title: Optimization of parameters for the detection of cerebral aneurysms: CT angiography of a model.
abstract: OBJECTIVE
  To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms.
  
  
  METHODS
  Model aneurysms were placed randomly at various branch points and scanned multiple times with spiral technique. The final analysis included 63 branch points and 22 aneurysms. Each spiral scan used a different parameter combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface display (SSD) and maximum intensity projection (MIP) algorithms and were interpreted by three readers for the presence or absence of aneurysm.
  
  
  RESULTS
  The receiver operating characteristic (ROC) curve area for 1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01 and P < .001, respectively). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statistically significant decrease in ROC curve area when increasing pitch from 1:1 to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the ROC curve areas for SSD images was greater than that of MIP images (P < .0001).
  
  
  CONCLUSIONS
  For cerebral aneurysm detection, narrow collimation is superior to wider collimation. Mild increases in pitch do not substantially degrade diagnostic accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.
authors.affiliation: Department of Radiology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
authors.forename: D F
authors.initials: DF
authors.lastname: Kallmes
authors.forename: A J
authors.initials: AJ
authors.lastname: Evans
authors.forename: R J
authors.initials: RJ
authors.lastname: Woodcock
authors.forename: R A
authors.initials: RA
authors.lastname: Omary
authors.forename: J E
authors.initials: JE
authors.lastname: Dix
authors.forename: B C
authors.initials: BC
authors.lastname: McNulty
authors.forename: C A
authors.initials: CA
authors.lastname: Holder
authors.forename: J E
authors.initials: JE
authors.lastname: Dion
mesh_terms: D000465:Algorithms; D002533:Cerebral Angiography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D012372:ROC Curve; D014057:Tomography, X-Ray Computed / Q000379:methods*