Spi Ch. 4

Front 1

How many parameters describe pulsed sound?

Back 1

5

Front 2

What are the parameters of pulsed sound?

Back 2

1) Pulsed Duration

2) Spatial Pulse Length

3) Pulse Repitition Period

4) Pulse Repitition Frequency

5) Duty Factor

Front 3

What type of soundbeam does diagnostic ultrasound use?

Back 3

Pulsed

Front 4

What is pulsed sound?

Back 4

A collection of cycles that travel together

Front 5

A pulse must have a ______ and a ______.

Back 5

A pulse must have a Beginning and an End.

Front 6

Does a pulse move as individual cycles or as a single unit?

Back 6

The entire pulse moves as a single unit.

Front 7

A pulse consists of ________ cycles, but propagates as a single ______.

Back 7

A pulse consists of Individual cycles, but propagates as a single Unit.

Front 8

How many components does pulsed ultrasound have?

Back 8

Two

Front 9

What are the components of pulsed ultrasound?

Back 9

Transmit (or talking) and Receive (or listening)

Front 10

Each particular ultrasound transucer emits a pulse with a ______ ________.

Back 10

Fixed Duration

Front 11

Can the pulse duration change for individual transducers?

Back 11

No

Front 12

What is pulse duration?

Back 12

The actual time from the start of a pulse to the end of that pulse.

Front 13

What units is pulse duration reported in?

Back 13

Units of Time such as microseconds

Front 14

What is the typical value of pulse duration?

Back 14

0.3 to 2.0 microseconds

Front 15

What is pulse duration determined by?

Back 15

Sound Source only

Front 16

Is pulse duration adjustable by the sonographer?

Back 16

No

Front 17

What is the relationship of pulse duration?

Back 17

1) Directly proportional to the number of cycles in the pulse

2) Directly proportional to period

3) inversely proportional to frequency

Front 18

What are the two characteristics of pulses with long duration?

Back 18

1) many cycles in the pulse

or

2) individual cycles with long periods

Front 19

What are the two characteristics of pulses with short duration?

Back 19

1) few cycles in the pulse

or

2) indivdual cycles with short periods

Front 20

In clinical imaging, how many cycles does a pulse typically contain?

Back 20

2 to 4 cycles

Front 21

Which type of pulse is more desirable in diagnostic imaging, and why?

Back 21

Shorter duration pulses are more desirable for imaging because they create images of greater accuracy.

Front 22

What is spatial pulse length?

Back 22

The distance that a pulse occupies in space from the start to the end of a pulse

Front 23

What units is spatial pulse length measured in?

Back 23

Distance such as millimeters

Front 24

What are the typical values of spatial pulse length?

Back 24

Spatial pulse length in soft tissue ranges from 0.1 to 1.0 mm

Front 25

What is spatial pulse length determined by?

Back 25

Both the source and the medium

Front 26

Is spatial pulse length adjustable by the sonographer?

Back 26

No. In a particular medium, a transducer's pulse has a fixed length that cannot change.

Front 27

What is the relationship of spatial pulse length?

Back 27

1) Directly proportional to the number of cycles in the pulse

2) Directly proportional to wavelength

3) inversely proportional to fequency

Front 28

What is the difference between pulse duration and spatial pulse length?

Back 28

Pulse duration is the time that a pulse is "on" and is typically measured in microseconds.

Spatial pulse length is the distance of the pulse end to end, typically measured in millimeters.

Front 29

What are the characteristics of longe pulse length?

Back 29

1) Many cycles in the pulse

2) Cycles with longer wavelengths

Front 30

What are the characteristics of short pulse length?

Back 30

1) Fewer cycles in the pulse

2) cycles with shorter wavelengths

Front 31

Which type of pulse is more desirable in diagnostic imaging, and why?

Back 31

Pulses of shorter length are desirable because they create more accurate images

Front 32

What is pulse repetition period?

Back 32

The time from the start of one pulse to the start of the next pulse.

Front 33

What is included in pulse repitition period?

Back 33

One pulse duration and one listening time

Front 34

What units is pulse repetition time measured in?

Back 34

Time

Front 35

What are the typical values of pulse repetition time?

Back 35

100 microseconds to 1 millisecond

Front 36

How many times longer is pulse repetition period compared to pulse duration?

Back 36

100 to 1000 times longer

Front 37

What is pulse repetition period determined by?

Back 37

Sound Source

Front 38

Besides sound source, what is the other determining factor of pulse repetition period?

Back 38

Imaging depth selected by the sonographer

Front 39

Is pulse repetition period adjustable?

Back 39

Yes.

Front 40

What happens when the sonographer adjusts the depth of view?

Back 40

The pulse repetition period is also altered

Front 41

The time from one pulse to the next is short when the system is imaging at what depths?

Back 41

Shallow depths

Front 42

The time from one pulse to the next is longer when the system is imaging at what depths?

Back 42

Deeper depths

Front 43

What is the relationship between pulse repetition period and period?

Back 43

Unrelated

Front 44

What is pulse repetition period related to?

Back 44

Only to the depth of view

Front 45

What is depth of view?

Back 45

Depth of view describes the maximum distance into the body that an ultrasound system is imaging.

Front 46

Does the sonographer control the depth of view?

Back 46

Yes

Front 47

What is the relationship between pulse repetition period and depth of view?

Back 47

Directly related

Example: As depth of view increases, pulse repetition period increases.

As depth of view decreases, pulse repetition period decreases.

Front 48

What are the two components of pulse repetition period?

Back 48

1) Transmit time or on time

2) Receive time or off time

Front 49

What is transmit time called?

Back 49

Pulse duration

Front 50

Can the sonographer change the pulse duration?

Back 50

No - it is characteristic of the transducer and is fixed

Front 51

When does the transducer receive reflections from anatomic reflectors in the body?

Back 51

During the receive or "listening" time

Front 52

Can the sonographer alter the listening time?

Back 52

Yes

Front 53

When can the sonographer alter the listening time?

Back 53

When adjusting the image depth

Front 54

With deeper imaging, what happens to listening time and the pulse repetition period?

Back 54

The listening time and pulse repetition period lengthen.

Front 55

With shallower imaging, what happens to the listening time and pulse repetition period?

Back 55

The listening time and pulse repetition period shorten.

Front 56

Which portion of the pulse repetition period is changed when the sonographer alters imaging depth?

Back 56

Only the listening time portion

Front 57

What is pulse repetition frequency?

Back 57

The number of pulses than an ultrasound system transmits into the body each second

Front 58

In pulse repetition frequency, which is more important? Cycles in each pulse or number of pulses created each second?

Back 58

Number of pulses created each second

Front 59

What units is pulse repetition frequency measured in?

Back 59

Hertz or per second

Front 60

What are the typical values of pulse repetition frequency?

Back 60

1000 to 10,000 hertz or 1000 to 10,000 pulses per second

Front 61

What is pulse repetition frequency determined by?

Back 61

Sound source

Front 62

Is pulse repetition frequency adjustable by the sonographer?

Back 62

Yes

Front 63

How can the sonographer change the pulse repetition frequency?

Back 63

By adjusting the depth of view

Front 64

When is the pulse repetition frequency higher during a scan?

Back 64

When the system is imaging shallow

Front 65

When is the pulse repetition frequency lower?

Back 65

When the system is imaging deeper

Front 66

What is pulse repetition frequency's relation to frequency?

Back 66

Unrelated

Front 67

How are pulse repetition frequency and depth of view related?

Back 67

Inversely related

Example: As depth of view increases, pulse repetition frequency decreases.

As depth of view decreases, pulse repetition frequency increases.

Front 68

An ultrasound machine is imaging to a depth of 2 cm. Would the pulse repetition frequency be described as high or low and why?

Back 68

High, because of the depth of view is shallow

Front 69

When the sonographer adjusts the depth of view to 20 cm, what happens to the pulse repetition frequency?

Back 69

The pulse repetition frequency becomes is reduced or becomes lower.

Front 70

What is the relationship between pulse repetition period and pulse repetition frequency?

Back 70

The are inversely related

Front 71

A longer pulse repetition period results in what type of pulse repetition frequency?

Back 71

A lower pulse repetition frequency

Front 72

A shorter pulse repetition period results in what type of pulse repetition frequency?

Back 72

A higher pulse repetition frequency

Front 73

What is the special relationship between pulse repetition period and pulse repetition frequency?

Back 73

They are a reciprocal of each each other

(they are multiplied together and equal the value of 1)

Front 74

Whic of these four values for pulse repetition frequency would have the longest pulse repetition period?

a) 2 kHz

b) 4,000 Hz

c) 6 Hz

d) 1 kHz

Back 74

C) 6 Hz

Explanation: Pulse repetition period is the reciprocal of pulse repetition frequency. This choice has the lowest pulse repetition frequency and, thus, the longest pulse repetition period.

Front 75

Four pulses have pulse repetition periods as listed below. Which of the following four waves has the highest pulse repetition frequency?

a) 8 seconds

b) 80 milliseconds

c) 5 milliseconds

d) 400 kiloseconds

Back 75

C) 5 milliseconds.

Explanation: The pulse with the shortest pulse duration will have the highest pulse repetition frequency

Front 76

Which of these four pulses with pulse repetition frequencies listed below has the shortest pulse repetition period?

a) 12 kHz

b) 6,000 Hz

c) 20 kHz

d) 1 kHz

Back 76

C) 20 kHz

Explanation: Pulse repetition period is the reciprocal of the pulse repetition frequency. This answer has the highest pulse repetition frequency and, thus, the shortest pulse repetition period.

Front 77

Four waves have pulse repetition periods as listed below. Which of the following four waves has the lowest pulse repetition frequency?

a) 8 seconds
b) 80 microseconds
c) 8000 nanoseconds
d) 800 milliseconds

Back 77

A) 8 seconds.

Explanation: The pulse with the longest pulse duration will have the lowest pulse repetition frequency.

Front 78

True or False

Two waves can have identical pulse repetition frequencies, even if their pulse repetition periods are different.

Back 78

False.

Explanation: Two waves can never have identical pulse repetition frequencies if their pulse repetition periods are different.

Front 79

True or False

Two waves can have identical pulse repetition frequencies, even if their frequencies are different.

Back 79

True.

Explanation: Frequency and pulse repetition frequency are unrelated.

Front 80

True or False

Pulse repetition frequency and pulse repetition period are determined only by the imaging depth.

Back 80

True

**This is a very important concept to remember

Front 81

What is duty factor?

Back 81

Duty factor is the percentage or fraction of time that the system transmits a pulse.

Front 82

What unit is used to measure duty factor?

Back 82

None.

Explanation: Duty factor is a percentage and is therefore dimensionless.

Front 83

What are the typical values for duty factor?

Back 83

0.002 to 0.005 or 0.2% to 0.5%

Front 84

Ultrasound systems spend a very ______ percentage of time transmitting and a very ______ percentage of time (99.8%) receiving.

Back 84

Ultrasound systems spend a very small percentage of time transmitting and a very large percentage of time (99.8%) receiving.

Front 85

What is duty factor determined by?

Back 85

Source

Front 86

Is duty factor adjustable by the sonographer?

Back 86

Yes

Front 87

What is the relationship between duty factor and depth of view?

Back 87

Inversely related

Front 88

Duty factor is higher when the system is imaging at what depths?

Back 88

Shallow depths

Front 89

Duty factor is lower when the system is imaging at what depths?

Back 89

Greater depths

Front 90

How is duty factor calculated?

Back 90

duty factor (%) = pulse duration / pulse repetition period x 100

Front 91

What are the maximum and minimum values for duty factor?

Back 91

Maximum duty factor value is 1 or 100%

Minimum duty factor value is 0%

Front 92

When is the duty factor of 0% reached?

Back 92

When the transducer is silent

Front 93

How does the sonographer change duty factor?

Back 93

Duty factor changes when the sonographer alters imaging depth

Front 94

What are four characteristics of shallow imaging?

Back 94

1) Less listening

2) shorter pulse repetition period

3) higher pulse repetition frequency

4) higher duty factor

Front 95

What are four characteristics of deep imaging?

Back 95

1) More listening

2) Longer pulse repetition period

3) Lower pulse repetition frequency

4) Lower duty factor

Front 96

If all other factors remain unchanged, what happens to the duty factor when the pulse repetition frequency increases? Does it increase, decrease, or remain the same?

Back 96

Increases

Front 97

If all other factors remain unchanged, what happens to the duty factor when imaging depth increases? Does it increase, decrease, or remain the same?

Back 97

Decreases

Front 98

If all other factors remain unchanged, what happens to the duty factor when the pulse repetition period increases? Does it increase, decrease, or remain the same?

Back 98

Decreases

Front 99

If all other factors remain unchanged, what happens to the duty factor when the sonographer uses a new transducer with a longer pulse duration? Does it increase, decrease, or stay the same?

Back 99

Increases

Front 100

What is the duty factor if the pulse duration is microsecond and the pulse repetition period is 1 millisecond?

a) 100%

b) 0.1

c) 0.01

d) 0.001

Back 100

d) 0.001

Front 101

Which of the following terms does not belong with the others?

a) high duty factor

b) shallow imaging

c) low pulse repetition frequency

d) short pulse repetition period

Back 101

C) low pulse repetition frequency

Explanation: Low pulse repetition frequency is associated with deep imaging. The other three choice are all associated with shallow imaging

Front 102

Which of the following terms does not belong with the others?

a) low duty factor

b) shallow imaging

c) low pulse repetition frequency

d) long pulse repetition period

Back 102

B) shallow imaging

Explanation: shallow imaging does not belong. The other three choices are all associated with deep imaging.

Front 103

When adjusting imaging depth, the system changes what 3 parameters of a pulse wave?

Back 103

1) pulse repetition frequency

2) pulse repetition period

3) duty factor

Front 104

What two parameters are characteristic of the pulse itself and inherent in the design of the transducer system?

Back 104

1) pulse duration

2) spatial pulse length

Front 105

What are the 4 parameters of a pulsed wave that are determined by the sound source?

Back 105

1) pulse duration

2) pulse repetition period

3) pulse repetition frequency

4) duty factor

Front 106

What is the only parameter of a pulsed wave that is determined by both the sound source and medium?

Back 106

Spatial pulse length

Front 107

What are the two parameters of a pulsed wave that does not change with imaging depth?

Back 107

1) Pulse duration

2) Spatial pulse length

Front 108

What are the building blocks of both pulsed and continuous waves?

Back 108

Individual cycles

Front 109

What are the parameters that can describe both pulsed and continuous wave sound?

Back 109

1) Period

2) Frequency

3) wavelength

4) propagation speed

Front 110

_____ is the time from the start of a pulse to the end of that pulse.

Back 110

Pulse duration is the time from the start of a pulse to the end of that pulse.

Front 111

_____ is the time from the start of a pulse to the start of the next pulse.

Back 111

Pulse repetition period is the time from the start of a pulse to the start of the next pulse.