front 1 "Mechanical energy transmitted by pressure waves in a medium" is an accurate description for:
A) audible sound only
B) all types of sound
C) ultrasound waves only
D) High-energy sound waves only | back 1 B) all types of sound
this is a general definition applicable to any sound wave |
front 2 SOund waves can travel through each of the following except?
A) air
B) water
C) vacuum
D) steel | back 2 C) vacuum
a vacuum has no molecules or "particle" to transmit sound waves |
front 3 Which of the following properties are common to all sound sources
A) They are larger than a wavelength
B) They cause vibrations in the medium
C) They produce transverse waves
D) they can not move back and forth | back 3 B) They cause vibrations in the medium
the only property applicable to all sound sources is they vibrate and consequently produce vibrations in the medium |
front 4 The speed of sound depends on which of the following?
A) wavelength
B) frequency
C) Medium
D) amplitude | back 4 C) Medium
sound speed depends on the density and stiffness of the medium |
front 5 In a sound wave, regions where the pressure is higher than normal are called regions of:
A) rarefraction
B) attenuation
C) compression
D) amplitude | back 5 C) compression
regions of compression have a higher density and higher pressure. The opposite is regions of rarefaction. |
front 6 Which of the following is a type of sound wave that can propagate through soft tissue?
A) transverse wave
B) longitudinal wave
C) shear wave
D) radio wave | back 6 B) longitudinal wave
only longitudinal sound waves travel through soft tissue; transverse waves (another name for shear waves) are severely attenuated; radio waves are not sound waves |
front 7 Units for pressure are:
A) Joules
B) Newtons
C) Pascals
D) None of these; pressure is unitless | back 7 C) Pascals
joules are units of energy
Newtons are units of force |
front 8 The time for one cycle of a wave is the
A) Duty factor
B) Period
C) wave duration
D) phase | |
front 9 If the frequency is 1 MHz, the period is
A) 1,000,000s
B) 100s
C) .01s
D) .000001 | back 9 D) .000001
period is 1/frequency = 1/1,000,000 = .000001 |
front 10 Deci-, centi-, milli-,and micro- mean?
A) 100, 1000, .1, and .000001
B) .1, 100, .001, and .000001
C) .1, .01, .001, and .000001
D) 10, 100, .001, and .000001 | back 10 C) .1, .01, .001, and .000001
deci = 1/10
centi = 1/100
milli = 1/1000
micro = 1/1,000,000 |
front 11 WHich of the following lists correctly arranges the materials according to their speeds of sound, from lowest to highest?
A) water, tissue, bone, air
B) bone, air, tissue, water
C) air, bone, water, tissue
D) air, water, tissue, bone | back 11 D) air, water, tissue, bone
air has the lowest and bone has the highest, water has a lower speed than average soft tissue |
front 12 The average speed of sound in soft tissue is taken to be?
A) 1300 m/s
B) 1460 m/s
C) 1540 m/s
D) 450 m/s | back 12 C) 1540 m/s
1540 m/s = 1.54 mm/μs = .154 cm/s |
front 13 The distance a wave travels during one period of oscillation of the source is the:
A) period
B) wavelength
C) speed of sound
D) depth of penetration | back 13 B) wavelength
wavelength is also sound speed divided frequency and for soft tissue it 1.54 mm/f(MHz) where f(MHz) is the frequency given in MHz |
front 14 The wavelength for 5MHz sound wave in tissue is about?
A) .3 mm
B) 3 mm
C) 1.54 m
D) 1.54 mm | back 14 A) .3 mm
wavelength = 1.54 mm / f(MHz) = 1.54 mm / 5 = .3mm |
front 15 If the frequency doubles the wavelength?
A) double
B) halves
C) increases four times
D) does not change | back 15 B) halves
wavelength is inversely proportional to frequency |
front 16 The acoustic impedance is found by multiplying the
A) attenuation
B) density by the speed of sound
C) density by the wave amplitude
D) speed of sound by the particle displacement | back 16 B) density by the speed of sound
this is the definition for the characteristic impedance of material |
front 17 If the density of Material B is 10% greater than that of Material A, and they have equal speeds of sound and attenuation values, the impedance of B is ___________ that of A.
A) the same as
B) 1% higher than
C) 10% lower than
D) 20% higher than | back 17 C) 10% lower than
impedance is directly proportional to the density, so if latter increases by 10% so does the impedance |
front 18 If the impedance on one side of an interface is two times the impedance on the other, the amplitude reflection coefficient is?
A) 1
B) .33
C) .1
D) .033 | back 18 B) .33
call the impedance of material 1 "1" that of material 2 "2".
R= (2-1)/(2+1) = .33
any other number will work as long as material 2's impedance is two times that of material 1 |
front 19 About what percent of the incident intensity is reflected at a soft tissue-bone interface?
A) 2% or lower
B) between 10% and 60%
C) 100%
D) 200% | back 19 B) between 10% and 60%
which can be verified by using impedance values in the text |
front 20 About what percent of the incident intensity is reflected at a soft tissue-soft tissue interface?
A) 2% or lower
B) between 10% and 60%
C) 100%
D) 200% | |
front 21 About what percent of the incident intensity is reflected at a soft tissue-air interface?
A) 2% or lower
B) between 10% and 60%
C) 100%
D) 200% | back 21 C) 100%
essentially all the sound is reflected at a tissue-air interface |
front 22 In order to produce refraction what condition(s) must be met at an interface?
A) perpendicular incidence, different sound speeds
B) perpendicular incidence, same sound speeds
C) nonperpendicular incidence, different sound speeds
D) perpendicular incidence, different acoustic impedance | back 22 D) perpendicular incidence, different acoustic impedance
for refraction to occur, the sound must be incident at an angle that is not perpendicular and the sound speeds must be different at the interface. |
front 23 Snell's law predicts?
A) the direction of the reflected beam
B) the amplitude of the incident beam
C) the directions of the transmitted beam
D) the amplitude of the transmitted beam | back 23 C) the directions of the transmitted beam
Snell's law relates the transmitted beam direction to the incident beam angle and the speeds of sound at the interface. Given any three of the four quantities lets you solve for the forth |
front 24 For angle between 0 degrees and 9 degrees, as the angle increases, the sine of that angle?
A) does not change
B) increases
C) decreases | back 24 B) increases
the sine increases as the angle increases from 0 to 90 degrees |
front 25 The best way to describe the role of ultrasonic scattering in diagnostic imaging is it
A) gives rise to diagnostic information
B) is responsible for echo enhancement
C) must be eliminated to give clear detail
D) results in greater acoustic exposure to the patient | back 25 A) gives rise to diagnostic information
scattering is the main source of echo signals in ultrasonography |
front 26 Interfaces that scatter ultrasonic energy are usually considered those that
A) are much larger than the ultrasonic beam
B) are much larger than the wavelength
C) are the size of or smaller than the wavelength
D) surround soft tissue-bone interface | back 26 C) are the size of or smaller than the wavelength
we usually say scatterers are smaller than the wavelength |
front 27 One advantage a diffuse reflector provides over a specular reflector is
A) exhibits less angular dependence of the reflection
B) does not attenuate the ultrasound beam
C) exhibits a greater acoustic impedance change
D) intersects only a small fraction of the beam | back 27 A) exhibits less angular dependence of the reflection
it reflects sound waves in all directions, so there is less of a dependance of the detected echo amplitude on the angle of the surface |
front 28 Decibels provide a convenient way to express the ________ two amplitudes of intensities
A) sum of
B) differences between
C) product of
D) ratio of | back 28 D) ratio of
decibels are used to quantify the ratio of two amplitudes or intensities |
front 29 Which statement is incorrect regarding ultrasound absorption?
A) it is part of attenuation
B) sound energy is converted to heat
C) it increases when the frequency increases
D) it is greater in fluid cavities | back 29 D) it is greater in fluid cavities
at MHz frequencies, sound absorption is very low in fluid cavities in the body, such as the bladder, compared to absorption in soft tissue |
front 30 The rate of attenuation, or attenuation coeffient, is expressed in?
A) µW/cm^2
B) µW
C) dB/cm
D) dB/cm^2 | back 30 C) dB/cm
dB/cm is used to express the attenuation coefficient |
front 31 If the attenuation coeffient of a tissue is .5 dB/cm at 1 MHz, it is probably _____ at 5 MHz
A) .1 dB/cm
B) .5 dB/cm
C) 2.5 dB/cm
D) 12.25 dB/cm | back 31 C) 2.5 dB/cm
attenuation can be assumed to be proportional to frequency. you are given the attenuation coeffient at 1 MHz, so multiply by 5 to get the value at 5 MHz |
front 32 Echo "enhancement" results from a structure having a:
A) Higher speed of sound than adjacent material
B) higher acoustic impedance than adjacent material
C) lower attenuation than surrounding material
D) Greater absorption rate than surrounding material | back 32 C) lower attenuation than surrounding material
enhancement results from good through-transmission in a mass or fluid-filled cavity |
front 33 The attenuation of an ultrasound pulse traveling 12 cm in a tissue that has an attenuation coefficient of 1 dB/cm is?
A) 1/12 dB
B) 1 dB
C) 12 dB
D) 13 dB | back 33 C) 12 dB
attenuation (in dB) is the attenuation coeffient
(dB/cm) x distance (cm) = 1 dB/cm x 12 cm |
front 34 WHich of the following conditions are minimal requirements for a sound wave to be classified as ultrasonic?
A) frequency above 10 kHz
B) frequency above 20 kHz
A) frequency above 10 kHz; intensity greater than 1 W/m^2
A) frequency above 20 kHz; longitudinal wave
A) frequency above 10 kHz; underwater propagation. | back 34 B) frequency above 20 kHz
high-frequency (grater than 20 kHz) sound waves traveling through media besides water are still ultrasound; the waves can be other than longitudinal if the medium will support their transmission. |
front 35 Calculate the wavelength for a 2 MHz ultrasound beam in soft tissue.
speed of the sound is 1540 m/s
f = 2 MHz = 2x10^6 s | back 35 .77 mm
λ = (1540 m/s) / (2 x 10^6) = .00077 m = .77 mm |
front 36 Calculate the wavelength for a 2 MHz ultrasound beam in soft tissue. | back 36 .154 mm
λst = 1.54 mm /f(MHz)
λst = 1.54 mm/10
λst = .154 mm |
