Module- Radiation Biology and Protection

What is radiation protection?

Physical, technical and procedural factor involved in protecting both patients and personnel from unjustified radiation exposure.

Requires understanding of the biological effects of radiation

What is the absorbed dose

the amount of energy absorbed per unit mass

responsible for biological damage

expressed in grays (GY)

Rad (radiation absorbed dose)

traditional unit of absorbed dose

Safe operating procedures

technique charts

positioning aids

protective clothing

personnel dosimetry

quality control

True or False

Can all living cells be damaged by ionizing radiation

true

Categories of biological damage

somatic and genetic

What are the biological effects of a threshold relationship

a point where a response to an increasing stimulus first occurs

biologic effects are observed only when the threshold is reached

What are the biological effects of a non- threshold relationship

any radiation dose has the potential to produce a biological effect

no radiation dose is believed to be safe

What is deterministic

Not random, will happen

What is stochastic

random, probabilistic

What are deterministic effects of radiation

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

have a threshold

Examples of deterministic effects

erythema (skin burns)

sterility

cataracts

What is stochastic effects of radiation

Probability of occurrence increases with dose

regarded as the main health risk from low dose radiation

Stochastic effects examples

chance of radiation induced leukemia is considerably greater after an exposure to a dose at 100 rad then at 1 rad but there will be no difference in the severity of the disease if it occurs

What are the fundamental principles of radiation protection

1. Net benefit

2. ALARA

3. dose limits

Describe Net Benefits of Principles of radiation protection

benefit vs risk, justify radiation exposure

medical exposure to radiation should be some benefit to individual

What does ALARA stand for

as low as reasonably achievable

What are dose limits

Dose limits are a quantity or amount of radiation exposure that must not exceed

pertains to doses received by an individual on a yearly basis or accumulated over a working lifetimes

intended to reduce probability of biological effects

What is occupationally exposed vs others

those individuals who are exposed at work vs others which includes members of the general population, excluding those who undergo medical exposure

What unit is occupational and other exposure expressed in

sieverts (Sv)

What are the cardinal principles of radiation protection

1. minimize time

2. maximize distance

3. maximize shielding

Describe cardinal principle 1: minimize exposure

exposure - exposure rate x exposure time

direct relationship- as exposure time increases, so does radiation dose received

reducing time serves to reduce motion blur

Describe cardinal principle 2: maximize distance

most effective means of protection from ionizing radiation

inverse square law- radiation intensity is inversely related to the square of the distance from the source

formula for inverse square law

-I 1/ I 2 = D2(²)/ D1(²)

Describe cardinal rule 3: maximizing sheilding

certain material reduce rad intensity when they are placed between source and exposed individual

made of lead and concrete

What is a primary protective barrier

a barrier is struck by primary or direct radiation

what is secondary protective barrier

provides shielding from scatter and leakage of radiation

Different types of shielding

1. gonadal shielding

2. personnel shielding

3. room shielding

4. x-ray tube shielding

What are the personnel protection techniques

filtration

technical factors

what is the filtration technique for personnel protection techniques

reduces amount of low energy photons that reach the patient

reduces scatter

what is the technical factor technique for personnel protection techniques

as energy of beam increases, radiation scatter moving in forward direction increases

amount of side scattered radiation is decreased

What are the personnel protection techniques using image receptors

high speed image receptors

correct processing

how does high speed image receptors assist in personnel protection technique using image receptors

less mA required

fewer photons available to produce scatter

How does correct processing assist personnel protection techniques using image receptors

reduce repeat exposures

reduces chance for personnel exposure