Biomedical Engineering Reference
In-Depth Information
in a two dimensional view of the structures emitting the radio waves.
Peter Mansfield developed the methods for mathematical analysis of
the waves, making imaging a real possibility. Today, the emitted waves
are translated by the computers in the MRI into a 3-dimensional image.
MRI works well in imaging because 70% of the body is comprised of wa-
ter, and (as discussed in Chapter 1) hydrogen is the only natural atom
that responds to NMR. Because the content of water varies significantly
between soft tissues and bone, so do the proton concentrations, which
gives sharp contrast between these tissues.
Within the soft tissues of the body, the differences are more subtle.
New contrast agents have been developed that selectively enhance the
images from different tissues. It has been said that as fluorescent probes
made possible optical imaging, that MRI contrast agents have done the
same for MRI, improving resolution to near cellular levels (as little as
Today, MRI is a standard tool in diagnosis: by the end of 2002,
60 million MRI images had already been taken!
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