In vivo human carotid artery atherosclerotic plaque characterization with high-resolution MRI at 3 and 7T

Embolisms, caused by (a) (ruptured) atherosclerotic plaque(s) in the carotid
artery, can cause a TIA or a stroke. Patients will
undergo a carotid endarterectomy for removal of these atherosclerotic lesions.
The relation between the composition of the
atherosclerotic plaque and 1) pre- and postoperative embolisms and 2) repeated
infarcts after surgery, were investigated in the
Athero-Express study. We found that patients with a fibrotic plaque had a lower
risk for repeated TIA or stroke than patient
groups with a more lipid-rich plaque. Patients with a more inflamed plaque
showed more embolisations (measured with Trans
Cranial Doppler (TCD)). In addition, a high number of neovasculature with
intraplaque bleeding was a strong predictor for
cardiovascular events throughout the whole body. Thus, the classically defined
measures for plaque vulnerability (plaque
bleeding, large lipid lakes and local inflammation) were all related with
adverse outcomes peri-operatively as well as follow up.
Recently, a 7T human MR scanner became available in Utrecht, creating the
possibility to visualize the carotid artery plaques
with a high resolution in vivo MRI in humans. For comparison with a standard,
the 3T human MRI scanner will also be used in
half of the patients. In this single center prospective study, 84 patients (42
per group) with stenosis of one the carotid arteries and included in
the athero-express bio bank will be included in this study. These patients will
be recruited from the department of vascular
surgery of the UMCU.
Therefore our main question is to investigate if particular plaque
characteristics are associated with clinically silent cerebral micro-infarcts.
Therefore we will use histology as a golden standard. Our secondary aim is to
visualize plaque characteristics,
associated with micro-embolism and post-operative stroke, by high resolution
MRI. Additionally, we want to visualize the
perfusion state of the brain pre- and postoperatively to see what the influence
is of the revascularisation of the brain.
With this data we will be able to visualise the carotid artery vessel wall and
obtain information of the composition of the plaque
and the consequences in the brain. Additionally, with the brain images we can
make statements about function of the brain and
its perfusion state pre-operatively and after revascularisation. Thereby we can
provide a basic understanding of the possible
consequences of atherosclerosis of the carotid artery for the brain.

Primary goal:
To investigate whether specific plaque characteristics are associated with
ischemic lesions, especially (clinically silent) cerebral micro-infarcts, we
will perform preoperative high resolution 3 and 7 Tesla MR plaque imaging in
patients undergoing CEA, and correlate our results with ischemic lesions seen
on follow-up (post-operative) MRI. As golden standard histology of the plaques
will be obtained.

Secondary goal:
To visualize plaque characteristics which have been associated with
micro-embolism and post-operative stroke with high-resolution 3 and 7 Tesla
MRI, and compare these results, so as to obtain knowledge regarding the full
use of MR imaging for determination of plaque composition.

Patients scheduled for an endarterectomy of (one of) the carotid arteries are
included via the vascular surgeon. These are patients
who have had a TIA or stroke, or asymptomatic patients with a partially
occluded carotid artery.(>70% stenosis)
1 day before surgery the patients are scheduled for an MRI scan of the
head/neck area in the 3T or 7T (patients are randomly assigned to a group).
During this MR scan the brain will be evaluated for micro infarct damage, as a
marker for embolisms. In the neck area, several MR images with several
weightings will be aqcuired for plaque visualization and characterization. This
will take 1 hour (including preparation of the
patient). The biggest area of the plaque (culprit lesion) will be located at a
certain distance from the carotid bifurcation. During
surgery the number of embolisms will be measured with TCD. During the operation
the plaque is removed immediately processed. The segment with the biggest
plaque (culprit lesion) is located and fixated in formalin for histological
analysis. This segment is cut and stained for presence of: collagen,
macrophages, smooth muscle cells, lipids, thrombus and endothelium
(microvessels(neovasculature)). (Athero-Express studie)
During a follow-up appointment with the surgeon (3 months after operation) a
second MRI scan will be made of the brain, to evaluate the results of the
operation and correlate with specific plaque components.

nearly negligible risks, only the gadolinium injection could lead to rare
side-effects, but by following exclusion criteria very strictly
this will be as minimal as possible.