Science Questions

What information do you get from CT images of the brain?

Sun, 12th Aug 2007

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Gobi asked:

What information do you get from CT images of the brain and how do you read them?


CT, or Computerised Tomography scanning  technology was a massive breakthrough in medicine.  It gave us the first 3-D views of the inside of the body without having to open people up.  CT scans rely on x-rays, which pass through the body and different tissues absorb different amounts.  Instead of shooting one x-ray straight through you, which gives a kind of x-ray shadow on a photographic plate, CT scanning shines lots of x-rays through the body at lots of different angles.  By taking a picture from every one of these angles a computer can then work out how much of the x-rays were soaked up by each tissue they went through, from each angle.  The computer can the use this information to build up a picture of what you look like inside in 3 dimensions.

CT scans can be made even more sensitive by adding contrast – heavy atoms of things like iodine or barium that soak up lots of x-rays.  This can help show up things like blood vessels compared to other tissue.

CT is very useful for looking at things like stroke, where you can look in the brain and see if there’s a blood clot or bleed – as blood contains a lot of iron is shows up quite well.


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