Ch 15 Computed Radiography Flashcards
CR is a type of ____
DR, it is just indirect
CR can produce better images at _______
lower patient dose
IP =
imaging plate
PD =
photodiode (circuitry)
PMT =
photomultiplier tube
PSL =
photostimulable luminescence (method of using a phosphor to store an image)
PSP =
photostimulable phosphor
SP =
storage phosphor
SPS =
storage phosphor screen
in CR the response to x-ray interaction is seen as:
trapped electrons in a higher energy metastable state (latent, not stable, energized)
PSL photostimulable luminescence is using an _____ to expose the IP and allow _____
different light (laser) to expose the IP and allow the latent image to be read
Many Compton interactions occur with outer-shell electrons sending them into an excited metastable state, when the electrons return to the ground state _____
visible light is emitted
True or False? over time the metastable electrons will return to ground state on their own?
True
the return of metastable electrons to the ground state can be accelerated or stimulated by ________
exposing the phosphor to intense infrared light from a laser (PSL)
the main PSP is _____
barium flurohalide
x-ray interaction with a photostimulable phosphor results in:
excitation of electrons into a metastable state
when metastable electrons return to their ground state:
visible light is emitted
the IP has lead backing that reduces _____ and improves _____
reduces backscatter and improves contrast resolution of the image receptor
thermoluminescent dosimetry (TLD) and stimulated luminescence (OSL) are:
the main radiation detectors used for occupational radiation monitoring
light is emitted when a TLD crystal is ____
light is emitted when a OSL crystal is ____
heated
illuminated
the beam diameter of the infrared light (laser) is:
50-100 micro meters
the diameter of the laser beam affects the:
spatial resolution of the CR imaging system
the laser beam causes metastable electrons to ________ with the emission of ______
return to the ground state with the emission of a shorter wavelength light in the blue region of visible spectrum
after the IP is erased if there is any residual latent image it is removed by:
flooding the phosphor with very intense white light
solid-state lasers produce _______ and therefore are less likely to ______
longer wavelength light and therefore are less likely to interfere with emitted light
daylight film processors are based on:
wet chemistry processing
the laser is the source of ______, however to spreads as it travels to the ______
source of stimulating light; travels to the rotating or oscillating reflector
the drive mechanisms of the CR reader move the imaging plate slowly along its long axis while an ______ causes the stimulating mirror to sweep rapidly across the IP
oscillating beam deflection mirror
_____ and ______ are the process of analog-to-dialog conversion (ADC)
Sampling and quantization
the image buffer is usually _____
a hard disc
a 14-bit CR image has _____ gray levels
16, 384
the principle source of noise on a radiographic image is ______
scatter radiation
______ patient radiation dose is possible with CR
lower
CR image contrast is _____ regardless of _____
constant regardless of radiation exposure
in CR images can be made at ____ kVp and _____ mAs, resulting in ______
higher kVp and lower mAs, resulting in reduction in patient radiation dose
CR should be performed at _____ techniques than screen-film
lower
CR is based on ____
PSL photostimulable luminescence
x-rays interact with an _____ and for a latent image by exciting electrons to a higher energy metastable state
SPS storage phosphor screen
in the CR reader the latent image is made visible by releasing the metastable electrons with a ______
stimulating laser light beam
on returning to the ground state electrons emit a ______ in proportion to the intensity of the x-ray beam
shorter wavelength
the emitted light signal is ____
digitized and reconstructed into a medical image
the value of each CR pixel describes _____
a linear characteristic curve over four decades of radiation exposure and a 10,000 gray scale
the wide latitude of CR results in ______
lower patient dose and improved contrast resolution
λs
laser, infrared light, longer λ, low frequency, low energy, monochromatic, more intense bright light, red, small diameter (50-100 micro meters), better spacial resolution, stimulates latent image
λe
emitted light, ultraviolet, shorter λ, higher frequency, higher energy, polychromatic, less bright, blue range, metastable electrons returning to stable state
the latent image is created by:
photoelectric effect trapping electrons
what are the phosphors that glow white?
Sbs
fog from phosphor in CR cassette is called ______
turbid
screen-film has ____ shades of gray and gives you _____ info and _____ spatial resolution
10³, less info, less spatial resolution
CR has ____ shades of gray and gives you ______ info and ____ spatial resolution
10^4, more info, more spatial resolution
dynamic range is:
the range of exposures that will give an acceptable radiograph
we view the manifest image using _____ vision
photopic, cones
horizontal trace is ___ info
useful
the more metastable electrons there are the _______
more to the manifest image
turbidity is ___ in color
cloudy
ghosting is ____
residual white left from the image, must use a brighter light to erase it, same laser used to read it but it has a bigger diameter
