Term
| What portion of federal code contains the equipment specifications for radiation protection? |
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Definition
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Term
| What is the requirement for the x-ray tube housing? |
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Definition
| Must not leak more than 100 milliRoentgens per hour at 1 m disance |
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Term
| What 3 factors affect beam quality? |
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Definition
type of generator, kVp, aluminum filtration |
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Term
| What type of beam energy does the type of generator affect? |
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Definition
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Term
| how does kVp affect beam quality |
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Definition
| controls TOTAL or MAXIMUM beam quality |
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Term
| how does aluminum filtration affect beam quality? |
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Definition
affects AVERAGE beam quality (more filtration, higher average quality) |
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Term
| For a machine with a maximum of less than 50 kVp the FDA requires how much total filtration? |
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Definition
| Minimum 0.5 mm aluminum equivalent |
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Term
| For a machine with a maximum 50 to 70 kVp the FDA requires how much total filtration? |
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Definition
| Minimum 1.5 mm aluminum equivalent |
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Term
| For a machine with a maximum of 70 or more kVp the FDA requires how much total filtration? |
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Definition
| Minimum 2.5 mm aluminum equivalent |
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Term
| What is the main purpose of filtration? |
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Definition
| To reduce entrance skin dose by removing low energy x-rays. |
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Term
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Definition
| inherent filtration + added filtration |
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Term
| What is inherent filtration? |
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Definition
| The glass of the window plus the circulating oil. |
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Term
| What is added filtration? |
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Definition
| The aluminum between the window and the top of the collimator |
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Term
| How often must x-ray beam quality be tested? |
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Definition
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Term
| The FDA requires a beam restricting device which must be what type of collimator? |
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Definition
| Variable aperture collimator (not just a fixed cone or cylinder) |
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Term
| What is the allowable margin of error for the beam restricting device? |
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Definition
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Term
| What is the requirement related to the top set of shutters of the collimator? Why? |
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Definition
| Must be as close to x-ray source (focal spot) as possible. To reduce chance of off-focus or "stem radiation". |
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Term
| What is stem radiation (aka off-focus radiation)? |
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Definition
Any radiation that is created outside the focal spot area (the focusing cup around the filament). |
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Term
| The distance from the light bulb in the illuminator assembly to the center of the mirror must be equal to what? |
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Definition
| The distance from the focal spot to the center of the mirror. |
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Term
| What is the minimum illumination level for the light field? |
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Definition
| 15 foot-candles at 100 cm SID |
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Term
| What is the name for the system that senses the size of the cassette and matches the light field to it? |
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Definition
| Positive beam limitation (PBL). |
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Term
| Before what year was a PBL mandatory? |
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Definition
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Term
| Why did the FDA stop requiring PBL on beam restriction devices? |
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Definition
| Because they were prone to malfunction |
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Term
| If a collimator is equipped with PBL, what must it also have? |
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Definition
| A manual switch in case of malfunction |
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Term
| FDA error of margin for beam restricting devices - a) without PBL? b) with PBL? |
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Definition
a) Without PBL - +/-2%
b) With PBL - +/-3% |
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Term
| What is the margin of error for beam alignment and how often must it be tested? |
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Definition
| Must be accurate within +/- 2%, tested once per year |
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Term
| What is the exposure limit for controlled areas? For uncontrolled areas? |
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Definition
Controlled - less than 100 mREM/week
Uncontrolled - less than 10 mREM/week |
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Term
| What two ways can a controlled area be marked? |
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Definition
| Universal radiation symbol or wording "Caution - radiation area." |
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Term
what are the limits for the wording used to label control areas:
Caution - radiation area
Caution - high radiation area
Caution - very high radiation area |
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Definition
Radiation - 5 mR/hr to 100 mR/hr
High radiation - 100 mR/hr - 500 R/hr
Very high radiation - more than 500 R/hr |
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Term
| How accurate must the SID indicator be and how often must it be checked? |
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Definition
| Within 2% of SID, checked once a year |
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Term
| The control panel must have these two indications of exposure: |
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Definition
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Term
| control panel must indicate in one of these three ways whenever the tube is energized: |
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Definition
| Meter (such as mAs meter), light, or audible signal |
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Term
| What is reproducibility and what is it a measure of? |
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Definition
| Two exposures using the same exposure factors should always produce the same amount of x-rays. It is a measure of how well the generator is performing. |
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Term
| What is the maximum variation allowed by FDA for reproducibility |
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Definition
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Term
| What is reciprocity and how much variation is allowed by FDA for it? |
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Definition
| Using the same mAs but different mA x sec should produce same amount of radiation. 10% variation allowed. |
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Term
| What is linearity and how much variation is allowed? |
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Definition
| A change in mAs should produce the same amount of change in exposure (doubling the mAs should double the exposure.) Variation allowed is 10%. |
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Term
| What is the minimum collimator-to-skin distance? Where is it measured from? |
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Definition
| 15 cm. Measured from the bottom of the collimator to the patient's skin. |
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Term
What is the minimum source-to-skin distance (SSD)? What is the recommended minimum SSD? |
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Definition
30 cm (12 inches) required; 38 cm (15 inches) recommended. |
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Term
| What must you not be able to do when outside the control booth's fixed barrier? |
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Definition
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Term
| How many times must x-rays scatter before reaching any opening in the control booth? |
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Definition
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Term
How large must the floor of the control booth be? This is to allow the tech to be at least ___ from the wall absorbing x-rays. |
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Definition
Floor must be 7.5 square feet to allow tech to be at least 15 cm from wall. |
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Term
| There is a theory floating around (unsupported by hard data) that the electromagnetic fields created by strong electrical currents can cause *** or *** |
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Definition
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Term
| what are the requirements for the wall of the control booth? |
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Definition
| must be fixed to the floor and extend up at least 7 feet. |
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Term
| If the control booth has a door, what is required? |
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Definition
| there must be a sensor in the control panel that will not allow exposure if door is not closed. |
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Term
| Where must the exposure switch be located in relation to any opening in booth |
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Definition
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Term
| What are the requirements for the window of the control booth? |
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Definition
| There must be one. It must be 1 sq foot in size, at least 5 feet from floor, and 1.5 mm lead equivalent OR at least 30% lead by weight |
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Term
| What is the FDA requirement for the tabletop thickness over the bucky? |
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Definition
| Must be at least 1.0 mm Aluminum equivalent, must not absorb more x-rays than that. |
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