2 Ch. 4: Describing Pulsed Waves

Question 1

In diagnostic u/s, ___ wave sound cannot create anatomic images.

Answer 1

continuous

Question 2

Define ‘pulsed sound’.

Answer 2

Short bursts of acoustic energy produced by imaging systems to create anatomic pictures; a collection of cycles that travel together.

Question 3

Pulse duration is…

Answer 3

the actual time from the start of a pulse to the end of that pulse aka transmit/talking/”on” time.

Question 4

Pulse duration is reported in units of…

Answer 4

time, such as microseconds.

Question 5

Pulse duration is determined by the…

Answer 5

sound source only.

Question 6

Is pulse duration adjustable?

Answer 6

No.

Question 7

Pulse duration is equal is the ___ in each pulse multiplied by the ___of each cycle.

Answer 7

number of cycles/period

Question 8

Pulse duration is ___ proportional to the # of cycles in the pulse.

Answer 8

directly. The more cycles, the longer the duration.

Question 9

Pulse duration is ___ proportional to the period.

Answer 9

directly. The longer the individual period of the cycles, the longer the duration.

Question 10

Pulse duration is ___ proportional to the frequency.

Answer 10

inversely. The higher the frequency, the shorter the duration must be.

Question 11

What two characteristics create pulses of LONG duration?

Answer 11

Pulses of long duration have either 1) many cycles in the pulse or 2) individual cycles with long periods.

Question 12

What two characteristics create pulses of SHORT duration?

Answer 12

Pulses of short duration have either 1) few cycles in the pulse or 2) individual cycles of short period.

Question 13

(Shorter/Longer) duration pulses are desirable for imaging because they create images of greater accuracy.

Answer 13

shorter

Question 14

Define ‘spatial pulse length’.

Answer 14

The distance that a pulse ocupies in sace from the start to the end of a pulse.

Question 15

Spatial pulse length is reported in units of…

Answer 15

distance, such as mm.

Question 16

Spatial pulse length is determined by…

Answer 16

both the source and the medium (because the wavelength of each cycle is determined by both, so is spatial pulse length).

Question 17

Is spatial pulse length adjustable?

Answer 17

No.

Question 18

Spatial pulse length is equal is the ___ in each pulse multiplied by the ___of each cycle.

Answer 18

of cyles/wavelength

Question 19

Spatial pulse length is ___ proportional to the # of cycles in each pulse.

Answer 19

directly. The more cycles, the longer the length.

Question 20

Spatial pulse length is ___ proportional to wavelength.

Answer 20

directly. The longer the individual wavelengths, the longer the pulse length.

Question 21

Spatial pulse length is ___ proportional to frequency.

Answer 21

inversely. The higher the frequency, the shorter the length must be.

Question 22

What two characteristics create long pulses?

Answer 22

Long pulses have either 1) many cycles in the pulse or 2) cycles with longer wavelengths.

Question 23

What two characteristics create short pulses?

Answer 23

Short pulses have either 1) fewer cycles in the pulse or 2) cycles with shorter wavelengths.

Question 24

Define ‘pulse repetition period’.

Answer 24

The time from the start of one pulse to the start of the next pulse (one ‘on’ time and one ‘off’ time).

Question 25

Pulse repetition period is reported in units of…

Answer 25

time, such as milliseconds (ms).

Question 26

Pulse repetition period is determined by the…

Answer 26

sound source only.

Question 27

Is pulse repetition period adjustable?

Answer 27

Yes, by adjusting the depth of view.

Question 28

How are pulse repetition period and depth of view related?

Answer 28

Directly. As one increases, the other increases.

Question 29

Does the sonographer adjust depth of view by changing the ‘on’ time (pulse) or the ‘off’ time (space between pulses)?

Answer 29

The ‘off’ or listening time.

Question 30

Define ‘pulse repetition frequency’.

Answer 30

The number of pulses that an u/s sound system transmits into the body each second. (PULSES, not CYCLES.)

Question 31

Pulse repetition frequency is reported in units of…

Answer 31

hertz (Hz), or ‘per second’.

Question 32

Pulse repetition frequency is determined only by the…

Answer 32

sound source only.

Question 33

Is pulse repetition frequency adjustable?

Answer 33

Yes, by adjusting the depth of view.

Question 34

How are pulse repetition frequency and depth of view related?

Answer 34

Inversely. As one increases, the other decreases.

Question 35

How are pulse repetition frequency and pulse repetition period related?

Answer 35

Inversely (as one increases, the other decreases) and reciprocally (multiplied together, the result is 1).

Question 36

Define ‘duty factor’.

Answer 36

The percentage or fraction of time that the system transmits a pulse.

Question 37

Duty factor is reported in units of…

Answer 37

Trick question! Duty factor is a percentage and has no units.

Question 38

Duty factor is determined by…

Answer 38

sound source only.

Question 39

Is duty factor adjustable?

Answer 39

Yes, by changing the depth of view.

Question 40

How are duty factor and depth of view related?

Answer 40

Inversely. As one increases, the other decreases.

Question 41

Duty factor is equal is the pulse ___ divided by the pulse ___ times 100.

Answer 41

duration/repetition period

Question 42

The maximum value for duty factor is…

Answer 42

1 or 100%. But that would be continuously transmitting, so imaging systems are always less than 100%.

Question 43

The minimum value for duty factor is…

Answer 43

0%. But that would be when the system is totally silent.

Question 44

Shallow imaging means ___ listening, ___ PRP, ___ PRF, and ___ duty factor.

Answer 44

less, shorter, higher, higher

Question 45

Deep imaging means ___ listening, ___ PRP, ___ PRF, and ___ duty factor.

Answer 45

more, longer, lower, lower