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who is the IRCP
- International Commission on Radiological Protection composed of 12 active members, a chairman, and 4 standing committees = on radiation effects, radiation exposure, protection in medicine and the application of IRCP
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who is the NCRP
- National Council on Radiation Protection and Measurement review recommendations formulated by ICRP. Determines the way ICRP recommendations are incorporated into U.S radiation protection criteria.
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who is the EPA
- Environmental Protection Agency established 12/2/1970. Created to bring several departments under one organization that would be responsible for protecting the health of humans and for safeguarding the natural environment. Facilitate the development and enforcement of regulations pertaining to the control of radiation in the environment.
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what is the job of an RSO
- responsible for developing an appropriate radiation safety program for the facility that follows internationally accepted guidelines for radiation protection. Review and maintain radiation monitoring records for all personnel and be available to provide counseling for individuals.
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What is the NCRP Report no. 116/160?
- Limitation of Exposure to Ionizing Radiation provides the most recent guidance on radiation protection. This report enunciates the goal of radiation protection.
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what is radiation hormesis
- is the hypothesis that a positive effect exists for certain populations that are continuously exposed to moderately higher levels of radiation
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how does the following effect radiation safety:
lead lined housing
leakage control
- lead lined housing = protects patient and tech from off focus radiation
- leakage control = allows continuous operation at high voltage, prevents electric shock and makes cooling of the tube possible
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how accurate must the coincidence between the beam and light field be with the luminance of light field
must not exceed 2% of the SID
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what is PBL
what is accuracy of this
- positive beam limitation
- it is automatically adjusted so that radiation field matches the size of the size of the image receptor.
- Must ensure beams is not larger than the IR 2-3% of SID
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what is the simplest of all beam limitations
aperature diaphragm
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cones:
used for radiographic exams of certain specific areas they are tubes that attache to the xray tube housing or collimator to limit xray beam to a predetermined size and shape
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what is added filtration
examples
this equates to how much aluminum equivalency
located btw glass window and collimator shutters
- mirror plastic cover aluminum sheet
- 1mm al/eq
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what is inherent filtration
list examples
what is the aluminum equivalency for this
- it is the filtration that is outside of the tube
- glass envelope encasing xray tube
- insulating oil surrounding tube
- glass window in the tube housing
- .5mm al/eq
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what do you use a compensating for
to even out unequal densities
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what is the total aluminum equivalency required for equipment operating above 70 kvp
2.5mm al/eq
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How much can gonadal shielding reduce female dose?
50%
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How much can gonadal shielding reduce male dose?
90-95%
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what general technical factors lower patient dose
high kvp low mAs
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extension cones are best for ____ radiography
spot
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what does filtration do
hardens the xray beam by eliminating lower energy photons
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define reproducibility
what is the accepted variance
- is the consistency in output in radiation intensity for identical generator settings from one individual exposure to the next
- it should produce the same exposure after a tech factor is selected
- 5% of the variance
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how do you calculate entrance skin exposure
mr/mas x mAs = mR
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upper shutter of the collimator box reduces ________
off focus radiation
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what is HVL
a measure of beam quality or effective energy of the xray beam a certain minimal hvl is required at a given kvp
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define linearity and its accepted variance
- consistency in output radiation intensity at selected kv settings when settings are changed from one ma station to another and produce the image or mAs
- 10% accepted variance
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what is the effect in using screen film combinations on pt dose
reduces pt dose by using faster films
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what are the effects of grids on pt dose
it improves contrast but increases pt. dose because you need more mAs
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what effect does the air gap technique have on pt dose
works like a grid removes scatter
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to minimize exposure how far must the patients skin be from the collimator box
15cm
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what is the appropriate luminance of a collimator light source
161 nit or equivalent to 15 ft candles
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what is the exposure rate limitation for fluorscopic units
20R/min
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what is mobile radiography source to skin distance
12''
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what is voluntary and involuntary motion in regards to the patient
- voluntary motion are movements that exist because the patietns age breathing patterns or conditions physical discomfort or mental instability
- involuntary motion is that of the digestive organs or a heart beat chills muscle spasms
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What is Genetically Significant Dose?
what is the GSD for the population of the US
- is the average annual gonadal dose to members of the population withing child bearing ages
- .20 mSv (20mrem)
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describe the ISL and formula
- the intensity of light decreases with an increase in distance. the decrease is inversely proportional to the square of the distance of the object from light source
- I1/I2 = d2 squared/ d1squared
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primary barriers are what and have how much lead
- are used to prevent primary radiation from reaching the other side. Walls lined with lead with the bucky on it and floor under the table
- 1/16'' lead
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what are secondary barriers and how much lead do they contain
- protect from scatter and leakage radiation like the ceiling and door and wall where we stand when making an exposure
- 1/32''
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a lead apron must have ____
a thyroid shield must have ____
protective eye wear must have ____
- .25-.5 pb/eq mainly .5mm
- .5mm
- .35
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bucky slot cover must have ___
.25 mm pb/eq
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diagnostic tube housing must keep leakage radiation to less than ____ mR/hour at ____ meter
100; 1
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where should the radiographer stand during a mobile procedure
what is the intensity of the beam at this point
- at a 90 degree angle to the xray beam scattering object (patient)
- 1/1000 of primary beam
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what is the workload factor
it is the amt of time that x-ray is delivering radiation during a week
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the most efficient type of gonadal shielding for use during fluoro is
flat contact shield
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the beam is most restricted when using what beam limitation device
extension cylinder
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describe the use factor
it is a quantity used to measure the portion of the beam "on time" during the week the beam is directed at a primary barrier
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