• Question: Its true that rays from nuclear reaction can makes the organs of human body 'mutated' or could harm them. Can we somehow reverse this effect and use nuclear energy to treat people with cancer or even more severe viruses and diseases?

    Asked by usman100 to Chris, Dave, David, Fiona, Jack on 22 Jun 2013.
    • Photo: David Freeborn

      David Freeborn answered on 22 Jun 2013:


      Yes! We use radiation all the time to treat cancer, and kill diseases!

      We think that about 10% of invasive cancers are caused by exposure to radiation. This is mostly not due to nuclear reactions, but due to a naturally occurring radioactive element called Radon, but also due to CT scans, nuclear radiation and the use of depleted Uranium in armour-penetrating explosives. It’s estimated that the Chernobyl disaster might have caused 6,000 excess deaths due to cancer.

      Ionising radiation is able to cause cancer by damaging the DNA in the cells. But if we fire enough radiation at the cells, it will be sufficient to kill them. X-rays are very commonly used as a form of cancer-treatment. One of the main difficulties is to aim the X-rays so that they hit the cancer cells as much as possible, but not the healthy cells in the body. To do that, the X-rays are normally fired from many different angles, converging at the point where the tumour is in the body. A lot of clever maths goes into working out precisely where to fire the X-rays and at what strength.

      Sometimes we implant small quantities of radioactive material directly into the cancerous part of the body. The idea is that they will decay, killing the cancer, but will be fully decayed before they have to time to also start damaging the rest of the body.

      Particle therapy, using heavier particles (protons and neutrons) than X-rays is now becoming more popular. That’s because, unlike X-rays, they won’t pass right the way through the body, but will eventually stop. If we judge things right, we can get it so the particles will hit the cancer cells but not go any further.

      We use ionising radiation to kill bacteria, viruses and even insects in foods too. Food irradiation is becoming increasingly common in a lot of countries. You can read about it here:
      http://en.wikipedia.org/wiki/Food_irradiation#X-ray_irradiation

    • Photo: Jack Miller

      Jack Miller answered on 22 Jun 2013:


      Hi Usman100,

      As David says, we do indeed currently use radiation for all of these sorts of therapies!

      I think perhaps the one thing that I should add is a description of what goes on, and why radiation can both cause and help cure cancer.

      When most people say the word ‘mutant’ or ‘mutation’, what comes to mind are lots of pictures from B-list movies and the Resident Evil video game series, filled with all sorts of unpleasant creatures and zombies. The truth couldn’t be more boring: a mutation is just a difference in your DNA relative to the rest of your species (or some subset thereof). You might know that our DNA consists of four chemical ‘letters’, ATG & C, which are small molecules joined together on a backbone. They form weak bonds called hydrogen bonds with ‘complementary’ molecules — A with T, G with C — and store information in a really space efficient form (that familiar double helix). In cells with organelles (collectively called eukaryotes), things are also complicated by the fact that we have usually have another copy of that information — DNA gets bundled up into space-efficient structures called chromosones, and (in humans) they come in nearly-identical pairs (except for the sex ones).

      When someone’s DNA is damaged, which is what happens when radiation causes a mutation, one of these chemical bases (letters) is changed into something else — usually another, equallyit sticks out as there’s a mismatch across the double helix — instead of A binding with T, say, we have A-A. This sticks out like a sore thumb (almost literally — it distorts the helical shape of DNA) and is picked up by the cell’s machinery. If possible, the damaged DNA is repaired, and if that isn’t possible it’s replaced with with another information from the other chromosone (if possible). If that isn’t possible, and you get enough of these events, then the cell knows that something has gone seriously wrong and it kills itself through a process called apoptosis.

      This is how radiation kills people — if you make enough of your cells die then, well, you will too. It also explains the shape of the graph of ‘radiation dose’ versus ‘chance of death’ — there’s a very big plateau at the start, where you can repair DNA damage, then an increasing region where you get more likely to get cancer (as these mutations are induced and things start to go wrong, but before apoptosis), before finally another great big plateau where you’re very likely to die.

      Radiation therapies exploit this graph by trying to give a high dose of radiation to a small volume inside a patient — the volume where the tumour is. This is quite a problem, as David said, as people aren’t uniform and how much radiation they absorb (and how much it takes to cause damage) vary in different tissues. There’s also a big experimental difficulty in delivering radiation to just the right place.

      Hope that helps!

      — Jack

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