Purpose
Correlate cerebral blood flow interhemispheric patterns observed with “arterial spin labeling” (ASL) technique with the presence of anatomic variants of Willis polygon (WP).
Methods and Materials
Patients:
We have studied prospectively 76 patients,
46 women and 30 men,
with mean age of 37’1 years (17-75 range),
who underwent a cerebral MRI for different purposes,
the most frequent in the following of Focal Epilepsy and Multiple Sclerosis.
Those patients who presented vascular or tumoral pathology were excluded from the study.
MRI
Explorations were performed in a 3,0T MRI (Trio,
Siemens) with the following parameters:
- Anatomical MPRAGE: 128x240x256 (1,2x1x1mm3),
TR=2300ms,
TE=2ms.
- Blood perfusion ASL: 64x64x18 (4x4x6,25mm3),
TR=3000ms; TE=16ms; TI1=700ms; TI2=1800ms.
Pulsatile...
Results
WP Anatomy
Angiographic analysis showed anatomical variants of WP in:
21 patients (28%) in anterior circulation (Figure 4)
48 patients (67%) in posterior circulation (Figure 5)
Afterwards 48 patients with variants in posterior circulation were classified in 3 groups depending on dominance:
Symmetric: 25
Right dominance: 9
Left Dominance: 16
Interhemispheric asymmetries of flow with ASL
Arterial spin labeling (ASL) is a non-invasive perfusion technique,
which gives us quantitative information of cerebral blood flow.
It’s been widely demonstrated its utility in different pathologies of nervous...
Conclusion
When evaluating maps of CBF obtained with ASL we should consider anatomy of Willis Polygon,
since interhemispheric asymmetries in CBF maps which could suggest some kind of hemodynamic compromise are in fact produced by anatomical variants.
Asymmetries are due essentially to a decreased CBF in posterior system irrigated from a fetal-type posterior cerebral artery.
References
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Van der Grond J,
Van Everdingen J et al.Circle of Willis Collateral Flow Investigated by Magnetic Resonance Angiography.
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2.
Jan van Laar,
P,
Van der Grond J,
Hendrikse,
J.Brain Perfusion Territory Imaging: Methods and Clinical Applications of Selective Arterial Spin-labeling MR Imaging.Radiology 2008; 246: 354-364.
3.Wentland A.L,
Rowley H.A,
VigenK.K.Fetal Origin of the Posterior Cerebral Artery Produces Left-Right Asymmetry on Perfusion Imaging.
AJNR Am J Neuroradiol 2010 31:448–53.
4.Hendrikse J,
Van Raamt F,
Van der Graaf Y.
Distribution of Cerebral Blood...