title: Reduced z-axis coverage in multidetector-row CT pulmonary angiography decreases radiation dose and diagnostic accuracy of alternative diseases.
abstract: OBJECTIVE
  To investigate the effect of a two-third reduction of the scanned length (i.e. 10 cm) on diagnosis of both pulmonary embolism (PE) and alternative diseases.
  
  
  METHODS
  247 consecutive patients suspected of acute PE had a CT pulmonary angiography (CTPA) of the thorax (standard length, L). Based on this acquisition, a second set of images was created to obtain a scan length of 10 cm caudally to the aortic arch (l). Images were anonymized, randomized and interpreted by two independent readers. The quality of enhancement, the presence of PE and the possible alternative and/or complementary diagnoses were recorded. A McNemar exact test investigated differences in discrepancies between readers and between scan lengths.
  
  
  RESULTS
  57 (23%) patients had an acute PE. Among l sets, PE was missed by both readers in one (1.8%) patient, because the unique clot was localized in a subsegmental artery out of the 10-cm range. There were discrepancies between L and l sets in 9 (3.6%) and 11 (4.5%) patients, by Readers 1 and 2 (p=0.820), respectively. Discrepancies between the readers of L sets and those between both sets were not different regardless of the reader (p>0.99). There were discrepancies between both sets for alternative and/or complementary diagnoses in 43 (17.2%) patients.
  
  
  CONCLUSIONS
  Although its performance in diagnosing PE is maintained, CTPA should not be restricted to a range of 10 cm centred over the pulmonary hilum, because alternative and/or complementary diagnoses could be missed.
  
  
  CONCLUSIONS
  (1) A 10-cm CTPA acquisition reduces the radiation dose by two-thirds as compared with a standard one, but does not impair the accuracy for the diagnosis of PE. (2) Significant alternative diagnoses are missed in 17.2% of patients when reducing the acquisition height to 10 cm.
authors.affiliation: Department of Radiology, Hôpital Erasme, Université libre de Bruxelles, Brussels, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Michalakis
authors.forename: C
authors.initials: C
authors.lastname: Keyzer
authors.forename: V
authors.initials: V
authors.lastname: De Maertelaer
authors.forename: D
authors.initials: D
authors.lastname: Tack
authors.forename: P A
authors.initials: PA
authors.lastname: Gevenois
mesh_terms: D000792:Angiography / Q000379:methods*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods