IP
what is the purpose of the light shielding layer?
soft polymer layer that protects the back of the cassette and often prevents light from affecting the image.
what device detects the emitted violet light in CR?
photomultiplier tube.
exposure terms in CR used by manufactures that indicate amount are ____, ____, and _____?
S, EI, IgM
IgM or logarithm of the median exposure has a _________ relationship to the amount of exposure?
direct relationship
what material converts light photons into electrons in in-direct DR?
amorphous silicon (a-Si)
what is the latent image in CR?
electronic image of trapped electrons stored in high energy traps.
what happens to the signal from the photomultiplier tube?
it is converted into a digital signal and stored for display.
S or sensitivity number has a ______ relationship to the amount of exposure?
inverse relationship
In digital radiography (DR) what are the two types of image production?
direct and in-direct
what is the role of the CCD (charge coupled device) in in-direct DR?
require scintillator material to produce light. light from scintillator strikes CCD and is converted into an electronic signal.
how is the latent image made visible?
exposing it to a laser beam
what does the light signal digitizer do in CR?
assigns numeric value to each pixel in a matrix, based on brightness and position of light.
A low S-number means _______?
overexposure
what type of system is in-direct DR?
3 step process, scintillator-based system.
what happens to the electronic signal from the CCD?
sent to analog-to-digital converter where it becomes a data set to form the digital image.
what happens when the laser interacts with the PSP plate?
electrons return to their valence bands with emission of violet light-light stimulated phosphorescence.
How are CR plates erased?
exposed to bright light
a High S-number means_______?
underexposure
what materials are used as scintillators in in-direct DR?
cesium iodide (Csl) or gadolinium oxysulfide
what does the thin-film transistor (TFT) do?
absorbs x-ray photons and instantly converts them into electrical signals using amorphous silicon or CMOS sensor.
what does the image plate reader do in CR?
employs the laser that reads the energy stored in the conductive layer, causing light to be emitted that in amplified by a photomultiplier.
what are the steps pf CR image processing in the correct order?
1. x-ray exposure
2. latent image formed
3. plate inserted into CR reader
4. laser scanning
5. photostimulated phosphorescence (release of violet light)
6. photomultiplier tube detects light
7. light converted to electrical signal
8. digitization- pixel values assigned
9. image displayed on monitor
10. plate erased with bright light
EI or exposure index has a _______relationship to the amount of exposure?
direct relationship
what does the scintillator do in in-direct DR?
converts x-ray photons into light photons.
What is the overall role of the TFT?
amplifies signal, and converts the signal to electronic signal