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If your not sure what answer should be entered, press the space bar and the next missing letter will be displayed. When you are all done, you should look back over all your answers and review the ones in red. These ones in red are the ones which you needed help on. Question: characteristics of radiation Answer: invisible, long-term, Question: Biologic Effects of Ionizing Radiation (BEIR) Committe VII risk model for exposure to low-level Answer: approx. 1 in 100 people are likely to develop solid cancer or leukemia from an exposure of 100 mSv above dose Question: Important for patient Answer: Good communication and quality assurance Question: Beam Answer: single most important factor in keeping patient dose to a minumum, only tissues of diagnostic interest should be iradiated -reduces pt dose, production of scattered radiation, improves quality of image Question: Beam typesAnswer: diaphragm, cone/cylinder, collimator Question: Answer: most efficient, to tube head, first set of shutters placed close to x-ray tube port window to control amt of image degrading "off-focus" radiation leaving tube, lead shutters (two adjustable)for length and width Question: diaphragmAnswer: elementary -dedicated , dental unit, trauma imaging equipment -flat piece of lead having a central opening with a size and shape that determines the size and shape of x-ray beam Question: Cone/cylinder -used for relatively small field size (paranasal )Answer: circular, lead-lined, slide into place in the tube head or onto the housing Straight-prox and dist diameters identical Flare-dist diameter greater than prox diameter -limited use, more efficient bcs beam restriction is closer to anatomy Question: Disadvantages of aperture and cone beam Answer: have a fixed opening size, only one field size at a distance Question: mAsAnswer: controls quantity, no on quality Question: Answer: controls quality, quantity Question: NCRP guideline for manual collimation must be within _____ of the SID.Answer: 2% Question: Positive beam -PBLAnswer: sensors located in Bucky tray or IR holder signal the collimator to open or close accordingly to the IR size being used, will provide a small unexposed border on all sides of the finished image -required by the NCRP to be withi Question: PBL requirements by Answer: -required by the NCRP to be 3% of SID for a single side and within 4% of SID for all 4 sides Question: NCRP guidelines for manual Answer: within 2% of the Question: Collimator -light localization apparatusAnswer: small light bulb to illuminate the field and a 45-degree angle to deflect the light. Question: T/F For the x-ray light field and x-ray field to correspond , the x-ray tube focal spot and the light bulb must be exactly the same distance from teh center of the mirror.Answer: TRUE Question: factors for patient safetyAnswer: high kVp, low mAs -also good bcs heat delivered to x-ray tube is and tube life is extended Question: Three-phase or high generatorsAnswer: stationary radiologic equipment, constant potential waveform, reduced patient Question: Inherent Answer: in, permanent -window of glass envelope (.5 mm Al) -thin layer of oil coolant/insulation surrounding the x-ray tube -tends to increase as tube ages, tungsten deposits Question: Filtration Answer: less than 50 kV = .5 mm Al 50-70 kV = 1.5 mm Al more tha 70 kV = 2.5 mm Question: organsAnswer: gones, lens, -froming organs Question: Whose to shieldAnswer: all women under 55, all men 65 Question: Gonad Answer: easier and more on males than on females Question: When to the gonadsAnswer: -when diagnostic permit -when pt is of reasonable reproductive age -when gonads lie in or within 5 cm of the collimated field Question: Contour shieldsAnswer: effective for gonads, shaped to enclose male reproductive organs, held in place by briefs, effective for oblique, erect, and fluro exams Question: shieldsAnswer: leaded material casts a shadow within the illuminated field that corresponds to shielded area, inially expensive but one time , can be used without contacting sterile fields, NOT TO BE USED IN FLUORO. Question: Mammography equipment with a molybdenum target has how much ?Answer: .025-.03 mm filtration Question: window in mammo is made of what?Answer: beryllium-low number (4) Question: filtrationAnswer: thin sheets of aluminum that are , collimator and its mirror Question: Why use PA of AP chest or spine?Answer: decrease dose to breast tissue to .1% of that received in AP, considerations are minimal Question: T/F Entrance skin dose is greater than exit dose.Answer: True -place radiosensitive organs away from the beam Question: Perform these in PA projection when possible.Answer: Skull, , abdomen, scoliosis series, spine Question: good Answer: helps gain 's trust and confidence with a thorough explanation Question: lead aprons during Answer: under patient Question: Minimum /reaction timeAnswer: length of the shortest exposure possible with a AEC Question: If the minimum response time is too high, how is this .Answer: needs fixed or will have density -preferable to decrease ma, but may decrease kV Question: Rare earth Answer: film/screen radiography -four times faster than tungstate phosphors Question: Advantage of digital Answer: lower dose due to x-ray beams are pulsed not continuous Question: gridsAnswer: function to remove a large percentage of scattered radiation mostly from Compton scatter, radiographic contrast Question: air-gap Answer: limited to imaging fairly thin parts (thick and tissues would require excessive and impractical radiation exposures) Question: equipment must be properly calibrated to give predictable . What two values need to be checked?Answer: linearity and Question: linearityAnswer: adjacent mA stations should be consistent 200 mA should be 2x exposure rate as 100 mA, any variation in intensity must not exceed 10% Question: Answer: consistency in exposure output during repeated exposures at a particular setting, any variation in output intensity must not 5% Question: High grids with low kVAnswer: BAD, discouraged because of unnecessary exposure Question: high grids affect on positioningAnswer: decreases positioning Question: low ratio Answer: used in radiography, more positioning latitude Question: 8:1 grid good for what kV ?Answer: up to 90 Question: 16:1 grid good for what kV ?Answer: 100 kV or Question: 10:1 or 12:1 grid used in what type of ?Answer: general equipment Question: T/F Moving grids call for less exposure than grids.Answer: False. They more exposure. Question: Ways to patient fluoro doseAnswer: -decrease length of exposure -use last image hold -keep pt as close to II as possible -use automatic brightness control setting with high kV, low mA -minimize "boost" and "mag" modes, low pulse rate -collimate to smallest of view Question: Ways to decrease patient dose cont.Answer: -use lowest practical pulse rate -change tube angle or patient position to spread dose over larger Question: NCRP guidelines for x-ray tube leakageAnswer: less than 100 mR/hr 1 meter from Question: -Skin distance for all radiographic procedures (NCRP)Answer: no less than 12 in -12 inches in mobile radiography -15 inches in stationary Question: (NCRP) tabletop intensityAnswer: than 10 R/min Question: Where should the focal spot location be ? (NCRP)Answer: outside of tube Question: How often should intensifying screens be and checked? (NCRP)Answer: every 6 Question: (NCRP)What type of switches are used?Answer: dead-man Question: (NCRP) How visible should the patient be to the ?Answer: RT should be able to see and communicate with the at all times Question: Answer: national council on protection and measurements Question: Principal function of x-ray tube Answer: patient skin dose |
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