Posted by: Thixia | April 16, 2008

MRI 9 of 14

MRI Images


Most imaging modalities use injectable contrast, or dyes, for certain procedures. MRI is no different. What is different is the type of contrast we use, how it works and why we use it.


Photo courtesy NASA
This MRI scan shows the upper torso in side view so that the bones of the spine are evident.


The contrast or dye materials used in X-ray and CT scan work in the same way because both areas use X-rays (ionizing radiation). These agents work by blocking the X-ray photons from passing through the area where they are located and reaching the X-ray film. This results in differing levels of density on the X-ray/CT film. These dyes have no direct physiologic impact on the tissue in the body. The contrast used in MRI is fundamentally different.

MRI contrast works by altering the local magnetic field in the tissue being examined. Normal and abnormal tissue will respond differently to this slight alteration, giving us differing signals. These varied signals are transferred to the images, allowing us to visualize many different types of tissue abnormalities and disease processes better than we could without the contrast.

Now that you know how MRI works, let’s find out what circumstances might call for an MRI scan.




  1. I really enjoy reading your blog, and nearly always learn something new, even though I have quite a lot of knowledge because my husband has MS. There is so much unknown about MS despite all the research. Thanks for enlightening us as to how the MRI works, it’s crucial to every MS suffered and carer.

  2. Barb,

    I am really pleased that you like my blog. I enjoy doing the research for it and writing the articles. And receiving kind comments like your make my work all worthwhile.

    Thank you,


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