As I understand, radiation therapy is basically directing highly concentrated x-rays/gamma radiation to kill tumors/cancer cells. I don’t quite get how, in this process of “shooting” high energy beams at the tumor, the skin/muscle cells don’t get damaged?
In: Biology
They do, but not as badly as the tumour.
The radiation is fired at the tumour from different directions. This means that the skin and other tissues only get part of the dose, and the tumour gets the full dose.
That’s what happened when my mum had radiotherapy for throat cancer. It still gave her terrible “sunburn” all round her face and neck.
The cancer cell can normally regenerate less good compared to healthy cell. Therefore damaging the cancer cells with radiation will probably kill them, why the normal body cells can heal the damages.
If you use proton or ion beams you can even target quite exact in which depth you want to do damages, as high energy ions don’t do so much damage as low energy ones.
Therefore you can calculate how long the beam has to go through your body until it loses enough energy to cause strong damages. If you do it right you choose the initial energy and the kind of beam the way that most damages are only done the cancer cells and not so much to healthy cells.
Adjusting the beam. Energy gets released at different depths and peaks a certain distance into the tissue. Beam could travel all the way past you and hardly do anything but add another CM of skin and it could all be dumped right into it. Combine that with the other things states here and it is pretty precise
The skin does take some damage but the beam is shot from different angles so the tumour received the full dose while each part of skin affected only received one fraction of that dose.
Source: I had radiotherapy to the brain in December just gone. There was a red patch of skin on my forehead that irritated easily e.g. went redder when I scratched it. It since seems fine though I have been warned to keep it out of the sun as much as possible for at least 18 months.
It’s because the soft tissue in your skin does not absorb those rays, so the rays just pass through. Look up “Liquid water absorption spectrum” since our bodies is mostly water. Low spectrum light, like radio waves, is not absorbed as well, same for high frequencies. Bones and tumors, etc, are different to skin, so they do absorb the rays.
It works the same way they can create images inside of a glass cube. Those glass cubes are cracked at specific points within the cube by directing multiple lasers at the same spot from different directions. No single bean is powerful enough to crack the glass but where they converge enough energy is directed to create a small crack. The radiation works the same way using X-rays instead of lasers. No single beam is very powerful but the point of convergence gets a much stronger dose of radiation.
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