Non-invasive MR imaging of vulnerable carotid artery plaque characteristics

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technique with high
soft tissue contrast and therefore the perfect non-invasive image modality to
visualize plaque composition and deformation. While imaging of plaque
composition is already well established, imaging of plaque deformation is far
more challenging because of the need for a high spatial resolution (in order to
visualise the various plaque components in the atherosclerotic plaque) together
with a high temporal resolution (in order to visualise different time phases
within the cardiac cycle. Recently, a new state-of-the-art MRI system has been
installed in our department and dedicated 32-channel carotid receiver coil has
been ordered to obtain a high MR signal of the carotid arteries in order to
meet these requisites. Our group has extensive experience in imaging various
aspects of atherosclerotic plaque, like its composition (using multi-contrast
sequences) and microvasculature (using dynamic contrast enhanced sequences). By
using this new advanced MRI equipment, we hypothesize that Magnetic Resonance
Imaging (MRI) is able to visualize the repetitive plaque deformation within the
cardiac cycle in the carotid arteries.

The objective is to study reproducibility of the assessment of repetitive
plaque deformation during the cardiac cycle in the carotid arteries by using
advanced MRI techniques and state-of-the-art hardware.

This study is designed as a prospective observational feasibility study. First,
15 healthy volunteers and 10 patients (known with carotid atherosclerotic
lesions of at least 2 mm thick and causing 30-99% stenosis [ECST measure]) will
undergo an MRI exam for the development and optimization of the new MRI
techniques. Second, 20 patients that are known with carotid atherosclerotic
lesions of at least 2 mm thick and causing 30-99% stenosis will undergo an MRI
exam to assess reproducibility of the new techniques and relate plaque
deformation to plaque composition. All MRI examinations will take place at the
Maastricht University Medical Centre+ (MUMC+).

All volunteers and patients will be subjected to an MRI exam where a standard
gadolinium-based contrast agent will be administered to the patients (not in
the healthy volunteers!). All subjects will be accurately screened for MRI
contraindications. With extensive screening for MRI contraindications, there
are only minimal risks associated with an MRI examination. These risks include
(1) heating of the patient by extensive use of RF pulses, (2) hearing damage by
the loud noises (3) peripheral nerve stimulation by the rapid switching of
magnetic gradients, (4) local burns, and contrast reactions. These risks are
minimized by the use of hearing protection, covering bare skin to avoid direct
contact with the coil wiring, and remaining within safety levels for the
gradient switching and RF pulses. Assessing the patients* kidney function,
using the glomerular filtration rate, minimizes the risk of a contrast
reaction. Patients with an estimated glomerular filtration rate (GFR) * 60
mL/min/1,73m2) or known allergy to gadolinium-based contrast agents will be
excluded. The custom-build, dedicated receiver coil that will be used in this
study, is a receiver-only coil that is fully decoupled during RF transmission,
i.e. the coil is only used to receive the MRI signal, and therefore does not
impose additional risks. As this custom-made coil, developed and built by MR
Coils (Utrecht, NL), is currently a one-off model, it lacks CE certification.
The Medical Instrumentation and Information Technology (MIT) department of the
Maastricht UMC+ is already working on the intake procedures. We would like to
emphasize that we will not investigate the performance of this coil, as we will
only use the coil for signal detection during MRI examinations. We already
performed an extensive risk analysis with the Medical Instrumentation
Technology department at the MUMC+. This risk analysis showed that the use of
this coil does not impose any additional risks to the patients compared to when
using a commercial Philips coil. In fact, Philips Healthcare delivers crucial
components to the manufacturer of the coils (MR Coils BV). Study results are
expected to contribute to improvement of vulnerable plaque detection for future
patients.