Pt protection Word Scramble

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Question	Answer
characteristics of radiation risks	invisible, long-term, cumulative
Biologic Effects of Ionizing Radiation (BEIR) Committe VII risk model for exposure to low-level radiation	approx. 1 in 100 people are likely to develop solid cancer or leukemia from an exposure of 100 mSv above background dose
Important for patient safety	Good communication and quality assurance programs
Beam restriction	single most important factor in keeping patient dose to a minumum, only tissues of diagnostic interest should be iradiated -reduces pt dose, reduces production of scattered radiation, improves quality of image
Beam restrictor types	aperture diaphragm, cone/cylinder, collimator
Collimator	most efficient, attached 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
Aperture diaphragm	elementary -dedicated chest, 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
Cone/cylinder -used for relatively small field size (paranasal sinuses)	circular, lead-lined, slide into place in the tube head or onto the collimator 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
Disadvantages of aperture and cone beam restrictors	have a fixed opening size, only one field size at a given distance
mAs	controls quantity, no affect on quality
kVp	controls quality, affects quantity
NCRP guideline for manual collimation must be within _____ of the SID.	2%
Positive beam limitation-PBL	sensors located in Bucky tray or other 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
PBL requirements by NCRP	-required by the NCRP to be within 3% of SID for a single side and within 4% of SID for all 4 sides
NCRP guidelines for manual collimation	within 2% of the SID
Collimator assembly-light localization apparatus	small light bulb to illuminate the field and a 45-degree angle mirror to deflect the light.
T/F For the x-ray light field and x-ray field to correspond accurately, the x-ray tube focal spot and the light bulb must be exactly the same distance from teh center of the mirror.	TRUE
exposure factors for patient safety	high kVp, low mAs -also good bcs heat delivered to x-ray tube is lower and tube life is extended
Three-phase or high frequency generators	stationary radiologic equipment, constant potential waveform, reduced patient dose
Inherent filtration	built 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
Filtration summary	less than 50 kV = .5 mm Al 50-70 kV = 1.5 mm Al more tha 70 kV = 2.5 mm Al
Radiosensitive organs	gones, lens, blood-froming organs
Whose gonads to shield	all women under 55, all men under 65
Gonad shielding	easier and more effective on males than on females
When to shield the gonads	-when diagnostic objectives permit -when pt is of reasonable reproductive age -when gonads lie in or within 5 cm of the collimated field
Contour shaped shields	effective for gonads, shaped to enclose male reproductive organs, held in place by disposable briefs, effective for oblique, erect, and fluro exams
Shadow shields	leaded material casts a shadow within the illuminated field that corresponds to shielded area, inially expensive but one time expense, can be used without contacting sterile fields, NOT TO BE USED IN FLUORO.
Mammography equipment with a molybdenum target has how much filtration?	.025-.03 mm molybdenum filtration
Glass window in mammo is made of what?	beryllium-low atomic number (4)
Added filtration	thin sheets of aluminum that are added, collimator and its mirror
Why use PA instead of AP chest or spine?	decrease dose to breast tissue to .1% of that received in AP, magnification considerations are minimal
T/F Entrance skin dose is significantly greater than exit dose.	True -place radiosensitive organs away from the entrance beam
Perform these exams in PA projection when possible.	Skull, chest, abdomen, scoliosis series, spine
good communication	helps gain patient's trust and confidence with a thorough explanation
lead aprons during fluoro	placed under patient
Minimum response/reaction time	length of the shortest exposure possible with a particular AEC
If the minimum response time is too high, how is this fixed.	needs fixed or will have excess density -preferable to decrease ma, but may decrease kV
Rare earth phosphors	film/screen radiography -four times faster than calcium tungstate phosphors
Advantage of digital fluoro	lower patient dose due to x-ray beams are pulsed not continuous
grids	function to remove a large percentage of scattered radiation mostly from Compton scatter, improve radiographic contrast
air-gap technique	limited to imaging fairly thin parts (thick and dense tissues would require excessive and impractical radiation exposures)
equipment must be properly calibrated to give predictable results. What two values need to be checked?	linearity and reproducibility
linearity	adjacent mA stations should be consistent 200 mA should be 2x exposure rate as 100 mA, any variation in output intensity must not exceed 10%
Reproducibility	consistency in exposure output during repeated exposures at a particular setting, any variation in output intensity must not exceed 5%
High ratio grids with low kV	BAD, discouraged because of unnecessary exposure required
high ratio grids affect on positioning	decreases positioning latitude
low ratio grids	used in mobile radiography, more positioning latitude
8:1 grid good for what kV range?	up to 90 kV
16:1 grid good for what kV range?	100 kV or more
10:1 or 12:1 grid used in what type of equipment?	general fixed equipment
T/F Moving grids call for less exposure than stationary grids.	False. They require more exposure.
Ways to decrease patient fluoro dose	-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 field of view
Ways to decrease patient fluoro dose cont.	-use lowest practical pulse rate -change tube angle or patient position to spread dose over larger area
NCRP guidelines for x-ray tube housing leakage	less than 100 mR/hr 1 meter from tube
Source-Skin distance for all radiographic procedures (NCRP)	no less than 12 in -12 inches in mobile radiography -15 inches in stationary radiography
(NCRP) Fluoro tabletop intensity	fewer than 10 R/min
Where should the focal spot location be indicated? (NCRP)	outside of tube housing
How often should intensifying screens be cleaned and checked? (NCRP)	every 6 months
(NCRP)What type of exposure switches are used?	dead-man switch
(NCRP) How visible should the patient be to the radiographer?	RT should be able to see and communicate with the patient at all times
NCRP	national council on radiation protection and measurements
Principal function of x-ray tube filtration	reduce patient skin dose

Created by: mmarnold2