Angiography For The Circle Of Willis | CT Protocols

Angiography For The Circle Of Willis | CT Protocols
Beginners Tips- CT Protocols

CT protocol- Circle of Willis

  • Suspected incidental intracranial aneurysm 
  • Subarachnoid aneurysm 
  • Arterial occlusion 
  • Arteriovenous malformation, etc. 
Patient Positioning
Supine with Headfirst, with Arms beside the trunk. 

Topogram Position/Landmark
Lateral; level of the vertex. 

Mode of Scanning

Scan Orientation
  • Starting Location-Level of the occipital squame. 
  • End Location-To the expected upper limit of the region of interest. 
Gantry Tilt

Field of View
Just including the region of interest.

Contrast Administration

The volume of Contrast
100-150 mL. 

Rate of Injection of Contrast
4-5 mL/sec. 

Scan Delay
20-25 sec. 

Slice Thickness in Reconstruction
1.0-1.5 mm. 

Slice Interval in Reconstruction
0.5-0.75 mm. 

Reconstruction Algorithm/Kernel

  • MPR
  • MIP
  • VRT
  • SSD 


  • The use of a headrest is recommended for head positioning. 
  • The use of the bolus tracking method for determining the optimal scan delay is preferred. 
  • A noncontrast scan in sequential mode should precede the angiography protocol as it will give the baseline scans, will determine the region of interest, and also are useful for subtraction images.
  • There should be no motion between the noncontrast and contrast scans besides using the same technical parameters if subtraction images are desired. 

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