Influence of Field Strength on Intracranial Vessel Conspicuity in Canine Magnetic Resonance Angiography

Eight neurologically normal beagles were imaged using three-dimensional (3D) time-of-flight magnetic resonance angiography (MRA) in a 3T magnetic resonance scanner. Four of the eight dogs were also imaged using a 1T unit for comparison. Ten intracranial arteries were consistently identified at 3T: external and internal carotid, basilar, vertebral, rostral cerebral, middle cerebral, caudal cerebral, rostral communicating, caudal communicating, and ventral spinal arteries. Only four were reliably identified at 1T with diagnostic spatial and contrast resolution. At 3 T, vessels as small as 1 mm were reliably detected. Vessel conspicuity was superior using the 3T system. An anatomic atlas of the canine circulus arteriosus cerebri using a 3T scan was constructed. The effect of MRA parameters on vascular spatial resolution a nd conspicuity are reviewed.