Page 43 - Curriculum Visions Dynamic Book

Measuring radiation doses
Scientists measure the radiation received with a unit called the rem (roentgen equivalent in man). A radiation level
of 10,000 rem will disrupt the central nervous system so much that people will die of radiation. Even a dose of 300 rem will kill half of the people exposed to it, while anything over 100 rem will most likely cause some form of injury.
If irradiation affects the cells of the bone, then enough cells may die to cause a loss of the natural ability of the body to resist infection. If the radiation affects the eyes, it may cause cataracts and loss of vision. It may also cause sterility.
It is difficult to determine the risks of low level radiation; even a body scanner will produce a rem of 0.1. This is why
it is important to protect people working with radiation, allowing them to work behind lead or thick concrete shields.
 A patient receiving radiation therapy.
Radiation therapy
 One way in which radiation can be used beneficially is to irradiate food. By subjecting food to massive doses of radiation, all harmful organisms are killed. Irradiation is therefore a very thorough technique of sterilisation. Some foods found in grocery stores are now sterilised by irradiation. The packaging should carry the symbol shown above.
Radiation therapy uses radiation to treat illness. In its use for cancer treatment, the patient is exposed to radiation from a cobalt-60 or iodine-131 source.
The amount of chosen doses of radiation is designed to kill the malignant (actively changing) cells without harming the rest of the body. This is possible because malignant tissues are more sensitive to radiation than healthy tissues.
The way the radiation is applied is normally from an external “cannon” that “fires” a high-energy beam which is focused at the target. The normal treatment is a few minutes a day for one or two months.
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