title: Cerebral CT angiography using a small volume of concentrated contrast material with a test injection method: optimal scan delay for quantitative and qualitative performance.
abstract: OBJECTIVE
  The objective of this study was to determine the optimal scan delay quantitatively and qualitatively in cerebral CT angiography (CTA) with a test injection method at the circle of Willis (cW).
  
  
  METHODS
  66 consecutive patients suspected of having unruptured intracranial aneurysms underwent CTA using 40 ml of 370 mg iodine ml(-1) contrast material (CM). After the time until CM arrival at the cW (T(cW)) was calculated, scan delay was divided into three groups according to T(cW) and scan duration (SD) between the second cervical vertebra and cW as follows: [(T(cW)+6)-SD] in 21 patients (Group A); [(T(cW)+8)-SD] in 23 patients (Group B); and [(T(cW)+10)-SD] in 22 patients (Group C). Arterial and venous attenuation in the intracranial vessels was measured. Mean attenuation values were compared quantitatively. The arterial enhancement and venous overlap at the cW and above the cW were qualitatively compared among the three groups.
  
  
  RESULTS
  Mean arterial attenuation in Groups B and C was significantly higher than that in Group A. Mean venous attenuation in Group C was significantly higher than those in Groups A and B. Arterial enhancement above the cW showed a significant difference between Groups A and C, and at the cW between Groups A and B, and Groups A and C. There was a significant difference in venous overlap among the three groups, except for that at the cW between Groups B and C.
  
  
  CONCLUSIONS
  Setting scan delay as [(T(cW)+8)-SD] s can produce the best performance both quantitatively and qualitatively.
authors.affiliation: Department of Radiology, Showa University Fujigaoka Hospital, Aoba-ku, Yokohama, Japan. momiji@mtc.biglobe.ne.jp
authors.forename: N
authors.initials: N
authors.lastname: Takeyama
authors.forename: K
authors.initials: K
authors.lastname: Kuroki
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Sai
authors.forename: N
authors.initials: N
authors.lastname: Okabe
authors.forename: Y
authors.initials: Y
authors.lastname: Kinebuchi
authors.forename: T
authors.initials: T
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Gokan
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D002533:Cerebral Angiography / Q000379:methods*; D002941:Circle of Willis / Q000000981:diagnostic imaging; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging*; D018538:Jupiter; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids / Q000008:administration & dosage*; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C053571:iopentol