Non-invasive techniques Imaging Techniques Used to Assess Atherosclerosis

Magnetic resonance imaging (MRI)

MRI produces extremely detailed pictures of body tissues and organs without the need for X-rays. Electromagnetic energy released when exposing a patient to radio waves in a strong magnetic field is measured and analysed by a computer, which then forms a two- or three-dimensional image. MRI provides detailed images of blood vessels without using any contrast material, although a special form of contrast may be given to make the images even clearer.

Limitations to this method include the complex equipment required and the difficulty in obtaining precise images because of the continuous motion of the heart.

The image below shows an MRI image relatively normal artery with little or no signs of atherosclerosis and the left carotid artery bifurcation with an atherosclerotic plaque with a necrotic core.¹

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Computed tomography (CT)

A traditional CT scan is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional views of the body. Cardiac CT uses the advanced CT technology with intravenous contrast dye. X-ray computed tomography provides cross-sectional images of the chest, including the heart and coronary blood vessels. The complex equipment required and the difficulty in obtaining precise images because of the continuous motion of the heart are also limitations to this method.

The image below is a CT scan of an artery showing the presence of atherosclerosis.

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*Photograph M175/302 (CVS 20): Zephyr/Science Photo Library.

Ultrasound (B-mode)

High resolution B-mode (brightness mode) ultrasound (also referred to as quantitative carotid B-mode ultrasound), uses high frequency sound waves and their echoes to create an image. The B-mode ultrasound makes it possible to non-invasively characterise arterial wall function in the carotid and brachial arteries by measuring IMT and wall stiffness. B-mode ultrasound has been used extensively in epidemiologic studies to quantify associations of risk factors with extracranial carotid atherosclerosis and atherosclerosis progression as well as associations of atherosclerosis (and atherosclerosis progression) with coronary events.

This image below shows an ultrasound of the common carotid artery depicting visualisation of the far wall IMT. The white arrow points to the intima-lumen interface and the grey arrow points to the intima-media interface, demarcating the intima-media thickness.

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*Reproduced with permission from Kastelein, JJP, Sager PT, de Groot E et al. Am Heart J 2005;149:234–239.

Reference:
1. Chu B et al. Stroke 2004;8:2444–2448.

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