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Ch 9 and 10

Radiation Protection - Dr Sonny

QuestionAnswer
Equivalent dose is the product of the average ____ in a tissue or organ and its associated ____ Absorbed dose and its associated weighting factor
How do you calculate equivalent dose EqD=D x W(R) >>>Dose x Weighting Factor of Radiation
What is effective dose (EfD) it is the product of the weighted equivalent doses for all irradiated tissues or organs
How do you calculate effective dose EfD= D x W(R) x W(T) -> Dose x Weighting Factor of Radiation x weighting factor of the tissue
10 rad of x-rays to the gonad region. What is the effective dose EfD= D x W(r) x W(T) so 10x1x.20=2 rem
What are the 5 committees who create standards regarding radiation ICRP, NCRP, UNSCEAR, NAS/NRC, IAEA
When was the ICRP created 1928
What is the ICRP and what does it do International Commission on Radiological Protection-Creates standards related to occupational and public protection (dose limits)
When was the NCRP created 1964
What is the NCRP and what does it do National Council on Radiation Protection and Measurement- Creates standards related to occupational and public protection and produce several reports
What is the UNSCEAR and what does it do United Nations Scientific Committee on Effects of Atomic Radiation- Creates standards related to risks of radiation
What year was UNSCEAR created 1955
What is the NAS/NRC and what does it do National Academy of Sciences/ Nat Research Council- Evaluates hum and environmental radiation exposures- Produces biological reports such as BEIR V report. This is the committee that uses the epidemiology data
When was the BEIR V report written and what is it 1990; Health Effects of Exposure to Low Levels of Ionizing Radiation.
What does IAEA do Measures atomic energy events/disasters
When was the IAEA created 1957
On a scale from 1-7 what would be a major accident 7
On a scale from 1-7, when does a radiation melt down transition from an "incident" to an "accident" 3 incident 4 accident
What are the 4 regulatory agencies who enforce the protection standards NRC, EPA, FDA, OSHA.
What is the NRC and what does it do National Regulatory Commission- Oversees nuclear energy industry and regulates the use of radioisotopes
When was the NRC (enforcer) created 1940
What is the EPA and what does it do Environmental Protection Agency; Controls radiation in the environment
When was the EPA created 1970
What is the FDA and what does it do Food and Drug Administration; regulates design and manufacture of electronic products including diagnostic x-ray
When was the FDA created 1930- Although it dates back to 1848 it wasn't known as FDA until 1930.
What is the OSHA and what does it do Occupational Safety and Health Administration (OSHA); enforces standards regarding workplace safety
When was OSHA created 1971
What are agreement states The majority of states in the US have entered into "agreements" with the NRC to assume responsibility for enforcing radiation protection regulations (AZ has the MRTBE, ARRA)
Facilities providing imaging must have an effective______ Radiation safety program
The NRC mandates the use of a _____ to enforce radiation safety Radiation Safety Officer
Who qualifies to be an RSO Can be an employee or an independent consultant- most of the time they are medical physicist, radiologist, or another certified individual
What does an RSO do Identifies and enforces corrections on radiation safety problems within the workplace
When was the concept of ALARA introduced and who introduced it 1954 by the NCRP- (ICRP created ORP)
What does nonstochastic mean Deterministic effect; threshold response
What is threshold response once the threshold is met the severity of the damage increases as the dose increases
In a nonstochastic effect the dose and the response are ____ proportional directly
Nonstochastic effect is normally seen with what type of radiation High LET (Alpha)
What are the early effects of a nonstochastic Erythema, decreases WBC, epilation, and (if whole body dose) Manifest Illness stage of ARS
What are the last effects of nonstochastic Cataracts, fibrosis, organ atrophy, and sterility
What does stochastic mean Probabilistic, non threshold, mutational, RANDOMLY occurring biologic changes
In a stochastic effect the chance of ____ rather than the severity is proportional to the dose of radiation Occurrence
Which one, nonstochastic or stochastic, is normally seen with cancers and genetic mutations Stochastic because they are random <- except skin cancer, it has a threshold and therefore it is nondeterministic
What is the cumulative effective dose (CED) or (CumEfD) A radiation workers lifetime effective dose must be limited to his or her AGE IN YRS (rem) x 10 mSv (or just the age in rem)
What is the annual whole body occupational exposure limit 5 rem per year
What is the annual occupational exposure limit for the lens of the eye 15 rem per year
What is the annual occupational exposure limit for the skin, hands, and feet 50 rem per year
What is the annual public exposure limit to the whole body .1 rem
What is the annual public exposure limit to the lens 1.5 rem
What is the annual public exposure limit to the skin, hands, and feet 5.0 rem
What is the exposure limit to the embryo or fetus for the entire pregnancy .5 rem
What is the monthly exposure limit for the embryo or fetus .05 rem
Leakage should not exceed ____ 100 mR/hr at 1 meter (3 ft)
The floor area behind the control booth should be no smaller than ____ 7.5 sq ft
What wall to the control booth should be at least ____tall 7 ft
The window on the control booth should be at least ____ big and ____ above the floor 1 sq ft and 5 ft from the floor
The window on the control should be ____ thick 1.5 mm Pb Eq
The exposure switch should be at least _____ from the open edge behind the protective barrier 30 inches
The tech should have full view of the ____ and any ____ to the room Patient and all entries
The x-ray table should have a maximum thickness of ____ 1 mm Al/Eq
The Bucky Cover should have ____ (filtration) .25 mm Pb
Collimation must be within ____ of the SID 2 percent
What is considered the simplest of all beam restricting devices Aperture diaphragm
What is the MOST COMMON beam limiting device Collimator
Which beam limiter is used in the dentist's office Cylinders and cones
What does a beam limiter do Reduces scatter to the tissue by reducing the exposure area thereby improving overall quality of the image.
On a rectangular collimator, what do the upper shutters do Reduce leakage (aka "off focus" "stem" ) radiation
On a rectangular collimator, what do the lower shutters do Narrows the beam; the lead plates mounted below the light source confine the primary beam to the ROI
What is skin sparing Patients skin should be at least 15 inches below the collimator
The light field must be no more than ____ of 40 inches 2 percent or (.8 inches)
What does a PBL do Automatically adjusts so that the radiation field matches the size of the image receptor
What is the purpose of a filter Absorbs low energy photons (20 keV or less); hardens the beam
Using filtration _____ patient skin dose Decreases
What is inherent filtration Glass envelope (&window), insulating oil around the tube
How much inherent filtration is required .5 mm Al/Eq
What is added filtration Anything added onto tube- aluminum, collimator and mirror
How much added filtration is required 2.0 mm Al/Eq
How much filtration should the variable collimator have 1.0 mm Al Eq
What is Total Filtration Inherent + Added
How much total filtration is required 2.5 mm Al/Eq (.5mm inherent + 2.0 mm added)
If the kVp is below 50 how much filtration is required 0.5 mm Al Eq
If the kVp is between 50 and 70 how much filtration is required 1.5 mm Al Eq
If the kVp is above 70 kVp how much filtration is required 2.5 mm Al Eq ( most diagnostic x-ray units operate at above 70 kVp therefore 2.5 mm Al Eq is normally required)
What is a HVL Half Value layer is the thickness of a designated absorber required to reduce the intensity of the primary beam by 50%
Some fluoroscopy tubes use ______ filtration for 80 to 100 kVp 3-4 mm Al/Eq
In Mammography what type of filter is used Molybdenum or rhodium these filters remove the lowest and highest energy photons
What filter is typically used for small to average sized breasts? Molybdenum
What filter is typically used for larger/dense breast tissue? Rhodium
In mammography, a glass window is not used because it diminishes contrast; instead ____ is used Beryllium
What is used in radiography to compensate for variations in patient density (can be used on AP foot) Wedge filters
What is a disadvantage to using a wedge filter Can cast artifact producing a longer scale of contrast
What is used to even out density differences between the mediastinum and lungs Trough filter
As the speed of film/screens increase diagnostic quality _____ Decreased
Beam restrictors and grids reduce the amount of ____ reaching the IR Scatter
Size of crystals, thickness of the layer & crystal concentrations all influence ____ Both the speed & resolution of a screen
What is spectral matching the light emitted from the screen matches the sensitivity of the film > This improves image quality & decreases exposure
Parallel grids are composed of alternating radiolucent _____ and radiopaque ___ Al, plastic or wood; and lead
The use of a grid will improve ___ and ____ Contrast and detail
You should always use a grid when patient thickness exceeds ____ 10 cm
When using a 5:1 grid it will remove ___ percent of the scatter 82-85 percent
When using an 8:1 grid it will remove ___ percent of the scatter 90 percent
When using a 12:1, 16:1 grid it will remove ___ percent of the scatter 96 percent
When using a kVp below 90 kVp you should use a ____ grid Any grid up to 8:1
When using a kVp above 90 kVp you should use a ____ grid Any grid above 8:1
Increasing the grid ratio will ___ patient dose Increase (because you have to increase your mAs)
Bucky (moving) grids absorb about _____more radiation than stationary grids but require increased exposure 10 - 15%
What is a Dose Creep overexposing a patient to possibly avoid repeat exposures
In CR the phosphor's sensitivity is equal to a ____ speed-screen 200
A fluoro unit operates at ____ to ____ mA 1.5-2
A fluoro unit operates at ____ to ____ kVp 75-110 kVp
A fluoro unit must use a minimum of ____ mm Al filtration however, ____ or greater may be preferred to reduce ____ 2.5 mm minimum, 3 mm or more is preferred because it reduces skin dose
What is the purpose of an image intensifier in a fluoro unit Increases the brightness of the real time image
What is brightness gain Minification gain x flux gain
What is Minification gain Ratio of input screen to the output screen squared
What is flux gain Brightness of the electrons in the intensifier- always based on a constant
What are the 3 advantages of using an image intensifier Increased brightness- improved radiologists perception, saves time for rad- no dark room or red goggles necessary, patient dose is reduced- low mA
_____ produce the greatest patient radiation exposure in radiology Fluoro exams
Primary exposure to RT/Radiologist is _____generated by the pt. when beam passes through patient Scatter
Lead aprons cover ____% of bone marrow in the body ~ 80%
Lead gloves should contain _____ to protect RT/Rads hands if it is necessary to place hands in primary beam .25 mm Pb Eq
Name the bones that contain active bone marrow that are protected by the apron Sternum, ribs, spine, pelvis- the skull is also an active bone marrow spot but it is not covered by lead, also the distal ends of long bones
Name 3 ways to minimize patient dose during a fluoro exam Pulse fluoro, collimate, ALARA
When doing fluoro exams on children it is possible to reduce exposure factors by as much as ____ to reduce dose 25 percent
Mobile fluoro units should not be closer than ____ from the patient 12 inches (30 cm)
Stationary fluoro units should not be closer than ____ from the patient 15 inches ( 38 cm)
There is a fluoro timer that will give an audible sound when it reaches _____ 5 minutes
Tabletop exposure CANNOT exceed ____ 10 R/min
Tabletop exposure SHOULD NOT exceed ___ 5 R/min
Maximum leakage from tube housing cannot exceed _____ 10 mR/hour @1 meter
The lead drape must contain at least _____ .25 mm lead equiv
During a myelogram you can use a retractable lead shield which must contain ___ lead .5 mm lead
The bucky slot shielding must contain ____ .25 mm lead
Exposure time is controlled by a ____ timer 5 minute
The Image intensifier must have a filtration equivalent of _____ 2 mm Pb
Placing the image intensifier as close to the patient as possible will ___ patient dose and ___ scatter Reduce and reduce
Positioning the x-ray tube under the patient will reduce scatter because backscatter goes towards the floor.
When using cinefluoro it is most common is use ___ film because it is less patient dose 35 mm
(Cine) When the frames/second is higher the patient dose _____ increases.
Typical cine tabletop dose is ____ 25 mR/frame