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66 Cards in this Set

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

output phosphor - zinc cadmium sulfide
the photocathode is made of
an alloy of antimony and cesium.
when the electron hit the output phosphor of an II tube, they are changed in _____ times more light photons than on the input side.
50-75 this light however is produced isotropically