What does an MRI actually show?

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For the second time in one month, I've heard the statement from medical professionals that an MRI does not show bone destruction, but does show damage to the blood vessels (soft tissues). I was always told by my own doctors that an MRI is the best diagnostic tool for ON/AVN because it shows what it going on inside the bone, layer by layer. This is true for all 13 of my own MRIs, taken over the past several years. Our NONF flyer depicts an MRI image of my own left knee which is quite dead and hollowed out from ON/AVN.

What is the real story, please? Does an MRI show bone damage or not?

Many thanks, Marie Shanahan ON/AVN Support Group Int'l, Founder/Director NONF, Exec. Director http://members.aol.com/MarieS1520/2bkn.html http://www.nonf.org

-- Marie Shanahan (AVNrie@aol.com), September 29, 2003


The answer to the question is 'yes and no'. To explain is not particularly simple. If one were to do an MRI on a cadaver (in which obviously all the tissue is dead) and on a live normal person, the two MRI's would look exactly the same. Therefore it would appear that the MRI cannot distinguish live bone from dead bone. However, in a human being, all the bone and all the tissue does not die at the same time. The living tissue around the dead tissue 'reacts' to the tissue that is dead, with an area of swelling (tissue fluid) and inflammation. This surrounding tissue has more water in it than normal and the MRI can show this difference. Therefore for practical purposes, in the clinical setting, the MRI can show whether the bone is involved with osteonecrosis or not. There are a few exceptions and some rare caveats, but MRI is the most reliable diagnostic tool short of taking out a piece of bone and looking at it under a microscope.

DS Hungerford

-- David S. Hungerford, M.D. (dhunger@jhmi.edu), February 03, 2004.

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