5. Radiation Protection Flashcards by J Y

what are the 2 types of personal dosimeters badges and what must be done before the dose can be read

what kind of dose do they measure

thermolumiscent or film types

requires processing to reveal cumulative dose received

How well did you know this?

Not at all

Perfectly

what are the 4 types of personal dosimeters

film badge

pocket ionizing chambers

thermoluminescent dosimeters

optically simulated luminescence

How well did you know this?

Not at all

Perfectly

how do film badges work and what change do they undergo when its exposed to radiation

what is it measured with and what can be used to identify energy range

radiation darkens the developed x-ray film
amount of darkening increases with absorbed dose

measured with a densitometer

filters used to identify energy range

How well did you know this?

Not at all

Perfectly

what is the crystal in thermiluminescent dosimeters

how does it work and what causes it to luminescence

amount of radiation dose is proportional to what

lithium fluoride crystal

traps and stores energy from ionising radiation
will luminescence if heated

measure intensity of light emitted and amount of light is proportional to radiation dose

How well did you know this?

Not at all

Perfectly

what is the crystal in optically stimulated luminesce dosimeters

how does it work and what causes it to luminescence

amount of radiation dose is proportional to what

aluminum oxide crystal

traps and stores energy from ionising radiation
will luminescence if illuminated

measure intensity of light emitted and amount of light is proportional to radiation dose

How well did you know this?

Not at all

Perfectly

what is the difference between what causes the luminescence for TLD and OSL dosimeters

TLD will luminescence if heated

OSL will luminescence if illuminated

How well did you know this?

Not at all

Perfectly

how does the pocket ionisation chamber work as a dosimeter

what is the absorbed dose proportional to

is processing required

can it be reused and reset

radiation incident on chamber produces ionisation

voltage difference is produced as gas is ionised
voltage is directly proportional to the absorbed dose

dose is read directly from dosimeter, no processing required

yes can be reset and reused

How well did you know this?

Not at all

Perfectly

what 2 types of radiation does a pocket ionisation chamber dosimeter measure

gamma

x-ray

How well did you know this?

Not at all

Perfectly

what 3 types of radiation does a film badge dosimeter measure

beta
gamma
x-ray

How well did you know this?

Not at all

Perfectly

what 3 types of radiation does a TLD measure

beta
gamma
x-ray

How well did you know this?

Not at all

Perfectly

what 3 types of radiation does a OSLmeasure

beta
gamma
x-ray

How well did you know this?

Not at all

Perfectly

what are 2 advantages to using a pocket ionisation chamber dosimeter

immediate reading

reasonably accurate

How well did you know this?

Not at all

Perfectly

what are 4 advantages to using a film badge chamber dosimeter

permanent legal record
most common
cheap
can re-read

How well did you know this?

Not at all

Perfectly

what are 2 advantages to using a TLD dosimeter

more accurate than film

durable, resistant to humidity

How well did you know this?

Not at all

Perfectly

what are 3 advantages to using a OSL dosimeter

more accurate than film

durable resistant to heat and humidity

can be re-read

How well did you know this?

Not at all

Perfectly

what are 5 disadvantages to using a pocket ionisation chamber dosimeter

no permanent legal record

reading can be lost

must be read each day

false readout if jarred/dropped

expensive

How well did you know this?

Not at all

Perfectly

what are 3 disadvantages to using a film badge dosimeter

must be measured

affected by heat and humidity

accuracy limited

what are 4 disadvantages to using a TLD dosimeter

no permanent/legal record

must be measured

cant reread

more expensive than film

what are 3 disadvantages to using a OSL dosimeter

no permanent/legal record

must be measured

more expensive than film

the effective dose must be well below what limits over how long

well below 20mSv per year averaged over 5 consecutive years or a max of 50mSv in any single year

what kind of dose is especially a problem and why

cumulative dose is a problem as the more radiation exposed to overtime = more mutations likely to occur

what are the 3 components to ALARA

shielding
distance
time

what is the equation for X-ray attenuation

I = Io e^(-ux)

I = radiation intensity after shielding
Io = radiation intensity before shielding
u = linear attenuation coefficient 
x= thickness of shielding material (cm)

what is the linear attenuation coefficient

the constant that describes the fraction of x-ray photons that are absorbed or scattered per unit thickness of a material

which is more attenuating - soft tissue or bone?

soft tissue

what does it mean in terms of preventing penetration of x-ray beams if there is a High linear attenuation coefficient

High linear attenuation coefficient = more effective at removing x rays and stopping them from passing though materials

what is the HVL

the thickness of material required to reduce the intensity of a radiation beam by half

what is the equation for HVL

HVL = ln(2)/u = 0.693/u

what is the relationship between HVL and u

inverse

HVL changes with what?

Half value changes with energy HVL increase as x ray energy goes up

what is the inverse square law

x-ray intensity is inversely proportional to the square of the distance from the source I is proportional to 1/d^2

what is the equation used when comparing the x-ray intensity at 2 distances

I2/I1 = (d1)^2/(d2)^2

what is exposure control in terms of distance

small changes in distance and location can make a significant difference to cumulative dose recieved

what is the principle of justification

any decisions that alters the radiation exposure situation should do more good than harm

what is the principle of optimisation of protection

the likelihood of incurring exposure the number of people exposed and the magnitude of their individual doses should all be kept as low as reasonably achievable taking into account economic and societal factors

what is the principle of application of dose limits

total dose to any individual from regulated sources in planned exposure situations other than medical exposures of patients should not exceed the appropriate limits specified by the commission

what is the purpose of structural shielding of imaging facilities

limit radiation exposures of employees and members of the public to acceptable levels

what do the primary and secondary exposure of an individual in an adjacent area to be protected mainly depends on what 5 factors

the amount of radiation produced by the source the distance between the patient and the radiation source time spent in adjacent area the amount of protective shielding between sources and individual distance between source and the individual

what 3 factors are considered the structural shielding of imaging facilities

location of x-ray sources orientation and location of x-ray beam for various acquisitions adjacent areas with typical occupancy and shielding design goals

in terms of primary and secondary radiation, the barrier thickness is a function of which equation

N x T/(P x d^2) ``` T = how many people are there at one time P = goal of how small do you want to limit it to N = # of patients per week D = distance (meters) from radiation source ```

what are the DRLs and what are they

diagnostic reference levels radiation dose levels for typical x-ray examinations for standard sized patients using standard equipment