Laura Nappi Study Guide - Radiation Safety Pt. 2

______________ breaks down one large dose into many smaller doses, which encourages the preservation of normal, healthy tissue

fractionation

During fractionation, tissues have time to ____________ themselves

repair

T/F: Fractionation is not as biologically effective as one large dose when irradiating tumors

True

Complications of normal tissues involved in radiation fields will depend on ______ per fraction

dose

A larger dose per fraction will lead to _______ (more/less) complications

more

___________ doses make recovery more difficult

larger

The smaller the volume of irradiated tissue, the ________ dose needed to produce a response

higher

What does the biologic effect of fractionation depend on?

the four "R"s

- repopulation

- redistribution

- repair of sublethal damage

- reoxygenation

remaining cells undergo mitosis and repopulate tissues; unfavorable for malignant tumor cells; favorable in healthy cells within the treatment field

repopulation

remaining cells transition to a different cycle of mitosis after irradiation

redistribution

healthy tissues repair the radiation damage when adequate oxygen is available; malignant tumor cells are more hypoxic than normal tissues and therefore they do not easily repair themselves

repair of sublethal damage

hypoxic tumor cells become more oxygenated and therefore more radiosensitive, which allows for more of the tumor to be destroyed

reoxygenation

_______ at the time of radiation exposure may determine a radiation-induced cancer

age

When are people most radiosensitive?

during childhood and an older age (bimodal)

Why are children considered more radiosensitive?

because there is a longer time frame for cancers to develop

Why are elderly people considered radiosensitive?

because of pre-existing malignant cells (this makes it harder for cells to repair and increases their radiosensitivity)

Normal tissue tolerances can be affected by ________________

comorbidities

Pacemakers are _____________ to radiation and are likely to fail with low doses of radiation

sensitive

what does the AAPM recommend to keep the dose between for pacemakers?

between 2-5 Gy

When the pacemaker is 10 cm from the field edge, the dose is approximately ______ of the target dose

1%

substances that increase the response to radiation

radiosensitizers

______________ allow for more cells to be killed

radiosensitizers

Examples of radiosensitizers

oxygen and chemotherapy like doxorubicin (adriamycin)

substances that decrease the response to radiation

radioprotectors

When do radio protectors need to be given?

at the same time as the radiation exposure

How do radioprotectors work?

they search for free radicals

What are examples of radioprotectors?

sulfhydryls and amifostine (Ethyol)

When a patient receives chemotherapy along with radiation, effects may be ____________

greater

Some chemotherapy agents make cells ________ sensitive to radiation

more

Chemotherapy agents may also affect the cell's ability to _________

repair

the ratio of the radiation dose needed to cause damage without a chemotherapy drug compared to the radiation dose needed with the chemotherapy drug

dose-effect factor (DEF)

What is the DEF when chemotherapeutic drugs have a sensitizing effect?

greater than 1

________________ can be used as a single treatment type or as a way to boost dose to a tumor along with external beam radiation therapy (EBRT)

brachytherapy

when treatments include a combination of brachytherapy and EBRT, longer __________ __________ will lessen the effects to highly proliferating tumors

protraction periods (time between HDR and EBRT)

________________ can help spare dose to normal tissues while increasing dose optimization to the tumor when used alone or with EBRT

brachytherapy

exposure factor in the diagnostic range that mainly controls beam quality or beam penetrability (beam energy)

kilovolt peak (kVp)

what controls radiographic contrast?

kVp

As kVp is _______________, less x-rays are absorbed by the patient and less dose to the patient

increased

higher kVp can ____________ Compton scatter, which contributes to patient dose

increase

What is the 15% rule?

increasing the kVp by 15% is equal to doubling mAs

if kVp is increased by 15%, what happens to the mAs?

the mAs is reduced by 50%

if the kVp is reduced by 15%, what happens to the mAs?

the mAs is doubled

What will the 15% rule affect?

contrast and the radiographic image

What does the 15% rule allow for?

the reduction of mAs and patient dose

exposure factor in diagnostic range that determines beam quantity

milliampere seconds (mAs)

as mA is increased, the ____________ of x-rays produced is increased proportionately

quantity

patient dose follows a __________ proportion with x-ray quantity

direct

the thickness of an absorber material that will reduce the beam to half of its original value

half-value layer (HVL)

the thickness of an absorber material that will reduce the beam to one-tenth of its original value

tenth-value layer (TVL)

1 TVL = ___ HVL

3.3 HVL

What are the three types of background radiation?

- terrestrial

- cosmic

- internal radioactive elements

this type of background radiation comes from naturally occurring elements in the earth's surface; can also exist in building materials; a person's exposure level varies based on where they liver

terrestrial radiation

What is an example of terrestrial radiation?

radon in soil

this type of background radiation comes from radiation produced from the sun and stars; exposure levels increase with increasing altitudes; air travel increases a person's exposure levels

cosmic radiation

this type of background radiation naturally exists in our body; the main source is potassium-40

internal radioactive elements

an attempt to keep harmful radiation exposure to as little as possible

ALARA (as low as reasonably achievable)

What are the three most important aspects of radiation protection?

time, distance, shielding

What is the best form of radiation protection in radiation therapy?

shielding

What is the annual occupational effective dose limit?

50 mSv (5 rem)

What is the cumulative occupational effective dose limit?

10 mSv x age (1 rem x age)

What is the occupational equivalent dose limit for the lens of the eye?

150 mSv (15 rem)

What is the occupational equivalent dose limit for the skin, hands, and feet?

500 mSv (50 rem)

What is the annual dose limit for continuous/frequent exposure for the public?

1 mSv (0.1 rem)

What is the annual dose limit for infrequent exposure for the public?

5 mSv (0.5 rem)

What is the annual dose limit for the lens of the eye (public)?

15 mSv (1.5 rem)

What is the annual dose limit for the skin, hands, and feet (public)?

50 mSv (5 rem)

What is the total dose limit for the embryo/fetus?

5 mSv (0.5 rem)

What is the monthly effective dose for the embryo/fetus?

0.5 mSv (0.05 rem)

the radiation worker should be monitored if they are expected to receive more than _______ of the effective dose equivalent

10%

areas that are strictly supervised by a RSO

restricted/controlled areas

restricted/controlled areas have an occupational limit of radiation and cannot receive more than _________ per year

1 rem

what is the dose equivalent limit for restricted/controlled areas?

areas that are not under the strict supervision of a RSO

unrestricted/uncontrolled areas

uncontrolled area cannot receive more than _____ rem per year

0.5

What is the dose equivalent limit for unrestricted/uncontrolled areas?

< 0.01 rem/week

a __________________ sign should be posted when a person may receive a dose > 0.005 rem (5 mrem) (0.05 mSv) in one hour at 30 cm from a radiation source

radiation area

A ____________________ sign should be posted when a person can receive a dose > 0.1 rem (1 mSv) in one hour at 30 cm from a radiation source

high radiation area

A ______________ sign should be posted when a person can receive more than 500 rads (5 gray) in one hour at 1 meter from a radiation source

very high radiation area

_______________ should be posted in areas where sources of radiations are used and/or stored

caution: radioactive materials

examples of area monitoring devices

- ionization chambers

- Geiger counters

- TLDs

- film

What type of barrier will be directly hit by the useful/primary radiation beam?

a primary barrier

weekly dose delivered at 1 m from the source for MV lianas

workload (W)

how is workload expressed?

as rad/week at 1 m

the amount of time the beams aimed at a barrier

use factor (U)

what is the flood use factor?

1

What is the wall use factor?

1/4

What is the ceiling use factor?

1/4 - 1/2

the amount of time the bordering rooms will be occupies

occupancy factor (t)

What is the occupancy factor for a room with full occupancy?

1

What is occupancy factor for a room with partial occupancy?

1/4

What is the occupancy factor for a room with occasional occupancy?

1/8 - 1/16

distance from the source to the are being protected; expressed in meters

distance (d)

Who is in charge of transporting radioactive wastes to storage and disposal sites?

Nuclear Regulatory Commission (NRC) and Department of Transportation (DOT)

a federal agency that regulates the safe use of radioactive materials and protects the public health in regards to radioactive materials

Nuclear Regulatory Commission (NRC)

an agency that regulates the removal, storage, and usage of nuclear waste

Environmental Protection Agency (EPA)

________ helps to supervise and regulate the transportation of hazardous radioactive materials

Department of Transportation (DOT)

How can nuclear waste be disposed of?

- flushing it into a sewer system after the material has gone through enough decay

- incineration

- burying the material

- transferring to a person with appropriate authorization

Radioactive materials can be disposed of after _____ half-lives

10

What are the main parts that make up the linear accelerator:

- drive stand

- gantry

- treatment couch

- console

- electronic cabinet

- modulator

Name the parts of the drive stand

- klystron

- waveguide

- circulator

- cooling system