Displays - Ch 15

Question 1

what are 5 characteristics of bistable display?

Answer 1

1. 2 choices only - black or white
2. on or off
3. high contrast *
4. narrow dynamic range *
5. poor contrast resolution

Question 2

what are 5 characteristics of gray scale display?

Answer 2

1. many shades of gray
2. multiples levels
3. low contrast
4. wide dynamic range
5. good contrast resolution

Question 3

what does the brightness control do?

Answer 3

related to the brilliance of the image

Question 4

what does the contrast control do? what kind of images are high contrast?

Answer 4

determines the range of brilliances that are displayed. Are the whites white and blacks black? bistable images

Question 5

what is analog display? examples?

Answer 5

Real world: a variable attains a continuum of values.
ex: actual weight of an individual or true length of a piece of string

Question 6

what is digital display? example?

Answer 6

computer world: a variable attains only discrete values.
ex: measuring weight on a digital scale

Question 7

what do scan converters do? why are these important?

Answer 7

changes the data format from penetrations (spokes) to horizontal lines of a display. made gray scale displays possible.

Question 8

how can an image be manipulated using a scan converter? example?

Answer 8

can be manipulated in bw the “storing” and “displaying” of the data.
Ex: black on white image can be inverted into a white on black image

Question 9

what is a digital scan converter?

Answer 9

a microprocessor that digitizes images. this converts the image into a string of zeroes and ones which are stored in memory. the numbers (digital image data) can be processed and then re-converted for display as an image.

Question 10

what is a pixel?

Answer 10

the smallest element of a digital picture. If we divide pic into a grid each square is a pixel.

Question 11

what is pixel density? what does it to?

Answer 11

pixels per inch; the more pixels per inch the more detail in the image, spatial or detail resolution.

Question 12

what is spatial resolution on a digital display determined by?

Answer 12

the pixel density

Question 13

what does spatial resolution pertain to?

Answer 13

related to the number of lines per frame

Question 14

what is a bit? how would you describe it?

Answer 14

Binary digit - the smallest amount of digital storage; Bistable = having a value of either zero or one.

Question 15

how are bits used? what does this mean?

Answer 15

a group of bits are assigned to each pixel to store the gray scale color assigned to that pixel. the more bits per pixel, the more shades of gray = better contrast resolution.

Question 16

what is a binary number? how do you know it’s considered binary?

Answer 16

a group of bits, a series of zeroes and ones; digital (computer-based) means binary.

Question 17

what is a byte? a word?

Answer 17

a group of 8 bits = byte; 2 bytes (16 bits) is a word

Question 18

binary numbers are based on _____. decimal numbers are based on _______.

Answer 18

2; 10

Question 19

digital means __________ not _______.

Answer 19

binary; decimal

Question 20

what is the formula for determining the number of gray shades displayed?

Answer 20

2^n, n being number of bits

Question 21

how many bits are needed to represent 10 shades of gray?

Answer 21

4 bits; bc 4 bits = 16 shades and 3 bits = 8. therefore, at least 4 bits are needed to display 10 shades of gray.

Question 22

in image processing, what is preprocessing? what is important about this?

Answer 22

manipulating the data before storage in the scan converter. once preprocessing occurs, the data is altered forever and cannot be reversed.

Question 23

what 6 things occur during preprocessing?

Answer 23

1. TGC
2. dynamic range
3. write magnification
4. fill-in interpolation
5. persistence (frame averaging)
6. spatial compounding

Question 24

what is dynamic range/ log compression? what does it do? can this be controlled by the sonographer?

Answer 24

related to ability of humans to see the gray scale difference in anatomic structures; log compression lowers the high echoes and boosts the low lvl echoes. the image data’s dynamic range is reduced. controlled by sonographer.

Question 25

what is postprocessing? what does it do? what is it performed on?

Answer 25

manipulating the data after it has been stored in the scan converter memory but prior to display; Increases versatility of the display process and can be undone; postprocessing is performed on frozen images.

Question 26

what two things are done during postprocessing?

Answer 26

read magnification and 3-D rendering

Question 27

processing is pre or post based on what?

Answer 27

on whether data is stored in the scan converter. if we have the info in image form, then it is post processing

Question 28

analog= ______ _________ digital =___________

Answer 28

real world; computers/digital

Question 29

how does analog to digital conversion work? what is used to do this?

Answer 29

electrical signals created by the PZT are analog, but a digital scan converter can only process computer info. Therefore, analog signal must be converted into digital form for input into the scan converter; digital-to-analog converter