Radiation Protection Flashcards
What is the primary purpose of filtration?
To reduce ESE to the patient
What is the total filtration needed for the following:
Below 50 kVp
50-70 kVp
Above 70 kVp
.5 mm aluminium
1.5 mm aluminum
2.5 mm aluminum
What is the best way to reduce involuntary motion
Short exposure time
What exposure factors are used for fluoroscopy?
Increased kVp, low mA
In fluoro, is entrance exposure or exit exposure greater?
Entrance
What is the minimum source to skin distance in fluoroscopy?
Fixed unit = 15” (38cm)
Mobile = 12” (30cm)
What is the greatest source of natural radiation?
Radon
What is the gretest source of artificial radiation?
Medical imaging
What is the minimum lead requirement for lead gloves?
.5 mm
What is the minimum lead requirement for gloves?
.25 mm
What is the minimum lead requirement for a thyroid shield?
.5
What is the minimum lead requirement for glasses?
.35
What is the minimum lead requirement for the bucky slot cover?
.25
What is the minimum lead requirement for spot film device protective curtain?
.25
What is the minimum lead requirement for clear lead-plastic overhead protective barrier?
.5
Where are primary protective barriers needed?
On surfaces that can be struck by the primary beam; barriers located perpendicular to the primary beam
What is the lead requirement in a primary protective barrier?
1/16” (.16cm or 1.6mm)
If the primary barrier is a wall, the lead must extend how far up from the floor?
7 ft (2m)
Is the control booth a primary or secondary barrier?
Secondary
Where are secondary protective barriers needed?
Surfaces that are struck with leakage and scatter radiation; barriers located parallel to the primary beam
What is the lead requirement in a secondary protective barrier?
1/32” (.08 cm or .8mm)
How much of the secondary barrier must overlap the primary barrier where the two meet?
1/2”
Type of dosimeter that relies on the ability of ionizing radiation to effect a density change on the film emulsion
Film badge
What type of attenuating filters are used in film badges?
Tin or copper
What are the benefits of film badges?
Effective for radiation over extended periods of time
Inexpenisve
Provide a permanent record
What is the functional component of a TLD?
Lithium fluoride
How is a TLD read?
Heating the lithium fluoride chip to the point of combustion; the light spectrum will change with changing levels of energy absorbed in the chip
Disadvantages of TLD?
More expensive than film badges
Once the chip is heated, it is destroyed; no permanent record
What type of dosimeter relies on the ability of the ionizing radiation to ionize a gas within a sealed chamber resulting in a change of a charged electrode
Pocket dosimeter
What is a pocket dosimeter good for?
Short-term monitoring or testing
What type of dosimeter gives an immediate reading?
Pocket dosimeter
Disadvantage of pocket dosimeter?
Prone to inaccurate readings; no permanent record
What is the benefit of pocket dosimeters?
Unit may be recharged and reused
What type of detector is in an OSLD?
Aluminum oxide
How is an OSLD read?
Laser light reads the sensing material which causes the material to become luminescent in proportion to the exposure
What type of filters are within an OSLD?
Aluminum, tin and copper
Rank the following dosimeters from most sensitive to least:
TLD
OSL
Pocket
Film badge
Pocket
OSL
TLD
Film badge
What is the annual whole body dose limit for occupational exposure?
50 mSv
What is the occupation exposure limit for lens of the eyes?
150 mSv
What is the cumulative effective limit?
10 mSv x age in years
What is the annual effective dose equivalent limit for public exposure?
5 mSv
What are the dose equivalent limits for the lens of the eyes, skin and extremities for public exposure?
50 mSv
