Final - Part 1 Flashcards
What is the phosphor layer of the CR imaging plate composed of?
Europium-activated barium fluorohalide.
The imaging plate is placed in a reader and scanned by a laser. What is the pattern of the laser movement called?
Raster Pattern
What does the photomultiplier tube do?
Multiplies/ amplifies light photons into larger, brighter light photons.
What is the difference between a PMT and a CCD?
A CCD collects light photons and converts them to digital information, whereas the PMT just amplifies the light photons.
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Protective layer:
Insulates the plate from handling. Made of thin, tough, clear plastic.
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Phosphor / Active layer:
Absorbs x-rays and stores the information. Traps the electrons during x-ray exposure.
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Conductor layer:
grounds the plate and absorbs some light
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Support layer:
gives support and rigidity to the plate
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Light shield layer:
prevents unwanted light from reaching the IP
Identify and describe the layers of a photostimulable phosphor plate/cassette:
Backing layer:
protects the back of the cassette
What is the main difference between direct and indirect digital radiography?
Direct systems use a 2-step process where indirect systems use a 3-step process. Indirect – converts x-ray photons to light photons and then converts the light photons to an electric signal. Direct – converts x-ray photons directly to an electric signal.
What is the photodiode layer made of in an indirect digital system?
amorphous silicon
In an indirect digital system, what are the two materials that are used as a scintillator?
Cesium iodide or gadolinium oxysulfide
A TFT is comprised of an array of very small components known as:
detector elements (Dels)
An imaging plate will lose ____% of its energy in 8 hours, so it should be processed soon after exposure.
25%
The scintillator in DR or the PSP in CR are known as ____. Lenses, fiber optics or a-Se transfer the x-ray-generated signal to the collecting elements. These are known as ______ elements. The collecting elements collect the charge or electric signal. Collecting elements are the _________, ____________, and ___________.
capture elements
coupling
photodiode
thin-film transistor (TFT)
Charge-coupled device (CCD)
During latent image production in computed radiography the remnant radiation exits the patient and strikes the CR cassette. This interaction gives energy to the electrons in the phosphors. Describe what two things can happen:
Electrons are released and divided into 2 groups. One group of electrons gives off some light. The other group of electrons remains trapped in the conductor layer
If the energy is retained in the electrons, they travel to the conductor layer where they become trapped. This is now referred to as the _____ image
Latent
When the cassette is placed in the image reader device or digitizer, the _____ is extracted and moved through the reader. This is known as the slow scan direction or ______. The PSP is scanned by a _____ laser. This is known as the fast scan direction. The laser gives energy to the trapped ___, which then escape to the phosphor layer. The phosphors then emit the latent image in to form of _____ light. The light is picked up by a _____ which amplifies the light and converts it to an electronic signal. The electronic signal is then sent to the _____ which converts it to a digital signal. The digital signal is then sent to the computer for viewing. The imaging plate is then erased by _______.
imaging plate (IP)
translation
helium-neon
electrons
blue-violet
photomultiplier tube (PMT)
analog-to-digital converter (ADC)
bright, white, fluorescent light
CR cassettes should be erased every _____ hours if not used.
48
