Study to investigate the sensitivity and specificity of 3.0 Tesla MRI, MRS and ultrasound imaging for carotid artery plaque dimension and composition assessment.

Atherosclerosis is a protracted and in fact lifelong progressive disease. Over
time, lipids accumulate in the artery wall forming fatty streaks, which
eventually can develop into atherosclerotic plaques (1). The later stages of
the process, from quiescent atherosclerotic plaque to an active plaque, have a
high risk of triggering acute vascular events, such as myocardial infarction
and stroke (1).
Much effort has been put in the development of novel drugs aimed to prevent
cardiovascular disease. Low Density Lipoprotein cholesterol (LDL-C) lowering
drugs, in particularly statins, play a pivotal role. The hypothesis that serum
lipid lowering results in decrease of lipid accumulation in the arterial wall
and thus atherogenesis, has formed the basis for successful drug developing
strategies (1;2).

To draw valid conclusions on determinants of disease and effectiveness of lipid
modifying therapeutic intervention, imaging of atherosclerosis can be used as a
validated tool to assess efficacy of novel compounds (3;4).
Although imaging arterial wall dimensions by B-mode ultrasound and
intra-vascular ultrasound have proven their value, longitudinal data of the
effects of cardiovascular drugs on arterial wall and plaque composition, in
particular of vulnerable plaques with lipid rich necrotic cores (LRNC), are
scarce.

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are
non-invasive imaging modalities that can potentially image plaque composition
in-vivo in human carotid arteries. MRI image acquisition at various weightings
enables visualisation of plaque composition. Calcification, haemorrhage,
fibrous cap and lipid rich necrotic cores can readily be distinguished,
providing information on plaque vulnerability. MRS gives a spectrum of
resonances, affording detection of specific chemical components through their
inherent frequency shift relative to water (5). In image guided MRS, an MR
image can be utilized to image and localize a plaque. Proton spectra can then
be collected from these plaques, such that the specific proton resonances of
lipid components in a mobile state, including cholesterol ester (CE), can be
identified (6).

Primary
To investigate sensitivity and specificity of 3.0 Tesla MRI and MRS for
dimension and composition assessment of carotid artery plaques, in particularly
those plaques with lipid rich necrotic cores (LRNC), with the aim to develop
these techniques to validated tools for clinical investigations and trials.

Secondary
To investigate sensitivity and specificity of carotid B-mode ultrasound imaging
as a pre-screening assessment of carotid plaques for MRI and MRS studies.

This is a non-invasive cross-sectional study, comparing carotid parameters of
in-vivo 3.0 Tesla MRI, MRS and B-mode ultrasound with histology specimens
collected at endarterectomy.

This study is conducted using non-invasive imaging technologies: MRI, MRS and
ultrasound imaging. There is no risk associated with participation.