Erdheim-Chester Disease

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Scans

Explanation of Scans, xrays and stuff

There are a number of diagnostic tests that can be used to see what is happening within the body.  These are divided broadly into radiographic and nuclear methods.

Standard x-rays (or radiographs) are pictures of body parts taken using x-rays.  These rays are a form of radiation. The picture produced is an image of the anatomy that has been targeted. Where the tissues are the densest the x-rays have the least ability to pass through the tissues (that is why bones are white on x-rays).

CT (computed tomography) uses x-rays to produce the image but the information gathered is used to make 3D images and more detailed views of the anatomy are possible.

Nuclear medicine scans are taken after a patient has had a, mildly, radioactive chemical (called an isotope) injected into their body. There are a number of these and the one that is used depends on the tissue being studied or looked for. The chemical is taken up by certain cells. When it decays (not the same as rotting!) it releases some radioactive particles. These are detected by a special camera and indicate where a tissue is in the body (such as a tumor or ECD tissue), and whether it is behaving normally (such as reacting to infection).

A PET scan is a Positron Emission Tomograph. An isotope chemical is injected and is taken up by some of the tissues. As it decays the radioactivity released is detected and then a computer analyses it into pictures showing where certain cell types are and whether they are behaving normally.  A PET CT produces 3D pictures .A standard PET produces 2D images.

An MRI is a Magnetic Resonance Image. Whatever is being looked at is subjected to a VERY strong magnetic field. This lines the atoms up in a certain way. When the magnet is turned off the atoms go back to there original position and in doing so they release radio frequencies that are picked up by sensors in the scanner. No radiation in these scans but don't wear anything metallic!

A skeletal survey is when they x-ray all your bones looking for bits that have been eaten away.

When having any scans done care should be taken with the contrast media used.  Contrast media can induce acute functional changes in kidney function.  For those with kidney issues it is important to ask your doctor whether you need a scan with contrast or not.

Last updated: Dec 8, 2009