xray physics chpt. 25
flux gain formula
# of output light photons / # of input x-ray photons
magnification mode results in:
1.better spatial resolution 2.better contrast resolution 3.higher patient dose
in a 25/17/12 multifield image intensifier (ii) which produces a smaller field of view and thus a more magnified image?
12 cm mode
Most image intensifiers have a brightness gain of?
5,000-30,000
a ___ converts the light signal from the output phosphor to an electronic signal
CCD
flow of the intensifier: the xray interacts with the input phosphor made of ___, which converts xrays to light. Then the light is converted to electrons by the __________ which is made of antimony cesium. The electrostatic focusing _____ directs the electrons from the _________ to the output phosphor. Then the output phosphor made of ZnCdS converts the electrons to _______.
CsI (cesium iodide) photocathode lenses photocathode light
magnification gain equation
MG= (Di/D0)^2 Di= diameter of input phosphor D0= diameter of output phosphor
A function of the fluoroscopic unit that maintains the overall appearance of the fluoroscopic image by automatically adjusting the kVp, mA or both
automatic brightness control (ABC)
the ability of the image intensifier to increase the illumination level of the image is called:
brightness gain
BG = MG x FG
brightness gain = magnification gain x flux gain
what is the input phosphor of the image intensifier made of?
cesium iodide (CsI)
_______ __________ _________ method to electronically convert the visible image on the output phosphor of the ii into an electrical signal
charge-coupled device
Where is the image intensifier located?
contained within a glass vacuum tube which amplifies the signal to brighten
duel field vs. trifield magnification
duel= 2 input sizes trifield= 3 input sizes
the photocathode turns light into __________.
electrons
this part of the image intensifier maintains a precise electron path from the photocathode to the output phosphor and is located along the length of the image intensifier
electrostatic focusing lens
the ________ is used for examinations of moving internal structures and fluids
fluoroscope
type of xray for dynamic, real time visualization of structures
fluoroscopy
Ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor
flux gain
the ability of an amplifier to increase the power of input signals
gain
what kind of technique is preferred for fluoroscopic studies?
high kVp and low mA
what is required for fluoroscopic studies for maximum image detail?
high levels of image brightness
the fluoroscopy television camera is attached to the __ with a lens coupling to accommodate a cine or a spot film camera
ii ( image intensifier )
Device that electronically improves and enhances radiographic images and transmits them to a television monitor
image intensifier
Complex electronic device that receives the image-forming x-ray beam and converts it into a visible-light image of high intensity
image intensifier tube
When magnification is increased while using an intensification tube, the patient's exposure ______.
increases
the part of the image intensifier that turns xrays to light?
input phosphor
Xrays that exit the patient and enter the image intensifier first interact with the
input phosphor(which is cesium iodide CsI)
part of the image intensifier that must be flawless and cannot disperse light?
input window
during each phase of the image intensifier, the signal gets:
larger (intensified)
what is the desired mA for fluoro studies?
less than 5 mA
the input phosphor turns xrays to ________.
light
the output phosphor turns electrons to ______
light
what needs to increase to compensate for a smaller field in a multifield ii?
mA automatically increases
mulifield image intesifiers produce different _________ of the image
magnification
The use of a smaller dimension of a multifield image intensifier tuble always results in a what
magnified image
"Fluoroscopy" is used to record ________:
moving body parts
Most image intensifiers are
multifield type
what is the charge of the photocathode?
negative
the electron lens use varying voltage to channel e- to the ______ _________
output phosphor
the part of the ii where accelerated electrons interact and produce light
output phosphor
the television camera tube converts light image from the ______ __________ of the image intensifier into an electrical signal that is sent to the television monitor
output phosphor
the part of the image intensifier that minimizes light reflection
output window
Photoemission occurs at the
photocathode
the _________ emits electrons when illuminated by the input phosphor
photocathode
the part of the image intensifier that turns light into electrons?
photocathode
Electron emission that follows light stimulation
photoemission
a smaller field in an ii results in less ________ and a ________ image
photons; dimmer
the kVp for fluoroscopic studies depend on what?
pt thickness of the body part being examined
structures in the eyes that are responsible for the sensation of vision are:
rods and cones
mA For fluoroscope studies are dependent on:
selected brightness, automatic brightness control, and pt. thickness
the part of the image intensifier that is glass or ceramic base for the phosphor (input phosphor)
substrate
the video signal is amplified and is transmitted by cable to the _________ _______, where it is transformed back into a visible image
television monitor
the 25/17/12 cm is a type of:
trifield tube image intensifier where the numbers represent 3 different field sizes of the input phosphor
the tv camera tube that is most used in television fluoroscopy
vidicon
the output phosphor is composed of
zinc cadmium sulfide (ZnCdS)
