Chapter 15 Flashcards
When was the first fluoroscope invented and by who?
1896 by Edison
1st fluoroscope was made with what type of screen?
Calcium tungstate
When was the image intensifier introduced?
1950s
Image intensifiers allowed for images to be _______ viewed through mirror optics and later, television monitors
Indirectly
What mA is used in fluoroscopy vs conventional x-ray?
Fluoro: .5 - 5 mA
Tradiational: 50 - 1200 mA
Benefits of low mA used in fluoro
Can be used for longer durtation with reduced risk of injury to the patient
Fluoro control panels are fitted with a timer that discountinues exposure at the __ minute mark
5 minute
What is an image intensifier and what does it do?
An electronic vacuum tube that converts the remnant beam to light, and then into electrons, then back into light
5 basic parts of the image intensifer
Input phosphor
Photocathode
Electrostatic focusing lenses
Accelerating anode
Output phosphor
The intensified light exiting the output phosphor is converted into ____________
electronic signal
Input phosphor is typically made of _____ and bonded to the _______ surface of the intensifier tube
Cesium iodide
Curved
Which phosphor is larger?
Input
What happens when radiation strikes the cesium iodide of the input phosphor?
Light is emitted
The photocathode is made of ________
cesium and antimony
After being exposed to light, the photocathode emits ______
electrons
What is the process called when the photocathode emits electrons?
Photoemission
The photocathode is curved in a way that directs the emitted electrons in same the direction, through the ____________
electrostatic focusing lenses
The focusing lenses are __________ charged plates
Negatively
The negative charge of the focusing lenses __________ the electrons in a focused direction, towards the ________
Repels
Accelerating anode
The purpose of the accelerating anode is to:
Direct the electrons at a consistent rate towards the output phosphor
The anode is supplied with a constant electric potential of:
25 kV
After exiting the accelerating anode, electrons stike the _______________
output phosphor
Output phosphor is made up of ___________
Silver-activated zinc cadmium sulfide
The output phosphor ________ electrons and coverts them into light
Absorbs
The light absorbed by the output phosphor is converted into
Electric signal
The ability of an image intensifier tube to convert radiation into light is referred to as
Brightness gain
Brightness gain =
Flux gain x minifiation gain
The ratio of the number of light photons at the output phosphor to the number of x-ray photons at the input phosphor
Flux gain
Flux gain represents the:
Systems efficiancy
The expression of how much an image is minified, meaning made smaller, from the input phosphor to the output phosphor
Minification gain
The expression of luminance at the output phosphor divded by the input exposure rate
Conversion factor
As the intensifier ages, it will slowly ________ it’s ability to intensify
Lose
Function that maintains the overall appearance of the image by adjusting kVp and mA as needed
Automatic Brightness Control (ABC)
When operating in magnification mode, ________ to the focusing lens within the intenisifier is ________
Voltage
Increased
What happens to the focal point when mag mode is being used
Shifts the focal point farther from the output phosphor (similar concept to OID)
Mag mode increases:
Spatial resolution and patient dose
Unequal magnification creates a form of shape distortion known as:
Pincushion appearance
The loss of brightness around the edges of the image
Vignetting
Television cameras used to display images included either:
Camera tubes or CCD
Camera tubes are the same diameter as the:
Output phosphor
Most common camera tube is the:
Vidicon tube
How is the vidicon tube connected to the output phosphor
Fiber optics or optical lenses
Vidicon tube is a _____ tube contained in a ______, which maintains a vacuum
Diode
Glass envelope
_____ end of the vidicon tube consists of an electron gun and control grid
Cathode
The electron gun in the vidicon tube provides a continous steam of _______, the control grid forms the stream into a _________
Electrons
Beam
Center of the vidicon tube contains coils that provide:
Alignment, focus and deflection
What is the purpose of the coils in the vidicon tube?
Accelerate and control the electron beam
The coils in the vidicon tube cause the beam to follow a specific pattern called a:
Raster pattern
______ end of the vidicon tube consists of a face plate, signal plate, and target
Anode
The signal plate in the vidicon tube is a __________ material that conducts electricity
Graphite
The target in the vidicon tube is a photoconductive layer made of:
Antimony trisulfide
In plumbicon tubes, the target is made of:
Lead oxide
The target in the plumbicon tubes acts as a __________ or a _________ depending on if it’s illuminated
Conductor or insulator
When using CCD in place of camera tubes, a series of __________ capacitors are used, with each capactior representing an individual pixel in the image
Metal oxide semiconductors
When using CCD, each pixel is made of photosensitive material that dislodges __________ when stimulated by light
Electrons
When using CCD, electrodes between each pixel, called ___________, are charged in sequence, which moves the signal down the row, where it is ultimately transferred to capacitors
Row gates
CCD TV cameras are _____ sensitive to a wider range of light intensity
More
Are fiber optics or optical lens systems more durable?
Fiber optics
Which type of connection, fiber optics or optical lens, allows for spot films?
Optical lens
TV monitor converts electrical signal from camera tubes or CCD back into:
Visible images
Older fluoro units used what type of monitors?
Cathode Ray Tube (CRT)
How did CRT monitors function?
Like camera tube systems, but in reverse
Typical monitors are called ______ line systems
525
High resolution monitors have ___ lines per frame
1024
Spot films are when a fluoro unit is used to take ______ images
Static
Film cameras use much _____ radiaiton than cassette-spot film systems
Less
Earlier versions of fluoro added in an ADC and computer between the camera tube and monitor. The ADC took the analog signal and converted it to:
Digital signal
Two forms of FPD systems
Indirect capture
Direct capture
The photodetector in indirect capture systems is:
Amorphous silicon
Direct capture systems use:
Amorphous selenium
Indirect capture uses scintillators that are made of either ________ or _______
Cesium iodide or gadolinium oxysulfide
In fluoro, FPDs use a ____________ to erase the detector between each individual frame
Light-emitting diode array
Current dynamic systems are capable of capturing up to _____ frames per second
60
The last frame captured is held for viewing on the monitor
Last hold image (LHI)
Collimation lines are visible on monitor
Virtual collimation
Reduces overall dose and noise by averaging multiple frames together
Frame averaging
Prebuilt algorithms that are meant to be used with specific body parts
Anatomic programs
Automatically adjusts technical factors to maintain optimum exposure levels
Automatic exposure rate control (AERC)
AERC can automatically adjust:
mA
kVp
Filtration
Pulse width
Electronic magnification is the selection of a ______ FOV
Smaller
At _____ pulses per second, the dose is about the same as continous fluoro
30
Amount of pulses that occur each second
Pulse rate
Length of each pulse
Pulse width
The amount of kinetic energy released in matter
Air Kerma
Max air kerma rate for fluoro
88 mGy/min
Used to measure exposure in air
Dose-area product (DAP)
Same as DAP - product of total air kerma and the area of the beam as it enters the patient
Kerma air product (KAP)
Type of monitors that offer superior resolution and displayed brightness
Liquid crystal display (LCD)
In LCD, the crystals within the crystal layer are ______ shaped and _________ liquid
Rod
Semi
In LCD, when ___________ is applied, the crystals organize into configurations that either block or allow light to pass through
Electric current
In LCD, a layer of _____ controls each individual pixel in the display
TFTs
Plasma monitors use _________ instead of a liquid crystal layer
Thin layer of pixels
In plasma displays, each pixel is made up of __ different subpixels, each filled with _____ and ______
3
Neon and xenon gas
In plasma, each of the subpixels are coated with a different phosphor that produces:
red, green or blue light
In plasma, the pixel layer is sandwiched between two _________ layers
Dielectric
In plasma, when electricty is passed through the dielectric layers, the gas within each subpixel is:
Ionized
In plasma, the liberated electrons release:
UV radiation
In plasma, UV radiation stimulates the phosphors while producing:
Visible light
Source-to-skin distance shoud be no less than _____ cm on for stationary fluoro units
38
Source-to-skin distance should be no less than _____ cm for mobile units/c-arm units
30
