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 acquisition,
obtaining relative maps (to the first acquired volume without “preparation” M0) of cerebral blood flow (CBF).
- TOF Angiography: 410x512x72 (0,41x0,41x0,5mm3),
TR=22ms,
TE=4,12ms.
Centered in WP.
Analysis.
Anatomy
First of all and based on angiographic study,
patients were classified in different groups according to the different anatomical variants described for anterior and posterior circulation of WP (Figures 1,
2 and 3).
After that,
for quantification of perfusion maps,
subjects who had anatomical variants of posterior circulation were classified again in 3 groups depending on dominance:
- Symmetric
- Right Dominance
- Left Dominance
Analysis.
Interhemispheric asymmetries of flow
Later on and blindly from anatomical results we analyzed visually interhemispheric asymmetries of CBF maps.
Finally,
a quantitative analysis of asymmetries was made:
- First,
ASL image was realigned to the MPRAGE,
- Then MPRAGE was standardized to the space of Montreal Neurological Institute (MNI) atlas,
and the same transformation was applied to ASL image,
- The last step was creating average images for the 3 groups (symmetric,
right and left).
*All steps were made with Statistical Parametric Mapping (SPM5) software.
*Quantification of average images was made in regions of interest “Automatic Atlas Labelling (AAL)” and MRIcron programme.