TFT, CCD, CMOS review questions
Manfufacturers make efforts to maintain a standard of less than _____ to ______ percent defective pixels.
0.1%: 0.2%
What are the 3 layer of flat panel detectors?
1st-x-ray converter 2nd TFT array 3rd glass substrate
A _____ degree drop can reduce dark noise by a factor of ________.
40: 100
Direct conversion uses _____ to turn x-rays into electron
Amorphous selenium
Which material is considered to be a photo conductor?
Amorphous selenium
Which is easier to repair a TFT or CCD?
CCD
what detector uses the bucket brigade?
CCD
Which is more susceptible to noise, a CCD or CMOS?
CMOS
Which type of system uses very little power?
CMOS
Which uses p-type and n-type transistors?
CMOS
Which material is the most common in indirect conversion
Cesium Iodide
What does CCD stand for
Charge-Coupled Device
What does CMOS stand for
Complementary metal oxide semiconductor
The choice of x-ray absorption material determines whether the detector is a direct or indirect _______ system.
Conversion
What does DQE stand for
Detective Quantum efficiency
What applications uses the CCD
Digital flouro stereotactic breast biopsy digital mammography general radiography (full body scanner)
____ _______ is the ratio of the sensitive are of the TFT array to the entire detector area.
Fill Factor
A process known as gain calibration of _______ _________ corrects flaws in the detector, such as dead pixels.
Flat fielding
What material is used in indirect conversion
Gadolinium oxysulfide and cesium iodide
The term image ______ TFT's is similar to double exposure with CR or film screen.
Lag
The _____ and _______ __________ components of a CCD have an effect on spatial resolution and noise.
Lens; fiber optic
A _____ absorbs x-rays and produces electrical charges
Photoconductor
What advantages of CCD over TFT?
Simple and Modular Easy to repair & replace Cheaper
Which detector can have both direct or indirect conversion
TFT
What does TFT stand for
Thin film transistor flat panel
In direct conversion the photons interact with _________
amorphous selenium
A system that uses scintillators that convert x-rays to light, light to electric charge, and store the charge in capacitors is known as a _________ _______ ________.
charge couple device
A system where each pixel or DEL has its own transistor, amplifier, digitization circuit, etc. is called a _________ __________ _________ _____________.
complimentary metal oxide semiconductor
Noise that occurs when there is a rise in temperature of the CCD chip is called ________ noise.
dark
The CCD and CMOS receptors work basically the same up until the read out of the chip for ___________.
digitization
With a CCD, the electrons are moved by ________ down the _______ unitl the readout row is reached. This may be referred to as the ________ __________.
rows; column; bucket brigade
What are the most common noise associated with CCD?
statistical noise Dark or current noise Amplification noise
