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66 Cards in this Set
- Front
- Back
The ______ of and xray tube produces light
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input phosphor
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the ______ changes light in to electrons
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photocathode
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the _______ changes the electrons from the photocathode into light
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output phosphor
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the component of and image intensifier that focuses the electrons across the tube is the______
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electrostatic lenses
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what is the function of the anode in an image intensifier
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accelerates the electrons across the tube and gives them kinetic energy
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the anode of the image intensifier ( does or does not) function like a target in an xray tube
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does not
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the anode of an image intensifier has a potential of _____
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25kVp or 25000 volts
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what did 1st generation Image intensifier used ________ as the input phosphor
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zinc cadium sulfide
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2nd generation image intensifiers use _____ as the input phosphor
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cesium iodide
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why is an image intensifier evacuated
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it allows control of electrons so that the don't run into gas or air molecules.
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the photocathode is made from ______ and _______ compounds
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antimony and cesium
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the output phosphor in an image intensifier tubes uses __________ as the phosphor material
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zinc cadium sulfide
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the resolution produced by the 1st generation image intensifiers was approx ________ line pairs per mm
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1-2
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the term resolution is defined as
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the ability of an imaging system to defferentiate small objects as being seperate images as they come closer together
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Name a reason that newer II's have better resolution than earlier generations
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Cesium iodide crystals can be packed togehter at a higher density level than earlier phosphors and act like fiber optic tubes to guids the light to the cathode
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the older mirror optical system used to view images from the output phosphor has ______ image quality and ______ brightness levels
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good image quality but poor brightness
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name 2 other disadvantages of mirror optical systems
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1. limited viewing angle
2. limited number of viewers |
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a beam splitting image intensifier allows both viewing and ______ of the fluoro image
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viewing and recording
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beam splitting systems use a semi transparent mirror/glass to direct about ______ % of output light to the TV camera
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10%
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beam splitting systems use a semi transparent mirror/glass to direct about ______ % of output light to the recording device
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90%
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the system in an image intensifier which is responsible for automatically maintaining image brightness as the intensifier is moved over different tissue types or thickness is known as ____(3 A)
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ABC - automatic brightness control
ABG - automatic brightness gain ABS - automatic brightness stabilization |
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the ABC system automaticallyt increases/ decreases _____ or ____ during the exposure as light output changes during the exam
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mA or kVp
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the II tube normally ________ image contrast
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decreases
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what is the main reason that fluoroscopy has increased statistical fluctuation that produces more noise and mottle in theses images
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fluoro uses very low mA levels ( 1-5mA) which means that it uses much less info than film CR or DR
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the 2 main methods of reducing noise in fluoro images is to either increase the ______ or ______ that is being used for the fluoro exposure or some combination of these two factors
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mA or kVp
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magnification produced by a point source in know as
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geometric magnification
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magnification produced by any source larger than a point source is know as ___________
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true magnification
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True magnification will always produce an image that is _____ than the size of the actual object
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larger
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name 2 exams or imaging areas where magnification radiography can be used
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mammography, orothopedics, angio/ interventional , pediatrics
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magnification radiography requires a FSS of _________ or smaller
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0.3mm
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why does magnification radiography use small FSS
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the use of a small FS will always increases image sharpness regardless of other factors.
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magnification radiography magnifies the iamge by increasing which distance factor
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OID
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grids are not needed in magnification exams because of the _______
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build in air gap technique
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what are 2 problemss with the use of a small FS size in magnification radiography
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1.excessive heat production- technique limitations
2.field size limitation |
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the amount or frequency of information that needs to be recorded in magnification is actually ___________ than that of non-magnified exams
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less than
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name one reason that a faster IR may be needed or can be used with magnification exams
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technique limitations / less information to be recorded
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what would an MF (magnification factor) of 1 mean
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image and object size are the exact same
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what is the glass envelope of an xray tube usually made of
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pyrex or tempered glass
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4 functions of the xray tube are
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1. support the xray tube
2. grounded for operator/ pt safety 3. acts as a thermal resevoir 4. absorbs isotropic radiation |
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the two main components of the cathode are the _____ and the _____ plus its metallic support assembly and the 3 conducting cables
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focusing cup and filament
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the conducting cables carry
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both low and high voltage
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the filament in the xray tube is an alloy made from blending
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tungsten and thorium
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the target metal in a rotating anode has the characteristics a a high ______ to increase the efficiency of xray production
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atomic number
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the target metal in a rotating anode has the characteristics of a high _________ to withstand the high temperature produced in xray
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melting point
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name 3 other function of the anode in an xray tube
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1. acts as a positive electrode of the electrical circuit
2. mechanically holds/supports the target 3. thermal conductivity/ holds high amounts of heat during the exposure |
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in modern xray tubes the anode disc in made from an alloy of
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tungsten and rhenium to allow for a greater thermal capacity
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the stem or neck of the rotating anode is made from ______ which is a poor heat conductor and helps to protect the ______ &________
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molybdenum which helps to protect the bearings and rotor
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___________ happens when at a high temperature but before the melting point of a particular metal
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vaporization
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the main purpose of fluoroscopy is to allow ________ viewing of the rasiographic image
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real time viewing
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the main disadvantage of fluoro is
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increased patient does and personel exposure
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direct fluoroscopy is also known as________
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conventional.
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Conventional fluoroscopy produced very ______ light levels
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LOW
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low light levels utilize night time vision which is called
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scotopic
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scotopic vision has very poor _______ and ______
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visual acuity and color and contrast perception
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the vision that utilizes the cones of the retina is
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photoptic
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photoptic vision allow for _______ times better visual acuity
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8-10
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the rods of the retina are concentrated where
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20-30 degrees off center
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4 safety features specific to fluoro equiptment
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1. automatic beam collimation
2. cumulative manual reset time 3. bucky tray slot cover 4. min table top to panel distance |
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the basic advantage of spot films over recording a film of full image of the same area on most types of IRs
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reduced patient does
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fluoro is normally done at mA level between
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1 to 3-5 mA
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the low mA levels is fluoro leeds to an increase in
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mottle noise
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when using a spot film in fluoro the mA is increased to
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100mA
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1st generation Image intensifiers were made of
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Input phosphors and output phosphor was zinc cadmium sulfide
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2nd generation image intensifiers were made of
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Input phosphor - cesium iodide
output phosphor - zinc cadmium sulfide |
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the photocathode is made of
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an alloy of antimony and cesium.
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when the electron hit the output phosphor of an II tube, they are changed in _____ times more light photons than on the input side.
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50-75 this light however is produced isotropically
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