One of the MRI's greatest advantages is its relative safety compared to some other imaging techniques. The first method for imaging the body, x-rays, which use radiation to create its images. Another advantage is that MRI's can image less dense tissues than x-rays can (Nordenberg, 1999). But where the MRI has a tremendous advantage over x-rays is in its ability to create 3-dimensional images. It also does a better job of showing contrast between dense parts of the body, such as bones, and softer tissue, than other imaging techniques (Nordenberg, 1999).

In medical use, MRI's focus on hydrogen atoms. The magnetic atmosphere the patient enters is a lop-sided one: the magnetic field generated will be stronger one side than the other, resulting in variances in resonance frequency, or how rapidly the hydrogen molecules vibrate in response to the magnetic field (Tro, 2006). That vibration, or reso

Other MRI's have been developed that can accurately image arteries, helping with the diagnosis of stenosis, or narrowing of arteries, as well as aneurisms, or balloon-like stretches in artery walls (Wikipedia, 2005).

nance, is artificially created and controlled by the very powerful magnets pulling on hydrogen molecules in the body. These patterns are translated by a computer into a detailed image of the body part being imaged. An MRI creates such clear images between dense tissue and softer tissue because softer tissue contains more water, and hence, more hydrogen (Gould, DATE).

One of the most recent developments in MRI technology has been that of weight-bearing images. Until this approach was developed, all MRI's were done with the patient lying flat on a table. Now, MRI's can be performed with the patient in a variety of other positions, including standing or bent in various ways (Wendling, 2005). The new positions can reveal problems that were hidden when doing a prone MRI.

MRI machines also use gradient magnets. These magnets are much weaker than the others, and their job is to cause the magnetic field to vary, and cause the MRI machine to focus on the selected part of the body.

The second kind is a permanent magnet. Permanent magnets must be very large, and can weigh many tons to generate a 0.4 tesla level strength.

Another dramatic development has been the fMRI, or functional MRI. The functional MRI can make images of the brain as it works by measuring neuron activity (Wikipedia, 2005). It can do this because the parts of the brain that are more active demand more oxygen. The fMRI uses magnetic fields to measure increases and decreases of oxygen levels in the hemoglobin of the patient's blood, thus mapping brain activity through time (Wikipedia, 2005).

Some common words found in the essay are:
Gould DATE, , Diffusion MRI, DATE MRI, Risks MRI, MRI MRI's, DATE MRI's, gould date, magnetic field, Specialized MRI's, wikipedia 2005, nordenberg 1999, diffusion mri, magnets resistive, resistive magnets, softer tissue, tissue softer tissue, imaging techniques, tissue softer, activity wikipedia 2005, magnets resistive magnets,
Approximate Word count = 1270
Approximate Pages = 5 (250 words per page double spaced)