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Highly radiosensitive cancer cells are rapidly killed by modest doses of radiation. These include leukemias , most lymphomas , and germ cell tumors . The majority of epithelial cancers are only moderately radiosensitive, and require a significantly higher dose of radiation (60–70 Gy) to achieve a radical cure.
Radiation used for cancer treatment is called ionizing radiation because it forms ions in the cells of the tissues it passes through as it dislodges electrons from atoms. This can kill cells or change genes so the cells cannot grow. Other forms of radiation such as radio waves, microwaves, and light waves are called non-ionizing.
A single cancer cell is invisible to the naked eye but can regrow into a new tumor, a process called recurrence. For this reason, the pathologist will examine the surgical specimen to determine if a margin of healthy tissue is present, thus decreasing the chance that microscopic cancer cells are left in the patient.
Radiation hormesis is the conjecture that a low level of ionizing radiation (i.e., near the level of Earth's natural background radiation) helps "immunize" cells against DNA damage from other causes (such as free radicals or larger doses of ionizing radiation), and decreases the risk of cancer. The theory proposes that such low levels activate ...
The risk for developing radiation-induced cancer at some point in life is greater when exposing a fetus than an adult, both because the cells are more vulnerable when they are growing, and because there is much longer lifespan after the dose to develop cancer.
There is a threshold dose which causes clinical radiation damage of cells in the body. [5] As the dose increases, the severity of injury increases. [5] This also impairs tissue recovery. [5] The IRCP also describes how cancer develops following radiation exposure. [5] This happens via DNA damage response processes. [5]
External beam radiation therapy (EBRT) is a form of radiotherapy that utilizes a high-energy collimated beam of ionizing radiation, from a source outside the body, to target and kill cancer cells. A radiotherapy beam is composed of particles which travel in a consistent direction; each radiotherapy beam consists of one type of particle intended ...
Involved site radiation is when the radiation oncologists give radiation only to those parts of the person's body known to have the cancer. [58] Very often, this is combined with chemotherapy. Radiation therapy directed above the diaphragm to the neck, chest or underarms is called mantle field radiation. Radiation to below the diaphragm to the ...