Radiation Protection Unit 3 - Radiation Safety Standards and Equipment in Diagnostic Imaging

Tube housing purpose

prevents leakage (off-focus) radiation

Positive beam limitation (PBL) purpose

automatically collimates field size to size of the IR

Automatic exposure control (AEC) purpose

limits exposure time when required radiation dose is met

Collimator upper shutters purpose

reduce off-focus and leakage radiation

Collimator lower shutters purpose

reduce penumbra; around the edges

Radiographic grid purpose

reduce scatter radiation and improve image quality, used if thickness of part is above 4 inches

The Radiation for Health and Safety Act of 1968 purpose

Authorized FDA to control the manufacturing and approve equipment; an equipment performance standard in which diagnostic x-ray equipment was included

The Code of Standards for Diagnostic X-Ray Equipment purpose

FDA list of safety requirements for equipment

NCRP Report #116 purpose

Monitor and reduce dose/stochastic effects of the general public and occupational

Leakage radiation limit

0.88 mGya/hr at 1 meter

Which organization or agency reviews regulations formulated by the ICRP and decides ways to include those recommendations in U.S. radiation protection criteria?

NCRP

SID indicator accuracy limit

+/- 2%

Minimum SSD for mobile unit

12 inches (30 cm)

Minimum SSD for fixed unit

15 inches (38 cm)

Reproducibility variance limit

Reproduce same image using same kVp and mAs, +/- 5%

Linearity variance limit

Linear relationship between mAs and receptor exposure as they increase, +/- 10%

Entrance skin exposure rate for fluoroscopy limit

88 mGya/min

Entrance skin exposure rate for HLCF limit

176 mGy/min

Minimum total filtration x-ray limit

2.5 mm AlEq

Minimum total filtration fluoroscopy limit

3 mm AlEq

HLCF skin dose range requiring a notation (per the FDA)

1-2 Gyt

Dose and timeframe of increased risk of intellectual disability

0.4 mSv in 0.8 seconds

Half-value layer definition

Amount of filtration that will reduce beam intensity by 50%

Scatter radiation definition

x-rays that interacted with patient and exit the body in any direction other than to the IR, provides no useful diagnostic information

Dose creep definition

unintentional increase in dose from increasing technique to reduce repeats

Radiation hormesis definition

idea that small amount of radiation exposure can be beneficial for the body

Action limits definition

determined by the facility, set to ensure occupational workers and public never meet dose of usually 1/10

EfD limiting system definition

EfD limits set by systems/regulations by organizations

The EfD limiting system is based on

the concept of cellular damage by radiation exposure and the associated risk of radiation-induced malignancy (stochastic effects)

EfD limiting system has been incorporated into

Title 10 of the Code of Federal Regulations, Part 220 (10 CFR 20)

Reason for an image intensifier

brightens the image

Reason for the cumulative timer

keeps track of the total exposure on time

Reason for pulse/intermittent fluoroscopy

reduces dose and extends tube life

Reason for the dead-man switch

Positive pressure on button that stops exposure when let go

Image intensifier placement (in regards to patient in fluoroscopy)

Above the patient

Operator position in regards to c-arm

Operator goes on side of intensifier

PBL vs. AEC

Limit field size to IR; control max time of exposure

EfD limit vs NID

maximum amount of exposure you should receive; minimum amount of exposure you should worry about

Linear nonthreshold vs linear threshold

stochastic effects: no safe dose, as dose increases risk increases; deterministic effects: "Safe" dose, as dose increases, severity increases

ICRP vs NCRP

International vs USA

NCRP vs NRC

NCRP: Advisory group, reduces radiation exposure in all types; NRC: regulatory group, focuses on nuclear industry

ICRP

Provides radiation protection guidance for occupational dose limits and public dose limits; only provides recommendations and does not enforce regulations

True/False: the ICRP is an international authority

true

True/False: the ICRP enforces regulations

false

NCRP

reviews recommendations from ICRP and determines how the ICRP recommendations are incorporated into U.S. radiation protection criteria (report 116 and 184)

Who enforce NCRP standards

federal and state agencies

True/False: the NCRP enforces regulations

false

NRC

oversee nuclear industry

EPA

concerned about radiation in the environment

FDA

Oversee manufacturing of equipment that produces ionizing radiation

OSHA

Regulates occupational exposure

Agreement states

Works with NRC, gives authority to state health department to monitor facilities that use ionizing radiation, gives licenses

RSO

Radiation safety officer

What are advisory groups responsible for

evaluating the relationship between radiation EqD and biologic effects and formulating risk estimates of somatic and genetic effects

What are national and state agencies responsible for

enforcing standards

List the four radiation protection standards organizations.

International Commission on Radiological Protection (ICRP), National Council on Radiation Protection and Measurements (NCRP), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and National Academy of Sciences/National Research Council Committee on the Biological Effects of Ionizing Radiation (NAS/NRC-BEIR)

What's the purpose of UNSCEAR?

Uses epidemiologic data to estimate risk of stochastic effects and studies of atomic bomb survivors

UNSCEAR evaluates human and environmental ionizing radiation exposures from

radioactive materials, radiation-producing machines, and radiation accidents

Which organization or agency reviews studies of biologic effects on ionizing radiation and risk assessment and provides the information to the ICRP for evaluation?

NAS/NRC-BEIR

True/False: the UNSCEAR is an enforcement agency

false

What's the purpose of NAS/NRC-BEIR?

Reviews studies of the biological effects of ionizing radiation and risk assessment based on early radiation workers, atomic bomb victims, and evacuees from Chernobyl

True/False: the NAS/NRC-BEIR is an enforcement agency

false

List the five U.S. regulatory agencies

Nuclear Regulatory Commission (NRC), Environmental Protection Agency (EPA), US Food and Drug Administration (FDA), Occupational Safety and Health Administration (OSHA), and Agreement States

Which agency is responsible for enforcing radiation protection standards?

The NRC

The NRC stands for

Nuclear Regulatory Commission

EPA stands for

Environmental Protection Agency

FDA stands for

US Food and Drug Administration

OHSA stands for

Occupational Safety and Health Administration

What are other responsibilities of the NRC?

Controls the possession, use, and production of atomic energy; oversees the nuclear energy industry

The NRC was formerly known as the

atomic energy commission

The NRC does not regulate or inspect ______ ___________ facilities

X-ray imaging

True/False: Illinois is an agreement state

true

Agreement states are responsible for

licensing and regulating the use of radioisotopes and enforcing radiation protection regulations

Who are agreement states performed by

state health departments

Which regulatory agency is responsible for the development and enforcement of regulations regarding radiation in the environment, such as radon?

The EPA

Which regulatory agency regulates the design and manufacture of electronic products, such as diagnostic x-ray equipment?

The FDA

The FDA conducts on-site inspections of X-ray equipment to protect against faulty manufacturing, particularly for which equipment

mammography

Which regulatory agency is responsible for regulations regarding an employee's "right to know" about hazards present in the workplace?

OHSA

Agreement states work with which regulatory agency to enforce radiation protection standards?

The NRC

All facilities that provide medical imaging services must have a:

Radiation Safety Committee and Radiation Safety Officer

OSHA requires that employees be made aware of

hazardous substances, infectious agents, ionizing radiation, and nonionizing radiation

How were the Radium Girls involved in OSHA

Fatally poisoned by the glowing paint they used on the job, they challenged workplace safety rules and exposed the dangers of radioactivity

List the responsibilities of an RSO.

Developing a radiation safety program, maintaining personnel radiation-monitoring records, and providing counseling and taking corrective actions

What is the typical background of a Radiation Safety Officer

medical physicist, health physicist, or radiologist

Briefly state the requirements of diagnostic x-ray equipment established by the Code of Standards in 1974.

Must have an automatic limitation of the beam (PBL), appropriate filtration minimums, exposure reproducibility and linearity, beam limitation in fluoroscopy, beam on indicators, and manual backup timers for AEC

The Code of Standards for Diagnostic X-ray equipment is strictly

an equipment performance standard

Dose limits were created to prevent _________ ________ effects and minimize the risk of __________ effects.

harmful biologic; stochastic

Deterministic effects are __________ related to the dose received

directly

What's the difference between early and late deterministic (tissue) reactions?

Early = Days, weeks, months... includes skin erythema, epilation, desquamation, etc; Late = Months, years... cataracts, fibrosis, sterility, etc.

What type of dose response relationship is associated with deterministic effects?

Linear threshold-type dose

What does linear threshold mean?

There is a specific amount of radiation that will cause an effect; a minimum dose is required before the effect appears

What type of dose response relationship is associated with stochastic effects?

Linear non-threshold-type dose

What does linear nonthreshold mean?

There is no specific amount of radiation that will cause an effect; this is why linear non-threshold is associated with the word risk

What dose-response relationship (linear threshold or linear non-threshold) is used for radiation protection standards?

Linear non-threshold since radiation protection standards focus on limiting stochastic effects

The ________ ______ ______ uses the ____________ _________ dose of ionizing radiation that results in a __________ risk of injury or genetic damage.

effective dose limit; uppermost boundary; negligible

The EfD limiting system is based on the idea that:

a linear non-threshold relationship exists between dose and biologic harm

Effective dose limits may be specified for

whole body, partial body, and individual organs

Whole-body dose limits protect against:

stochastic effects that harm the blood-producing organs/trunk of the body

Lens of the eye dose limits protect against:

radiation-induced cataracts

Skin and extremity dose limits protect against:

deterministic effects that harm the skin/extremities, including skin erythema or epilation