X-rays have an effect on living things. As x-rays are absorbed, they change the structure of tissues, and may cause burns or destruction if the exposure is long enough. Some types of x-rays are able to affect the genes, the elements in the germ cells or reproductive organs by which hereditary traits are passed on from generation to generation. This can effect the total picture of heredity.
At the present time, the genetic effects of diagnostic radiology are thought to be undetectable hazards. The radiation dose of genetic significance from diagnostic radiology is estimated to be about twenty millirem/year.
Many physicians believe that at the present, the total benefits of diagnostic x-rays are often misused and over-used by some physicians. X-ray studies have been of great benefit to many people, but the possibility for harm must be discussed before a decision to do an x-ray examination is made.
Some physicians proclaim that there is no proof that the low levels of radiation involved in diagnostic x-rays have ever harmed anyone.
The ultraviolet radiation from the sun and the x-rays produced in a machine have like properties, but medical x-rays are more energetic and more penetrating.
There is no precise evidence that diagnostic x-rays of other regions besides the trunk are harmful to adults. Some scientists believe that x-rays may cause damage in proportion to the quantity of dose involved, and if the reproductive organs are in the direct x-ray beam, such x-rays may possibly damage future generations as well as exposed individuals. If risk is related to dose, then there is not a safe level. Therefore, every examination should be carefully considered.
Other risks related to the x-ray examinations include the injections of contrast media used to outline certain organs, arteries, or blood vessels. Most of the time, the risks are low and consist of mild allergic reaction to the contrast medium. However, we must bear in mind that some contrast studies, like those of the heart or brain, can cause strokes or other serious complications if not done with special care.
Medical professionals, who insist that x-ray examinations are completely harmless are either remiss or misinformed. High dose procedures should not be done ordinarily or without special concern on the part of the patient and administering physician.
The possible danger from x-rays and other forms of radiation has a great deal of the time gone unnoticed in the past because the damaging radiation cannot be seen or felt. Unless people are exposed to large quantities of radiation, any indications of damage are not seen until a while after exposure, maybe a number of years and even then it is hard to prove that x-ray exams caused it.
There are three units commonly discussed in dealing with possible biological effects of x-rays and other types of radiation. They are the roentgen, the rad, and the rem. The roentgen is an estimated measure of the radiant energy to which an individual or object is exposed, meanwhile the rad and rem provide a measure of the quantity of energy actually absorbed by an exposed object. One roentgen, rad, or rem represents a huge amount of radiation when compared to the average natural background dose received annually. The prefix milli means 1/1000 so that 1 rem = 1000 Mrem. Used in terms of the smaller units, the average whole body dose in the U.S. due to background radiation is 84 millirems per year.
The average abdominal dose used from diagnostic x-ray is just slightly less than the abdominal dose received from natural background radiation in the U.S.
Known effects that are associated with diagnostic x-rays are of two types. One set of effects directly affects the health of the exposed individual. We term these somatic effects. The set that affects the health of the off-spring is termed genetic effects, which are produced when the reproductive organs are exposed to radiation.
When very high doses of radiation are absorbed radiation sickness and sometimes death occurs within a few days or weeks after exposure.
It is believed that radiation to the reproductive organs of humans can cause offspring to have a higher rate of mental retardation, cancer, ill health, and birth abnormalities.
It is difficult to establish an exact relationship between biological damage and dose for low levels of radiation. It is assumed under the linear non-threshold hypothesis any amount of radiation absorbed by an individual, no matter how small, involves some risk to the health of that individual and/or his or her potential offspring. Some people believe the threshold hypothesis is closer to the truth. It is believed with the threshold hypothesis that radiation does not involve a health risk until a person is exposed to a certain amount. Below this, there is no damage over the threshold, there might be. (See Figure 8 and end of unit.)
When ionizing radiation, like an x-ray passes through a cell, the cell may be damaged or destroyed. With both ionizing radiation and x-ray the amount of cell damage is approximately proportional to the amount of radiant energy or dose absorbed, regardless of how small.
Each x-ray examination adds directly to an individual’s risk in proportion to the dose to which a patient is subjected. It is desirable to keep the total radiation dose received by a patient as low as possible. It is necessary to realize that the risks associated with each x-ray examination must be considered in regards to the potential benefits of that same examination. Past history of radiation exposure should not influence a decision to conduct an examination if needed.
There are substantial benefits of diagnostic x-rays. They may save your life. However, avoid routine examinations or prescribing x-ray examination for yourself. Do not avoid an x-ray examination if your physician can adequately explain why there is a real need for it.
Here are several suggestions you can use when dealing with x-rays.
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1. Ask your physician to explain what identifiable benefit will result from an x-ray.
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2. Ask if it is possible to use the results of previous x-ray diagnosis instead of new ones.
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3. If you are a woman you should avoid x-rays of lower back unless there is a serious condition.
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4. Avoid fluoroscopy if your physician acknowledges that ordinary x-ray film will provide necessary information.
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5. Check out equipment and facilities. In general you will receive significantly less radiation exposure at a facility which is under the supervision of a full-time radiologist.
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6. Check out the x-ray machine operator. Try to discourage operator from doing repeated x-rays due to sloppy techniques.
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7. Co-operate with the operator during x-ray exposures.
Exposing sex cells to radiation is like firing a bullet into a computer. There is no way to tell what change will result, or whether it will be harmful.
Fortunately, most people are not exposed to too much radiation. The most cautious health experts stress that there is no safe dose of ionizing radiation. We will always live with some natural background radiation, but we must be more alert to other human-made sources that have become common in this century.
Despite the gains made in x-ray technology, many people are still exposed to unnecessary risk from x-rays. An estimated third of all diagnostic x-rays are not needed.
Although there is growing concern about the misuse of x-rays, no one doubts that they are the most valuable tools in medicine.
Doses for Typical X-Ray Examinations in Millirads
|
Average no.
|
Estimated
|
|
of films per
|
“effective”
|
|
exam (a)
|
dose per exam (c)
|
Mammography
|
2*/per breast
|
300-600
|
Upper GI
|
4.3
|
150-400
|
Thoracic Spine
|
3*
|
150-400
|
Lower Gl
|
2.9
|
90-250
|
Lumbosacral Spine
|
3.4
|
70-250
|
Lumbar Spine (LS)
|
2.9
|
50-180
|
Intravenous Pyelogram (IVP)
|
5.3
|
50-150
|
Cervical Spine
|
3.7
|
40-80
|
Cholecystography
|
3.3
|
25-60
|
Abdomen or KUB
|
1.6
|
10-60
|
Skull
|
4
|
20-50
|
Lumbo-pelvic
|
1.4
|
5-35
|
Chest (radiographic)
|
1.6
|
5-35
|
Dental (whole mouth)
|
16*
|
10-30*
|
Hip or Upper Femur (thigh)
|
3*
|
2-25*
|
Shoulder
|
2*
|
2-25*
|
Dental (bitewing)
|
3*
|
5*
|
Extremities
|
2.7
|
5*
|
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(a) U.S., Department of Health, Education, and Welfare (FDA) Publication 73-8047, Population Exposure to X-rays U.S. 1970, (Rockville, MD.: Public Health Service, November 1973).
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(c) Preliminary estimates based on work in progress: P.W. Laws and M. Ross, “A Somatic Dose Index for Diagnostic Radiology,” to be presented at the second Annual Meeting of the Health Physics Society (Atlanta, GA.: 3/77).
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*Estimated by author.
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High Risk Contrast X-Ray Examinations*
Type of Study
|
Method
|
Uses
|
Bronchogram
|
dye** injected in
|
outlines bronchial
|
|
to lung bronchi
|
tree
|
|
(air passages)
|
Cerebral angiogram
|
dye injected into
|
outlines blood
|
(arteriogram)
|
carotid and/or
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vessels in neck and
|
|
vertebral arteries
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brain
|
|
in neck
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Coronary angiogram
|
dye injected into
|
outlines heart
|
(arteriogram)
|
chambers of heart
|
chambers, valves,
|
|
|
and surrounding
|
|
|
arteries and veins
|
Pulmonary
|
dye injected into
|
outlines blood
|
angiogram
|
pulmonary arteries
|
vessels (arteries
|
(arteriogram)
|
as they leave heart
|
and veins) in lungs
|
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*Source: Arthur Levin, Talk Back To Your Doctor (New York: Doubleday, 1975).
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**Dye is an obsolete term. “Contrast agent” is preferable.