| Term | Definition |
|---|
| Ionization | The removal of orbital electrons from atoms when struck by x-rays; responsible for biological damage |
| Dose rate | Amount of x-ray given over a period of time; the greater the rate, the greater the chance of tissue damage |
| Area or volume of tissue | The greater the amount of tissue exposed to x-rays, the greater the chance of tissue damage |
| Age | Factor where the younger the person exposed (including fetus), the greater the chance of tissue damage |
| Specific tissue sensitivity | Refers to certain tissues in the body that are more sensitive to x-rays than other tissues; due to simplicity of structure and mitotic rate |
| Most Sensitive | Pertaining to x-ray sensitivity: reproductive cells, bone marrow, lens of the eye |
| Least Sensitive | Pertaining to x-ray sensitivity: skin, nerve tissue, muscle |
| Possible radiation effects | Cancer/leukemia; cataract formation, life-span shortening; genetic mutations in ova or sperm; possible when x-ray protection methods are not followed |
| Collimation | Allows us to restrict the size of the x-ray field, reducing area of tissue exposed |
| High kVp Exposures | will more readily pass through the patient to the film and not get absorbed as much in the tissues |
| Shielding | Consists of at least 0.5 mm of lead equivalency; protects sensitive tissues |
| Shadow shield | Is suspended above the radiographic beam defining system and casts a shadow over the protected body area (eg gonads) |
| Filtration | 2.5 mm of aluminum equivalency is placed by equipment manufacturers beneath the x-ray tube and above the collimator; filters out all non-penetration x-rays that would only damage skin |
| Dosimeter | Should be worn in the region of the collar and outside the lead apron if lead is being worn; monitors how much radiation a technologist receives on the job (dose limit has been set at 5 rem per year); replaced on a quarterly basis (every 3 months) and analyzed by an outside lab |
| Common Radiation Units of Measurement | Quantities may be expressed in either traditional units of measurement or SI units of measurement; metric prefixes, such as "m" for "milli", enable us to express small amounts as used in our field |
| Exposure | Used to measure x-ray in air; units of measurement: "Roentgen" (T), or "Coulombs/kilogram" (SI) |
| Absorbed dose | Used to measure amount of x-ray absorbed by matter; units of measurement: "rad" (T), or "gray" (SI) |
| Dose equivalent | Used to measure radiation effects on biological tissue; units of measurement: "rem" (T) or "sievert" (SI) |
| 5 rem per year/5,000 mrem | The radiation dose limit for technologists |
| Millirem (mrem) | Equal to .001 rem |
| 100 mrem per year | Exposure limit for students |
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