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Friday, 29 March 2024
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Radiology Safety
Radiation Shielding
'Safety' in Radiology News (11) and in Radiology Resources (8)
Radiation Shielding
Radiation shielding is the process of limiting the penetration of radiation into the environment, by blocking with a barrier made of impermeable material. This protective barrier is usually formed of a material with high density, for example lead that absorbs the radiation.
Radiation sources are self-shielded with absorbing material incorporated into the equipment, adjacent to the source to reduce stray radiation to the surrounding area below dose limits.
Rooms with x-ray or other radiation equipment are additionally shielded with lead-lined walls to reduce the radiation exposure to humans within the facility. The amount of shielding required to protect against different kinds of radiation depends on how much energy they have. The shielding calculations are based on the half value layer of the primary radiation beam. Sufficient half value layers of shielding are calculated to reduce the radiation exposure outside the room to reasonable levels.
Personal shielding requirements depending on the type of radiation:
Alpha rays are shielded by a thin piece of paper, or even the outer layer of human skin. Unlike skin, living tissue inside the body, offers no protection against inhaled or ingested alpha radiation.
Beta particles, depending on their energy can penetrate the skin. Shielding and covering, for example with heavy clothing, is necessary to be personally protected against beta-emitters.
Gamma rays and x-rays penetrate the body and other matter. Dense shielding material, such as lead, is necessary for protection. The higher the radiation energy, the thicker the lead must be. Lead aprons protect parts of the body against stray radiation.

See also Radiation Safety.
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Absorber
Absorbers consist of material that stops ionizing radiation. For example, lead, steel and concrete attenuate x-rays. Alpha particles and most beta particles can be stopped or absorbed by a sheet of paper or thin metal.
The absorption depends on the atomic number, density, thickness, etc. of the used material.
The interactions between the radiation and the absorber are three major processes: photoelectric absorption, Compton scattering, and pair production.

See also Absorption.
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Lead Equivalence
The thickness of lead affording the same attenuation, under specified conditions, as the material in question. Used as shielding value for e.g. control windows, protective wear, etc.
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Direct Radiation
Direct radiation is emitted from the target or source that passes though the collimator opening.
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Secondary Radiation
Secondary radiation is the result of absorption of other radiation in matter. It could be either electromagnetic or particulate in nature.
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Leakage Radiation
Leakage radiation is all radiation escaping from within the source assembly except for the useful beam. It is primarily controlled through the design of the tube housing and proper collimator filtering.
• View DATABASE results for 'Leakage Radiation' (3).Open this link in a new window.
Scattered Radiation
Scattered radiation is caused by interaction of the primary radiation with matter. The interaction with matter could cause a change in direction (scattering) and a reduction in energy.
From a radiation protection point of view, scattered radiation is assumed to come primarily from interactions of primary radiation with tissues of the patient.
• View DATABASE results for 'Scattered Radiation' (3).Open this link in a new window.
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- Woody Allen
 
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 [last update: 2023-11-06 02:01:00]