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Questions and Answers
What percentage of radiation exposure in the U.S. is primarily attributed to radon and thoron?
What percentage of radiation exposure in the U.S. is primarily attributed to radon and thoron?
In what year did a significant increase in ionizing radiation exposure from medical procedures occur, necessitating revised estimates?
In what year did a significant increase in ionizing radiation exposure from medical procedures occur, necessitating revised estimates?
Which source of radiation exposure in the U.S. is the second largest contributor, closely following background radiation?
Which source of radiation exposure in the U.S. is the second largest contributor, closely following background radiation?
Which principle should technologists adhere to in order to minimize radiation exposure?
Which principle should technologists adhere to in order to minimize radiation exposure?
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What type of radiation exposure increases at higher elevations due to cosmic radiation?
What type of radiation exposure increases at higher elevations due to cosmic radiation?
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What was the percentage increase in CT studies performed between 1997 and 2006?
What was the percentage increase in CT studies performed between 1997 and 2006?
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Which of the following is the least significant source of radiation exposure in the U.S.?
Which of the following is the least significant source of radiation exposure in the U.S.?
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What primarily distinguishes the ionization density of alpha particles from that of x-rays?
What primarily distinguishes the ionization density of alpha particles from that of x-rays?
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What unit is used to express the radiation dose equivalency in the SI system?
What unit is used to express the radiation dose equivalency in the SI system?
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How does a dosage of 1 Gy from an alpha particle compare to 1 Gy from an x-ray in terms of biological damage?
How does a dosage of 1 Gy from an alpha particle compare to 1 Gy from an x-ray in terms of biological damage?
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In terms of radiation effects, what characterizes deterministic effects?
In terms of radiation effects, what characterizes deterministic effects?
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What is the former unit of dose equivalency before SI units were accepted?
What is the former unit of dose equivalency before SI units were accepted?
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What does the weighting factor estimate in relation to radiation types?
What does the weighting factor estimate in relation to radiation types?
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How is the relationship between absorbed doses measured in terms of Gy and rads?
How is the relationship between absorbed doses measured in terms of Gy and rads?
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What is the level of lead equivalence commonly found in protective aprons and gloves used in x-ray rooms?
What is the level of lead equivalence commonly found in protective aprons and gloves used in x-ray rooms?
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What percentage of studies found proper glove use monitored in a university setting?
What percentage of studies found proper glove use monitored in a university setting?
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What is the whole-body limit for radiation workers set by the ICRP to avoid stochastic effects?
What is the whole-body limit for radiation workers set by the ICRP to avoid stochastic effects?
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How does the allowable radiation limit for pregnant workers compare to that of nonpregnant workers?
How does the allowable radiation limit for pregnant workers compare to that of nonpregnant workers?
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Which piece of personal protective equipment is least commonly used among radiology personnel?
Which piece of personal protective equipment is least commonly used among radiology personnel?
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What is the lifetime accumulation limit set by the NCRP for radiation workers?
What is the lifetime accumulation limit set by the NCRP for radiation workers?
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Which agency in the United States is responsible for defining federal exposure standards for radiation workers?
Which agency in the United States is responsible for defining federal exposure standards for radiation workers?
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What is the average annual limit for radiation exposure recommended by the NCRP for adult radiation workers?
What is the average annual limit for radiation exposure recommended by the NCRP for adult radiation workers?
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What is the recommended maximum radiation exposure for the general public, excluding medical use?
What is the recommended maximum radiation exposure for the general public, excluding medical use?
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What is the maximum dose allowed in any one year for radiation workers according to the ICRP?
What is the maximum dose allowed in any one year for radiation workers according to the ICRP?
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What distinguishes stochastic effects from deterministic effects regarding radiation exposure?
What distinguishes stochastic effects from deterministic effects regarding radiation exposure?
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What is the maximum permissible dose (MPD) intended to signify?
What is the maximum permissible dose (MPD) intended to signify?
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What is the role of the International Commission on Radiological Protection (ICRP)?
What is the role of the International Commission on Radiological Protection (ICRP)?
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Describe the image (cover right).
Describe the image (cover right).
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Describe the image (cover right).
Describe the image (cover right).
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Describe the image (cover right).
Describe the image (cover right).
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Describe the image (cover right).
Describe the image (cover right).
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Study Notes
Radiation Protection
- Diagnostic radiology aims for maximum diagnostic information with minimal patient, personnel, and public radiation exposure. This is achieved by following guidelines and using personal protective equipment (PPE).
- X-rays are difficult to see or feel, making disregard of the occupational hazards associated with them easy. Veterinarians and technologists sometimes display a cavalier attitude toward ionizing radiation safety, putting themselves at risk medically and legally.
- While digital radiography has improved image quality in veterinary imaging, the minimal cost and time investment in retakes further encourages disregard for safe practices.
- General principles of radiation protection form the basis for a safe workplace. Specific recommendations are subject to local, state, and federal regulations.
Radiation Units
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Radiation exposure and absorption are different concepts. Not all tissue absorb radiation equally; some tissues absorb more radiation effectively than others. This means exposure to the same dose of radiation will result in different absorbed doses in different tissues.
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The biologic effect of the same absorbed dose also varies depending on the type and energy of radiation. A weighting factor (quality factor) is used to estimate the difference in biologic effectiveness of various radiation types.
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X-rays and gamma rays have a weighting factor of 1.
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Beta particles (electrons) have a weighting factor of 1.
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Neutrons with <10 keV have a weighting factor of 5.
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Neutrons with 10-100 keV have a weighting factor of 10
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Neutrons with 100 keV-2 MeV have a weighting factor of 20
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Alpha particles have a weighting factor of 20
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Radiation exposure, absorption, and dose equivalent have their own units of measurement. Originally, these were defined in the centimeter-gram-second (CGS) system. In 1977, the International System of Units (SI) was developed for universal adoption. However, the CGS units are still used in the United States.
Exposure
- Radiation exposure is based on the amount of ionization in air that the radiation produces. Quantified by the amount of electrical charge resulting from ionization. Expressed in SI units as coulombs per kilogram of air (C/kg).
- One roentgen equals a charge of 2.58 C/kg in air.
Absorbed Dose
- X-ray absorption efficiency varies widely between materials. Lead, for example absorbs much more efficiently than water.
- This difference in absorption efficiency results in differing absorbed doses in tissue types exposed to the same exposure dose.
- The SI unit for absorbed dose is the gray (Gy). One gray is the amount of radiation leading to the absorption of 1 joule/kg of tissue.
- The older unit, rad, equals 100 ergs/g of tissue.
Dose Equivalent
- The same absorbed dose from different types of radiation may not produce the same biologic effect.
- A large, heavily charged particle, such as an alpha particle, creates many ionizing events that are close together, unlike a small, less-charged particle. This leads to higher ionization density (alpha particle) and greater biologic damage than in x-rays
- The magnitude of this difference is estimated by the weighting factor.
- The SI unit of dose equivalency is the sievert (Sv); the Sv is derived from the product of the absorbed dose in Gy and the weighting factor.
- The older unit rem is the product of the absorbed dose in rads and the weighting factor (1 Gy = 100 rads, 1 Sv = 100 rem)
Practical Considerations
- Technologists must be aware of radiation risks. Proper training in patient positioning, equipment operation, and PPE use is crucial.
- ALARA (as low as reasonably achievable) principle should be followed, considering distance, time, and shielding.
Time
- Examination duration is closely related to the number of images taken.
- Minimizing time can be achieved via sedation or anesthesia of non-compliant patients. Staff rotation reduces cumulative exposure for each individual.
- Retakes, which are less labor-intensive with digital imaging, however increase personnel dose.
Shielding
- Protective equipment like aprons, gloves, thyroid shields etc. should be used. State and federal regulations regarding radiation protection standards exist.
- Proper use of shielding and collimation is essential
- Personnel must be shielded from the primary beam and scattered radiation.
- Correct positioning and collimation techniques are necessary, avoiding placement of body parts in the primary x-ray beam during radiography
- X-ray-induced biological damage and potential genetic or somatic effects must be reduced in all patients.
Radiation Safety
- Radiation safety guidelines are in place to prevent unnecessary exposure of workers and the public.
- Procedures and regulations must conform with local guidelines.
Personnel Dose Monitoring
- Personnel dose monitoring is used to check the adequacy of radiation safety programs.
- Radiation badges consist of radiation-sensitive materials like Aluminum oxide or Lithium fluoride that measure exposure levels from trapped electrons.
- Badges should be analyzed often (quarterly, or monthly for pregnant workers), to allow for detection of exposure issues sooner, hence, reducing the risks of adverse effects.
Radiation Supervisor
- A dedicated radiation supervisor is essential, overseeing training in radiation procedures and equipment use.
- Supervisors need to create written procedures for radiation exposure for workers, oversee radiation surveys, and ensure warning signs are present. They need to establish and maintain an organized procedure, and periodically evaluate procedures to ensure compliance.
- Yearly radiation safety seminars are necessary for ongoing learning and compliance.
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Description
This quiz covers the essential principles of radiation protection, specifically in the context of diagnostic radiology and veterinary imaging. It addresses the risks associated with ionizing radiation exposure and emphasizes the importance of following guidelines and using personal protective equipment. Understanding the concepts of radiation exposure and absorption is crucial for maintaining safety in the workplace.
