title: Pre-operative classification of abdominal aortic aneurysms with spiral CT: the axial source images revisited.
abstract: OBJECTIVE
  The differentiation of supra-, juxta- and high infrarenal abdominal aortic aneurysms (AAA), which is essential for good surgical management, remains problematic. This prospective study assessed the value of highly overlapping vs. contiguous axial spiral computed tomography (CT) reconstructions in the pre-operative assessment of AAA.
  
  
  METHODS
  Thirty-five patients with abdominal aortic aneurysms were studied with spiral CT (10 mm collimation, pitch 1). Axial reconstructions were performed at 2 and 10 mm increments and compared with surgical findings. Using each protocol, the aneurysms were classified as infra-, juxta- or suprarenal. Observers also assessed visualization of main and accessory renal artery origins and identification of other surgically relevant vascular anomalies.
  
  
  RESULTS
  The 2 mm protocol correctly identified 29/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; two infrarenal aneurysms were overestimated as suprarenal. The 10 mm protocol correctly classified 25/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; five infrarenal aneurysms were overestimated as juxtarenal (n = 3) or suprarenal (n = 2) and one case was equivocal. Correct classification was thus 94% using the 2 mm protocol and 83% with the 10 mm protocol (P = 0.063). All 70 main renal artery origins were visualized with the 2 mm protocol, while the 10 mm protocol missed six (P = 0.03) The 2 mm protocol identified 10 accessory renal arteries, four of which were missed by the 10 mm protocol. Both protocols demonstrated five surgically relevant venous anomalies.
  
  
  CONCLUSIONS
  Spiral CT with highly overlapping axial reconstructions correctly classified 94% of abdominal aortic aneurysms; overlapping reconstructions were particularly useful in differentiating high infrarenal from juxtarenal aneurysms.
authors.affiliation: Department of Imaging, Hammersmith Hospital, Royal Postgraduate Medical School, London, UK.
authors.forename: T
authors.initials: T
authors.lastname: Albrecht
authors.forename: H R
authors.initials: HR
authors.lastname: Jäger
authors.forename: M J
authors.initials: MJ
authors.lastname: Blomley
authors.forename: A
authors.initials: A
authors.lastname: Lopez
authors.forename: J
authors.initials: J
authors.lastname: Hossain
authors.forename: N
authors.initials: N
authors.lastname: Standfield
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000145:classification / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012077:Renal Artery / Q000002:abnormalities / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*