Ultrasound Physics

Question 1

Low FPS and Low Q gives what?

Answer 1

Better Axial resolution

Question 2

Time for a soundwave to return from reflector?1 cm deep?

Answer 2

13 microseconds

Question 3

What structure is unlikely to reflect sound waves?

Answer 3

Urinary bladder contents

Question 4

If intensity is attenuated -30 db, what is the percent intensity now?

Answer 4

relative intensity = 10log(I2/I1)

• 30 = 10 log (I2/I1)
• 3 = log (I2/I1)

10^-3 = I2/I1

I2 = 0.001 I1

Which is 0.1%

Question 5

For US safety you should follow?

Answer 5

ALARA (As Low As Reasonably Possible)

Question 6

lateral resolution is improved

Answer 6

On one of the answers as I recall?

Question 7

What type of flow is normal in vessels?

Answer 7

Blunt.

Question 8

Is laminar flow normal in most vessels?

Answer 8

No

Question 9

What is duplex imaging?

Answer 9

combination of 2d B mode and pulsed doppler acquisition

Question 10

What does high Q mean?

Answer 10

Not sure, but I think answer is increased bandwidth?

Question 11

Phased array US is used for?

Answer 11

Cranial US

Question 12

Matching layer refers to?

Answer 12

The weird answer with the acoustic step down. Talks about intratissue blah blah but mentions acoustic step down.

Question 13

Damping results in?

Answer 13

better axial resolution?
Also higher bandwidth
shorter pulses
more frequencies
lower quality factor
lower intensity

Question 14

Is “change operating frequency an answer”?

Answer 14

Yes, to something.

Question 15

speed of sound is highest in?

Answer 15

Bone

Question 16

Sound speed depends on?

Answer 16

Stiffness and density

Question 17

Are there bioeffects at 100W/whatever?

Answer 17

Yes. He is being tricky dick with units. Slide says no bio effects under 100 milliwatts/whatever

Question 18

What is Q factor = to?

Answer 18

Q factor = operating frequency/bandwidth

Question 19

MI refers to?

Answer 19

Cavitation

Question 20

Highest doppler shift vessel will be?

Answer 20

Aorta

Question 21

Harmonic echoes detected at 3mhz?

Answer 21

6 mhz

Question 22

When fluid moving towards transducer it is colored?

Answer 22

Red

Question 23

To avoid aliasing do what?

Answer 23

Increase PRF to adjust velocity scale to wider range

Question 24

Harmonic imaging improves what resolution?

Answer 24

Lateral and elevational

Question 25

What is power doppler good for?

Answer 25

Sensitive to slow flow

Question 26

Focusing improves what?

Answer 26

Axial resolution

Question 27

Multiple focal zone US takes longer, why?

Answer 27

Multiple pulses used to generate one line

Question 28

How do you adjust for depth of field?

Answer 28

With time gain compensation

Question 29

Does damping increase bandwidth?

Answer 29

yes

Question 30

1/2 value layer is the amount need to attenuate beam by what?

Answer 30

3 db (50% reduction)

Question 31

What does spatial pulse length determine?

Answer 31

Axial resolution

Question 32

What does spatial pulse length determine?

Answer 32

Axial resolution

Question 33

Cystic structures demonstrate what artifact?

Answer 33

Posterior acoustic enhancement

Question 34

The duodenum he shows has what artifact?

Answer 34

reverberation

Question 35

Answer to question about which angle and frequency give highest doppler shift?

Answer 35

10 mhz and parallel

Question 36

Is frequency likely to change between tissues?

Answer 36

No, is determined by the sound source

where as speed and wavelength are influenced by the medium

Question 37

Quality factor = ?

Answer 37

Operating frequency/bandwidth

Question 38

Power doppler relies on _______ _______ rather than doppler frequency signal?

Answer 38

return doppler signal strength

Question 39

Disadvantage of harmonic imaging?

Answer 39

Degrades axial resolution

Question 40

Tissue heating is of greates concern in what modality of US?

Answer 40

Spectral Doppler