Intracranial vessel wall MR imaging at 3.0 and 7.0 tesla in patients with TIA or ischemic stroke of the posterior circulation

Intracranial atherosclerosis is an important cause of ischemic stroke and
transient ischemic attack (TIA). Development of atherosclerotic lesions occurs
silently over a longer period of time, until they become symptomatic. Most
non-invasive intracranial imaging methods (transcranial Doppler, MRA, CTA) are
based on visualizing the lumen of the intracranial vasculature, thereby giving
indirect information about the underlying vessel wall abnormalities caused by
atherosclerosis. Because of arterial remodelling in which the luminal diameter
remains equal despite the presence of an underlying atheroma, these
lumenography techniques may result in underdiagnosis of intracranial
atherosclerosis.

At the UMC Utrecht, within the 7.0 tesla group of Prof Luijten, an MRI sequence
at 7.0 tesla was developed specifically for imaging of both healthy and
abnormal intracranial vessel walls, and is currently being used in an on-going
study (IVI Study) including patients with (transient) ischemia in the anterior
cerebral circulation. Previous intracranial vessel wall MR imaging studies have
mainly focused on the anterior circulation, where ischemia is most common.
Ischemic stroke or TIA in the posterior circulation accounts for approximately
20 to 30% of all ischemic events. We hypothesize that arterial vessel wall
abnormalities are also common in the posterior circulation, and are an
important underlying cause of obstruction of arteries in the intracranial
posterior circulation and subsequent ischemic stroke. Ultimately, for wide
clinical application of intracranial vessel wall imaging, a translation has to
be made to lower field strength MR scanners (3.0 tesla). Therefore, based on
the 7.0 tesla intracranial vessel wall MR imaging protocol, we have developed a
3.0 tesla protocol for clinical implementation.

The primary objective of the current study is to compare the presence or
absence of arterial vessel wall abnormalities in the intracranial posterior
circulation in patients with TIA or ischemic stroke with those of healthy
controls using 7.0 tesla MRI.

The secondary objective is to assess the sensitivity of 3.0 tesla MRI to detect
the vessel wall abnormalities visualised with 7.0 tesla MRI.

Tertiary objectives will be:
(i) characterization of intracranial arterial vessel wall atheroma,
specifically unstable atheroma by evaluating the signal characteristics on
multiple MRI sequences, including enhancement after contrast administration;
(ii) to compare the presence of intracranial arterial vessel wall abnormalities
between patients with posterior and anterior circulation TIA or ischemic
stroke, by combining our data with those of the on-going IVI Study;
(iii) to assess the possible correlation between the observed arterial vessel
wall abnormalities and the occurrence of vascular events during follow-up.

This study is a single-center, prospective case-control study. Intracranial
vessel wall imaging will be performed with a 3.0 tesla and a 7.0 tesla MRI
scanner in patients with TIA or ischemic stroke of the posterior circulation,
and age- and sex-matched healthy controls, combined with standard clinical
imaging of the brain on these platforms.

Baseline characteristics of all patients and healthy controls will be collected
at inclusion into our study. All participating subjects (ischemic stroke/TIA
patients and healthy controls) will undergo one 3.0 tesla and one 7.0 tesla MRI
examination. In patients, both MRI examinations will be performed as soon as
possible, but at the latest within 3 months, after the onset of ischemic
symptoms. A minimum of 12 hours is taken in between both examinations, to make
sure the contrast agent has washed out sufficiently. Clinical follow-up of the
patients will be performed at 3 months and at 1, 2, and 3 year(s) after study
inclusion, consisting of a brief survey conducted by telephone, and by
collecting data on recurrent vascular events. The healthy controls will not
receive clinical follow-up.

The results of this study will further unravel the contribution of intracranial
atherosclerosis to posterior circulation ischemia, and its prevalence in
patients with ischemic stroke as well as healthy individuals. The translation
of 7.0 tesla intracranial vessel wall MR imaging to 3.0 tesla will make wide
clinical application possible. There will be no direct benefits for the
individual subjects participating in this study. But in the future we feel that
the aforementioned MR measurements of intracranial atherosclerosis may be
important to guide decisions about preventive treatment in patients with a high
risk of (recurrent) stroke.

Risk assessment MRI:
To the best of our knowledge there are no short- or long-term risks involved of
having an MRI scan. Participants are not requested to have any precautions or
actions prior to or following to the MRI exam.

Risk assessment contrast agent:
The contrast agent Gadobutrol (Gadovist ®) is used. This is the standard
contrast agent used in MR imaging examinations in the clinical setting, and as
such it is administrated to thousands of patients every year at the UMC
Utrecht. Gadovist is registered in the Register of Pharmaceuticals (RVG 25318).
A standard amount of 0.1 mL/kg bodyweight will be administered.