14 Displays Flashcards
What are characteristics of a bistable display?
2 choices - black or white On or off High contrast Narrow dynamic range Poor contrast resolution
What are characteristics of a gray scale display?
Many shades of gray Multiple levels Low contrast Wide dynamic range Good contrast resolution
What are the controls of the display?
Brightness - brilliance of image
Contrast - range of brilliancies that are displayed
What is analog?
Real world - variable attains a continuum of values
What is digital?
Computer world - variable attains only discrete values
What are scan converters?
Changes data format from penetrations (spokes) to horizontal lines of a display
What is a pixel?
Smallest element of a digital picture
What is pixel density?
Pixels per inch - more pixels = more detail, spatial or detail resolution
What determines spatial resolution on a digital display?
Pixel density
What is spatial resolution related to?
Number of lines per frame
What is a binary digit (bit)?
Smallest amount of digital storage
What is better with more bits per pixel?
Contrast resolution
What is a binary number?
Group of bits
What is a byte?
Group of 8 bits
What is a word?
2 bytes (16 bits)
How do you calculate the number of gray shades that a collection of bits can represent?
- Find out how many bits are assigned to each pixel
- Multiply the # 2 by itself the same # of times as there are bits
2^n, n = # of bits
What is image preprocessing?
Manipulating the data before storage in the scan converter and cannot be reversed TGC Log compression Write magnification Fill-in interpolation Persistence (frame averaging) Spatial compounding
What is log compression?
Ability of humans to see gray scale differences in anatomic structures - lowers high level echoes and boosts low level echoes
What is image postprocessing?
Manipulating data after it has been stored in the scan converter memory but prior to display
Read magnification
3-D rendering
What type of images is postprocessing used?
Frozen images
What is an analog-to-digital converter?
Analog signal (electrical signals by the PZT) converted into digital form for input into the scan converter
What is digital-to-analog conversion?
Conversion of info in scan converter to analog form to display
Describe flow of information through an ultrasound system.
Master Synchronizer > Pulser > Beam Former (beam steering) > Transducer > Receiver (preprocessing) > Scan Converter (A to D > Digital data > D to A) > Display > Image Archive