Digital Imaging Powerpoint Notes

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Digital Radiography (DR) is characterized by
The use of reusable receptors
Computed radiography is also referred to as
PSP technology
Examples of computer devices that store memory are
floppy disk
diskette
optical disk
Computers operate using ___ ____ language
Binary Machine
Each binary number is called a
Bit
An eight bit word is called a
Byte
When the main power to the computer is turned off, ___ erased
RAM
When the main power to the computer is turned off,___ is maintained.
ROM
Computerized digital images consist of a __ of picture elements, each with a video display value or gray shade.
Matrix
When matrix size is increased and pixel size goes down
Spatial resolution decreases
Contrast increases
If the digital FOV is 1280 and the display matrix is 128, the pixel size would be
10
Each pixel in a digital display matrix is located according to its what?
Electronic address
The relationship between digital image resolution is ____ and ___
Direct with matrix size
indirect with pixel size
Resolution is controlled by
pixel size
Which of the choices would produce the highest spatial frequency and contrast? Why?
Large intestine, liver, Pancreas, or 5mm Gallstone
Gallstone, its the smallest structure (small structures produce high frequency and high contrast)
Which image processing information is related to each other?
point processing
local processing
geometric processing
Local area processing includes?
It relies on the application of kernels to pixels.
Kernels are ultimately applied to the entire pixel data set.
Spatial filtering is an example of local area processing.
What does the deviation index (DI) do?
COmpares entrance dose to the detector to a reference industry standard target dose
When the quality of a digital detector is inspected for purchase, the preferred detector for purchase would have a..
DQU of 68% and MTF of .80%
An S value of 200 represents
an exposure to the IP of 1 mR
When changing exposure so the mAs doubles using computed radiography (CR), the radiographer should expect
An EI number increase
An S number decrease
The response to radiation exposure with a digital receptor is ___
linear
Noise on a digital image is the summation of inherent electron system noise and quantum mottle noise. Of these two, the radiographer can improve the noise on an image by
Increasing the exposure technique
Increasing the mAs
Grossly overexposed digital images will demonstrate
a loss of contrast
An x-ray exposure taken at 80 kVp has an average energy of __ keV
35
CR systems acquire clinical information by
laser scanning a PSP plate
Of the many types of digital image procedures performed in a contemporary medical imaging department, the largest file sizes are typically generated by
MRI
The size of a digital file size is determined by the
Bit depth
Pixel size
Matrix
The window level controls
image density
The window width controls
image contrast
In digital image processing, an overexposed or underexposed image can be modified to achieve an acceptable lookthrough a histogram analysis. This is the result of the digital processing technique of
Histogram stretching
Histogram modification
Rescaling
The window width changes are also called
Gray Scale expansion
Enhancing visibility of detail
Gray scale compression
In digital image technology, once the image data is sent to PACS..
the data is fixed and not able to be reprocessed
When using a Fuji CR system in the fixed mode of operation
The system will not correct for exposure inadequacies and adjust for density problems
Your exposure techniques must be accurate, similar to film/screen technology
In digital image processing, the digital data set is arranged into a histograph distribution in order to determine the
Exposure index
Values of interest (VOI)
The purpose of a LUT is to
Apply a predetermined scale of contrast to the digital data set
If a radiographer applied an extremity LUT to a low contrast area like an abdomen radiograph data set, the image would demonstrate
high contrast
FActors associated with Moire effect are
It results from a conflict in spatial frequencies between the grid frequency and laser scanning frequency.
It produces useless diagonal dark lines across the finished image.
It is eliminated with ultra-high grid frequencies 178-200 lpi.
A common feature between indirect and direct DR technology is
Thin Film Technology (TFT)
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