title: Diagnosis of pulmonary emboli and image quality at CT pulmonary angiography: influence of imaging direction with multidetector CT.
abstract: OBJECTIVE
  To determine whether there was a significant difference in the prevalence of emboli detected when patients underwent computed tomography pulmonary angiography (CTPA) in a craniocaudal direction versus a caudocranial direction.
  
  
  METHODS
  This was a prospective study of 203 consecutive patients attending for CTPA for suspected pulmonary embolus. Imaging was performed on a multisection Siemens Volume Zoom CT machine, with bolus tracking centred on the main pulmonary artery after intravenous administration of contrast at 3 ml/s. Patients were examined in a single breath-hold, from the top of the aortic arch to the highest point of the diaphragm, in a randomly assigned cranio-caudal (group A), or caudo-cranial (group B) direction. Images were reviewed on a workstation in a cranio-caudal direction jointly by two radiologists unaware of the original imaging direction. The presence, number and position of arterial emboli were noted, and a subjective assessment of overall image quality and opacification of upper and lower lobe vessels (grade 1, 2, 3, or 4) was made.
  
  
  RESULTS
  Emboli were detected in 46 patients. There was no significant difference in the prevalence of emboli detected in the two groups [group A craniocaudal direction n=22, group B caudocranial direction n=24 (p=0.76)]. Imaging direction did not significantly influence overall image quality (p=0.07), however, there was a significantly greater proportion of patients in group A with grade 1 opacification of the upper lobe arteries (p=0.02).
  
  
  CONCLUSIONS
  Imaging direction does not significantly influence the diagnosis of pulmonary emboli but it does significantly improve the upper lobe pulmonary arterial enhancement with fewer non-diagnostic images, and on that basis we recommend that craniocaudal direction be used for CTPA studies.
authors.affiliation: Department of Radiology, The Mater Misericordiae University Hospital, Dublin, Ireland. gormlaith@eircom.net
authors.forename: G C
authors.initials: GC
authors.lastname: Hargaden
authors.forename: E C
authors.initials: EC
authors.lastname: Kavanagh
authors.forename: P
authors.initials: P
authors.lastname: Fitzpatrick
authors.forename: J G
authors.initials: JG
authors.lastname: Murray
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods / Q000592:standards*