rapid triage when IV contrast is contraindicated. Contrast-enhanced CTA was highly sensitive for intramural hematoma, suggesting that unenhanced imaging may not always be needed. Acute aortic syndrome imaging protocols should be optimized to reduce radiation dose.
authors.affiliation: Department of Radiology, Montefiore Medical Center and Albert Einstein College of Medicine, 111 East 210th St, Gold Zone, Bronx, NY 10467, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lovy
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Rosenblum
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Levsky
authors.forename: Alla
authors.initials: A
authors.lastname: Godelman
authors.forename: Benjamin
authors.initials: B
authors.lastname: Zalta
authors.forename: Vineet R
authors.initials: VR
authors.lastname: Jain
authors.forename: Linda B
authors.initials: LB
authors.lastname: Haramati
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D001018:Aortic Diseases / Q000000981:diagnostic imaging*; D001027:Aortography / Q000379:methods*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003287:Contrast Media; D005260:Female; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013577:Syndrome; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; D007472:Iohexol; C038192:iopromide; C044834:iodixanol