Video: Comparing the Frequencies of X-Rays Used in X-Ray Therapy to Those of X-Rays Used in X-Ray Imaging

Do the X-rays used in X-ray therapy have a higher frequency, a lower frequency, or the same frequency as those used in X-ray imaging?

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Video Transcript

Do the X-rays used in X-ray therapy have a higher frequency, a lower frequency, or the same frequency as those used in X-ray imaging?

Okay, so in this question, we’re comparing the frequencies of X-rays used in X-ray therapy and X-ray imaging. So let’s first recall that, in X-ray imaging, X-rays are sent into a patient’s body because some parts of the body, such as bones and teeth, will absorb X-rays, whereas other parts, such as flesh and soft tissue, will not absorb X-rays. Therefore, some of the X-rays pass out the other side of the human body and then hit a screen placed behind the patient. This then results in an image of the inside of the patient forming on the screen because the regions of the screen that remain white are the regions where no X-rays have interacted with the screen because those X-rays were absorbed by the bone in the patient’s body. Whereas the regions that go dark are regions where X-rays have interacted with the screen because they’ve been able to pass through the patient’s body due to interacting with regions that as soft tissue, which don’t absorb X-rays very well.

And so the end result of this is an image that shows the contrast between regions that do absorb X-rays and regions that don’t absorb X-rays, resulting in an image of the inside of the patient’s body. Now in X-ray imaging, all we’re trying to do is to take an image of the patient’s body as we’ve mentioned already. We do not want to damage the patient’s body using the X-rays that we’re sending into the patient because, remember, X-rays are a form of ionizing radiation, which we can recall is radiation that has enough energy to ionize atoms. Now, if these X-rays that we’re sending into our patient were to ionize lots of the cells in this patient’s body, then this could seriously damage the cells that these atoms were making up, therefore greatly harming the patient. This is exactly what we do not want to happen. We want to minimize the risk of any ionization occurring when we pass X-rays into a patient. And so to minimize this risk, we use low-energy X-rays.

Now, let’s contrast this with X-ray therapy. Let’s say we’ve now got a patient who’s got a cancerous tumor in their body. In this case, what we can do is to use high-energy X-rays and target them towards the tumor specifically so that these high-energy X-rays will have a high chance of ionizing the atoms forming cells in the tumor. This ends up killing the cells in the tumor and therefore shrinking the tumor. In other words, we’re using high-energy X-rays to treat cancer. And so what we’ve realized is that X-ray imaging uses low-energy X-rays, whereas X-ray therapy uses high-energy X-rays.

However, in this question, we’ve been asked to compare the frequencies of the X-rays used in X-ray therapy and X-ray imaging. Well, at this point, we can recall a property of electromagnetic waves, the fact that the energy of an electromagnetic wave is directly proportional to the frequency. In other words, an electromagnetic wave with high energy is also going to have a higher frequency. And from this we can deduce that, in X-ray imaging, we use low-frequency X-rays, whereas in X-ray therapy, we use high-frequency X-rays, which means that the X-rays used in X-ray therapy have a higher frequency than the X-rays used in X-ray imaging. And that is the answer to our question.

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