Spatial misregistration of vascular flow during MR imaging of the CNS: cause and clinical significance.
Spatial misregistration of signal recovered from flowing spins within vascular structures is a common phenomenon seen in MR imaging of the CNS. The condition is displayed as a bright line or dot offset from the true anatomic location of the lumen of the imaged vessel. Its origin is the time delay between application of the phase- and frequency-encoding gradients used to locate spins within the plane of section. The principal condition necessary for the production of spatial misregistration is flow oblique to the axis of the phase-encoding gradient. Flow-related enhancement (entry slice phenomenon), even-echo rephasing, and gradient-moment nulling contribute to the production of the bright signal of spatial misregistration. Familiarity with the typical appearance of flow-dependent spatial misregistration permits confirmation of a vessel's patency; identification of the direction of flow; estimation of the velocity of flow; and differentiation of this flow artifact from atheromas, dissection, intraluminal clot, and artifacts such as chemical shift.
Larson
T C
TC
Department of Radiology, University of California, San Francisco 94143-0620.
Kelly
W M
WM
Ehman
R L
RL
Wehrli
F W
FW
D001783:Blood Flow Velocity; D002528:Cerebellar Neoplasms / Q000098:blood supply; D002536:Cerebral Arteries / Q000503:physiopathology; D002550:Cerebral Veins / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006391:Hemangioma / Q000098:blood supply; D006801:Humans; D008279:Magnetic Resonance Imaging; D012016:Reference Values; D012039:Regional Blood Flow