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  1. #1
    Join Date
    Jul. 7, 2007
    Posts
    207

    Default comparing xrays

    There's a long semi-boring story that goes with this question, but can someone answer this for me.

    Say you have two exported images (jpegs) of digital xrays of a horse's navicular bone -- one several years older than the other. An expert/vet tells you they can't evaluate navicular changes because the views are not at the same density -- the old xrays are 70% white and 30% black and the new ones are 50% white and 50% black.

    Would getting the original x-rays fix this problem or does it have to do with how the originals were taken?



  2. #2
    Join Date
    Jul. 10, 2001
    Posts
    6,675

    Default

    Your question is not easily answered. The best answer, is, it depends. How well do you understand signal processing?

    You would not need to get the originals. All you would need to do is to normalize the densities by averaging the histograms of each x-ray. Then you would have equivalent images (this is a bit over simplified).

    Yes, the original power directed through the tissue does directly affect the "density" of the image but as I said, you can adjust that in post image signal processing. Many image processing software packages can do this now (NIH Image J, for example). Most doctors are not concerned with this though.

    Reed



  3. #3
    Join Date
    Jul. 7, 2007
    Posts
    207

    Default xrays

    Not in the know re signal processing, but I do have the original xray that is not 50/50 and efilm light. Could it be something as simple as a contrast adjustment? I notice that numbers change as I adjust the contrast...



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