title: Quality of extracranial carotid evaluation with 256-section CT.
abstract: OBJECTIVE
  To date, no systematic evaluation of image quality has been performed on the 256-section multidetector CT scanner for extracranial carotid evaluations. We evaluated image quality, patient dose, and examination time and compared these parameters with a 64-section multidetector CT.
  
  
  METHODS
  We reviewed extracranial CTA scans obtained on a 256-detector CT scanner in 50 consecutive patients. Image quality was analyzed for artifacts and vessel contrast opacification from the aortic arch to the skull base, dose to patient, and scan time. Results were compared with a control group of 50 patients imaged on a 64-section CT scanner. A Fisher exact test was used to analyze both groups with respect to vessel contrast opacification and presence of artifacts, and a Student t test was used to assess differences in patient dose between the 2 groups.
  
  
  RESULTS
  Quantitative and qualitative evaluations revealed >95% acceptable vessel opacification at all levels measured on the 256-section scanner. Scan time was improved (4 seconds on 256-channel). There were fewer artifacts related to metallic streak on the 256-channel CTA study, and DLP was lower on the 256-channel CTA (113.9 versus 159.8 mGy).
  
  
  CONCLUSIONS
  The 256-channel CTA imaging protocol for carotid arteries yielded similar vessel contrast opacification compared with the 64-channel CTA but with fewer metallic artifacts, a modest decrease in scan time, similar image quality, and a statistically significant reduction in radiation dose of 10%.
authors.affiliation: Section of Neuroradiology, Department of Radiology, Fletcher Allen Health Care, Burlington, VT, USA. JJohnson57@partners.org
authors.forename: J M
authors.initials: JM
authors.lastname: Johnson
authors.forename: M S
authors.initials: MS
authors.lastname: Reed
authors.forename: H N
authors.initials: HN
authors.lastname: Burbank
authors.forename: C G
authors.initials: CG
authors.lastname: Filippi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002339:Carotid Arteries; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult