Lecture 1 Flashcards
Conventional radiography involves acquisition using _______?
Film-screen combination
Imaging plate contains a photostimulable______ . What does this do?
phosphor; stores the latent image of the body part until it is processed
What are imaging plate phosphors made of?
Barium Fluorohalide doped with Europium
Differentiate between the IP of Standard Resolution & High Resolution
Standard - IP has a thick phosphor layer, High - IP has thinner phosphor layer
Due to the thinner phosphor layer, high resolution IP’s have what two characteristics?
Greater resolution & sharpness
Why is the back side of the cassette lead lined?
To prevent back scatter radiation from reaching the IP; back scatter can cause image arteficats
In the CR Imaging Chain
1. The IP phosphor is scanned with a _____.
2. This releases ______ in the form of _______.
3. Special electronics convert the light into an ___________ to produce the _________ on the computer screen.
- laser
- stored energy; visible light
- electronic light; digital image
In the CR Imaging Chain, the special electronics include the photomultiplier tube. What does this tube do?
hint: light signals
Converts weak visible light signals into electrical signals
Which component in the CR imaging chain enables the IP to be reused after exposure? How is this done?
Erasure unit. It is exposed to an intense white light to erase the image.
T or F. IP will absorb more low-energy scatter compared to old film/screen cassettes.
True
T or F. IP is sensitive to background radiation.
True
What can digital detectors be classified as?
Direct or Indirect
In terms of converting x-rays, differentiate between Indirect & Direct flat panels.
Indirect flat panels convert x-rays to light photons that are then measured by CCD/CMOS or Si photodiode and TFT array.
Direct flat panels convert x-rays directly to electrons that are measured by a TFT.
T or F. Indirect flat panels achieve higher spatial resolution by undergoing thorough steps.
False. Direct flat panels achieve higher spatial resolution by skipping the visible light step that can blur the images as the light spreads.
What do Thin Film Transistors do?
hint: capacitor
Amplify electrical signals and store these in form of an electrical charge (on a capacitor).
During direct conversion, detectors convert x-rays directly to __________ through a(n) ________ ________ detector.
When the x-rays interact with aSe what is the resulting production?
Detectors convert the x-rays directly to an electrical signal through an Amorphous Selenium detector.
X-rays interact with aSe to produce electrons and hole pairs.
What is indirect conversion?
Indirect conversion is a two-step process in which the x-ray energy is converted into light and then converted into an electric signal.
What device does indirect conversion use to convert the x-ray energy into light?
A scintillator
What is a scintillator? What is it made of?
A scintillator is a device that glows when hit by high energy x-ray photons. It is made of cesium iodide.
In indirect conversion, what is the photodiode made of? What does the photodiode do?
The photodiode made of Amorphous Silicon converts the light into an electric signal.
What does CCD and CMOS stand for?
CCD - Charged-Coupled Device
CMOS - Complementary Metal Oxide Semiconductor
What is the oldest type of indirect conversion detector used to acquire a digital image?
CCD
Which provides a faster read out CCD or TFT arrays?
CCD
T or F. Fiber optics or lenses used to spread light in CCD/CMOS detectors.
F. Fiber optics or lenses are used to funnel light to smaller size CCD or CMOS chip.
