Metals in medicine
Metals in medicine

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Metals in medicine

2.2 X-ray contrast agents

One way of improving the differentiation between tissues when using X-rays is to use a contrast agent.

This is a substance which, in this instance, preferentially absorbs X-rays and hence shows up more clearly the organs into which it is injected or introduced. (Another type of contrast agent is used in MRI, as you will see later on in the course.)

  • Can you suggest one property of an X-ray contrast agent that would influence its absorbance?

  • The contrast agent should have a high atomic number, since this will lead to greater absorbance.

There are a variety of these agents available, the oldest of which is barium sulfate.


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