The ALARA principle is an important principle for any worker, exposed to radiation, to fully understand and apply in every day use.
What is ALARA?
ALARA stands for “As Low As Reasonably Achievable”, a safety principle specifically designed to reduce radiation doses and releases of radioactive materials. ALARA is a regulatory requirement for all radiation safety programs¹. The ALARA principle also factors in the technologic and economic considerations, while keeping radiation doses and releases of radioactive materials to the environment as low as reasonably achievable.
What is the biological basis of ALARA?
“The biological basis for radiation protection assumes a conservative estimate of radiation dose versus effect, termed “linear hypothesis.” This hypothesis states that, any dose, no matter how small, may inflict some degree of detriment. “This detriment takes the form of an postulated risk of cancer and genetic damage.” While the risk of cancer and genetic damage exists in the absence of radiation, exposure to ionizing radiation increases the level of risk.
Radiation safety programs strive to lower doses, in most situations this can be accomplished, but may involve more costly practices. The ALARA philosophy serves as a balance between dose reduction and economic considerations. There comes a point that the costs outweigh the benefit of further dose reduction.
ALARA Philosophy And Safety
An effective radiation safety and ALARA program is only possible when a commitment to safety is made by all those who are involved in the use of radiation. This may include members of the radiation safety committee, radiation safety division staff, medical personnel, research faculty, and all radiation workers.
Medical and research facilities will have a radiation safety manual that provides guidelines for the responsibilities and best practices which are consistent with both the ALARA concept and state regulatory requirements. Although these guidelines may vary by state, there is a regulatory requirement that requires radiation workers to adhere to legal dose limits for regulatory compliance, as well as an ALARA investigation dose level which serves as alert points for radiation worker radiation safety practices.
3 ALARA Safety Measures For Mitigating External Radiation Hazards
- Time: It’s important to minimize your time of radiation exposure.
- Distance: Doubling the distance between your body and the radiation source will divide the radiation shielding exposure by a factor of 4.
- Shielding: Using absorber materials such as lead for X-rays and gamma rays is an effective way to reduce radiation exposures.
Time and distance are two factors that can be controlled by the operator. However, lead shielding is more complex, since there are a variety of shielding options available. Radiation shielding is based on the principle of attenuation, which is the gradual loss in intensity of any energy through a medium. Lead acts as a barrier to reduce a ray’s effect by blocking or bouncing through a barrier material. When X-Ray photons interact with matter, the quantity is reduced from the original x-ray beam.
Protection From X-Rays
The purpose of lead shielding is to protect the patients (when not being examined), X-Ray department staff, visitors and the general public, as well as the people working near the X-Ray facility. There are three sources of radiation that must be shielded; secondary or scattered (originates via the patient), primary (the x-ray beam), and leakage (from the x-ray tube).
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