Lesson 7 Flashcards
Image memory
Is a continuous process as you scan, where the image frames are stored here as information
What is another term for image memeory?
Digital memory
Freeze frame
Holding and displaying one frame out of the sequence
- shows the last frame
Cine loop
Storing of the last several frames before freezing
How many frames can the cine loop hold?
100-130
What is each frame made up of?
Matrix’s of tiny blocks called pixels
What does it mean if you have more pixels?
You will have better resolution
- the more you have the better
What does each pixel contain?
Information about the brightness (intensity/amplitude) at a particular anatomical position
What are pixels known as?
Memory elements
Bits
Numbers that are stored in the memory elements (pixels) according to the intensity of the echoes received from the corresponding anatomical positions
What can 1 matrix only show?
2 shades of gray
- black or white
What is it called when you are only working with 2 shades of gray?
Bistable
What happens when you have more bits?
You get more shades of gray
What can each pixel have?
Multiple bits
What are multiple bits known as?
Binary digits
What does each column in our binary table represent?
A bit
What do the numbers in your table create?
The number of the different shades of gray
Why do computer memories and processors use binary numbers to carry out their functions?
Because they contain electronic components (switches) that operate in only 2 states
- either 0 or 1
What is detailed resolution usually limited by? (2)
- SPL
- Beam width
- rather than pixel density and the memory
How many different numbers can you create with 2 bits?
2^2 = 4
- different shades of gray
How many different numbers can you create with 3 bits?
2^3 = 8
- different shades of gray
How many different numbers can you create with 8 bits?
2^8 = 256
- different shades of gray
What do the majority of US machines use for bits?
6-8 bits
How many shades of gray can humans see?
100
What does more bits/pixels allow?
More shades of gray and better resolution
What is the number binary system?
It is an alternative to the decimal (arabic) number system
- they simplify the design of computers and related technologies
Contrast resolution
Begin to be able to separate 2 different echoes as 2 different shades of gray
What is the formula for contrast resolution?
CR = dB/# of shades
- CR = contrast resolution
- dB = dynamic range (in decibles)
- # of shades = bits per pixel
How do you convert bits to shades?
2^x
Do we have better or worse contrast resolution with bits/pixels?
Better
- we want the smallest number possible for contrast resolution
Is dynamic change operator dependent?
Yes
Is bits and pixels operator dependent?
No
- manufacture dependent
What does it mean if you have more shades of gray? (2)
- More contrast
2. Grainier images
What does it mean if you have less shades of gray? (2)
- Less contrast
2. Smoother images
How many bits are in 1 byte?
8
How many bits and bytes are in 1 kilobyte? (2)
- Bits = 8192
2. Bytes = 1024
Digital-to-analog converter
Once a frame is preprocessed, stored in the image memory, pulled from the image memory and post processed, it is ready to be sent to the display
- digital memories (numbers) –> voltage for display
What does digital-to-analog converter require?
Analog signals
What does voltage for display determine?
The echo brightness that is going to be displayed
