Chapter 4

Equation for pulse repetition frequency

PRF x PRP = 1 or PRF = 1/PRP

Pulse repetition frequency is the reciprocal of?

Pulse repetition period

__________ is the time from the start of the pulse to the start of the next pulse

Pulse repetition period

Spatial pulse length equation

SPL (mm) = # cycles x wavelength (mm)

Shallow imaging

-Less listening -Shorter PRP -Higher PRF -Higher duty factor

Deep imaging

-More listening -Longer PRP -Lower PRF -Lower duty factor

Four waves have pulse repetition period as listed below which of the following four waves has the lowest pulse repetition frequency? A 8 s B 80 microseconds C 8000 ns D 800 ms

A 8 s

By changing the imaging tab which of the following does the operator also change (more than one may be correct)? A pulse repetition frequency B Duty factor C Propagation speed D pulse repetition period E amplitude F spatial pulse length

A Pulse repetition frequency B Duty factor C pulse repetition period

What determines the pulse duration? A The source of the wave B The medium in which the pulse travels C both A and B D neither A nor B

A The source of the wave

A sonographer adjusting maximum imaging depth of an ultrasound system. Which of the following also changes? (more than one answer may be correct.) A pulse repetition period B wavelength C pulse repetition frequency D frequency

A and C

A sonographer is using a 3 MHz transducer and changes to a 6 MHz transducer. The imaging depth remains unchanged. Would each of the following parameters increase, decreased, or remain the same? A period B frequency C wavelength D speed E intensity (initial) F PRF G pulse repetition period

A decreases B increases C decreases D remains the same E remains the same F remains the same G remains the same

The pulse duration is expressed in the same units as the A period B PRF C wavelength D density

A period

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, decreased, 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 pulse repetition period

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 adjust the depth of view of an ultrasound scan from 8 cm to 16 cm. Would each of the following parameters increase, decrease or remain the same? A period B frequency C wavelength D speed E amplitude F pulse duration G PRF H duty factor I spatial pulse length J pulse repetition period

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

Spatial pulse length is

The distance of the pulse end to end

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

The duty factor is 0.001 or 0.1%, 0.001÷1.0 = 0.001.

What is the duty factor in the pulse duration is 1 microsecond and the pulse repetition is 1 ms?

The duty factor is 0.001, or 10^-3. 10^-6 divided by 10^-3, or 0.001.

What are the maximum and minimum values for duty factor

The maximum value is 1 or 100% this value is only achieved with continuous wave sound The minimum value of duty factor is 0% which only exist when the transducer is silent

Duty factor

The percentage or fraction of time that the system transmits a pulse No units Determined by the sound source Yes it is adjustable

The speed of 5 MHz continuous wave is 1.8 km/s. The waves then post a duty factor of 0.5. Calculate the new propagation speed.

The propagation speed for post and continuous wave sound is the same in this case 1.8 km/S. It depends only upon the medium through which the sound travels.

Pulse duration is

The time the pulse is on

Pulse Duration (PD)

These sonographer cannot change the pulse duration because it is a characteristic of the transducer and has a fixed value

True or false. The sonographer cannot change the duration of a sound pulse unless the transducers are switched.

True Pulse duration depends upon the interaction of the pulser electronics of the machine and transducer.

True or false? The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged.

True Pulse duration is the timespan that a pulse exists. It is determined by the system and the transducer. It remains constant for a particular transducer.

True or false? The sonographer alters the duty cycle when adjusting the maximum imaging depth of a scan.

True The duty cycle is the percentage of time that an ultrasound system is creating an acoustic wave. Duty factor decreases when depth of view increases because the system needs more time to listen for reflections.

True or false? While imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system are the same.

True The overall length of the pulse is equal to the wavelength multiplied by the number of cycles in a pulse. Using a particular ultrasound system and transducer, the pulse length cannot change.

The pulses produced by both systems travel at the same speed in the patient.

True all sound waves travel in the same medium at identical speeds. Frequency and speed are unrelated

True or false. Two waves can have identical PRFs even if they're frequencies are different

True this is a very important concept

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false. The duty factor is increased.

True. Duty cycle is calculated by dividing the pulse duration by the pulse repetition period. In this example the PRP is unchanged. By changing to a transducer with a longer pulse duration while the PRP stays constant, the duty factor increases.

True or false? The pulse repetition frequency and the frequency are unrelated.

True. PRF and frequency are unrelated. The PRF is determined only by the depth of view. The frequency is determined by the characteristics of the transducer.

True or false. Two waves can have identical PRFs even if their periods are different

True. Period and pulse repetition frequencies are unrelated

What happens to the pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan? A increases B decreases C remains the same D cannot be determined

c. remains the same

On what does the pulse repetition period depend? A The source of the sound wave B The medium through which the pulse travels C both a and B D Neither a Nor B

A the source of the sound wave

While using the same ultrasound machine and transducer, which of the following can a sonographer alter? (More than one answer maybe correct) A pulse repetition period B PRF C frequency D duty cycle E pulse duration

A,B, and D. While adjusting the desired maximum imaging depth in an exam, the sonographer adjust the pulse repetition period and the PRF. The duty factor is also altered. Unlike choice A,B, and D the frequency of the ultrasound and the pulse duration are fixed once a transducer is selected. These parameters cannot be altered.

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

decreases

__________ is the time from the start of a pulse to the end of that pulse

pulse duration

Pulse duration equation

pulse duration (μs) = # of cycles in pulse x period (μs)

The pulse repetition frequency of ultrasound produces a transducer typical of diagnostic imaging systems A can be changed by the sonographer B depends on the medium through which the sound travels C is unchanged as long as the same ultrasound system is used D has nothing to do with the clinical imaging

A. The pulse repetition frequency PRF is inversely related to the maximum imaging depth that is achieved during an exam. As the sonographer increases the maximum imaging death, the PRF must decrease. This occurs because the transducer must wait a longer time for echoes to return from deeper deaths. Sonographers, therefore, altar the PRF when they adjust the maximum imaging depth.

In diagnostic imaging, what establishes the pulse repetition frequency? A The source of the sound B The medium through which the sound travels C both a and B D neither a nor B

A. The sole determinant of the pulse repetition frequency is the source of the acoustic wave, the ultrasound system. The medium through which the sound travels does not directly affect the pulse retention frequency.

Pulse repetition period And imaging depths are directly related

As depths of you increase pulse repetition period increases. As depth of you decreases depth repetition period decreases.

Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4 MHz frequency, and the other produces sound at a 6 MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length? A The 6 MHz pulse B The 4 MHz pulse C they are the same D cannot be determined

B The 4 MHz pulse

What are the units of pulse repetition frequency PRF? A seconds B 1/seconds C mm/micros D seconds^-2

B pulse repetition frequency is the number of pulses that are produced by the ultrasound system in one second. PRF has the same units of frequency, and these units are hertz, Hx, or per second.

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

What is the importance of describing sound beam intensities in a variety of ways with regard to space and time? A it allows better transducer design B it's important when studying bioeffects C it optimizes image quality D harmonics can be measured

B. Describing the intensity of sound beams as they vary in time and in space is important in the study of bio effects.

While using a particular imaging system, what happens to the duty factor when the depth of view increases? A increases B decreases C unchanged

B. Duty factor is inversely related to death of view. As the system images to a greater depth, the system requires more time to listen for reflections, as the duty factor decreases. The duty factor is the fraction or percentage of time that an imaging system is transmitting. It is equal to the pulse duration divided by the pulse retention period. Under normal operation, the pulse duration never changes. However, as death of view increases, the pulse repetition period increases.

Which of the following terms does not belong with the others? A increased depth of view B increased duty factor C increased pulse repetition period D decreased pulse repetition frequency

B. Increased duty factors are related to shallower imaging. The other three selections are considered with a deeper imaging.

When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF? A PRF increases B PRF decreases C remains unchanged

B. When the depth of view is increased, the system waits and listens a longer time for reflections. This reduces the systems ability to send out as many pulses per second. Hence, as imaging depth increases, the pulse repetition frequency decreases. Imaging depth and PRF are inversely related.

Pulse duration

the actual time from the start of a pulse to the end of that pulse Units of time Determined by the source Not adjustable

Spatial Pulse Length (SPL)

the distance that a pulse occupies in space from the start to the end of a pulse Measured in distance Determined by the source and medium Not adjustable

Pulse Repetition Frequency (PRF)

the number of pulses that an ultrasound system transmits into the body each second Measured in Hz Determined by the sound source Not adjustable

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

C 20 kHz

Four pulses have pulse repetition period 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

C 5 ms

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

C Low PRF is associated with deep imaging. The other three choices are associated with shallow imaging.

Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth? A Increases B Decreases C remains the same D cannot be determined

C remains the same

What are the units of pulse duration? A units of frequency (Hz) B msec only C units of time D units of distance

C units of time

pulse repetition period

the time from the start of one pulse to the start of the next pulse Measured by time Determined by the sound source Yes it is adjustable

Which of the following best describes the spatial pulse length? A frequency multiplied by wavelength B PRF multiplied by wavelength C wavelength multiplied by the number of cycles in the pulse D duty factor multiplied by the wavelength

C wavelength multiplied by the number of cycles in the pulse

Which of these four values of pulse repetition frequency would have the longest pulse repetition period? A. 2 kHz B. 4,000 Hz C. 6 Hz D. 1 kHz

C. 6 kHz

In diagnostic imaging, what determines the spatial pulse length? A The ultrasound system B The medium through which the pulse travels C both a and B D neither a nor b

C. Both A and B

The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units? A Time B Hertz C meters D none; it is unitless

C. Meters

Which intensity is most closely correlated to tissue healing? A SPTP B SATP C SPTA D SATA

C. The SPTA intensity relates most closely to tissue temperature elevation.

In the case of post ultrasound, what is the maximum value of the duty factor? A 100% B 1 C less than 100% D none of the above

C. This question is a bit tricky. When dealing with a pulsed ultrasound system, at least a tiny bit of time must be spent listening rather than transmitting. Therefore, the percentage of time transmitting must be less than 1 or 100%. If the percentage equals 100%, the system is continuous wave. The correct choice, C, distinguishes between pulsed and continuous wave by stating that the maximum value of the duty cycle must be less than 100% for a pulsed system.

Which of the following terms does not belong with the others? A increased depth of view B decreased duty factor C Increased pulse repetition period D decreased spatial pulse length

D Spatial pulse length is unrelated to alterations in depth of view. The other three selections are all related to deeper imaging.

What is the typical value for the duty factor (also call the duty cycle) of pulsed sound waves used in diagnostic imaging? A 0.001 msec B 0.001 kg/cm^3 C 0.75 D 0.001

D. Duty factor, or duty cycle, is the percentage or fraction of time that an ultrasound system produces an acoustic signal, or is transmitting. Typically, ultrasound transducers spend the vast majority of time receiving, and only a small fraction of time transmitting an acoustic signal.

The pulse repetition frequency is the A product of the wavelength and propagation speed B reciprocal of the period C sum of pulse duration and listening time D reciprocal of pulse repetition period

D. The PRF and the pulse repetition period are reciprocal. For example, if the PRF is 100 per second, then the pulse repetition period is one-hundredth of a second. If the system creates 500 pulses per second, then the pulse repetition period is 1/500 of a second.

What is the value of the duty cycle for continuous wave ultrasound? A 100 B 1% C 1000% D none of the above

D. The duty factor for continuous wave ultrasound is 1.0 or 100%. This means that the transducer is producing an acoustic signal at all times. None of the answers indicate this: 100 is not 100%, 1% means one-hundredth and is incorrect, and 1000% means 10 times and is also false.

What is the pulse duration equal to? A frequency multiplied by period B period multiplied by wavelength C The number of cycles in the pulse divided by the wavelength D period multiplied by the number of cycles in the pulse

D. period multiplied by the number of cycles in the pulse

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

Decreases

Spatial Pulse Length (SPL)

Directly proportional to the number of cycles in the pulse Directly proportional to wave length Inversely proportional to frequency

Duty factor equation

Duty Factor (%) = Pulse Duration / Pulse Repetition period X 100

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false. The pulse repetition period is increased.

False . Pulse repetition period is determined by the depth of view. In this case, the maximum depth is unchanged. So the pulse repetition period is also unchanged.

True or false a sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth.

False A sonographer cannot change the pulse duration. It has a constnat value, and is not dependent on imaging depth.

True or false. A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulses propagation speed.

False The sonographer cannot change the pulse duration-it is a fixed feature of the transducer and the ultrasound system.

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

False two waves can never have a denticle PRFs if their pulse repetition periods are different

The maximum imaging depth that during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false. The frequency is increased.

False. After reading the information in the question, you will note that nothing is stated regarding the frequency of sound emitted by the transducer. Therefore, nothing can be concluded regarding the frequency.

True or false. The pulse duration cannot be changed under any circumstances or by any action of the sonographer.

False. Sonographer can alter the pulse duration by using a different transducer or ultrasound system.

True or false. The PRF of the 6 MHz transducer is greater than the PRF of the 3 MHz transducer.

False. The PRF is derived from the maximum imaging depth as established by the sonographer. The PRF changes only when the imaging depth changes. Since the depth of you for both systems is the same, the PRF's are also the same.

True or false? The duty factor is a characteristic of an ultrasound and transducer system and does not change as long as the system components remain unchanged.

False. The only duty cycle changes when the sonographer adjust the maximum imaging depth during the exam.

The maximum imaging death during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false. The pulse repetition frequency is increased

False. The pulse repetition frequency and pulse repetition period are reciprocal's. If the pulse repetition period is unchanged, the PRF must also remain unchanged.

Characteristics that create short pulse lengths

Fewer cycles in the pulse Cycles with shorter wavelengths

If all other factors remain unchanged what happens to the duty factor (increase decrease remains the same) when the pulse repetition frequency 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 long pulse duration?

Increases

How are pulse Repetition frequency and depth of you related?

Inversely related As depth of you increases pulse repetition frequency decreases As depth of view decreases pulse repetition frequency increases

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

Inversely related They are reciprocals A longer pulse repetition period result in lower pulse repetition frequency A shorter pulse repetition period results in a higher pulse repetition frequency

Characteristics that create long pulses

Many cycles in the pulse Cycles with longer wavelengths