First of all, we have to know that, Radiation basically damages the DNA, which is some kind of “instruction manual” of cells.
In uncontrolled radioactive events (e.g nuclear explosion, long-therm sunbathing etc.), your whole body exposed damaging radiation. This radiation, distrupt the “instruction manuals” of your healthy cells. The distruption may be too intense, so that cells are no longer work properly anymore and instantly die.
OR (in a small posibility) the distruption may change the dividing characteristics of healthy cells via changing instruction manual. So they divide non-stop mannerwithout control. (Normally, cell division is strictly controlled in healthy cells). If the distruption of instruction manual leads to uncontrolled division, we call it cancer.
And now… Let’s back to good side of radiation. Why, radiation is used to cure cancer?
Let’s remember that what I said in the begining of my answer?
[…] The distruption may be too intense, so that cells are no longer work properly anymore and die. […]
Radiation treatment specialists use that work principle to cure cancer. They use radiation to kill “just” cancer cells by focusing the radiation on just cancerous cells, not healty cells (see picture below). High dose of radiation, completely distrupt theinstruction manuals of cancer cells, so that cancer cells are no longer work/divide properly, and instantly die. So we call this therapy as Radiotherapy.
In here, we see patient, that will take radiation therapy. The device that you see, will send radiation at different angles. These radiation angles are intersected at cancer region. So cancer region take higher amount of radiation than other healthy regions. The nurses will go out in treatment session, because of protection from radiation.
- In radiotherapy, healthy cells are also affected. But the damage is minimal in comparison with cancer cells.