Module 1

Question 1

An increase in which one of the following will increase sound intensity?
A. frequency

B. power

C. velocity

D. beam area

Answer 1

B. Power. Intensity is power divided by area; if power is increased and the area remains the same, intensity increases proportionately.

Question 2

Which of the following is true at a specular reflector if the angle of incidence is 10 degrees, speed of sound in medium 2 is 4,000 m/s, and speed of sound in medium 1 is 1,000 m/s?

A. the angle of reflection is 20 degrees

B. the transmitted beam has a different frequency

C. the angle of incidence is normal

D. the transmitted angle is approximately 40 degrees

Answer 2

D In this case the speed of sound in medium 2 is greater than the speed of sound in medium 1. This will refract the beam away from normal incidence with an angle of transmission greater than the angle of incidence. The only possible correct answer is 40 degrees. The answer is determined by multiplying the angle of incidence the ratio of the speed of sound in medium 2 to the speed of sound in medium 1. The angle of reflection always equals the angle of incidence. Frequency is a constant.

Question 3

Which of the following limits the upper end of the frequency range that can be used in diagnostic ultrasound?

A. propagation speed

B. duty factor

C. tissue penetration

D. image resolution

Answer 3

C Tissue penetration. Higher frequencies produce excellent resolution. However, the use of higher frequencies is limited by their ability to penetrate.

Question 4

Which of the following propagates sound at a similar speed to soft tissue?

A. fat

B. bone

C. air

D. water @ 50o C

Answer 4

D Water at 50 degrees Celsius. The speed of sound in bone is very high and very low in air. The speed of sound in fat is less than soft tissue (1460 m/s).

Question 4

Which of the following determine the wavelength of a sound wave?

A. frequency and speed of sound

B. spatial pulse length and density

C. frequency and density

D. period and pulse duration

Answer 4

A The Wave Equation shows us that wavelength is directly proportional to the speed of sound and inversely proportional to frequency. If speed of sound increases, wavelength increases; if frequency increases, wavelength decreases. Remember that speed of sound is determined by the medium and only changes if the medium changes. Frequency is determined by the transducer and is a constant in all media.

Question 5

Go-return time in soft tissue is measured at 208 µs. What is the calculated reflector distance if the ultrasound machine is calibrated to the average speed of sound in soft tissue?

A. A) 4 cm

B. B) 8 cm

C. C) 12 cm

D. D) 16 cm

Answer 5

D Go-return time in 1 cm of soft tissue is 13 µs. Reflector distance may be determined by dividing go-return time by 13 µs. Therefore, 208 µs ÷ 13 µs = 16 cm. If the medium is not soft tissue, then the range equation must be used to determine the reflector distance.

Question 6

Refer to the adjacent image. Which term best describes the sonographic characteristic of the measured mass relative to the surrounding tissue?
A. hyperechoic

B. cystic

C. hypoechoic

D. heterogeneous

E. anechoic

Answer 6

A The mass is brighter than the surrounding liver tissue. It is correctly described as being hyperechoic relative to the surrounding liver.

Question 7

Which of the following is an acoustic variable?

A. frequency

B. wavelength

C. pressure

D. propagation speed

Answer 7

C Pressure is an acoustic variable. An acoustic variable is a measurable parameter within the medium that changes as sound propagates through the medium. The four acoustic variables are pressure, density, temperature, and particle motion.

Question 8

When an echo returns to the transducer, what are the two essential values of the echo the machine uses to provide a grayscale display?

A. frequency and amplitude

B. go-return time and amplitude

C. frequency and phase shift

D. speed of sound and amplitude

Answer 8

B To produce a grayscale display, each echo is assessed for two essential values. The go-return time is used to calculate the distance to the interface using the range equation. Echo amplitude is the strength of the echo. Echo amplitude determines the brightness (grayscale) of the interface on the display.

Question 9

Which of the following is the same value for infrasound, sound, or ultrasound propagating in air?

A. sound frequency

B. speed of sound

C. period

D. wavelength

Answer 9

B Speed of sound is determined by the medium and is unrelated to frequency. The terms infrasound, sound, and ultrasound simply describe different sound frequencies based on the human audible range. Period and wavelength both depend on frequency.

Question 10

If a sound beam is refracted as it crosses a specular interface, what must have changed at the interface?

A. sound frequency

B. speed of sound

C. acoustic impedance

D. density

Answer 10

B Refraction can only occur at oblique incidence - never at perpendicular or normal incidence. Refraction will occur at oblique incidence if there is a change in speed across the interface. If the speed of sound in medium one and medium two is the same, regardless of the angle of incidence or the impedance values of the media, refraction will not occur.

Question 11

Which of the following is the same quantity as 100 mW?

A. 0.01 Watt

B. 0.1. Watt

C. 1.0 Watt

D. 10 Watt

Answer 11

B 1000 mW = 1 Watt. 100 mW = 0.1 Watt

Question 12

Which of the following must be known to calculate the intensity reflection coefficient at a specular interface?

A. sound frequency

B. acoustic impedance

C. wavelength

D. pulse length

Answer 12

B Reflection coefficient at a specular interface can be determined if the acoustic impedances (Z) of the media are known. It is the acoustic mismatch between the impedances of the media that determines the percentage of the incident energy that is reflected at a specular interface.

Question 13

At oblique incidence under which condition will the angle of transmission always be the same as the angle of incidence?

A. when the acoustic impedance of two media is equal

B. when the angle of incidence is oblique

C. when the speed of sound in two media is equal

D. when the density of two media is equal

Answer 13

C Refraction cannot occur at oblique incidence unless there is a change in the speed of sound across the interface.

Question 14

What is the unit of attenuation coefficient?

A. dB

B. dB/cm

C. bel

D. megahertz

Answer 14

B Attenuation coefficient is the rate of amplitude (or intensity) reduction per unit distance. It depends on the medium and frequency. The unit of attenuation coefficient is dB/cm.

Question 15

As an ultrasound pulse propagates through various soft tissues, which of the following is the most constant?

A. amplitude

B. acoustic impedance

C. frequency

D. speed of sound

Answer 15

C Frequency is determined by the transducer and is not affected by the medium. Amplitude decreases at a given rate due of attenuation. Acoustic impedance and speed of sound are determined by the medium and vary slightly from one soft tissue to another.

Question 16

Which of the following can be used to calculate the attenuation coefficient?

A. wavelength and pulse repetition frequency

B. attenuation and path length

C. speed of sound and acoustic impedance

D. temporal peak and temporal average intensity

Answer 16

B Attenuation is equal to the product of attenuation coefficient and path length. If attenuation and path length are known, the equation can be used to solve for the attenuation coefficient.

Question 17

The initial intensity for a transducer is 100 mW/cm2. At a distance of 1 cm the intensity is attenuated by 3 dB. How much intensity remains?

A. 97 mW/cm2

B. 50 mW/cm2

C. 33 mW/cm2

D. 25 mW/cm2

Answer 17

B 3 dB of attenuation represents a decrease in intensity by a factor of 2. In this example, the initial intensity value is 100 mW/cm2, therefore the new intensity value is 50 mW/cm2.

Question 18

At normal incidence, what must be different in the tissues for reflection to occur?

A. density

B. speed of sound

C. acoustic impedance

D. viscosity

Answer 18

C Reflection occurs when there is an acoustic impedance mismatch. The larger the impedance mismatch, the stronger the reflect

Question 19

In which component of an ultrasound system are the echo signals stored until a complete image is formed?

A. the pulser

B. the receiver

C. the memory

D. the display

Answer 19

C Memory is the component in which the echo signals are stored until a complete image is formed. Once the image is formed it is read from memory and sent to the display.

Question 20

At a distance of 3 cm from the transducer, the sound beam has been attenuated by 3 dB. What is the attenuation at a distance of 6 cm?
A. 6 dB

B. 9 dB

C. 12 dB

D. 24 dB

Answer 20

A Attenuation is directly proportional to path length. If path length increases by a factor of 2, attenuation will increase by a factor of 2. In this example, path length is doubled from 3 cm to 6 cm thus attenuation doubles from 3 dB to 6 dB.

Question 21

Material A and B have the same density. Material B has a speed of sound 10% higher than material A. What is the acoustic impedance of material B?

A. same as material A

B. 10% less than material A

C. 10% more than material A

D. may be more or less depending on other factors

Answer 21

C Acoustic impedance is directly proportional to both the speed of sound and density. Given equal densities, if the speed of sound of material B is 10% higher than material A, the acoustic impedance of material B must be 10% higher.

Question 22

In which of the following situations will refraction at a specular interface occur?

A. the acoustic impedances of medium 1 and 2 are not the same

B. there is oblique incidence and a change in propagation speed

C. there is normal incidence and no change in propagation speed

D. there is oblique incidence and a change in acoustic impedance

Answer 22

B Refraction will occur if there is oblique incidence and a change in propagation speed across the interface.

Question 23

Which of the following affects the amount of energy reflected back to the transducer at a specular interface like the respiratory diaphragm?

A. angle of incidence

B. frequency

C. speed of sound

D. reflector distance

Answer 23

A Incidence angle is an important factor in reflection from a specular reflector. Generally, the brightest echoes are seen when the sound beam is perpendicular to the specular reflector.

Question 24

Which of the following affects the amount of scatter from a large interface with a rough surface? A. frequency B. receiver gain C. pulse repetition frequency D. angle of incidence

Answer 24

A The strength of scattering is very dependent on frequency. Scattering increases with frequency. On the other hand, scattering is independent of the angle of incidence.

Question 25

Refer to the adjacent image. Which statement best describes the attenuation characteristic of the measured uterine mass? A. appears to have average attenuation B. appears to have below average attenuation C. appears to have above average attenuation D. appears to be associated with acoustic enhancement

Answer 25

C The measured mass is a typical uterine myoma. There is evidence of mild acoustic shadowing associated with the mass which is typical for a mass with above average attenuation compared to normal myometrium.

Question 26

In a given sound beam travelling through different media, if the wavelength changes it is due to a change in which of the following? A. the beam intensity B. the PRF C. the frequency D. the speed of sound

Answer 26

D The wave equation shows us that wavelength depends on the speed of sound and the frequency. However, frequency is determined by the transducer and remains constant in the beam regardless of the speed of sound. Thus, in a given beam, if wavelength changes, it is because speed of sound has changed.

Question 27

Under which condition is the angle of incidence, reflection, and transmission always the same value? A. whenever the angle of incidence is 0o B. whenever the beam is at oblique incidence C. whenever the acoustic impedances of the two media are the same D. whenever the densities of the two media are the same

Answer 27

A An angle of incidence of 0o is called normal incidence. At normal incidence, the angle of incidence, reflection, and transmission are always the same (0).

Question 28

Which boundary will produce the strongest reflection? A. fat/kidney B. water/soft tissue C. fat/muscle D. air/soft tissue

Answer 28

D The greater the acoustic (impedance) mismatch, the stronger the echo produced at an interface. The acoustic impedance of air is vastly different than soft tissue. Any interface with air results in a strong bright echo.

Question 29

The initial sound intensity is 80 mW/cm2. What is the intensity after 6 dB of attenuation? A. 160 mW/cm2 B. 80 mW/cm2 C. 40 mW/cm2 D. 20 mW/cm2

Answer 29

D 20 mW/cm2. Step 1: memorize the fact that 3 dB represents a reduction in intensity by a factor of 2. For every 3 dB of attenuation, the intensity in the beam will decrease by 50%. Step 2: determine how many 3 dB "blocks" there are in the attenuation value given. In this case, attenuation is 6 dB. 6 dB = 3 dB+3dB. Thus 6 dB = 1/2x1/2=1/4. Intensity has been reduced by a factor of 4. Step 3: apply the factor to the initial intensity. In this case, the initial intensity is 80 mW/cm2. 80 mW/cm2 x 1/4 = 20 mW/cm2

Question 30

If wave amplitude is increased by a factor of 4, by what factor does intensity increase? A. 2 B. 4 C. 8 D. 16 E. 32

Answer 30

D Intensity is proportional to amplitude squared (I= A2) Increasing the amplitude by a factor of 4 results in intensity increasing by a factor of 42 = 16.

Question 31

What is the period of a 5 MHz sound wave? A. 0.2 us B. 0.5 us C. 5 us D. 2 s

Answer 31

A 0.2 us. The reciprocal unit for MHz is μs. The reciprocal of 5 is 0.2. 0.2 μs is the reciprocal of 5 MHz.

Question 32

Decreasing the power output control on a system by 3 dB will have what effect on beam intensity? A. intensity will double B. intensity will decrease by a factor of 2 C. intensity will increase by a factor of 4 D. intensity will decrease by a factor of 4 E. intensity will not be affected by the change in the power output control

Answer 32

B Intensity is directly proportional to power. Therefore, if power output decreases by 3 dB, intensity will also decrease by 3 dB. A 3 dB decrease in intensity or power is a decrease by a factor of 2.

Question 33

If the power output control is changed from -9 dB to -12 dB, what will be the effect on the output power of the transducer? A. output power will not be affected B. output power will increase by a factor of 2 C. output power will be reduced by a factor of 2 D. output power will increase by a factor of 3 E. output power will decrease by 3 mW

Answer 33

C The difference between -9 dB and -12 dB is -3 dB which represents a power (or intensity) reduction by a factor of 2.

Question 34

With reference to the line diagram, what is the phase difference between waves A and B? A. 45o B. 90o C. 180o D. 270o E. 360o

Answer 34

B One complete cycle can be divided into 360o. Wave B has a starting position exactly one-quarter cycle later than wave A. One-quarter of 360o is 90o.

Question 35

Which of the following best describes the wavelength in soft tissue for a 3 MHz pulse? A. 0.5 mm B. 1.5 mm C. 15 mm D. 1.5 cm E. 15 cm

Answer 35

A The wave equation tells us that “wavelength is equal to the speed of sound divided by frequency”. Speed of sound in soft tissue is 1.54 mm/µs. Therefore, 1.54 mm/µs ÷ 3 MHz is approximately 0.5 mm.

Question 36

A 5 MHz transducer with a 5 cycle pulse is pulsed at a rate of 1,000 pulses per second. What is the pulse repetition period? A. 1µs B. 1 ms C. 0.1 s D. 100 µs E. 1000 ms

Answer 36

B Pulse repetition period is equal to the reciprocal of pulse repetition frequency (1/PRF). Therefore, 1 ÷ 1000 = 0.001 seconds. None of the lettered options have this answer therefore a unit conversion must be made. To convert to ms from seconds, multiply the answer by 1000. Therefore, 0.001 x 1000 = 1 ms. Another way to do it is to recognize the 1000 pulses per second is a PRF of 1 kHz. The PRP is the reciprocal of the PRF. Therefore, the PRP is 1 millisecond (Recall that the prefix “milli” is the reciprocal of “kilo”), thus the reciprocal of 1kHz is 1 millisecond. Note that frequency (5 MHz) and number of cycles per pulse (5) are distractors and not required to determine the answer. This is also a two part question which tests your ability to determine pulse repetition period from the information provided, and your ability to do unit conversion. You can expect a few of this type of question in the final examination and on the registry examination. Be prepared!

Question 37

Which of the following is the best choice for the pulse duration for the pulse in the previous question? A. 10 s B. 1 s C. 0.1 s D. 1 ms E. 1 µs

Answer 37

E Pulse duration is the product of period and the number of cycles in the pulse. Thus, you must determine the period of the wave. Period is the reciprocal of frequency (1/frequency). Frequency is 5 MHz, therefore period (µs) is equal to 1 ÷ 5 (MHz) = 0.2 µs. There are 5 cycles in the pulse therefore pulse duration is equal to 1 µs (0.2 µs x 5). A simpler method is remember that the pulse duration in diagnostic ultrasound is extremely short, and is typically around 1 μs.

Question 38

Which of the following best represents a typical Duty Factor in diagnostic ultrasound? A. 0.0001 B. 0.001 C. 0.01 D. 0.1 E. 1

Answer 38

B Duty factor describes the fraction of time that a system is actively pulsing compared to the total time. In diagnostic ultrasound this is an extremely small fraction of the time. Duty factor can be calculated by taking the ratio of the PD to the PRP. A typical PD is 1 μs and a typical PRP is 1 ms. This gives a ratio of 1/1000 = 0.001 (remember the units must be converted). Duty factor is unitless. 0.001 could also be expressed as 0.1%.

Question 39

“Heterogeneous” is a term used to describe the echogenicity of tissue. True False

Answer 39

B False. “Heterogeneous” is a term that describes the texture of tissue. Echogenicity is the brightness of the echoes and is described using terms such as “hyperechoic”, “hypoechoic”, “isoechoic”, and “anechoic”.

Question 40

A pulsed transducer operating at a frequency of 1 MHz generates a 5 cycle pulse. What is the spatial pulse length of the emitted wave travelling in soft tissue? A. 1.54 mm B. 3.08 mm C. 7.70 mm D. 15.4 mm E. 0.77 mm

Answer 40

C Spatial pulse length is equal to wavelength multiplied by number of cycles in the pulse. Wavelength must be determined in this case as it is not given. The propagating medium is soft tissue therefore wavelength is speed of sound (1.54 mm/µs) divided by frequency (1 MHz) which is equal to 1.54 mm. Spatial pulse length is 7.7 mm (1.54 mm x 5).

Question 41

The circumference of a fetal head is measured at 240 mm. What is the circumference in centimeters? A. 240 cm B. 24 cm C. 2.4 cm D. 0.24 cm E. 2400 cm

Answer 41

B A unit conversion. To convert from millimeters to centimeters, divide by 10 (240 mm ÷ 10 = 24 cm). I also remind you that the unit of circumference is any unit of distance or length (mm, cm, m, etc..). Think of a racetrack. The horses race from the starting gate to the finish line on a track which is usually oval. The distance for the race is measured in miles (a unit of distance).

Question 42

Which is the correct order for speed of sound from fastest to slowest? A. bone, fat, soft tissue, air B. air, fat, soft tissue, bone C. bone, air, fat, soft tissue D. soft tissue, fat, bone, air E. bone, soft tissue, fat, air

Answer 42

E The speed of sound in bone is very high compared to soft tissue. The speed of sound in air is very low compared to soft tissue. Therefore, you must choose an answer where the highest value is bone and the lowest value is air. The possibilities in this case are A and E. The speed of sound in fat is a little lower than in soft tissue therefore E is the correct answer.

Question 43

Which of the following units would be suitable to indicate the cross-sectional area of the sound beam in the near field? A. cubic centimeters B. micrometers C. millimeters D. square centimeters E. centimeters

Answer 43

D The unit of area is any unit of distance squared. The only choice in this case is D. Cubic centimeters is a unit of volume, and B, C, and E are all units of distance or length.

Question 44

The intensity of a sound beam at the transducer surface is 1 W/cm2 and 2,000 mW/cm2 at the focal point. What is the relative increase in intensity due to the focusing of this sound beam? A. 0 dB B. 0.3 dB C. 3 dB D. 6 dB E. 30 dB

Answer 44

C Another one of those two part questions! First, you must do a unit conversion (convert W/cm2 to mw/cm2. To convert form W/cm2 to mW/cm2, multiply by 1000. The next part of the question is to determine the dB value of the intensity increase. The intensity has increased by a factor of 2. This is a 3 dB increase. Note: you are not allowed to use a calculator for the final examination in the course or for the registry examination. Therefore, the best approach is to memorize some key decibel - intensity ratios as instructed in the course. 3dB represents an increase in intensity or power by a factor of 2. Memorize this!

Question 45

In pulsed ultrasound, which is the correct order from highest to lowest temporal intensities? A. temporal peak, pulse average, temporal average B. temporal average, pulse average, temporal peak C. temporal peak, temporal average, pulse average D. pulse average, temporal peak, temporal average E. temporal average, temporal peak, pulse average

Answer 45

A Temporal peak intensity is always the highest temporal intensity. Temporal average intensity is always the lowest. Pulse average intensity is always a value between temporal peak and temporal average.

Question 46

Sound is all of the following EXCEPT: A. longitudinal wave B. fluctuating pressure wave C. mechanical energy D. ionizing radiation E. a propagating wave of energy

Answer 46

D Sound may be described in many different terms. It is a type of radiant energy. However, it is NOT ionizing radiation. Sound does NOT have enough energy to ionize atoms.

Question 47

Which phenomenon occurs due to wave interference from scatterers? A. acoustic shadowing B. focal enhancement C. harmonic echoes D. acoustic speckle E. refractive shadowing

Answer 47

D Speckle is the sonographic pattern produced by the interaction of echoes generated from a group of scatterers.

Question 48

Under which condition are temporal average and temporal peak intensity equal? A. when a transducer is pulsed at a pulse repetition frequency rate lower than 1,000 B. when the media effectively has no attenuation C. when a transducer is focused D. when a transducer is operated in the continuous wave mode E. when the duty factor is less than 1

Answer 48

D In continuous wave mode the sound is being transmitted 100% of the time. In this mode there is no variation in temporal intensity since the sound is always on. The temporal average and temporal peak intensities are always equal.

Question 49

Describing scattering, which of the following is FALSE? A. echo strength typically less than for specular reflection B. contributes valuable information about organ parenchyma on sonograms C. backscatter is very dependent on the angle of incidence D. scattering decreases the amplitude of the incident wave E. scattered echo strength is very dependent on frequency

Answer 49

C Scattering is angle independent. It is dependent on frequency but, unlike specular reflection, it is not dependent on the angle of incidence.

Question 50

Which of the following is the best choice for the log of 987? A. 4.3 B. 2.99 C. 3.8 D. 8.7 E. -2.4

Answer 50

B The log of 987 must be slightly less than the log of 1,000, but must be greater than the log of 100. The best choice is 2.99. It cannot be -2.4 because a negative log is the log of a number less than 1.

Question 51

Beam intensity is attenuated by 2 dB/cm in soft tissue. What is the approximate frequency being used? A. 1 MHz B. 2 MHz C. 3 MHz D. 4 MHz E. 5 MHz

Answer 51

D 4 MHz. The attenuation coefficient in soft tissue is approximately 0.5 dB/cm X frequency ( MHz). The frequency = AC/0.5 dB/cm = 2 dB/cm/0.5 dB/cm = 4 MHz.

Question 52

V1 = 1,200 m/s; V2 = 2,400 m/s. If the beam is incident at the interface at 0o, what will be the angle of transmission? A. 0o B. 12o C. 24o D. 60o

Answer 52

A Angle of transmission = 0o. There is no refraction at normal incidence.

Question 52

Which of the following is the best choice for the percentage of sound that is reflected at an interface if the acoustic impedances of the two media are 0.1 Rayls and 10.6 Rayls? A. 4% B. 26% C. 48% D. 82% E. 96%

Answer 52

E 96%. (No meed to calculate). There is a huge acoustic impedance mismatch between the two media (0.1 and 10.6).

Question 52

At a specular interface, the strongest echo is received when the beam is at normal incidence to the interface. True False

Answer 52

A True. The strongest echo is generated when the beam is at normal incidence.

Question 53

The decibel scale is a logarithmic scale. True False

Answer 53

A True. The decibel scale is a logarithmic scale.

Question 54

If the angle of transmission and the angle of incidence are NOT equal, what has happened? A. rarefaction B. reflection C. refraction D. retraction

Answer 54

C Refraction. Refraction is “bending the beam”.

Question 55

Which of the following is in the correct ascending order (lowest to highest temporal intensities)? A. TP, PA, TA B. TA, TP, PA C. PA, TA, TP D. TA, PA, TP

Answer 55

D TA, PA, TP. TA is the average temporal intensity; it is the lowest. TP is the instantaneous temporal peak intensity; it is the highest. PA falls between the two.

Question 56

Logarithmic scales are used to compress wide ranges of numbers into smaller more manageable values. True False

Answer 56

A True. Logarithmic scales are used to compress wide ranges of numbers into smaller more manageable values.

Question 57

What is the unit for sound intensity? A. watt B. mW/cm2 C. Rayl D. meters per second

Answer 57

B The unit for sound intensity is mW/cm2.

Question 58

Select the term which best applies. ____________ structures are histologically uniform throughout. A. homogeneous B. heterogeneous C. solid D. benign

Answer 58

A Homogeneous. Homogeneous structures are histologically uniform. They will have a homogeneous texture on the ultrasound display.

Question 59

In a decibel question, if Intensity or Power is being described you will use the “20 log equation”. True False

Answer 59

B False. In a decibel question, if Intensity or Power is being described you will use the “10 log equation”.

Question 60

All of the following are inherent characteristics of simple cysts EXCEPT: A. bright backwall B. acoustic enhancement C. anechoic contents D. septations

Answer 60

D Septations should not be seen in a “simple cyst”

Question 61

Given Z skin = 20 and Z transducer = 60, which of the following is the best choice for the Z gel? A. 10 B. 20 C. 40 D. 60 E. 70

Answer 61

C 40. Gel is an “impedance matcher”. The acoustic impedance of gel is designed to fall between the acoustic impedance of the skin and the acoustic impedance of the transducer. This will reduce reflection at that interface and improve the transmission and reception of sound.

Question 62

What is the log of 100? A. 1 B. 2 C. 3 D. 4

Answer 62

B 2. 10 2 = 100

Question 63

Whenever there is no change in anything, the decibel value will be ____ decibels. A. 0 B. 1 C. 2 D. 3

Answer 63

A 0 dB. Whenever there is no change in anything, the decibel value will be 0 dB (decibels).

Question 64

The period of a 3 MHz sound wave is 0.33 µs. What is the approximate period if the transducer is changed to 6 MHz? A. 0.08 µs B. 0.16 µs C. 0.33 µs D. 0.66 µs

Answer 64

B 0.16 µs. Period is inversely related to frequency. Thus, increasing the frequency by a factor of 2 will decrease the period by a factor of 2.

Question 65

Echoes will be mislocated too far from the transducer if the speed of sound is slower than 1540 m/s. True False

Answer 65

A True. If the speed of sound is slower than expected, the go-return times will be longer than they should be. The calculated distance to interfaces will be increased.

Question 66

The speed of sound is directly proportional to which of the following? A. frequency B. period C. the stiffness of the medium D. the density of the medium E. amplitude

Answer 66

C The stiffness of the medium. The speed of sound in a medium is directly proportional to the stiffness of the medium. Stiffer media such as solids propagate sound faster than more elastic media such as liquids. Liquids propagate sound faster than gases.

Question 67

If wave amplitude is doubled, what happens to intensity? A. doubled B. no change C. halved D. quadrupled E. quartered

Answer 67

D Intensity is proportional to (amplitude)2. Therefore, if amplitude is doubled intensity is proportional to (2)2. Intensity is increased by a factor of four.

Question 68

If the speed of sound is faster than 1540 m/s, echoes will be mislocated too close to the transducer. True False

Answer 68

A True. If the speed of sound is faster than expected, the go-return times will be shorter than they should be. The calculated distance to interfaces will be decreased.

Question 69

If power is increased by a factor of 3, what happens to Intensity? A. increased by a factor of 3 B. decreased by a factor of 3 C. increased by a factor of 9 D. decreased by a factor of 9 E. no change in Intensity

Answer 69

A Increased by a factor of 3. Power and Intensity are directly proportional to each other.

Question 70

Increasing the power control on a system by 3 dB will have what effect on beam intensity? A. increase by a factor of 2 B. decrease by a factor of 2 C. increase by a factor of 4 D. decrease by a factor of 4 E. no change

Answer 70

A Increase by a factor of 2. Intensity and Power are directly proportional. A 3 dB change is an increase by a factor of 2.

Question 71

Fat propagates sound a little more slowly than soft tissue. This would indicate that fat is a slightly less stiff (more elastic) medium than soft tissue. True False

Answer 71

A True. Fat propagates sound at approximately 1440 m/s which is approximately 6% slower than soft tissue. This would indicate that fat is a less stiff (more elastic) medium, since propagation speed is directly proportional to stiffness.

Question 72

The calibration speed for diagnostic ultrasound systems is 1,540 m/s. True False

Answer 72

A True. Ultrasound systems are programmed with a calibration speed of 1540 m/s. This is the value used in the Range Equation.