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97 Cards in this Set
- Front
- Back
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define xrays
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electromagnetic radiation with shorter wavelength than visible light
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anode
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postively charged electrode
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cathode
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negatively charged electrode
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electromagnetic radiation
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method of transporting energy through space-- distinguished by wavelength, freq, & energy
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the 2 charactersitics of electromagnetic radiation
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particles & waves
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4 main components of an atom
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1. proton
2. neutron 3. electron 4. nucleus |
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electrons
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negatively charged particles that travel around the nucleus
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xrays with a _______ wavelength have a ______ frequency
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shorter, higher
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what penetrates farther? xrays with shorter wavelengths or longer wavelengths?
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shorter
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xray beam is composed of:
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bundles of energy that travel in a wave
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7 physical properties of xrays
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1. wavelength is variable and is related to energy of radiation
2. travel is in a straight line 3. x rays can penetrate materials that absorb or reflect light 4. certain substances fluoresce 5. x rays produce an invisible image on photographic film 6. xrays have ability to excite or ionize atoms 7- xrays cause biologic changes in living tissue |
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xrays are generated when:
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fast-moving electrons collide with any matter
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the collision of electrons at the anode in an xray tube results in ______ & ______
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x-radiation, heat
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the man who discovered xrays
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Wilhem Conrad Roentgen
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kilovoltage peak [kVp]
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peak energy of the xrays which determines the penetrating power of the xray beam
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milliamperage [mA]
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amount of electrical energy being applied to the filament-- the # of xrays being produced during the exposure
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purpose of an xray tube
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to produce controlled xray beam
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the 5 elements necessary for xray production
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1. source of electrons
2- method of accelerating the electrons 3. obstacle-free path for the passage of high-speed electrons 4. target for the electrons 5. tube to provide a vacuum environment |
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xray tube consists of a ______ and an ______ encased in a ______ ______
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cathode, anode, glass envelope
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2 purposes of the cathode
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1. provide a source of electrons
2. to direct those electrons towards the anode |
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the cathode consists of a ______ that emits electrons when ______
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filament, heated
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the filament in the cathode is made of _______
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tungsten
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2 types of anodes
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1. stationary
2. rotating |
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construction of anode consists of:
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a beveled target placed on a cylindric base
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what type of cells are most sensitive to radiation?
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rapidly dividing cells [growth, gonadal, neoplastic, metabolically active]
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what other tissues are very sensitive to radiation?
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bone, lymphatic, dermis, leukopoietic, hemopoietic
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which 2 types of personnel are prohibited from assisting in radiographic procedures
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1. those under age 18
2. pregnant women |
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the 2 types of tissue damage that can occur from radiation exposure
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1. somatic
2. genetic |
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somatic damage
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damage to the body that manifests within the lifetime of the recipient
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what type of cells are most sensitive to radiation?
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rapidly dividing cells [growth, gonadal, neoplastic, metabolically active]
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what other tissues are very sensitive to radiation?
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bone, lymphatic, dermis, leukopoietic, hemopoietic
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variable that controls quality of xray beam
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kVp
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variable that controls quantity of xray beam
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mA
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the electrical current that heats the filament is measured in _______
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milliamperes
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exposure time
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period during which the xrays are permitted to leave the xray tube
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2 advantages to using high mA settings
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1. allows for shorter time settings
2. greater amount of xrays are produced |
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the equation used to determine mAs
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mA x time[in seconds] = mAs
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kVp
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- kilovoltage peak
- related to the penetrating power of the xrays |
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the _____ the kV, ______ the electrons are accelerated
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higher, faster
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higher kVp settings produce _______ beams & allow for ______ mA settings
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more-penetrating, lower
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Santes' rule equation
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(2 x thickness) + 40 = kVp
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Source-image distance [SID]
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the distance b/t the source of the xrays & the image receptor/film
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as SID is decreased, the xray intensity is ______
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increased
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inverse square law
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the intensity of the beam varies inversely according to the square of the distance
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the most common SID in vet. med. ranges from ____ to _____ cm [____ to ___ inches]
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90-100cm [36-40 inches]
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mAs control the _______ _____ of xrays and the kVp controls the _____ _____ of the xrays
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total number, penetrating power
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radiographic density
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the degree of blackness/darkness on a radiograph
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radiographic contrast
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the density difference b/t adjacent places on radiograph
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a radiograph that has many black areas and is dark when viewed has _____ density
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high
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3 factors affecting rad. density
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1. mAs
2. kVp 3. thickness & type of tissue being radiographed |
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body parts that have greater thickness absorb more xrays, resulting in ______ image on radiograph
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lighter
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subject contrast
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difference in density & mass of 2 adjacent anatomic structures
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a radiograph with ______ contrast exhibits many black & white tones
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high
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for bone, you want _____ contrast & ____ kVp
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high, low
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for soft tissue, you want ______ contrast & ______ kVp
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low, high
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5 things radiographic contrast is influenced by:
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1. subject contrast
2. kVp level 3. scatter radiation 4. film type 5. film fog |
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the primary factor that affects density is:
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the mAs
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when correct mAs setting is used, contrast depends primarily on _____ setting
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kVp
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if kVp is too low, the resulting radiograph will appear ________
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grey & white [soot & whitewash]
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increased kVp causes excess ______ _____
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scatter radiation
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scatter radiation
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non-image-forming radiation that is scattered in all directions b/c of objects in the path of the xray beam
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scatter radiation primarily originates from _______
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the patient
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the most effective way to reduce backscatter is:
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limiting the size of the xray beam
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scatter radiation causes contrast to be ______
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decreased
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what mechanism is used to reduce scatter radiation when high kVp settings are needed?
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grid
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grid
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device placed b/t the patient & the radiographic film that is designed to absorb scatter radiation
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grid focus
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distance from xray tube to the grid
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if grid us used outside of the specified grid focus range, ____ ____ can occur
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grid cutoff
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grid cutoff causes that part of the image to appear _______ with distinct ____ ____ on the film
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lighter, white lines
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3 ways that grid cutoff can occur
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1. improper centering of xray tube
2. tilting the xray tube laterally 3. having grid upside down |
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3 things that determine grid efficiency
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1. height
2. thickness 3. number of lead strips |
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4 types of grids
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1. linear
2. crisscrossed 3. focused 4. pseudo focused |
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linear grid has ______ lead strips that allow primary xrays through to the film
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parallel
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advantage of linear grid
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it allows the radiographer to angle the xray tube along the length of grid w/o loss of primary radiation from grd cutoff
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crisscross grid consists of _____ _____ ____ _____
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2 superimposed linear grids
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advantage of crisscross grid
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maximum amount of scatter radiation is absorbed
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disadvantage of crisscross grid
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it cannot be used with oblique techniques requiring angulation of xray tube
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focused grid is made up of lead strips that are ____ ____ so that they focus on central point of grid
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slightly angled
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unfocused grid has lead strips that are ______ when viewed in a cross-section
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parallel
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pseudofocused grid is a combo of _____ & _____ grids
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parallel, focused
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disadvantage of unfocused grid
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can be used effectively only with small xray fields
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are grids delicate & expensive?
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yes
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radiographic detail
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the definition of the edge of an anatomic structure on a radiograph
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lack of radiographic detail can result from 3 main factors:
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1. geometric unsharpness
2. geometric distortion 3. geometric magnification |
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2 types of geometric distortion
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1. elongation distortion
2. foreshortening distortion |
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to maintain accurate geometric projection, the subject must be ______ to image receptor/film
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parallel
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elongation distortion
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when subject is not directly underneath the xray beam
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foreshortening distortion
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when one side of subject is farther away from the source of light that the other
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foreshortening distortion is common when xraying what type of disease?
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dog with severe hip dysplasia
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describe an xray cassette
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rigid, lightproof film holder designed to hold the film & intensifying screens in close contact
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intensifying screens convert x-ray radiation into ____ ____ which produces a ____ ____ onto the film
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visible light, latent image
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a cassette should be cleaned with ____ & ____
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mild soap & water
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3 properties that determine the efficiency of a screen
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1. must have high level of xray absorption
2. must have high xray-to-light conversion 3. there must be little/no afterglow once radiation has ceased |
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intensifying screens are sheets of ____ ____ _____
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luminescent phosphor crystals
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you can use ____ mAs settings when intensifying screens are used
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lower
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when the phospor crystals are struck by xradiation, the crystals ____
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flouresce
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the 4 layers of an intensifying screen
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1. base
2. reflective 3. phosphor crystal 4. protective |
