Chapter 10: Dose Limits for Exposure to Ionizing Radiation

Cancerous neoplasms caused by exposure to ionizing radiation is called a:

Radiation-induced malignancy

Optimization for radiation protection is synonymous with what concept:

ALARA concept

Documents that identify the necessary training and experience for an RSO

Code of Federal Regulations (§10 CFR 35.50 and §10 CFR 35.900)

Public law passed by Congress for establishing and overseeing electronic product radiation control including diagnostic x-ray equipment

Radiation Control for Health and Safety Act of 1968

The regulatory agency that has the power to enforce radiation protection standards in the United States

Nuclear Regulatory Commission (NRC)

“Indicates the ratio of the risk of stochastic effects attributable to irradiation of a given organ or tissue (T) to the total risk when the whole body is uniformly irradiated”

Tissue weighting factor (WT)

The international authority on the safe use of sources of ionizing radiation. Responsible for providing clear and consistent radiation guidance through its recommendations for occupational dose limits and public dose limits

International Commission on Radiological Protection (ICRP)

Lifetime EfD limit is recorded as:

CumEfD limit

Naturally occurring and/or accelerator-produced materials

NARM

The United Nations Committee that evaluates human and environmental ionizing radiation exposures from a variety of sources, including radioactive materials, radiation-producing machines, and radiation accidents

United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)

The agency responsible for regulations concerning an employee’s “right to know” about hazards that may be present in the workplace

Occupational Safety and Health Administration (OSHA)

Federal legislation requiring the establishment of minimal standards for the accreditation of educational programs for persons who perform radiologic procedures and the certification of such persons

Consumer-Patient Radiation Health and Safety Act of 1981

Established by health care facilities to trigger an investigation to uncover the reason for any abnormal exposure received by individual staff members

Action limits

Set of numeric dose limits that are based on calculations of the various risks of cancer and genetic (hereditary) effects to tissues or organs exposed to radiation

EfD limiting system

U.S. Regulatory Agency that conducts an ongoing product radiation control program, regulating the design and manufacture of electronic products, including diagnostic x-ray equipment

Food and Drug Administration (FDA)

An upper boundary limit for radiation workers for yearly whole-body exposure (excluding personal medical and natural background exposure) of 50 mSv/yr

Annual occupational EfD limit

An annual EfD level that provides a low-exposure cutoff level that has been determined to be a dose of negligible risk, meaning that a reduction of individual exposure is unnecessary

Negligible individual dose (NID)

Usually a medical physicist, health physicist, radiologist, or other individual qualified through adequate training and experience. This person is designated by a health care facility and approved by the NRC and the state

Radiation safety officer (RSO)

The scientific journals published by the ICRP

Annals of ICRP

The sum of both external and internal whole-body exposures is considered when establishing this limit

Effective dose (EfD)

Publications that list studies of biologic effects and associated risk of groups of people who were either routinely or accidentally exposed to ionizing radiation

BEIR reports

Concerns the upper boundary dose of ionizing radiation that results in a negligible risk of body injury or hereditary damage

EfD limit

Applies to complete x-ray systems and major components manufactured after August 1, 1974

Code of standards for diagnostic x-ray equipment

Publications that provide the most recent guidelines on radiation protection for the United States

National Council on Radiation Protection and Measurements (NCRP) reports

Biologic somatic effects of ionizing radiation that can be directly related to the dose received

Tissue reactions

Why have scientists developed occupational and nonoccupational EDLs for exposure to ionizing radiation?

A. To eliminate all harmful effects of low-level ionizing radiation exposure

B. To minimize the risk of harmful biologic effects to the general public, patients, and radiation workers

C. To promote the theory of radiation hormesis

D. To be comparable to the risk occurring in both nonsafe and safe industries

B. To minimize the risk of harmful biologic effects to the general public, patients, and radiation workers.

Which of the following is the upper boundary dose of ionizing radiation that results in a negligible risk of body injury or hereditary damage?

A. Skin erythema dose

B. Tissue weighting factor

C. Negligible individual dose (NID)

D. Effective dose limit (EDL)

D. Effective dose limit (EDL)

Fundamental radiation protection standards governing occupational radiation exposure may be found in which of the following documents?

A. 5 CFR 10

B. 10 CFR 20

C. The ALARA Manual

D. Public Law 90-602

B. 10 CFR 20

Which of the following groups are radiation protection standards organizations?

1. ICRP

2. NCRP

3. UNSCEAR

All 3

The NCRP recommends that radiation exposure be kept:

as low as reasonably achievable (ALARA)

Which of the following concepts is behind the establishment of the EfD limiting system?

A. Negligible risk

B. Organ and tissue radiosensitivity

C. Radiation hormesis

D. Radiation exposure and associated risk of possible radiation-induced malignancy

D. Radiation exposure and associated risk of possible radiation-induced malignancy

The term mutagenesis refers to which of the following?

A. Irradiation of DNA of somatic cells leading to abnormalities in new cells as they divide in that individual

B. Birth defects from irradiation of the unborn child in utero

C. Cancer caused by ionizing radiation exposure

D. Somatic and hereditary effects of ionizing radiation caused by low-level exposure

A. Irradiation of DNA of somatic cells leading to abnormalities in new cells as they divide in that individual

Biologic somatic effects of ionizing radiation that can be directly related to the dose received, exhibit a threshold dose below which the response does not normally occur, and above which the severity of the biologic damage increases as the dose increases, are classified as:

Tissue reactions

Congress passed the Radiation Control for Health and Safety Act (Public Law 90-602) in 1968 to protect the public from the hazards of unnecessary radiation exposure resulting from:

Electronic products, excluding diagnostic x-ray equipment

Which of the following are classified as late tissue reactions caused by high-level radiation exposure that occur months or more after that exposure?

1. Cataract formation

2. Organ atrophy

3. Radiation-induced malignancy

1 and 2 only

What term is used for a beneficial result in groups of individuals from continuing exposure to small amounts of radiation?

Radiation hormesis effect

In addition to the annual occupational EDL established for radiation workers, the NCRP recommends a lifetime EDL, which is found by multiplying an individual’s age in years by:

10 mSv

For individual members of the general public not occupationally exposed, the NCRP recommended an annual EDL of _________ for continuous (or frequent) exposures from artificial sources of ionizing radiation other than medical irradiation and natural background and a limit of ______ annually for infrequent exposures.

1 mSv; 5 mSv

Current radiation protection philosophy is based on the assumption that a linear nonthreshold relationship exists between ________ and ________.

radiation dose; biological effect

A set of numeric dose limits that are based on calculations of the various risks of cancer and genetic (hereditary) effects to tissues or organs exposed to radiation defines:

EfD limiting system

Previously, the NRC was known as the:

Atomic Energy Commission (AEC)

The Radiation Effects Research Foundation is a group run by the government of:

Japan, primarily to study the atomic bomb survivors of Hiroshima and Nagasaki

In 1991 the ICRP recommended that the annual EDL for occupationally exposed persons be reduced from _______ to ________.

50 mSv to 20 mSv

Which agency is responsible for regulations regarding an employee’s “right to know” with regard to hazards that may be present in the workplace?

Occupational Safety and Health Administration (OSHA)

The risk to a radiographer from radiation exposure may be equated with:

Occupational risk in generally safe industries

Because the tissue weighting factors (WT) used for calculating EfD are very small for some organs, an organ that is associated with a low weighting factor may receive an unreasonably large dose. In contrast, the EfD for the whole person remains within the total allowable limit. Therefore, special limits are set for the crystalline lens of the eye and localized areas of the skin, hands, and feet to prevent unwanted:

1. Tissue reactions

2. Stochastic effects

3. Probabilistic effects

1 only

Late tissue reactions (i.e., cataract formation) have a high probability of occurring when entrance radiation doses exceed:

2 Gy

Established organ or tissue weighting factors for calculating the EfD include a “remainder” that takes into account additional tissues and organs, some of which are the:

1. Brain

2. Small intestine

3. Uterus

All 3

In International System (SI) units, the CumEfD limit for the whole body of an occupationally exposed person who is 26 years old is:

260 mSv

NARM stands for:

Naturally Occurring Radioactive Materials

True or False: The ICRP functions as an enforcement agency for radiation protection purposes.

False, the ICRP recommends guidelines and policies, but does not enforce them.

True or False: Future radiation protection standards are expected to continue to be based on risk.

True

True or False: The Radiation Effects Research Foundation is a group run by the government of Japan primarily for the purpose of studying the atomic bomb survivors.

True

True or False: The NRC regulates and inspects x-ray imaging facilities.

False; the NRC provides guidelines but does not directly regulate individual facilities.

True or False: In 1991 the ICRP recommended that the annual EfD limit for occupationally exposed persons be reduced from 50 to 20 mSv as a result of newer information obtained regarding the Japanese atomic bomb survivors in whom the risk of radiation from the atomic bomb detonations was estimated to be approximately three to four times greater (more damaging) than previously estimated.

True

True or False: Health care facilities that provide imaging services do not need to have an effective radiation safety program.

False; effective radiation safety programs are essential for protecting patients and staff from unnecessary exposure.

True or False: EDLs may be specified for whole-body exposure, partial-body exposure, and exposure of individual organs.

True

True or False: Quantitative values for radiation risks are derived from the complete injury that may be caused by radiation exposure.

True

True or False: The Center for Devices and Radiological Health (CDRH) is responsible for credentialing radiographers.

False; the CDRH oversees the regulation of medical devices and radiation-emitting products, but credentialing is managed by professional organizations.

True or False: Late tissue reactions may occur months or years after high-level radiation exposure.

True

True or False: The ICRP is considered the international authority on the safe use of sources of ionizing radiation.

True

True or False: The NRC publishes rules and regulations in Title X of the Code of Federal Regulations.

True

True or False: The FDA facilitates the development and enforcement of regulations pertaining to the control of radiation in the environment.

False; The FDA does not facilitate the development and enforcement of regulations pertaining to the control of radiation in the environment; the EPA does.

True or False: For high–dose-rate fluoroscopic procedures, entrance exposure rates as great as 200 mGya/min are possible.

True

True or False: Internal action limits are established by health care facilities to trigger an investigation when the limits are exceeded to uncover the reasons for any unusual high exposures received by individual staff members.

True

True or False: Because a stochastic event is an all-or-none, random effect, ionizing radiation will normally induce some cancers within a large general population, but determining beforehand which members of that population will develop cancer is not possible.

True

True or False: The embryo-fetus is particularly insensitive to radiation exposure

False; the embryo-fetus is particularly sensitive to radiation exposure, especially during the first trimester of pregnancy.

True or False: EfD limits include radiation exposure from natural background radiation and exposure acquired when a worker undergoes medical imaging procedures.

False; EfD limits do not include background radiation or exposure acquired when a worker undergoes medical imaging procedures.

True or False: To limit radiation exposure for pregnant radiation workers and the unborn during potentially sensitive periods of gestation, the NCRP “recommends” a monthly EqD limit not exceeding 0.5 mSv (50 mrem) per month to the embryo-fetus and a maximum limit during the entire pregnancy not to exceed 5.0 mSv (500 mrem) after declaration of the pregnancy.

True

True or False: The NRC does not require the name of the RSO on a health care facility’s radioactive materials license

False; the NRC does require the name of the Radiation Safety Officer (RSO) on a health care facility's radioactive materials license.

True or False: Lifetime survival data seems to indicate that Japanese atomic bomb survivors with moderate radiation EqD totals of 5 to 50 mSv (0.5 to 5 rem), the equivalent of 1.5 to 15 years of natural radiation, have a reduced cancer death rate compared with a normally exposed control population.

True

True or False: Employers are not required by law to evaluate their workplace for harmful agents or to provide training and written information to their employees.

False; employers are required by law to evaluate their workplace for harmful agents and to provide training and written information to their employees.

True or False: The CDRH falls under the jurisdiction of the FDA

True

True or False: The concept of radiation hormesis is that there exists a beneficial result in groups of individuals from continuing exposure to small amounts of radiation.

True

True or False: All imaging personnel should be familiar with NCRP recommendations.

True

Because medical imaging professionals share the responsibility for patient safety from radiation exposure and are subject themselves to such exposure in the performance of their duties, they must be familiar with __________, __________, and _______ guidelines.

Previous, existing, new

Since its inception in 1928, the ICRP has been the leading international organization responsible for providing clear and consistent radiation protection guidance through its recommendations for occupational and public __________.

dose limits

In the United States, the NCRP is a _________, _________, private corporation

nongovernmental, nonprofit

NAS/NRC-BEIR is an advisory group that reviews studies of ________ effects of ionizing radiation and _______ assessment.

biologic, risk

The EPA has oversight authority for specific areas such as determining the action level for _______.

radon exposure

The NRC formally licenses users of _______ materials.

radioactive

The NRC mandates that a ______________ committee be established for a facility.

radiation safety

Separate ____________ are set for occupationally exposed individuals and for the general public

dose limits

ALARA may also be referred to as _____________.

optimization of radiation protection

Cancer and genetic alterations are examples of ___________ effects.

Stochastic

The limit for any education and training exposures of individuals under the age of 18 years is an EfD of ______ mSv annually.

1

The ALARA concept adopts an extremely conservative model concerning the relationship between ionizing radiation and potential _________.

risk

Because stochastic event is an all-or-none, _________ effect, ionizing radiation will normally induce some cancers within a large general population but determining beforehand which members of that population will develop cancer is not possible.

random

To fulfill the responsibilities of the RSO, a facility must grant the RSO the authority necessary to implement and _________ the policies of the radiation safety program.

enforce

Stochastic responses to ionizing radiation may be determined with the use of both the ___________ and ___________ dose–response curves.

linear; linear-quadratic

Revised concepts of radiation exposure and ________ have brought about recent changes in NCRP recommendations for limits on exposure to ionizing radiation.

risk

The lifetime fatal risk in hazardous occupations such as logging and deep-sea fishing is many times __________ than the occupational risk associated with radiation exposure.

greater

Epidemiologic studies of atomic bomb survivors exposed in utero provided conclusive evidence of a dose-dependent increase in the incidence of severe intellectual disability for fetal doses greater than approximately ______ Sv.

0.4

Referring to the previous statement (number 18), the most significant risk for radiation-induced intellectual disability occurred when the embryo-fetus was exposed _______ to _______ weeks after conception.

8, 10

The EfD limiting system is an attempt to equate the various risks of _________ and _________ effects on the tissues or organs that were exposed to radiation.

cancer, genetic

The CumEfD limit pertains to the _____________.

whole body

In addition to limits for occupationally exposed individuals, the NCRP also recommends EDLs for ______________ exposed individuals who are not undergoing medical examinations.

nonoccupationally (members of the public)

For education and training purposes, the ________ dose limits apply to students of radiography as to individuals under 18 years of age.

same

The sum of both ___________ and ______________ whole-body exposures is considered when an effective dose limit is being established.

external, internal

The NCRP has established an annual occupational EDL of ______ mSv (not including medical and natural background exposure) for the whole body, and a lifetime EfD in mSv that does not exceed _______ mSv times the occupationally exposed person’s age in years.

50, 10