Ultrasound Physics

Front 1

Which of the following waves has the longest period?
A: 2MHz
B: 4,000 Hz
C: 6 Hz
D: 1kHz

Back 1

C: 6 Hz. the wave with a fq. of 6 Hz has the longest period. period and fq have an invers relationship

Front 2

Which of the following periods has the longest frequency?
A: 8 s
B: 80 microsecs
C: 8 Ms
D 800 ks

Back 2

B: 80 microsecs is the period that has the highest fq. period and fq have an invers relationship

Front 3

Identify all the waves that are inaudible (more than one answer may be correct)
A: 4 MHz
B: 400 kHz
C: 28 Hz
D: 2 Hz

Back 3

A B D

Front 4

Which of the following waves has the shortest period?
A: 12 kHz
B: 6,000 Hz
C: 205 Hz
D: 1 kHz

Back 4

A: 12 kHz the highest freq. has the shortest period

Front 5

Of the 4 waves whose periods are listed below, which has the lowest frequency?
A: 8 s
B: 80 microseconds
C: 8 Ms
D: 800 ks

Back 5

C: 8 Ms the wave with the longest period has the lowest freq.

Front 6

What are the units of wavelength?

Back 6

millimeters

Front 7

What are the units of frequency?

Back 7

Hz

Front 8

What are the units of intensity

Back 8

W/cm^2

Front 9

What are the units of propagation speed?

Back 9

meters/second

Front 10

What are the units of period?

Back 10

second

Front 11

What are the units of power?

Back 11

watts

Front 12

Does the medium or the sound source determine the parimeters for wavelength?

Back 12

both

Front 13

Does the medium or the sound source determine the parimeters for frequency?

Back 13

sound source

Front 14

Does the medium or the sound source determine the parimeters for intensity (initial)?

Back 14

sound source

Front 15

Does the medium or the sound source determine the parimeters for propagation speed?

Back 15

medium

Front 16

Does the medium or the sound source determine the parimeters for period?

Back 16

sound source

Front 17

Does the medium or the sound source determine the parimeters for power (initial)?

Back 17

sound source

Front 18

Does the medium or the sound source determine the parimeters for amplitude?

Back 18

sound source

Front 19

Using a particular ultrasound system and transducer can wavelength be changed by the operator?

Back 19

no

Front 20

Using a particular ultrasound system and transducer can frequency be changed by the operator?

Back 20

no

Front 21

Using a particular ultrasound system and transducer can intensity be changed by the operator?

Back 21

yes

Front 22

Using a particular ultrasound system and transducer can propagation speed be changed by the operator?

Back 22

no

Front 23

Using a particular ultrasound system and transducer can period be changed by the operator?

Back 23

no

Front 24

Using a particular ultrasound system and transducer can power be changed by the operator?

Back 24

yes

Front 25

Using a particular ultrasound system and transducer can amplitude (inital) be changed by the operator?

Back 25

yes

Front 26

If the power of a beam is 1 watt and the area is 5 cm^2 what is the beam's intensity?
A; 5 W/cm^2
B; 1 W/cm^2
C; 0.2 W/cm^2
D; 1 watt

Back 26

C; 0.2 W/cm^2 Intensity has units of W/cm^2. We must find out how many watts and divide them by the number of cm^2. 1 watt. area is 5cm^2. Thus the intensity is 1/5 or 2 W/cm^2

Front 27

if intensity remains the same while the power is doubled, what happened to the beam area?
A; quadrupled
B; doubled
C; halved
D; unchanged

Back 27

B; doubled If intensity remains unchanged, then whatever happens to power must also happen to area. In this case, power has doubled, therefore area must have doubled as well

Front 28

A sound beam travels a total of 10 cm in 2 seconds. What is the speed of sound?
A; 10 cm/sec
B; 2 cm/sec
C; 5 cm/sec
D; 0.2 cm/sec

Back 28

C; 10 cm/2 sec= 5 cm/sec
speed=distance/time

Front 29

What is the wavelength of 3 Mhz sound in soft tissue?
A; 0.51 m
B; 0.51 km
C; ; 0.51 mm
D; ; 0.51nm
E; 0.51 micrometers

Back 29

C; 0.51 mm. In soft tissue the wavelength is 1.54 mm divided by frequency in MHz

Front 30

What is the wavelength of a wave with an unknown frequency in soft tissue?
A; 0.51 microseconds
B; 0.51 m/s
C; 0.51 pascals
D; 0.51watts
E; 0.51 mm

Back 30

E is the only answer with units of distance

Front 31

which of the following are considered acoustic variables? (more than one answer may apply)
A; frequency
B; density
C; particle motion
D; temparture
E; period
F; pressure

Back 31

Density particle motion, pressure

Front 32

which of the following are considered acoustic parimeters? (more than one answer may apply)
A; frequency
B; density
C; distance
D; pressure
E; period

Back 32

frequency, period

Front 33

the effects of tissue on sound waves are called?

Back 33

acoustic propagation properties

Front 34

the effects of a medium on an ultrasound wave are called?

Back 34

acoustic propagation properties

Front 35

the effects of the medium an ultrasound are called?

Back 35

acoustic propagation properties

Front 36

how are the acoustic velocity and density related?

Back 36

inversely

Front 37

how are the elasticity and speed of sound and density related?

Back 37

inversley

Front 38

how are the acoustic velocity and comperssibilty related?

Back 38

inversley

Front 39

how are the stiffness and souind speed related?

Back 39

directly

Front 40

how are the freq and sound speed related?

Back 40

unrelated

Front 41

how are the freq and intensity related?

Back 41

unrelated

Front 42

how are the power and freq related?

Back 42

unrelated

Front 43

how are the wave length and intensity related?

Back 43

unrelated

Front 44

how are the wave length and freq related?

Back 44

inversly

Front 45

how are the freq and period related?

Back 45

inverse f=1/p or p=1/f

Front 46

which of these four values for pulse rep freq would have the longest pulse rep period?
A; 2kHz
B; 4000 hZ
C; 6 hz
D; 1 kHz

Back 46

four pulses have PRP as listed below which have the highest PRF?
A; 8 sec
B; 80 millisec
C; 5 ms
D; 400 ks

Front 47

C 6 Hz

Back 47

C; 5 ms the smaller seconds are the

Front 48

four waves have PRP as listed below, which has the lowest PRF
A; 8s
B 80 microseconds
C 8000 ns
D 800 ms

Back 48

A 8000 ns the pulse with the longest pulse duration will have the lowest freq

Front 49

2 waves can have indentical PRF even if their pulsePRP are different. True or false

Back 49

false. 2 waves can never have idnetical PRFs if their PRP are different

Front 50

2 waves can identical PRF's even if their periods are different T F?

Back 50

true period and pulse freq are unrelated

Front 51

2 waves can have idnetical PRF even if thier freq are diff.
T OR F?

Back 51

true freq and PRF are unrelated

Front 52

PRF and PRP are determined only by the imaging depth?
T F?

Back 52

true, this is a very important concept to understand

Front 53

if all other facxtors remain unchanged, what happend to the duty factor (increase, decrease, same) when the PRF increases?

Back 53

increases

Front 54

if all other factors remain unchanged. what happens to the duty factor (increas, decrease, unchange) when imaging depth increases?

Back 54

decreases

Front 55

if all other factors remain unchanged. what happens to the duty factor (increas, decrease, unchange) when PRP increases?

Back 55

decreases

Front 56

if all other factors remain unchanged. what happens to the duty factor (increase, decrease, unchange) when the sonographer uses an new transducer with a longer pulse duration?

Back 56

increases

Front 57

what is the duty factor if the pulse duration is 1 microsecond and the PRP is 1 ms?
A 100%
B 0,1
C 01
D 0.001

Back 57

D 1,000/1,000,000

Front 58

Which of the following terms does not belong with the others?
A high duty factor
B shalow imaging
C low PRF
D short PRP

Back 58

C low PRF is associated with deeper imaging the other 3 choices are all associated with shallow imaging

Front 59

which of the following terms doesn't belong with the others/
A low duty factor
B shallow imaging
C Low PRF
D long PRP

Back 59

B shallow imaging does not belong the other 3 choices are all associated with deeper imaging

Front 60

PRF is the reciprocial of what?

Back 60

PRP

Front 61

by changing the imaging depth, which of the following does the operator also cange (more than 1 may be correct)
A PRF
B duty factor
C propagaiton speed
D PRP
E amplitude
F SPL

Back 61

A PRF
B duty factor
C PRP

Front 62

the speed of a 5 MHz CW is 1.8 km/sec. the wave is then pulsed with a duty factor of 0.5 calculate the new propagation speed

Back 62

the propagtion speed for PW is the same as CW at 1.8 Km/s. It depends only upon the medium.

Front 63

what is the duty factor if the pulse duration is 1 microsecond and the PRP is 1 ms?

Back 63

the duty factor is 0.001 or 10^-3 10^-6/10^-3

Front 64

what is the duty factor if the Pulse duration is 1 ms and the PRP is 1 sec?

Back 64

0.001 or 0.1% 0.001/1=0.001

Front 65

a reduction in the intensity of a sound beam to 1/2 of its orginal value is ______dB

Back 65

-3dB

Front 66

a reduction in the intensity of a soundbeam to 1/4 of iths orginal value is _______dB?

Back 66

-6dB

Front 67

-10dB means that the intensity is reduced to _____ of its orginal value?

Back 67

1/10

Front 68

dB is mathmatical representation with a ______ scale
A logarithmic and relative
B division and relative
C longitudinal and relative
D logarithmic and ablsoute

Back 68

A

Front 69

T or F? we need on intensity to calculate dB's?

Back 69

false, we need 2 intensities

Front 70

a wave's intensity is 2 mW/cm^2. there is a change of +9dB. what is the final intensity?
A 6mW/Cm^3
B 2mW/Cm^2
C 16mW/Cm^2
D 16microW/Cm^2

Back 70

C

Front 71

every 3 dB change means that the intensity will __________

Back 71

double

Front 72

a reduction in the intensity of a sound beam to 1/2 of its orginal value is ____________dB

Back 72

-3 dB

Front 73

a reduction in the intensity of a sound beam to 1/4 of its orginal value is ____________dB

Back 73

-6 dB

Front 74

-10 dB means that the intensity is reduced to ____ or its orginal value

Back 74

1/10

Front 75

dB is a mathmatical represenation with a ______
scale
A logarithmic and relative
B division and relative
C longitudinal and relative
D logarithmic and absolute

Back 75

A

Front 76

T or F? we need only one intensity to calculate dB

Back 76

F we need 2

Front 77

A wave's intensity is 2 mW/cm^2. there is a change of +9 dB. what is the final intensity?
A 6mW/cm^3
B 2mW/cm^2
C 16mW/cm^2
D 16microW/cm^2

Back 77

C

Front 78

every 3 dB change means that the intensity will ________

Back 78

double

Front 79

every 10dB change means that the intensity will ________

Back 79

increase 10 times

Front 80

if the final intensity of a sound beam is more than the final intensity, then the gain in dB is _____ (+or -)

Back 80

+

Front 81

if the final intensity of a sound beam is less than the final intensity, then the gain in dB is _____ (+or -)

Back 81

+

Front 82

as the path length increses, the attenuation of ultrasound in soft tissue _______

Back 82

increases

Front 83

attenuation in lung tissue is ( les, greater than or the same) attenuation in soft tissue?

Back 83

greater than

Front 84

attenuation in bone is _______ attenuation in soft tissue?

Back 84

greater than

Front 85

attenuation in air is ______ than soft tissue?

Back 85

greater than

Front 86

what are the units of attenuation?

Back 86

dB

Front 87

in a given medium, attenuation is unrealted to the speed of sound? T or F?

Back 87

true annenuation and propagtion speed are unrealated

Front 88

what is the relationship between ultrasound freq and the attenuation coefficent in soft tissue?

Back 88

in soft tissue, the attenuation coeffieient in dB per centimeter is approx 1/2 of the Ultrasound freq in MHz

Front 89

what aer the units of the half-value layer thickness?

Back 89

distance, centimeters

Front 90

as freq decreases, depth of penetration _____

Back 90

increases

Front 91

as path lenght increases the half bondry layer _____

Back 91

remains the same

Front 92

impedence is a characteristic of ________

Back 92

.only the medium

Front 93

as the pathe length increses, the attenuation coeffiecent of ultrasound in soft tissue ( decrease, increase, same)

Back 93

same

Front 94

acoustic impedence Z = ___X____

Back 94

Density P X propagation speed C

Front 95

2 media A and B have the same densities the speed of sound in the medium A is 10% higher than B which medium has the higher acoustic impedence?

Back 95

medium A 's acoustic impedence is higher. recall that Z =P X C

Front 96

impedence is important in ____at boundries

Back 96

reflections

Front 97

a pulse of ultrasound is prpagating in soft tissue like liver. the pulse strkes a boundary with a differernt soft tissue at normal incidence? what portion of the intensity is reflected back toward the transducer? why?

Back 97

a small percentage less than 1 % the difference in Z of 2 soft tissues directly determines the inetnsity refletion coeffecent

Front 98

sound is traveling in a medium and strikes a boundry with normal incidence. if 63% of the waves intensity is feflected back, what percent is transmitted?

Back 98

37%

Front 99

a pulse of ultrasound is propagating in bone and strikes an interface at 90 degrees. A giant reflection is created
-from these facts alone what can be said about the impedence of bone?

Back 99

nothing can be stated about the inpedence of bone or soft tissue givin the info

Front 100

sound is traveling in a medium and orthogonally strikes a boundry with a different medium. Althogh the media are very different no reflection is created, How can this be?

Back 100

with normal incidence, reflections occur only when the impedences of the 2 media at the interface are different

Front 101

sound is traveling from bone to soft tissue. the Z of the media differ siginfcantly and 90% of the beams intensity is reflected. what % of the intensity is transmitted?

Back 101

100% must be accounted for so 10 % must be transmitted

Front 102

a pulse of ultrasound propagates in soft tissue such as liver. The pulse strikes a soft tisssue-soft tissue interface with oblique incidence. Some of the sound energy is transmitted. To what extend is the transmitted beam refracted?

Back 102

the transmitted beam undergoes little to no refraction. a transmitted beam is refracted when the propagation speeds are different. because the tissues on bothe sides are soft tissues. their speeds are nearly identical

Front 103

a sound pulse travels in medium 1 and strikes an interface with antoher tissue, Medium 2 @ 30 degrees. the angle of transmission is 10 degrees. from these facts what can be said about
-the speed of sound in medium 1

Back 103

given only this info, we can say nothing about the speed of sound in mdeium 1 or 2. However, because the beam refracted significantly (a 20 degree change) the speeds of the 2 media are very different.