Unit 1 Exam Review

Question 1

Another name for image on the screen

Answer 1

Frame

Question 2

What technique is used for U/S?

Answer 2

Pulse-Echo Technique

Question 3

What is a B-scan?

Answer 3

Gray-scale scan that scans in an anatomic cross-section.

Question 4

How is Doppler produced?

Answer 4

Echoes from moving objects have different frequencies.

Question 5

What frequencies can humans hear?

Answer 5

20kHz or 20,000Hz

Question 6

What is the propagation speed of sound in soft tissue?

Answer 6

1.54 mm/us

Question 7

What affects propagation speed in a medium?

Answer 7

Stiffness and less by the density of the medium.

Question 8

What can determine period and frequency?

Answer 8

The source only.

Question 9

Which results in better resolution: pulsed U/S or continuous U/S?

Answer 9

Pulse U/S

Question 10

How are PRP and Depth of View (DOV) related?

Answer 10

Directly; PRP inc./DOV inc.

Question 11

What is the typical DF for sonography?

Answer 11

0.1 - 1.0%

Question 12

What is the typical DF for Doppler?

Answer 12

0.5 - 5.0%

Question 13

How are DF and DOV related?

Answer 13

Inversely

Question 14

What kind of bandwidth do U/S pulses have?

Answer 14

Broadband- short pulses & low Q-factor

Question 15

What kind of events have narrow bandwidth?

Answer 15

Non-imaging transducers (therapeutic probes) with continuous wave or long duration pulses.

Question 16

Amplitude is always squared. What does this mean?

Answer 16

If amp is doubled, it’s inc. by a factor of 4.

Question 17

What’s true about U/S beam intensity?

Answer 17

Intensity varies at different depths and at different side to side locations.

Question 18

What button allows you to compensate for attenuation?

Answer 18

TGC (Time gain compensation)

Question 19

Does the propagation speed change after leaving the transducer?

Answer 19

NO

Question 20

What happens to attenuation as Frequency increases?

Answer 20

Attenuation dB increase: 0.5dB of atten/cm for each MHz of freq.

Question 21

Range Equation (mm)=

Answer 21

1/2 x [prop speed (mm/us) x pulse round trip travel time (us)]

Question 22

What does positive and negative dB mean?

Answer 22

positive the signal strengthens / negative means the signal is less than original.

Question 23

Relate positive decibels and intensity:

Answer 23

3 dB (Double); 10 dB (ten times)

Question 24

Relate negative decibels and intensity:

Answer 24

-3 dB (halved); -10 dB (1/10)

Question 25

What happens to PD if the number of cycles in a pulse is reduced?

Answer 25

PD is decreased.

Question 26

What happens to intensity if beam area decreases (focusing)?

Answer 26

Intensity increases.

Question 27

Compare attenuation in the lung and soft tissue.

Answer 27

Atten. high in lung than S.T. because of air.

Question 28

Compare attenuation in bone and soft tissue.

Answer 28

Atten. higher in bone than S.T.

Question 29

What happens to attenuation with longer distances?

Answer 29

It increases, limiting imaging depth.

Question 30

Relate frequency and attenuation.

Answer 30

Freq. inc. / atten. inc. (directly)

Question 31

What has pulses with short duration and length (wide bandwidth)?

Answer 31

Imaging transducers

Question 32

How are impedance, density, and prop speed of the medium related?

Answer 32

Directly proportional

Question 33

What if impedance of 2 media is equal?

Answer 33

No reflection.

Question 34

What affect does the difference in impedance have on IRC and echo intensity?

Answer 34

If the difference increases, the IRC and echo intensity increases.

Question 35

Why do we use coupling medium (gel)?

Answer 35

The large difference in impedance (air/tissue) = nearly total reflection.

Question 36

How does density affect prop speed?

Answer 36

Density inc. / Prop speed dec.

Question 37

What media has highest prop speed?

Answer 37

Bone then liquid then air (gases are lowest).

Question 38

What part of PRP changes with altered DOV?

Answer 38

Only the listening time, not the pulse itself!