Contrast, Spatial & Temporal Res - Ch 12

Question 1

what is contrast resolution? what is good and bad resolution here?

Answer 1

visualizing a variety of gray shades in an image; few gray shades = poor res many gray shades = good res

Question 2

what is detail spatial resolution? what affects this? what is good resolution here?

Answer 2

visualizing detail in an image; affected by axial res, lateral res, line density (closeness of scan lines), monitor, as well as other factors; fine detail

Question 3

what is real-time imaging?

Answer 3

a series of frames displayed in rapid sequence to give the impression of constant motion, a movie.

Question 4

what is temporal resolution? aka? what would make this resolution better?

Answer 4

the ability to accurately locate moving structures at any particular instant in time; resolution pertaining to time; high frame rate = better temp res.

Question 5

what is temporal resolution determined by? units? typical value?

Answer 5

depends only upon frame rate, more images per sec improves temporal resolution; frame rate = Hz; 20 - 100 Hz

Question 6

by what 2 factors is temporal resolution determined?

Answer 6

aka frame rate is determined by two settings 1. imaging depth and/or
2. # of pulse per image

Question 7

frame rate is limited by what two factors?

Answer 7

1. the speed of sound in medium and/or 2. imaging depth

Question 8

why is speed a fundamental limitation of temporal resolution?

Answer 8

sonographer can adjust depth, but the speed of sound in a medium cannot be changed.

Question 9

what are 4 settings under sonographer control that affect temporal resolution? what do 3 of these factors have in common?

Answer 9

1. max imaging depth
2. # of pulses per scan line (multi-focus system)
3. sector size
4. line density (lines per degree of sector). 2-4 change the number of pulses in each single image

Question 10

under what 3 settings does temporal resolution improve?

Answer 10

1. when image is shallower or made of fewer pulses
2. less time to create an image
3. more frames created each sec

Question 11

under what 3 settings is temporal resolution degraded?

Answer 11

1. when image is deeper of made of more pulses
2. more time to create an image
3. frame rate decreases

Question 12

with regard to max imaging depth, what will create a frame in less time? why is this?

Answer 12

shallow depth of view makes a frame faster and improves temporal resolution; imaging to a shallow depth requires less listening, greater depth = longer listening

Question 13

what happens to frame rate if the imaging depth of view is doubled?

Answer 13

frame rate will be halved

Question 14

what is the frame rate and temporal resolution quality with shallow imaging? deep imaging?

Answer 14

higher frame rate, better temporal resolution; lower frame rate, worse temporal resolution

Question 15

with regard to pulses per scan line, what will create a frame with fewer pulses?

Answer 15

single focus systems use fewer pulses which = improved temporal resolution

Question 16

how many pulses are used in a single focus system?

Answer 16

1 pulse per scan line

Question 17

multi-focus systems use multiple pulses per scan line, what does this do? what is an example of this type of system?

Answer 17

this lowers frame rate and reduces temporal resolution. annular phased arrays

Question 18

single focus = fewer pulses how does the affect the other factors? what about multi-focus?

Answer 18

higher frame rate, better temp resolution; lower frame rate, worse temporal resolution (takes longer)

Question 19

improving image quality often degrades what?

Answer 19

temporal resolution (lowers the frame rate)

Question 20

how many pulses does a multi-focus system send?

Answer 20

multiple pulses down each scan line, one for each focal point

Question 21

how do multi-focus systems affect temporal resolution? why is that?

Answer 21

degrades temporal resolution; reduces frame rate and improves lateral resolution

Question 22

with regard to sector size, what will create a frame with fewer pulses? what does this do?

Answer 22

smaller sector angle creates images with fewer pulses, improving temporal resolution

Question 23

with regard to line density, what will create a frame with fewer pulses? what does this do?

Answer 23

low line density images use fewer pulses and have better temporal resolution. this also degrades spatial resolution.

Question 24

what is line density in a sector image?

Answer 24

the number of scan lines per degree of sector.

Question 25

what is line density in a rectangular image?

Answer 25

the number of scan lines per cm

Question 26

when line density is low _______ __________ is high

Answer 26

temp resolution

Question 27

in short, what improves temporal resolution?

Answer 27

factors that shorten the time required to make each frame increase frame rate and improve temp resolution

Question 28

summarize what reduces temporal resolution

Answer 28

factors that lengthen the time required to make a frame will reduce frame rate and reduce temp resolution

Question 29

how is image quality affected by temporal resolution?

Answer 29

as temp res improves, image quality degrades

Question 30

what is a problem that can occur with low frame rates (poor temp res)?

Answer 30

short duration physiologic events may be missed, these can occur bw frames

Question 31

what is Tf?

Answer 31

time required to make a frame

Question 32

what relationship does Tf have with frame rate (FR)? what does this mean?

Answer 32

they’re reciprocals. when a frame is made quickly, many frames are created per sec. when frame is made slowly = few frames per sec.

Question 33

what is the equation for Tf and FR? typical values?

Answer 33

Tf x FR=1; FR = 20 - 100 Hz Tf = .01 to .05 secs

Question 34

when one frame is created in 1/10 of a sec, what is the frame rate?

Answer 34

10 Hz bc 10/sec