Which form of radiation is used to kill cancer cells?

Focussed bursts of gamma rays are used in radiation therapy to kill cancer cells. (From Science8 book Mcgraw-Hill Ryerson text book-page 160)

AnswerThe type of radiation used depends on the type of cancer and the type of treatment prescribed.

Gamma rays are best for deep-seated cancers, where the radiation is directed from a source outside the body. Gamma rays can pass through a good deal of tissue before being absorbed.

Sometimes, a particular trace element is absorbed by just one organ in the body - for example, iodine is specific to the thyroid gland. So, radioactive iodine can be ingested in food as a radiation source to treat thyroid cancers, because the radiation will not affect other organs in the body. In this case, short-range alpha radiation is used. Alpha rays are actually high energy particles, rather than electromagnetic radiation.

AnswerIt is inoizing radiation that is used to kill cancer cells, and it comes in two "flavors" for our use. One is electromagnetic, like X-rays or gamma rays. The other is particulate, like high energy neutrons, protons and electrons (to name some). The former is broadly applied to treating cancer, and there are a number of approaches as discussed above. We don't use particulate radiation - or at least we didn't, other than alpha particles. Remember that alpha particles don't have much penetration power. A sheet of paper will stop them, and an alpha source must be implanted right on top of a cancerous body to provide effective therapy.

The proton is being used now in radiation treatment. It has pretty good penetration power, and it has this very "friendly" plot of its ability to go through tissue. In looking at a beam of protons in proton therapy, protons penetrate outer layers easily, and do some damage. The farther they penetrate, the more damage they do, and the damage increases dramatically. Then it peaks quickly (the so-called Bragg peak) and drops like a rock. There is a very strict limit on the "range" of the particle stream as far as what gets damaged. The beam won't "go through you" like an X-ray or gamma ray. Recall that the difference between those two forms of electromagnetic radiation is that the latter have higher energies and greater power to penetrate tissue.

Note that ionizing radiation doesn't kill every cell it passes through, but it does more damage and is more lethal to cells with "high rates of function" than other cells. That means cells that are "really active" like cancer cells (or cells of the digestive tract, the bone marrow and the hair folicles to name a few) take the most damage.