Chapter 15 Flashcards
Displays and Image Storage
____ images are composed of only two shades, black and white.
Bistable
____ images are composed of black, white and many shades of grey in between.
Grayscale
____ the amount of black, white an grey in an image.
Contrast
____ the lightness or darkness of an image.
Brightness
Define the role of the scan converter.
Stores information first and later displays it. It changes the format of the data from spoke format into video format.
Old technology used ____ scan converters.
Analog
New technology uses ____ scan converters
Digital
____ numbers are “real world” numbers (1, 2, 3, 4, 5…). They have an unlimited and continuous range of values.
Analog
____ numbers are associated with computer devices. They use discrete values. Finite number of choices.
Digital
What is the analog scan converter?
The first form of scan converter - converts info from analog to digital.
Analog scan converters have ____ spatial resolution.
Excellent
Advantages of a digital scan converter:
- Uniformity – consistent greyscale quality of image
- Stability – image does not fade or drift
- Durability – image is not affected by age or heavy use
- Speed – nearly-instant processing
- Accuracy – error-free
Two important parts of a digital scan converter are:
Pixel and bit
The ____ is the smallest building block of a digital picture
Pixel
Each ____ is a single shade of grey.
Pixel
Pixel ____ is the number of pixels per inch
Density
Spatial resolution improves with ____ pixel density and decreased pixel ____.
High; Size
A ____ is the smallest amount of computer memory
Bit
A bit is bistable, it has a value of either ____ or ____.
0 or 1
A ____ ____ is a group of bits. Made up of 1’s and 0’s.
Binary number
A byte is a group of ____ bits of computer memory.
8
A ____ is two bytes (16 bits)
Word
To determine the number of ____ ____, multiply the number 2 by itself the same number of times as there are bits.
Gray shades
How many shades of gray are displayed with 5 bits of memory?
2^5 = 2 x 2 x 2 x 2 x 2 = 32 shades of gray
What is another name for digital number?
Binary number
Any processing before storage is called ____.
Preprocessing
Examples of preprocessing are:
TGC’s, compression (2D), write magnification, persistence, spatial compounding, edge enhancement, and fill-in interpolation.
Any processing after storage is called ____.
Postprocessing
Preprocessing ____ be reversed once performed; postprocessing ____ be reversed
Cannot; Can
Examples of postprocessing are:
Changes to a still image, black/white inversion, read magnification, 3-D rendering.
____ (a.k.a. zoom) enlarges a portion of the image to fill the entire screen.
Magnification
There are two different forms of magnification used in ultrasound systems:
- Read magnification
- Write magnification
____ magnification occurs after image storage in the scan converter. This is postprocessing.
Read
____ magnification occurs during data acquisition before image storage in the scan converter. This is preprocessing.
Write
List 6 points that describe read magnification.
- Uses old data
- Postprocessing
- Larger pixel size
- Same # of pixels as the original ROI
- Unchanged spatial resolution
- Unchanged temporal
List 6 points that describe write magnification.
- Acquires new data
- Preprocessing
- Identical pixel size
- More pixels than in the original ROI
- Improved spatial resolution
- May improve temporalresolution resolution (fewer scan lines)
____ ____ creates very long sound pulses which contain a wide range of frequencies.
Coded excitation
Where does coded excitation occur?
In the pulser
During ____ ____, ultrasound information is obtained from different angles and combined to form single image.
Spatial compounding
Spatial compounding will ____ frame rate and temporal resolutions.
Reduce
____ ____ is an advanced technique used to reduce speckle artifact and noise by dividing the reflected signal into “sub-bands” of limited frequencies.
Frequency compounding
Edge enhancement make the picture look ____.
Sharper
Another term for temporal compounding is ____ or ____ ____.
Persistence or temporal averaging.
____ ____ is a technique which uses a number of previous frames that are superimposed on the current frame.
Temporal compounding
Temporal compounding produces a ____ image with ____ noise, higher signal to noise ratio, and improved image quality
Smoother; Reduced
What is fill-in interpolation?
A sophisticated computer program that predicts the gray scale levels of missing data by using the gray scale levels of neighboring pixels to predict the missing info.
Fill-in interpolation is a ____ function.
Preprocessing
What does PACS stand for?
Picture Archiving and Communications System
____ describes labs in which images and other medical info are digitized and stored on a large computer network.
PACS
What does DICOM stand for?
Digital Imaging and Computers in Medicine
____ is a set of rules or protocols that allows and imaging system to share information on a network.
DICOM
____ ____ are charts from pen writers.
Paper media
____ ____ are computer discs, computer memory, magnetic tape, video tape.
Magnetic media
____ ____ ____ are photographs, flat films, multiformat camera film.
Chemically mediated photographs
____ ____ are laser discs, compact discs.
Optical media
____ ____ are picture archiving and communications system. Images and reports are digitized and stored on a large computer network.
PACS systems
____-____ ____ is a combination of magnetic and laser (optical) technology. Often used to store/archive PACS studies.
Magneto-optical storage
