Ultrasound Physics Exam 1

refraction

Occurs only when two conditions are satisfied: oblique incidence and different propagation speeds of the two media.

C. 8 Ms

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

imaging depth

PRF and PRP are determined only by what?

inversely, reciprocals

Period and frequency are _____________________ related. They are _________________ of one another.

decreases

Period increases as frequency ____________________.

compressed and rarefied

Sound must have molecules which are ______________ and ________________ alternately in order to propagate.

pulsed wave

Sound that is made up of individual cycles that travel as a unit. Used in ultrasound.

solids

Sound travels fastest through _______________________.

longitudinal

Sound waves are ___________________ waves.

audible sound

Sound waves with a frequency between 20 Hz and 20 kHz

ultrasound

Sound waves with frequencies above 20,000 Hz (20 kHz)

infrasound

Sound waves with frequencies below 20 Hz.

sound source and medium

Spatial pulse length is determined by what?

axial

Spatial pulse length/2 = _________________ resolution.

Rayleigh scattering

Special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength.

stiffer

As materials become _______________, the speed of sound in the material increases.

dense

As materials become more ____________, the speed of sound in the material decreases.

directly

Attenuation and frequency are related how?

greater

Attenuation is _____________ in higher frequency sound than in lower frequency sound.

pulse length

Axial resolution is determined by what?

increases

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

120, second

For a flat screen TV with a frame rate of 120 Hz, this means that __________ events are occurring each ____________.

longitudinal, axial, range, radial, depth

For axial resolution, a mnemonic is used: LARRD. What does this stand for?

A. 8 s

Four waves have pulse repetition periods as listed below. Which of the following four waves has the lowest pulse repetition frequency? A. 8 s B. 80 µs C. 8000 ns D. 800 ms

increase

If the depth in increased, what happens to the pulse repetition period? (decrease, increase, stays the same)

1 W/cm^2, 4W/cm^2

If the initial area of a sound beam is 4cm^2 and the initial power is 4 W, what is the initial intensity? If the area is then halved and the power doubled, what is the final intensity?

0.2 W/cm^2

If the power in a beam is 1 watt and the area is 5 cm^2, what is the beams intensity?

greater

If there are more cycles in a pulse, the numerical value of range resolution is ________________. (greater, lesser, the same)

increase

If there is an increase in power and area remains unchanged, what is the change in intensity? (decrease, increase, stays the same)

increase

If you increase power, amplitude will _________________.

perpendicular

In a transverse wave, particles move in a direction that is ____________________ to the direction that the wave propagates.

2 to 4

In clinical imaging, a pulse typically contains _______________ cycles.

0.2% to 0.5%

In clinical imaging, duty factor (DF) ranges from:

C. 2.25 mm

In soft tissue, a 3 cycle, 1 MHz pulse has a pulse length equal to 4.5 mm. What is the axial resolution? A. 3 mm B. 1 mm C. 2.25 mm D. 1.54 mm

1.54 mm

In soft tissue, sound with a frequency of 1 MHz has a wavelength of ___________.

lateral

High frequencies help __________________ resolution in the far field.

directly, proportionally (power= amplitude^2)

How are power and amplitude related?

compression = increased pressure, rarefaction = decreased pressure

How does pressure relate to areas of compression and rarefaction?

duty factor (%) = pulse duration/PRP x 100

How is duty factor calculated?

proportionally

How is intensity related to power?

speed (m/s) = frequency (Hz) x wavelength (m)

How is propagation speed determined?

3,000,000

How many Hz is 3MHz?

3dB

How many decibels of attenuation has occurred by the time the sound beam has penetrated to the half value layer?

10

How many millimeters are in a centimeter?

7,000,000,000 ns

How many nano seconds are in 7 seconds?

B. 4MHz

Identify the wave that is ultrasonic: A. 400 mHz B. 4 MHz C. 28 Hz D. 2 Hz

degrades

If a new pulsed transducer has many more cycles in its pulse, the image accuracy ______________. (improves, degrades, remains the same)

decreases

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

multiply

Increasing by a factor means to ________________ by that number.

amplitude^2

Intensity is proportional to _____________________.

no

Is pulse repetition frequency related to frequency?

acoustic propagation

The effects of the medium upon the sound wave.

biological effects

The effects of the sound wave upon the biological tissue through which it passes.

C. 5MHz

The frequency of a continuous acoustic wave is 5MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency? A. 0.5 B. 0.5 MHz C. 5 MHz D. 10 MHz

sound source

The frequency of an ultrasound wave is determined by what?

amplitude (Pa, g/cm^3, cm)

The height of a wave's crest.

sound source

The intensity of a wave is determined by what?

long

Two characteristics which create ____________ pulses are many cycles in the pulse and cycles with longer wavelengths.

0.7 x 10^-1

What is 7/10 in scientific notation?

7.5 m

0.0075 km equals _________________ m.

1000

1 second equals _____________ ms.

d deci

10^-1

c centi

10^-2

m milli

10^-3

µ micro

10^-6

n nano

10^-9

da deca (deka)

10^1

h hecto

10^2

k kilo

10^3

M mega

10^6

G giga

10^9

by 9

A sonographer increases the amplitude of a wave by a factor of 3. How has the power changed?

pulse

A collection of cycles that travel together.

wave

A disturbance that transfers energy from place to place.

decibel (dB)

A logarithmic unit of sound intensity.

1350 Rayls

A medium has a density of 1.00 kg/m^3 and a propagation speed of 1350 m/s. Calculate the impedance:

in-phase, constructive

A pair of waves are considered ______________ when their peaks occur at the same time and at the same location. These waves are considered _____________ waves.

horizontal

A particle within a transverse wave is traveling vertically. What is the direction of the wave's propagation?

specular reflection

A reflection created when sound is reflected off of a smooth surface in only one direction in an organized manner.

decrease, remains the same, remains the same, decreases, remains the same

A sonographer is using a 3 MHz transducer to image a patient's thyroid and switches to a 5 MHz transducer for better image quality. Would each of the following parameters increase, decrease or remain the same? * Period * PRF * Intensity * Wavelength * Speed

C. 27dB

A sound beam travels 9cm in soft tissue. The attenuation coefficient is 3dB/cm. What is the total attenuation that the sound beam experienced? A. 9 dB B. 3 dB C. 27dB D. 18 dB

B. medium 2

A sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2 at 30˚. The angle of transmission is 10˚. In which medium does sound travel slowest? A. medium 1 B. medium 2 C. cannot be determined

C. 0%

A sound wave strikes a boundary with normal incidence. The impedances of the two media are identical. What percentage of the sound wave is refracted? A. 100% B. 75% C. 0% D. 25% E. 90%

4,000 mW/cm^2

A wave's intensity is 4 mW/cm^2, there is a change of 30 dB. What is the final intensity?

.625 mW/cm^2

A wave's intensity is 5mW/cm^2, there is a change of -9dB. What is the final intensity?

12dB

A wave's starting intensity is 3 mW/cm^2, the final intensity of the wave is 48 mW/cm^2. What decibel change occured?

elevational

Annular phased arrays have the best ___________________ resolution.

axial resolution (mm)

Ability of a system to display two structures that are very close together when the structures are parallel to the sound beam's main axis.

energy

All waves carry _____________ from one location to another.

decreases

Amplitude _________________ as sound propagates through the body.

C. it is now one-fourth as large

An acoustic wave is traveling through soft tissue. Its intensity undergoes six decibels of attenuation. How does the final intensity of the wave relate to the intensity of the wave when it started its journey? A. it is now four times larger B. it is now six times larger C. it is now one-fourth as large D. it is now one-tenth as large

A, B, and D

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

C. A is three times as long as B

Compare two sound waves, A and B. The frequency of wave A is one-third that of wave B. How does the period of wave A compare with the period of wave B? A. A is one-third as long as B B. A is the same as wave B C. A is three times as long as B D. cannot be determined

B. slower

Compared to soft tissue, the speed of an acoustic wave through lung tissue is _____________. A. faster B. slower C. equal D. cannot be determined

3.75 lbs.

Convert 60oz. to lbs.

divide

Decreasing by a factor means to _______________ by that number.

vibrations that travel through the air or another medium as an audible mechanical wave

Define sound.

inversely

Density and speed are ______________ related.

increase

Does increasing the PRF increase or decrease the duty factor?

increases

Duty factor _______________ with shallow imaging.

sound source

Duty factor is determined by what?

slice thickness

Elevational resolution is also known as _________________ resolution.

lateral, angular, transverse, azimuthal

Lateral resolution has other names which are remembered by using the mnemonic LATA. What does this stand for?

width of the sound beam

Lateral resolution is determined by the _____________________.

longer, shorter

Listening time is ___________ with deep imaging and ____________ with shallow imaging.

A-4, B-1, C-3, D-2, E-6, F-5

Match the following prefixes with their meanings. A. mega. 1. hundreds B. hecto 2. thousands C. milli 3. thousandths D. kilo 4. millions E. nano 5. billions F. giga 6. billionths

medium

Material through which a wave travels

sound

Mechanical wave in which particles in the medium move.

4%

Medium 1 has an impedance of 3,030 Rayls and medium 2 has an impedance of 4,500 Rayls. Calculate the intensity reflection coefficient:

logarithms

Multiples of 10

period, frequency, amplitude, power, intensity, wavelength, propagation speed

Name the seven acoustic parameters.

pressure (Pa), density (kg/cm^3), distance (cm, mm)

Name the three acoustic variables.

perpendicular, orthogonal, right angle, 90 degrees

Normal incidence is also called:

sound source

Power is determined by what?

medium

Propagation speed is determined by what?

inversely, reciprocals

Pulse Repetition Period and Pulse Repetition Frequency are _______________ related and are ______________ of one another.

sound source

Pulse duration is determined by what?

inversely

Pulse repetition frequency and depth of view are ____________ related.

sound source, depth of view

Pulse repetition frequency is determined by what? It is directly related to what?

sound source, depth of view

Pulse repetition period is determined by what? It is directly related to what?

n, µ, m, c, d, da, h, k, M, G

Put the metric system in order from smallest to largest. (giga, nan, micro, mega, hecto, kilo, milli, deci, centi, deca)

shorter

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

propagation speed

The ____________________ of all sound waves are identical while traveling in a specific medium.

stiffness

The ability of an object to resist compression.

lateral resolution

The ability to distinctly identify two structures that are very close together when they are side by side or perpendicular to the sound beams main axis.

impedance (rayls)

The acoustic resistance to sound traveling in a medium.

pulse duration (µs)

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

3 watts (27/9=3)

The amplitude of an acoustic wave decreases from 27 Pa to 9 Pa. If the initial power in the wave was 27 watts, what is the wave's final power?

reflection, incidence

The angle of ________________ equals the angle of ________________.

interference

The combination of two or more waves that results in a single wave.

intensity (W/cm^2)

The concentration of energy in a sound beam.

pressure (Pa)

The concentration of force on an area.

density

The concentration of mass in a volume.

wavelength (length mm, meters)

The distance of length of one complete cycle.

half-value layer thickness (cm)

The distance sound travels in a tissue that reduces the intensity of sound to one-half its original value.

spatial pulse length (mm)

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

20 lb/in^2 (60 lb/in^2-20 lb/in^2 divided by 2)

The maximum value of the density of an acoustic wave is 60 lb/in^2 while the minimum density is 20 lb/in^2. What is the amplitude of the wave?

distance

The measure of particle motion.

attenuation coefficient (dB/cm)

The number of decibels of attenuation that occurs when sound travels one centimeter.

frequency (Hz)

The number of particular events that occur in a specific duration of time.

pulse repetion frequency (Hz)

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

duty factor (%)

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

sound source

The period of an ultrasound wave is determined by what?

Watts (W)

The power of an ultrasound wave can be reported using what units?

propagation speed (mm/µs, m/sec)

The rate at which a sound wave travels through a medium.

power (W)

The rate of energy transfer or the rate at which work is performed.

diffuse reflection

The reflection of waves in many directions from a rough surface.

density

The relative weight of a material.

1.8 km/ sec, speed only depends on medium

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.

A. higher than

The speed of sound propagating through bone is ___________ soft tissue. A. higher than B. lower than C. equal to D. cannot be determined

pulse repetition period (ms)

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

period (µs)

The time it takes a wave to vibrate a single cycle, or the time from the start of one cycle to the start of the next cycle.

B. the same

The wavelength of an acoustic wave is _______________ when it is pulsed rather than continuous. A. longer B. the same C. shorter

attenuation

The weakening of sound waves as they travel in the body. Decrease in intensity, power and amplitude of sound waves.

reflection, scattering, absorption

Three processes that contribute to attenuation.

C. frequency^4

To which of the following is Rayleigh scattering related? A. half of the wavelength B. square root of propagation speed C. frequency^4 D. PRF^2

false

True/False: The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.

short

Two characteristics which create ____________ pulses are fewer cycles in the pulse and cycles with shorter wavelengths.

C. both are the same

Two ultrasound systems produce acoustic pulses. A pulse from System 1 has a wavelength of 0.5 mm, 4 cycles/pulse, and a pulse repetition period of 1.2 msec. The pulses from System 2 have a wavelength of 1.0 mm, 2 cycles/pulse, and a pulse repetition period of 1.8 msec. Which ultrasound system will have a lower numerical value of axial resolution? A. System 1 B. System 2 C. both are the same D. cannot be determined

small, large

Ultrasound systems spend a very ___________ percentage of time transmitting and a very ____________ percentage of time receiving.

inversely

Wavelength and frequency are ____________ related.

sound source and medium

Wavelength is determined by what?

period, frequency, amplitude, power, intensity

What 5 parameters are determined by sound source only?

pulse duration, pulse repetition period (PRP), pulse repetition frequency (PRF), duty factor, spatial pulse length

What are the 5 parameters that are needed to completely describe pulsed sound?

pressure, density, particle motion

What are the three acoustic variables?

amplitude, power, and intensity

What are the three bigness parameters of a sound wave?

stiffness, density

What are the two characteristics of a medium that affect the speed of sound?

transmit time (on time) and receive time (off time)

What are the two components of pulse repetition period?

watts/cm^2

What are the units of intensity?

C. remains the same

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

1.24 x 10^-7

What is 0.000000124 in scientific notation?

5.25 x 10^6

What is 5,250,000 in scientific notation?

D. 0.001

What is a typical value for the duty factor of pulsed sound waves used in diagnostic imaging? A. 0.001 m/sec B. 0.001 kg/cm^3 C. 0.75 D. 0.001

path length and frequency

What is attenuation determined by?

resolution

What is the ability to accurately distinguish two structures lying close together called?

C. 1,754 m/s

What is the best estimate for the speed of sound in tendon? A. 1,000 m/s B. 1,540 m/s C. 1,754 m/s D. 5,400 m/s

pulse duration = time, spatial pulse length = distance

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

wavelength= distance, period= time

What is the difference between wavelength and period?

0.001 (10^-6/10^-3)

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

wavelength= speed of sound/frequency

What is the formula for wavelength?

3

What is the log of 1,000?

4x larger

What is the meaning of a 6dB change?

d

What is the metric symbol of 1/10?

wavelength

What is the only parameter that is determined by both the sound source and the medium?

B. 0.06 to 0.5 µs

What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1 s B. 0.06 to 0.5 µs C. 0.2 to 1 ms D. 10 to 100 ns

micro (µ)

What is the reciprocal of Mega (M)?

milli (m)

What is the reciprocal of kilo (k)?

0.51 mm

What is the wavelength of 3 MHz sound in soft tissue?

0.77mm (1.54mm/2 Hz)

What is the wavelength of a sound with a frequency of 2 MHz in soft tissue?

medium and frequency of sound

What two factors does the half-value layer thickness depend on?

stays the same

What will be the effect on pulse duration if the imaging depth is increased? (decreases, increases, stays the same)

transmitted

Whatever sound is not reflected must be ________________.

B. PRF decreases

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

different

When a sound beam strikes a tissue boundary orthogonally, reflection occurs only if the media on either side of the boundary have _________________ impedances.

+3dB

When a wave's intensity doubles, the relative change is _____.

+10dB

When a wave's intensity increases 10-fold, the relative change is ______.

-10dB

When a wave's intensity is reduced to 1/10 of its original value, the relative change is?

doubled

When a wave's power is doubled, the intensity is ______________.

-3dB

When the intensity is reduced to 1/2 its original value, the relative change is?

is halved

When the power in an ultrasound beam is unchanged and at the same time the beam area doubles, what happens to the intensity? A. it doubles B. is halved C. is quartered D. remains the same

out-of-phase, destructive

When two waves are ___________________, their peaks occur at different times, and so do their troughs. These waves are considered ______________ waves.

E. peak-to-peak amplitude

Which of the following best describes the line identified by letter A? A. amplitude B. period C. frequency D. wavelength E. peak-to-peak amplitude

A. amplitude

Which of the following best describes the line identified by the letter C? A. amplitude B. peak-to-peak amplitude C. frequency D. wavelength E. none of the above

D. wavelength

Which of the following best describes the line identified by the letter D? (may have more than one correct answer) A. period B. peak-to-peak amplitude C. frequency D. wavelength E. amplitude

intensity, power and ampitude

Which of the following can be changed by the sonographer using a particular ultrasound system? * wavelength * frequency * intensity * propagation speed * period * power * amplitude (initial)

B. they all carry energy from one site to another

Which of the following is true of all waves? A. they travel through a medium B. they all carry energy from one site to another C. their amplitudes do not change D. they travel in a straight line

D. decreased spatial pulse length

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

elevational

____________________ resolution is improved with the use of One and One half dimensional arrays.

B. increased duty factor

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. 5 Hz

Which of the following values for PRF would have the longest pulse repetition period? A. 5,000,000 Hz B. 5 Hz C. 5 MHz D. 5 kHz

C. 6 Hz

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

D

Which of the lines above, A, B, C, or D, is most likely the be the reciprocal of frequency?

B

Which of the lines above, A, B, or C is most likely to be determined by the source and the medium?

D. water, blood, fat, muscle, bone, air

Which of these lists indicates media with increasing attenuation of ultrasound? A. water, lung, soft tissue, bone, air B. lung, air, soft tissue, bone C. lung, fat, muscle D. water, blood, fat, muscle, bone, air

C. .003 kHz

Which of these pulse repetition frequencies would have the longest pulse repetition period? A. 4 Hz B. 5 kHz C. .003 kHz D. 2500 Hz

wavelength

Which parameter is determined by both the sound source and the medium?

propagation speed

Which parameter is determined by the medium only?

A. 2 cycles/pulse, 4 MHz

Which transducer has the best axial resolution? A. 2 cycles/pulse, 4 MHz B. 4 cycles/pulse, 4 MHz C. 4 cycles/pulse, 2 MHz D. 2 cycles/pulse, 2 MHz

A, C, and D

While using the same ultrasound machine and transducer, which of the following can a sonographer alter? (more than one may be correct) A. PRP B. frequency C. PRF D. duty cycle E. Pulse duration

IRC (intensity reflection coefficient)

[(z2 - z1) / (z2 + z1)]^2

shorter, higher quality

___________ wavelengths are created by high frequency sound which produces ____________ images.

lateral

_______________ resolution = beam diameter

high

________________ frequency transducers have the best longitudinal resolution.

phased array

adjustable or multiple focusing

power/area

intensity =

ITC (intensity transmission coefficient)

transmitted intensity/incident intensity x 100