In Vivo Assessment and Visualization of Intracranial Arterial Hemodynamics with Flow-Sensitized 4D MR Imaging at 3T
S. Wetzela,
S. Meckela,
A. Frydrychowiczb,
L. Bonatic,
E.-W. Raduea,
K. Schefflerd,
J. Hennigb and
M. Marklb
a Department of Medical Radiology, Institute of Neuroradiology, University Hospital of Basel, Basel, Switzerland
b Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany
c Department of Neurology, University Hospital of Basel, Basel, Switzerland
d Department of Medical Radiology, MR-Physics, University Hospital of Basel, Basel, Switzerland
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Fig 1. Normal 3D blood-flow patterns and velocities of the circle of Willis by using 3D streamline visualization reveal complex flow patterns and segmental changes in absolute blood-flow velocities (color-coding indicates local blood flow velocity magnitude). Additional streamline visualization was performed in a short segment of the superior sagittal sinus transecting the axial 3D volume (top left, white arrow).
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Fig 2. Time-resolved 3D particle traces for 4 successive systolic timeframes illustrating blood flow in parts of the circle of Willis in 2 healthy volunteers with axial (ax) slab orientations. Color-coding corresponds to the local blood-flow velocity magnitude. A, Overview of the anterior part of the circle of Willis. Simultaneous systolic filling and local blood-flow characteristics of the left and right C1, M1, and A1 segments can clearly be appreciated. B, Targeted view of the left carotid siphon exhibiting complex-flow helical patterns and segmental-flow acceleration.
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Fig 3. Time-resolved 3D particle traces in 4 consecutive systolic timeframes illustrate the filling of the right carotid siphon. Note the complex and counter-clockwise helical flow pattern (if viewed along the flow direction) in the C5 segment (open arrow). The emitter plane from which particle traces were released from equidistant grid points is indicated by the solid white arrow. In the superior sagittal sinus (asterisk), particle traces demonstrate lower flow velocities and thus reduced tracer length compared with arterial blood flow.
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Fig 4. Time-resolved 3D particle trace visualization for a patient with occlusion of the LCA. A, TOF-MRA demonstrating occlusion of the LCA and a small anterior communicating artery (small arrows). B, Arterial filling of the large intracranial vessels for 2 systolic timeframes indicating the absence of flow evolution at the level of the distal left ICA (open white arrows). Blood-flow patterns and systolic filling on the nonoccluded right side are clearly visualized. C and D, Collateral blood flow from right to left via a small anterior communicating artery. C, The emitter plane is localized at the right A1 segment. The crossflow via the small anterior communicating artery to the left A1 segment (arrows) is clearly visible. D, The emitter plane localized in the left A1 segment depicts the retrograde flow direction within that vessel segment.
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