Dose Limits for Exposure to Ionizing Radiation

Question 1

What is a radiation dose?

The amount of radiant energy absorbed by an ___ object per unit ___.

Because we know exposed to radiation will cause biological effects on ___ and ___ cells, scientist have set ___ standards.

The information can be found in Report NO 116 of the ___ ___ on ___ ___ and ___ (NCRP) .

Answer 1

What is a radiation dose?

The amount of radiant energy absorbed by an irradiated object per unit mass.

Because we know exposed to radiation will cause biological effects on somatic and genetic cells, scientist have set protection standards.

The information can be found in Report NO 116 of the National Council on Radiation Protection and Measurement (NCRP) .

Question 2

Dose Limits

Exposure of the general public, patients, and radiation workers to ionizing radiation must be limited in order to ___ the risk of harmful ___ effects.

Occupational and nonoccupational ___ dose (EfD) limits and ___ dose (EqD) limits for tissues and organs such as the lens of the ___, ___, ___, and ___ have been developed for radiation safety purposes.

An EfD limiting system has been incorporated into Title 10 of the Code of Federal Regulations, Part 20, a document prepared and distributed by the U.S. Office of the Federal Register.

The rules and regulations of the ___ ___ ___ (NRC) and fundamental radiation protection standards governing occupational radiation exposure are included in this document.

Answer 2

Dose Limits

Exposure of the general public, patients, and radiation workers to ionizing radiation must be limited in order to minimize the risk of harmful biologic effects.

Occupational and nonoccupational effective dose (EfD) limits and equivalent dose (EqD) limits for tissues and organs such as the lens of the eye, skin, hands, and feet have been developed for radiation safety purposes.

An EfD limiting system has been incorporated into Title 10 of the Code of Federal Regulations, Part 20, a document prepared and distributed by the U.S. Office of the Federal Register.

The rules and regulations of the Nuclear Regulatory Commission (NRC) and fundamental radiation protection standards governing occupational radiation exposure are included in this document.

Question 3

Basis of EfD Limiting System

• Basis of the EfD limiting system
• Concept of radiation exposure and of the associated risk of radiation-induced ___
• Resource for revised recommendations:
• National Council on Radiation Protection and Measurements (NCRP) Report No. 116
• International Commission on Radiological Protection (ICRP) Report No. 60
• Future radiation protection standards are expected to continue to be based on ___.
• Reasons medical imaging professionals must be familiar with ___, ___, and ___ guidelines for radiation safety
• They share the ___ for patient safety from radiation exposure.
• They are subject to radiation exposure in the performance of their ___.
• Radiographers may obtain the required knowledge by becoming familiar with the functions of the various ___ groups and ___ agencies.

Answer 3

Basis of EfD Limiting System

• Basis of the EfD limiting system
• Concept of radiation exposure and of the associated risk of radiation-induced malignancy
• Resource for revised recommendations:
• National Council on Radiation Protection and Measurements (NCRP) Report No. 116
• International Commission on Radiological Protection (ICRP) Report No. 60
• Future radiation protection standards are expected to continue to be based on risk.
• Reasons medical imaging professionals must be familiar with previous, existing, and new guidelines for radiation safety
• They share the responsibility for patient safety from radiation exposure.
• They are subject to radiation exposure in the performance of their duties.
• Radiographers may obtain the required knowledge by becoming familiar with the functions of the various advisory groups and regulatory agencies.

Question 4

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

Established in ___

Evaluates ___ and ___ ionizing radiation exposures from:

• ____ materials
• Radiation-producing ___
• Radiation ___

Answer 4

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

Established in 1955

Evaluates human and environmental ionizing radiation exposures from:

• Radioactive materials
• Radiation-producing machines
• Radiation accidents

Question 5

Radiation Protection Standards Organizations

There are ___ major organizations responsible for evaluating the relationship between radiation ___ and induced ___ effects. These organizations are also concerned with formulating ___ estimates of ___ and ___ effects of irradiation.

Answer 5

Radiation Protection Standards Organizations

There are four major organizations responsible for evaluating the relationship between radiation EqD and induced biologic effects. These organizations are also concerned with formulating risk estimates of somatic and genetic effects of irradiation.

Question 6

Summary of Radiation Protection Standards Organizations

Answer 6

Question 7

US Regulatory Agencies

1. Nuclear Regulatory Commission (NRC) - Federal agency to control the ___, ___ and ___ of ___ energy in the interest of national security. Main focus is the ___ energy industry
2. Environmental Protection Agency (EPA) - to bring several departments together for the protection of the health of ___ and ___ environment. DIRECT the ___ AGENCIES
3. US Food and Drug Administration (FDA) - Conducts an ongoing product radiation control program, regulating the ___ and ___ of ___ products, including x-ray equipment
4. Occupational Safety and Health Administration (OSHA) - Functions to monitor employment in industry, Regulates the concerns for the employee’s right to know with regard to ___ that may be present in the workplace
5. Agreement States - NRC has the authority to enter into ___ contacts with ___ governments. Helps with licensing the ___ and other ___ materials with each state

Answer 7

US Regulatory Agencies

1. Nuclear Regulatory Commission (NRC) - Federal agency to control the possession, use and production of atomic energy in the interest of national security. Main focus is the nuclear energy industry
2. Environmental Protection Agency (EPA) - to bring several departments together for the protection of the health of human and natural environment. DIRECT the FEDERAL AGENCIES
3. US Food and Drug Administration (FDA) - Conducts an ongoing product radiation control program, regulating the design and manufacturing of electronic products, including x-ray equipment
4. Occupational Safety and Health Administration (OSHA) - Functions to monitor employment in industry, Regulates the concerns for the employee’s right to know with regard to hazards that may be present in the workplace
5. Agreement States - NRC has the authority to enter into written contacts with state governments. Helps with licensing the radioisotopes and other radioactive materials with each state

Question 8

Objectives of the NCRP

Answer 8

Objectives of the NCRP

Question 9

As Low as Reasonably Achievable (ALARA) Concept

Principle put forth in ___ by the ___

Radiation exposure should be kept “___ ___ ___ ___ ___” with consideration for ___ and ___ factors

Described by ___ as “the continuation of ___ radiation protection programs and ___ which traditionally have been ___ in keeping the average and individual exposures for ___ workers well ___ the limit”
Procedures should be clearly described in a facility’s radiation ___ program.

To define ALARA, health care facilities usually adopt ___ levels (Level ___ and Level ___).

Answer 9

As Low as Reasonably Achievable (ALARA) Concept

Principle put forth in 1954 by the NCRP

Radiation exposure should be kept “as low as reasonably achievable” with consideration for economic and societal factors

Described by NCRP as “the continuation of good radiation protection programs and practices which traditionally have been effective in keeping the average and individual exposures for monitored workers well below the limit”
Procedures should be clearly described in a facility’s radiation safety program.

To define ALARA, health care facilities usually adopt investigational levels (Level I and Level II).

Question 10

Model for the ALARA Concept

An extremely conservative model with respect to the relationship between ___ radiation and potential ___

Relationship is assumed to be completely ___ and without any ___

In the interest of safety, risk of injury should be ___ rather than ___

Answer 10

Model for the ALARA Concept

An extremely conservative model with respect to the relationship between ionizing radiation and potential risk

Relationship is assumed to be completely linear and without any threshold

In the interest of safety, risk of injury should be overestimated rather than underestimated

Question 11

Rationale for Radiation Protection

Purpose of Radiation Protection

1. to ___ radiation exposure to ___ (___)
2. to ___ radiation exposure to ___

Early Effect of Radiation (from ___ doses within ___, ___ or ___)
Examples: ___ depression, skin ___, ___, ___ damage, ___ dysfunction and ___.

Late Effect of Radiation (occurs ___ or ___ later)
Examples: radiation induced ___

Answer 11

Rationale for Radiation Protection

Purpose of Radiation Protection

1. to lessen radiation exposure to self (cells)
2. to lessen radiation exposure to offspring

Early Effect of Radiation (from high doses within minutes, days or weeks)
Examples: hematologic depression, skin erythema, epilation, chromosome damage, gonadal dysfunction and death.

Late Effect of Radiation(occurs months or years later)
Examples: radiation induced cancer

Question 12

Radiation-Induced Responses of Concern in Radiation Protection

Deterministic effects
Biologic ___ effects of ionizing radiation that can be ___ related to the dose ___

Exhibit a ___ dose ___ which the response does not normally occur and ___ which the severity of the biologic damage ___ as the dose ___

These effects typically occur only after ___ doses of radiation. However, they could also result from ___-term individual ___ doses of radiation sustained over several ___.

Effects can be either ___ deterministic effects or ___ deterministic effects

Answer 12

Radiation-Induced Responses of Concern in Radiation Protection

Deterministic effects
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

These effects typically occur only after large doses of radiation. However, they could also result from long-term individual low doses of radiation sustained over several years.

Effects can be either early deterministic effects or late deterministic effects

Question 13

Radiation-Induced Responses of Concern in Radiation Protection

Stochastic (probabilistic) effects
___, ___, ___ occurring biologic ___ changes; mutational refers to changes to ___ cells that would affect the individual when the ___ divide, as opposed to ___, which refers to changes to ___ cells that would affect future ___

Their chances of occurrence increase with each ___ ___.
Examples: ___ and ___ alterations

May be demonstrated with the use of both the ___ and the ___- ___ dose-response curves

Answer 13

Radiation-Induced Responses of Concern in Radiation Protection

Stochastic (probabilistic) effects
Mutational, nonthreshold, randomly occurring biologic somatic changes; mutational refers to changes to somatic cells that would affect the individual when the cells divide, as opposed to genetic, which refers to changes to germ cells that would affect future generations

Their chances of occurrence increase with each radiation exposure.
Examples: Cancer and genetic alterations

May be demonstrated with the use of both the linear and the linear- quadratic dose-response curves

Question 14

Summary of Both Early and Late Deterministic and Stochastic (Probabilistic) Effects

Answer 14

Summary of Both Early and Late Deterministic and Stochastic (Probabilistic) Effects

Question 15

Objectives of Radiation Protection

Radiation protection has two explicit objectives:

1. To ___ any clinically important radiation-induced ___ effect from occurring by adhering to ___ limits that are ___ the ___ levels
2. To ___ the risk of ___ responses to a conservative level as weighted against ___ needs, ___, ___ acquired, and ___ considerations

Answer 15

Objectives of Radiation Protection

Radiation protection has two explicit objectives:

1. To prevent any clinically important radiation-induced deterministic effect from occurring by adhering to dose limits that are beneath the threshold levels
2. To limit the risk of stochastic responses to a conservative level as weighted against societal needs, values, benefits acquired, and economic considerations

Question 16

Current Radiation Protection Philosophy

Both ___ and ___ responses to ionizing radiation were considered in developing the present ___ limiting recommendations.

Current radiation protection philosophy is based on the assumption that a ___ ___ relationship exists between ___ dose and ___ response.

Even the most minuscule dose of radiation has a ___-___ potential to cause some ___.
Ionizing radiation possesses a ___ (Radiation ___) and a ___ potential.
When employed in the healing arts for the welfare of the patient, the potential ___ of exposing the patient to ionizing radiation must far ___ any potential ___.

Answer 16

Current Radiation Protection Philosophy

Both genetic and somatic responses to ionizing radiation were considered in developing the present EfD limiting recommendations.

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

Even the most minuscule dose of radiation has a non-zero potential to cause some harm.
Ionizing radiation possesses a beneficial (Radiation Hormesis) and a destructive potential.
When employed in the healing arts for the welfare of the patient, the potential benefit of exposing the patient to ionizing radiation must far outweigh any potential risk.

Question 17

Monitoring of Personnel

Requirements: Monitoring of personnel is mandatory if radiation exposure is likely to receive –
___% of the ___ ___ dose-equivalent.

Dosimetry is ___ of ionizing radiation doses to personnel

Personnel Dosimeters – measures ___ radiation

Radiation Safety Officer (RSO) -responsible for all radiation ___ concerns

Answer 17

Monitoring of Personnel

Requirements: Monitoring of personnel is mandatory if radiation exposure is likely to receive –
10% of the annual effective dose-equivalent.

Dosimetry is MEASUREMENT of ionizing radiation doses to personnel

Personnel Dosimeters – measures external radiation

Radiation Safety Officer (RSO) -responsible for all radiation safety concerns

Question 18

Nuclear Regulatory Commission NRC

Radiology personnel to receive an annual effective dose limit of ___ mSv for ___ body.

Public has an annual effective dose limit of ___ mSv.

NOTE: The general public dose is ___/___ of the amount allowed for ___ doses.

Answer 18

Nuclear Regulatory Commission NRC

Radiology personnel to receive an annual effective dose limit of 50 mSv for whole body.

Public has an annual effective dose limit of 5 mSv.

NOTE: The general public dose is 1/10 of the amount allowed for occupationally doses.

Question 19

Annual Dose Limits

Effective dose limit for a Radiographer during a ___ week period is ___ mSv.

ANNUAL Effective dose limit for:

• lens of the eye is ___ mSv.
• all other organs is ___ mSv.

ANNUAL Effective dose limit for Student radiographers under 18 yrs. of age is ___ mSv.

Answer 19

Annual Dose Limits

Effective dose limit for a Radiographer during a 13 week period is 30 mSv.

ANNUAL Effective dose limit for:

• lens of the eye is 150 mSv.
• all other organs is 500 mSv.

ANNUAL Effective dose limit for Student radiographers under 18 yrs. of age is 1 mSv.

Question 20

Cumulative Whole-Body Effective Dose Limit:

EfD = ___ mSv X One’s ___ in ___

Example: If you are 25 X 10 mSv = 250 mSv per year (also known as ___ effective dose)

Answer 20

Cumulative Whole-Body Effective Dose Limit:

EfD = 10 mSv X One’s age in years

Example: If you are 25 X 10 mSv = 250 mSv per year (also known as lifetime effective dose)

Question 21

Answer 21

Question 22

Radiation Hormesis Theory

This is a concept that there is a ___ aspect of individuals or groups from continuing ___ to ___ amounts of radiation. (page 196)

In Report No.5 of the National Academy of Science on the Biological Effects of Ionizing radiation (BEIR V) based the ___ atomic bomb survivors.

However, this theory is ___ proven at the time and the medical radiation industry will continue to follow a rigid principles of ___ and ___-___ concept for radiation protection purposes.

Answer 22

Radiation Hormesis Theory

This is a concept that there is a beneficial aspect of individuals or groups from continuing exposure to small amounts of radiation. (page 196)

In Report No.5 of the National Academy of Science on the Biological Effects of Ionizing radiation (BEIR V) based the Japanese atomic bomb survivors.

However, this theory is not proven at the time and the medical radiation industry will continue to follow a rigid principles of ALARA and no-threshold concept for radiation protection purposes.