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Ch 9 and 10
Radiation Protection - Dr Sonny
| Question | Answer |
|---|---|
| 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 |
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