DMS216 Physics Ch. 4-5

A. Remains the same B. Remains the same C. Remains the same D. Remains the same E. Remains the same F. Remains the same G. Decreases H. Decreases I. Remains the same J. Increases

A sonographer adjust the depth of view of an ultrasound scan from 8 cm to 16cm. Would each of the following parameters increase, decrease, or remain the same? A. Period B. Frequency C. Wavelength D. Speed E. Amplitude (initial) F. Pulse duration G. PRF H. Duty factor I. Spatial pulse length J. Pulse repetition period

A, B, D

By changing the imaging depth, which of the following does the operator also change (more than 1 may be correct)? A. PRF B. duty factor C. propagation speed D. PRP E. amplitude F. spatial pulse length

more; longer; lower; lower

Deep imaging requires________ listening, ________ PRP, _______ PRF, and _______ duty factor.

pulse duration/PRP x 100

Duty Factor (%)=?

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

Duty factor

Sound source only

Duty factor is determined by?

inversely related

How are PRF and depth of view related?

directly

How are PRP and depth of view related?

measured over the entire cross-sectional area of the sound beam, and over all time

I sata

measured at the location where intensity is maximum, averaged over the transmit time (pulse duration)

I sppa

measured at the location where intensity is maximum and averaged over all time, both the transmit and receive times

I spta

measured at the location where intensity is maximum, and at the instant in time when the most powerful part of the pulse passes

I sptp

increases

If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when PRF increases?

decreases

If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when imaging depth increases?

increases

If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when the sonographer uses a new transducer with a longer pulse duration?

Yes, by adjusting the depth of view

Is PRF adjustable by sonographer?

No. The sonographer cannot alter pulse duration while using a particular ultrasound system and transducer.

Is pulse duration adjustable?

No. The sonographer cannot alter pulse length.

Is spatial pulse length adjustable?

yes, by changing the image depth

Is the PRP adjustable by the sonographer?

yes, by changing the depth of view

Is the duty factor adjustable?

sound source

PRF is determined by the

PRP

PRF is the reciprocal of ____

depth of view

PRF is unrelated to frequency. It is related ONLY to ______.

1/PRP

PRF=?

inversely

PRP and PRF are related how?

sound source

PRP is determined by the

depth of view

PRP is unrelated to period, it is related only to

1

PRP x PRF=?

1/PRF

PRP=?

The maximum value

Peak

The actual time from start of a pulse to the end of that pulse (not including the listening time)

Pulse Duration (PD)

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

Pulse Repetition Frequency (PRF)

taking the average intensity during the pulse duration (transmit time)

Pulse average intensity (Ipa)

Sound source only

Pulse duration is determined by

# of cycles in the pulse and the period

Pulse duration is directly proportional to

frequency

Pulse duration is inversely proportional to

# of cycles/frequency (MHz)

Pulse duration=?/?

# cycles x period

Pulse duration=_______ X ________

Intensity

Pulsed is the average _______ for the pulse duration only (not listening time.

Transmit- talking to or "on" time; Receive- listening to or "off" time

Pulsed ultrasound has two components:

spatial average temporal average

SATA

spatial peak pulse average

SPPA

spatial peak temporal average

SPTA

tissue heating

SPTA is the most relevant intensity with respect to

spatial peak, temporal peak

SPTP

less; shorter; higher; higher

Shorter imaging requires _______ listening, _______ PRP, _______ PRF, and _______ duty factor.

The beam's intensity at the location where it is maximum

Spatial Peak Intensity (Isp)

the average intensity across the beam's entire cross-sectional area

Spatial average intensity (Isa)

spatial average intensity

Spatial peak intensity is always higher than the?

# of cycles in a pulse and wavelength

Spatial pulse is directly proportional to

frequency

Spatial pulse is inversely proportional to?

# of cycles x wavelength

Spatial pulse length=?

averaging the intensity during the entire pulse repetition period- both the transmit and receive times

Temporal average intensity (Ita)

measuring the intensity of the beam at the instant in time of its maximal value

Temporal peak intensity (Itp)

SPTP, Im, SPPA, SPTA, SATA

The rank of intensities from largest to smallest

image depth

The sonographer can alter the listening time when adjusting the?

The propagation speed for pulsed and continuous wave sound is the same (1.8 km/sec)

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

0.3 to 2.0 microseconds

The typical value of pulse duration in diagnostic ultrasound is?

1,000-10,000 Hz

The typical values of PRF

0.2% to 0.5%

The typical values of duty factor

0.1 to 1.0 mm

The typical values of spatial pulse length

True

True or False. PRF and PRP are determined only by the imaging depth.

True

True or False. Two waves can have identical PRFs, even if their frequencies are different.

False

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

many cycles in the pulse; cycles with longer wavelengths

Two characteristics create long pulse length:

many cycles in the pulse or individual cycles with long periods

Two characteristics create pulses of long duration:

few cycles in the pulse or individual cycles with short periods

Two characteristics create pulses of short duration:

Fewer cycles in the pulse; Cycles with shorter wavelengths

Two characteristics create short pulse length:

units of distance (mm)

Units for spatial pulse length

Hz

Units of PRF

units of time (microseconds)

Units of pulse duration

A. 100%; B. 33%; C. 0%; D. 50%

What are the duty factors of the 4 patterns that appear in Fig. 4.13?

spatial, peak, average, temporal, pulsed

What are the five key words that are related to the intensity of pulsed waves

maximum is 100% or 1; minimum is 0%

What are the maximum and minimum values for duty factor?

transmit and receive time

What are the two components of PRP?

100 us to 1 ms

What are the typical values of PRP?

time (ms)

What are the units of PRP?

maximum distance into the body that an ultrasound system is imaging

What is depth of view?

a collection of cycles that travel together

What is pulsed sound?

D

What is the duty factor if the pulse duration is 1 microsecond, and the pulse repetition period is 1 ms? A. 100% B. 0.1 C. 0.01 D. 0.001

0.001 or 0.1%

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

0.001

What is the duty factor if the pulse duration is 1 us, and the pulse repetition period is 1 ms?

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

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

it decreases

When a sonographer adjusts the depth of view to 20 cm, what happens to the PRF?

PRP; PRF; duty factor

When adjusting imaging depth, the system changes the ________, _________, and ________.

D

Which of the following best describes the duty factor? A. AxB B. A/E C. D/E D. A/C E. ExF F. (A+B)/C

D

Which of the following describe line A? A. frequency B. PRP C. period D. pulse duration E. duty factor F. amplitude

D

Which of the following describes line A? A. frequency B. PRP C. period D. spatial pulse length E. duty factor F. amplitude

F

Which of the following describes line B? A. frequency B. PRP C. period D. pulse duration E. duty factor F. amplitude

B

Which of the following describes line C? A. frequency B. PRP C. period D. pulse duration E. duty factor F. amplitude

C

Which of the following describes line D? A. frequency B. PRP C. period D. pulse duration E. duty factor F. amplitude

C

Which of the following describes line D? A. frequency B. PRP C. wavelength D. pulse duration E. duty factor F. amplitude

F

Which of the following describes line E? A. frequency B. PRP C. period D. pulse duration E. duty factor F. none of the above

E

Which of the following describes line F? A. frequency B. PRP C. period D. pulse duration E. peak-to-peak amplitude

C

Which of the following terms does not belong with the others? A. high duty factor B. shallow imaging C. low PRF D. short pulse repetition period

B

Which of the following terms does not belong with the others? A. low duty factor B. shallow imaging C. low PRF D. long pulse repetition period

B

Which of the patterns in Fig. 4.13 indicates a system with a deep imaging depth?

D

Which of the patterns in Fig. 4.13 indicates a system with a superficial imaging depth?

C

Which of these four pulses with PRFs listed below has the shortest pulse repetition period? A. 12 kHz B. 6,000 Hz C. 20 kHz D. 1 kHz

c

Which 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

A and C

Which two of the patterns in Fig. 4.13 identify an ultrasound system that cannot perform anatomic imaging?

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

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

lengthen; shorten

With deeper imaging, the listening time and the pulse repetition period _______. With shallower imaging, the listening time and the PRP_______.

pulses

With regard to PRF the number of cycles in each pulse are meaningless. We are interested ONLY in the number of ____ created each second

pulse duration

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

PRP

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

The mathematical middle value

average

Biophysical results of the interaction of sound waves and tissue

bioeffects

inversely

duty factor and depth are ____ related

period; frequency; wavelength; propagation speed

parameters that describe both pulsed and continuous waves

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

pulse repetition period (PRP)

refers only to the transmit time (pulse duration)

pulsed

refers to distance or space

spatial

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

spatial pulse length

sound source and medium

spatial pulse length is determined by

Refers to all time, transmit and receive

temporal

none, it's a percentage

units of duty factor

W/cm2

All intensities have units of?

Locations; times

An ultrasound beam does not have the same intensity at different______ and ______.

high

An ultrasound machine is imaging to a depth of 2 cm. would the PRF be described as high or low?

A. Remains the same B. Remains the same C. Remains the same D. Remains the same E. Increases F. Increases G. Remains the same H. Remains the same I. Remains the same J. Remains the same K. Remains the same

A sonographer is using a 3 MHz transducer and increases the output power to visualize structures that are positioned deeper in the patient. No other controls are adjusted. Would each of the following parameters increase, decrease, or remain the same? A. Period B. Frequency C. Wavelength D. Speed E. Power (initial) F. Intensity (initial) G. Pulse duration H. PRF I. Duty factor J. Spatial pulse length K. PRP

A. Decreases B. Increases C. Decreases D. Remains the same E. Remains the same F. Remains the same G. Remains the same

A sonographer is using a 3MHz transducer and changes to a 6 MHz transducer. The imaging depth remains unchanged. Would each of the following parameters increase, decrease, or remain the same? A. Period B. Frequency C. Wavelength D. Speed E. Intensity (initial) F. PRF G. PRP

C

Four pulses have pulse repetition periods as listed below. Which of the following four waves has the highest pulse repetition frequency? A. 8 s B. 80 ms C. 5 ms D. 400 ks

a

Four waves have pulse repetition periods as listed below. Which of the following four waves has the lowest PRF? a) 8 s b) 80 us c) 8000 ns d) 800 ms

the average intensity during the most intense half-cycle

Imax (Im)

pulse duration, pulse repetition period, pulse repetition frequency, duty factor, and spatial pulse length

In addition to the seven parameters of a sound wave, there are five parameters that are needed to completely describe pulsed sound. List them.

2 to 4

In clinical imaging, a pulse typically contains how many cycles?