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Radiobiology
Chapter 15: Management of Imaging Personnel Radiation Dose
| Term | Definition |
|---|---|
| Broad-beam x-ray transmission factor (B) | the ratio of air kerma behind a barrier of material thickness "x" to the value of air kerma at the same location with no intervening barrier |
| Bucky slot shielding device | a protective device made of at least 0.25 mm lead equivalent that automatically covers the Bucky slot opening in the side of the x-ray table during fluoroscopic examination; protects radiographer and radiologist from gonadal radiation exposure |
| control-booth barrier | a permanent secured protective barrier for imaging personnel that is located in an x-ray room that contains housing for permanent or nonportable radiographic equipment; regarded as secondary barrier device because primary beam is never directed toward it |
| controlled area | a region that is occupied only by occupationally exposed personnel and others under direct supervision |
| cumulative effective dose limit (CumEfD) | a radiation worker's lifetime EfD must be limited to their age in years times 10 mSv; this limit pertains to the whole body |
| distance | important method of protection from ionizing radiation; imaging personnel receive significantly less radiation exposure by standing farther away from a source of radiation because of the ISL governs the decrease in radiation level with increased distance |
| inverse square law (ISL) | expresses the relationship between distance and intensity (quantity) of radiation; the law states: "The intensity of radiation is inversely proportional to the square of the distance from the source." |
| leakage radiation | radiation generated in the x-ray tube that does not exit from the collimator opening but partially penetrates the protective tube housing and, to some degree, the sides of the collimator |
| occupancy factor (T) | a factor used to modify the shielding requirement for a particular barrier by taking into account the fraction of the work week during which the space beyond the barrier is occupied |
| primary protective barrier | barrier designed to prevent primary or direct radiation from reaching personnel or members of general public on other side; located perpendicular to the undeflected line of travel of the primary x-ray beam |
| primary radiation | well confined radiation that emerges directly from the x-ray tube collimator and moves without deflection toward a wall, door, viewing window, and so on; also called direct radiation or useful beam |
| scatter radiation | all the deflected radiation that arises from the interaction of an x-ray beam with the atoms of a patient or any other object in the path of the beam |
| secondary protective barrier | barrier that affords protection from secondary radiation only; as such, it is not designed to intercept the direct x-ray beam or to provide adequate attenuation of the beam |
| shielding | radiation-absorbent barrier of appropriate thickness used to provide protection from radiation; most common materials used for structural barriers are lead and concrete; accessory devices are made of lead-impregnated vinyl |
| time | method of radiation protection that reflects the fact that the amount of radiation a worker receives is directly proportional to the length of time that the individual is exposed to ionizing radiation |
| uncontrolled area | area such as a nearby hallway or corridor that can be frequented by the general public |
| use factor (U) | for primary radiation, the use factor represents the portion of beam-on time that the x-ray beam is targeted or directed at a particular barrier during the week; also known as beam direction factor |
| workload (W) | essentially the radiation output weighted time that an x-ray machine is actually delivering radiation during the week; specified either in units of mAs per week or mA-min per week |
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