title: Can the unenhanced phase be eliminated from dual-phase CT angiography for chest pain? Implications for diagnostic accuracy in acute aortic intramural hematoma.
abstract: OBJECTIVE
  The purposes of this study were to retrospectively assess the frequency of acute aortic intramural hematoma and evaluate whether the elimination of the unenhanced imaging acquisition series from the dual-phase MDCT angiography (CTA) protocol for chest pain might affect diagnostic accuracy in detecting intramural hematoma and justify the reduced radiation dose.
  
  
  METHODS
  From October 2006 to November 2012, 306 patients (mean age, 65.0 years) with acute chest pain underwent emergency CTA with a 64-MDCT scanner. Two experienced cardiovascular radiologists, blinded to the diagnosis, assessed the images in two different sessions in which enhanced (single-phase CTA) and combined unenhanced and contrast-enhanced (dual-phase CTA) findings were evaluated. Sensitivity, specificity, and accuracy along with 95% CIs were calculated. Surgical and pathologic diagnoses, including findings at clinical follow-up and any subsequent imaging modality, were used as reference standards.
  
  
  RESULTS
  Thirty-six patients were suspected of having intramural hematoma; 16 patients underwent both surgery and transesophageal echocardiography (TEE), and the remaining 20 underwent TEE. Single-phase CTA showed a higher number of false-negative and false-positive results than dual-phase CTA. With intramural hematoma frequency of 12% (95% CI, 8.38-15.91%), sensitivity, specificity, and accuracy were 94.4% (81.3-99.3%), 99.3% (97.4-99.9%), and 98.7% (96.7-99.6%) for combined dual-phase CTA and 68.4% (51.4-82.5%), 96.3% (93.2-98.2%), and 92.8% (89.3-95.4%) for single-phase CTA. Dual-phase was significantly better than single-phase CTA with respect to sensitivity (p=0.002), specificity (p=0.008), overall accuracy (p<0.001), and interrater agreement (p=0.001).
  
  
  CONCLUSIONS
  The frequency of acute aortic intramural hematoma is similar to that previously reported. The acquisition of unenhanced images during the chest pain dual-phase CTA protocol significantly improves diagnostic accuracy over single-phase CTA.
authors.affiliation: 1 Department of Radiology, Foundation IRCCS Cà Granda Maggiore Policlinico Hospital. Via Francesco Sforza, 35-Milan, Italy.
authors.forename: Alessandro A
authors.initials: AA
authors.lastname: Lemos
authors.forename: John C
authors.initials: JC
authors.lastname: Pezzullo
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Fasani
authors.forename: Marta
authors.initials: M
authors.lastname: Gullo
authors.forename: Caterina
authors.initials: C
authors.lastname: Giannitto
authors.forename: Roberto
authors.initials: R
authors.lastname: Lo Gullo
authors.forename: Pietro R
authors.initials: PR
authors.lastname: Biondetti
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D001018:Aortic Diseases / Q000000981:diagnostic imaging*; D017023:Coronary Angiography / Q000379:methods*; D005260:Female; D006406:Hematoma / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT angiography; acute chest pain; aortic intramural hematoma