Published online by Cambridge University Press: 06 July 2010
Introduction
The first magnetic resonance imaging (MRI) of the whole body, achieved in 1980 was followed by rapid advances in this technology as scientists and manufacturers recognized the enormous potential of this new technique. The initial results from imaging the breast were disappointing as it was not possible to distinguish cancer from the surrounding parenchymal tissue. The introduction of intravenous paramagnetic contrast in the early eighties changed this and the first studies demonstrating the potential of this technology to detect breast cancer were published.
Precessing hydrogen protons in the body are lined up along the main axis of a powerful magnetic field. A radiofrequency pulse is used to flip these protons 90° or 180°. The image is created from the different times it takes for the protons to relax back to the main axis. The images can be given different contrast weightings depending on the timing and repetition of the radiofrequency pulse. Breast parenchymal tissue has a long relaxation time and cancerous tissue is very slightly longer than this. Paramagnetic contrast agent shortens the relaxation time considerably with the leaky vascular cancers taking up the contrast to a greater extent and more rapidly than the background tissue.
Magnetic resonance technique
In order to create high-quality images a dedicated bilateral breast coil is used in a high field (>1.5T) strength machine.
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