Radiation Injuries
Definition
Radiation injury, also known as radiation sickness, results from exposure to excessive radiation. The seriousness of the condition depends on the type of radiation, amount of radiation, length of exposure time, and the part of the body affected. Radiation can be defined as the process of emitting energy in the form of particles or waves. Radiation is emitted by atoms in the process of changing, whether the atomic action is a naturally occurring or humanly directed process.
Description
Found throughout the universe, radiation comes in many forms. The better known forms of radiation include light, television and radio waves, microwaves, and radar, which generally do not cause injury. There are a number of potentially damaging forms of radiation including, for example, x rays, gamma rays, the energy emitted by radioactive substances such as uranium, and the radiation generated during nuclear reactions. Perhaps the most infamous events associated with widespread radiation injury and sickness occurred during the atomic bombing of Hiroshima and Nagasaki, Japan, which helped bring about the end of World War II, and the more recent nuclear meltdown at Chernobyl in 1986.
Radiation exposure can occur as a single large exposure, referred to as acute; or as a series of small exposures over time, referred to as chronic. Radiation sickness is generally associated with acute exposure. Chronic exposure is usually associated with delayed medical problems such as cancer and premature aging.
Radiation can cause damage by separating molecules into electrically charged particles, a process known as ionization. Some forms of ionizing radiation include cosmic rays, gamma rays, and x rays. Ionizing radiation damages deoxyribonucleic acid (DNA), which causes genetic mutation.
Several units of measure are used to quantify radiation energy. The roentgen, named after Wilhelm Conrad Roentgen, who discovered x rays in 1895, measures ionizing energy in air. A rad (short for radiation) indicates the transferred absorbed dose. The rem (taken from "Roentgen equivalent man") measures tissue response.
A roentgen generates approximately one rad of effect, producing approximately one rem of response. The gray and the sievert are international units equivalent to 100 rads and rems, respectively. A curie, named after the French physicists (Pierre and Marie Curie) who first began working with radiation, is a measure of radioactivity given off by a radioactive element. The average annual human exposure to natural background radiation is roughly 3 milliSieverts (mSv).
Radiation is pervasive. For example, the sun generates cosmic rays, and there are traces of radioactive elements in the air (radon), as well as in the Earth (uranium and radium, among others). Any amount of ionizing radiation will produce some damage.
Although the earth's atmosphere protects us from most of the sun's radiation, living at 5,000 ft (1,700 m) altitude in, for example, Denver, Colorado, doubles the exposure to radiation; and a flight in a commercial airliner increases it 150-fold.
Ionizing radiation is used for medical diagnosis and treatment, most commonly in the form of x rays and CT scans. Nuclear medicine employs radioactive isotopes to diagnose and treat medical conditions. Radioactive elements localize to specific tissues, giving off tiny amounts of radiation. Detecting that radiation provides anatomical and functional information. Radioactive chemicals are also used in the treatment of certain conditions, most common of which is the overactive thyroid. Because the thyroid is the only gland that utilizes iodine, all iodine in the body is concentrated there. A radioactive isotope of iodine (I-131) will gradually destroy overactive thyroid tissue.
Before the potential dangers posed by excessive radiation exposure were known, those who first began working with x rays frequently died from its long-term effects, most commonly leukemia. Doses now used for medical examinations are ordinarily too small to be of concern. Methods of magnification, lead shielding, and a greater awareness of the risks have nearly eliminated the danger from diagnostic radiation. However, no level of exposure is completely safe.
It is believed that radiation is responsible for less than 1% of all human disease and for approximately 3% of all cancers. This figure does not include lung cancer from environmental radon, which is difficult to determine because such effects are confounded by tobacco's similar effects. Because cancers are usually faster growing than their host tissues, they can be selectively killed by carefully measured radiation. This is most true of the lymphomas. Other cancers are less radiosensitive. Whenever radiation is used to treat cancer, care must be taken to measure the dose and aim it accurately. Even so, many cancers differ so little from the surrounding tissue that undesirable damage is unavoidable.
Newer techniques of directing radiation now provide greater safety. The gamma knife is a new surgical tool that focuses radiation with a high degree of accuracy in three dimensions, sparing surrounding tissue from radiation injury.
Causes and symptoms
Radiation damage depends upon the amount of radiation, the time over which it is absorbed, and the susceptibility of the tissue. The fastest-growing tissues are the most vulnerable, because radiation as much as triples its effects during the growth phase. Bone marrow cells that produce blood are the fastest-growing cells. Fetuses are also extremely vulnerable. Germinal cells in the testes and ovaries may be rendered useless by very small doses of radiation. More resistant cells include those of the skin. Brain cells are most resistant because they grow the slowest.
The most common symptoms of radiation sickness include:
- nausea and vomiting
- diarrhea
- skin burns (redness, blistering)
- weakness, fatigue, exhaustion, fainting
- dehydration
- inflammation of areas (redness, tenderness, swelling, bleeding)
- hair loss
- ulceration of the oral mucosa
- ulceration of the esophagus and gastrointestinal system
- vomiting blood
- bloody stool
- bleeding from the nose, mouth, gums, and rectum
- bruising
- sloughing of skin
- open sores on the skin
Exposure over time causes accumulating damage, which if not sufficient to kill cells, distorts their growth and causes scarring and cancers. In addition to leukemia, cancers of the thyroid, brain, bone, breast, skin, stomach, and lung are more likely to occur.
Mortality and morbidity risk are dictated by the total dose absorbed.
- Massive doses incinerate tissue immediately.
- A sudden whole-body dose over 50 Sv produces such profound neurological, heart, and circulatory damage that patients die within two days.
- Doses in the 10-20 Sv range strip intestinal lining and lead to death within three months from vomiting, diarrhea, starvation, and infection.
- Victims receiving 6-10 Sv all at once usually experience bone marrow failure and death within two months, due to loss of blood coagulation factors and the protection against infection provided by white blood cells.
- Those exposed to 2-6 Sv may survive if they are treated with blood transfusions and antibiotics.
- One or 2 Sv produces a brief, non-lethal sickness with vomiting, loss of appetite, and generalized discomfort.
Treatment
It is important to ascertain the dose received as early as possible, so that attention can be directed to those victims in the 2-10 Sv range who might survive with treatment. Blood transfusions, protection from infection, and possibly the use of blood formation stimulants save many victims in this category.
Radiation exposure usually damages the skin and requires careful wound care, dead tissue removal, and possible skin grafting. Infection control is imperative.
Alternative treatment
Studies strongly suggest that diets rich in free radical scavengers, also known as antioxidants, are recommended. The more commonly recommended antioxidants include beta-carotene, vitamins E and C, and the trace mineral selenium. Beta-carotene is present in yellow and orange fruits and vegetables. Vitamin C can be found in citrus fruits. Traditional Chinese medicine (TCM) and acupuncture, botanical medicine, and homeopathy all have contributions to make to recovery from radiation injuries.
Prognosis
Prognosis depends on the amount of exposure to radiation and the corresponding level of injury. High doses of radiation can be fatal, and minimal exposure can have virtually no effect. Some exposures may affect victims later in life, in the form of slow-growing cancers or reproductive difficulties.
Health care team roles
Physicians diagnose and treat radiation injuries. Nurses administer appropriate medications and otherwise supervise patient care. X-ray technologists can help prevent radiation exposure to themselves and to their patients by making sure equipment is proper working order and that appropriate preventative measures, such as the use of shields and radiation badges, are taken.
