Radiation is used in a wide range of meical applications. They range from diagnosis of disease, therapy and research. Although radiation is dangerous when exposed to it improperly, it is an extremely effective treatment of cancers.
Radiation therapy works by damaging the DNA of cancerous cells. This DNA damage is caused by one of two types of energy, photon or charged particle. The damage caused is either direct or indirect ionization of atoms which make up the DNA chain. The indirect ionization happens as a result of the ionization of water, which forms free radicals, which then damage the DNA.
In photon therapy, the radiation effect is through free radicals. Due to the cells ability to repair single-strand DNA damage, double stranded DNA breaks. This proves to be the most significant technique to cause cell death.
Doses and delivery of photon radiation therapy is measured in gray (Gy) and varies depending on the type and stage of cancer being treated. A typical does for a solid epithelial tumor will range from 60 to 80 Gy where lymphomas are treated with 20 to 40 Gy.
There are three main divisions of radiation therapy, external beam radiation therapy or teletherapy, brachytherapy or sealed source radiation therapy, and systemic radioisotope therapy or unsealed source radiotherapy. The techniques differ in the position of the radiation source. The radiation can either be outside of the body, sealed radioactive sources placed in areas under treatment or systemic radioisotopes given by infusion or oral ingested.