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Magnetic resonance imaging

What is MRI?
How is MRI performed?
Benefits of MRI
Limitations of MRI
History of MRI

What is MRI?

Magnetic Resonance Imaging (MRI) is an imaging technique that uses a powerful magnet and radio waves to obtain cross-sectional images or "slices" of the inside of the body. MRI can be used to produce pictures of the inside of the breast, taken from several different angles, and does not use X-rays.

MRI is not routinely used for breast screening but is often used to investigate suspicious areas of the breast first detected with mammography or physical breast examination. MRI can sometimes be helpful in providing diagnostic information about a suspicious area in women who have dense breast tissue (usually younger women) where X-ray mammography is not totally reliable. Researchers are investigating whether breast MRI may be useful in screening younger women with a strong family history of breast cancer who may be at high risk of breast cancer. Find out more at the MARIBS website.

A sequence of MRI slices.

MRI 1 MRI 2 MRI 3

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How is MRI performed?

The patient is positioned lying face down on a padded table inside the MRI system opening where a magnetic field is created by a large magnet. During the examination, a radio signal is turned on and off. Atoms in the body absorb this energy which is then echoed or reflected back out of the body. These echoes are continuously measured and converted into images of the breast. In order to improve the quality of the images, a contrast agent (dye) may be injected into the arm before or during the examination to show areas with a good blood supply. Typically, an MRI examination of the breast takes between 30 and 60 minutes.

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Benefits of MRI

It allows images to be taken from almost any angle with good clarity.
It is highly sensitive and can sometimes detect small abnormalities missed by other examinations.
It is excellent at imaging breast implants and surrounding breast tissue.
It is effective at imaging dense breast tissue, often found in younger women.
It can be used to evaluate the extent of breast cancer and therefore help indicate the most appropriate treatment.
It can help determine whether breast cancer has spread to the chest wall or the lymph nodes in the armpit (axilla).

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Limitations of MRI

It cannot always distinguish between cancerous and non-cancerous abnormalities, which can lead to unnecessary breast biopsies.
It cannot reliably detect microcalcifications that can indicate breast cancer, but these are easily identified on mammograms.
It is an expensive examination, costing several times that of a screening mammogram.
It takes longer than mammography, both for the examination and the subsequent interpretation of the images.
It requires the injection of a contrast agent.
It is not yet widely available for breast imaging.

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History of MRI

1946	The magnetic resonance phenomenon was discovered independently by two scientists working in the United States. Felix Bloch (Stanford) and Edward Purcell (Harvard) were both awarded the Nobel Prize for Physics for their discovery.
1950-70	Magnetic resonance spectroscopy became a widely used technique for the analysis of small samples, showing that different materials resonate at different magnetic strengths.
1971	Raymond Damadian, an American doctor, demonstrated that tumour samples could be differentiated from normal tissue using MR. Scientists began to consider using magnetic resonance for the detection of disease.
1973	Magentic resonance imaging (MRI) was developed by Paul Lauterbur, a Chemistry Professor from New York, and scientists at Thorn-EMI and Nottingham University.
1977	First demonstration of magnetic resonance imaging of the whole body.
1980	Clinical trials of the first MR imaging prototypes.
1984-	Clinical use of MRI has spread.
Present	Research continues into using this technique to characterise benign from malignant tissue.

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