title: The optimization of scan timing for contrast-enhanced magnetic resonance angiography.
abstract: OBJECTIVE
  To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time.
  
  
  METHODS
  Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods.
  
  
  RESULTS
  Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method.
  
  
  CONCLUSIONS
  The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Kyungpook National University, Taegu, South Korea. jonglee@knu.ac.kr
authors.forename: J J
authors.initials: JJ
authors.lastname: Lee
authors.forename: P J
authors.initials: PJ
authors.lastname: Tirman
authors.forename: Y
authors.initials: Y
authors.lastname: Chang
authors.forename: H K
authors.initials: HK
authors.lastname: Ryeom
authors.forename: S K
authors.initials: SK
authors.lastname: Lee
authors.forename: Y S
authors.initials: YS
authors.lastname: Kim
authors.forename: D S
authors.initials: DS
authors.lastname: Kang
mesh_terms: D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007275:Injections, Intravenous; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA