Ch. 6-7 Flashcards
The impedance of a medium is
a. equal to density x propagation speed
b. directly proportional to density and inversely proportional to propagation speed
c. directly proportional to propagation speed and inversely proportional to density
d. inversely proportional to density and propagation speed
A. Equal to density X propagation speed
the ratio of particle pressure to particle velocity within the imaging field is
a. noise
b. interference
c. impedance
d. incidence
C. Impedance
Which of the following produces the least resistance to the transmission of the beam?
a. blood
b. bone
c. fat
d. muscle
A
An example of a nonspecular reflector is
a. diaphragm
b. liver tissue
c. vessel walls
B
At an interface of 0.25 Rayls and 0.75 rayls, what percentage of intensity is reflected?
a. 25%
b. 50%
c. 75 %
d. 100 %
A
The amount of reflection at an interface of two different media is determined by
a. the index of refraction
b. the frequency of the beam
c. Snell’s Law
d. The differences in impedances
D
Which of the following might occur at an interface of two different media?
a. reflection
b. refraction
c. production of harmonics
d. complete transmission
A&B
Specular reflection occurs when
a. frequency is small compared to the wavelength
b. the reflector surface is slightly irregular
c. the reflecting surface is smooth
d. the angle of incidence is perpendicular
C
The range equation refers to
a. calibration
b. distance to reflector
c. attenuation
d. field of view
B
For a specular reflector
a. the angle of reflection is equal and opposite the angle of incidence
b. the angle of reflection is greater than the angle of incidence
c. the angle of reflection is less than the angle of incidence
A
As frequency increases, backscatter
a. is not affected
b. increases
c. decreases
d. is eliminated
B
The angle at which total reflection occurs is called
a. diffraction angle
b. angle of total impedance
c. critical angle
d. warp angle
C
Which of the following refers to an angle of 45 degrees?
a. orthogonal
b. acute
c. obtuse
d. normal
e. perpendicular
B
An angle of 123 degrees is
a. orthogonal
b. acute
c. obtuse
d. normal
e. perpendicular
C
The incidence is said to be _______ if it strikes the boundary at 90 degrees.
a. normal
b. direct
c. oblique
d. orthogonal
A&D
What units are used for the intensity reflection coefficient (IRC)?
a. watts
b. W/cm2
c. dB
d. none of these
D
What is the result when the transmitted intensity is divided by the incident intensity?
a. IRC Intensity Reflected Coefficient
b. ITC Intensity Transmitted Coefficient
c. BUC Beam Uniformity Coefficient
d. none of the above
B
What is the result of adding the IRC and ITC together?
a. 1.0 or 100%
b. incident intensity
c. Beam Uniformity Coefficient
A
What is the maximum value possible for either the IRC or ITC?
a. 100%
b. less than 100%
c. 1 %
d. Unlimited
A
What is required for reflection to occur?
a. a difference in propagation speeds
b. a difference in impedance
c. an angle between zero and 90 degrees
d. a difference in density
B
The amount of reflection increases as the differences in impedances increase?
a. true
b. false
A
When two media have the same level of impedance, but the propagation speeds are different, what will occur?
a. a large reflection
b. a small reflection
c. no reflection
d. no reflection with some refraction
C
When the angle of reflection is equal and opposite the angle of incidence, this refers to Snell’s Law.
a. a. true
b. false
B
A sound wave, with an intensity of 50 W/cm 2, strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
a. 50W/cm2
b. 25W/cm 2
c. 0 W/cm2
d. 100%
e. 0%
D
A sound wave, with an intensity of 50 W/cm2, strikes a boundary and is totally reflected. What is the reflected intensity?
a. 50W/cm2
b. 25W/cm2
c. 0 W/cm2
d. 100%
e. 0%
A
The intensity transmission coefficient of sound is 99.9%. What percent of sound is reflected back to the transducer?
a. 100%
b. 0%
c. 99.9%
d. 0.1%
D
No refraction can occur at an interface of medium 1 and medium 2 if the impedances are the same
a. True
b. False
B
Refraction at an interface when there are differences in
a. impedance
b. propagation speeds
c. densities
d. depth
B
The change of beam direction from medium 1 into medium 2 is called
a. rarefaction
b. reflection
c. reverberation
d. refraction
D
What part of beam response does Snell’s Law explain?
a. transmission
b. reflection
c. refraction
d. intensity
C
Refraction can occur with both normal and oblique incidence?
a. true
b. false
B
What conditions are necessary for refraction to occur?
a. normal incidence and different densities
b. normal incidence and different propagation speeds
c. oblique incidence and different levels of impedance
d. oblique incidence and different propagation speeds
D
Refraction always occurs if the propagation speeds are different between two media at the boundary.
a. true
b. false
B
If the angle of incidence is 32 degrees and Medium 1 has a propagation speed of 1,457 m/sec and impedance of 1.44 Rayls and Medium 2 has a propagation speed of 1,644 m/sec and an impedance of 1/26 Rayls, which will occur to transmitted beam?
a. angle is greater than 32 degrees
b. angle is equal to 32 degrees
c. angle is less than 32 degrees
d. cannot tell from this information
A
If the angle of incidence is 45 degrees and medium one has a propagation speed of 1,547 m/sec and medium 2 has a propagation speed of 1,745 m/sec, what occurs with transmission?
a. it is greater than 45 degrees
b. it is less than 45 degrees
c. it is equal to 45 degrees
d. cannot tell from this information
A
. If the beam passes from soft tissue into fat at an oblique angle, what happens to the angle of transmission
a. the angle increases
b. the angle decreases
c. the angle does not change
d. cannot tell from this information
B
Sound wave strikes a boundary at 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%
C
The impedance of medium 1 is 8 rayls and the propagation speed is 1450 m/sec. The impedance of medium 2 is 6 rayls and the propagation speed is 1.855km/s. A sound beam strikes the boundary between the media and is both partially transmitted and reflected. The angle of the incident sound beam is 30 degrees. What is the angle of reflection?
a. 15 degrees
b. 30 degrees
c. 60 degrees
d. 90 degrees
B
How much will a 3.5 MHz pulse attenuate from a path length of 2 cm in soft tissue?
a. 7 dB
b. 3.5 dB
c. 17 dB
d. 1.75 dB
B
In soft tissue, the attenuation is
a. affected by the slope of the TCG slides
b. increased with shorter wavelength
c. not a consideration with newer digital scan converters
d. increased with tissue thickness
D
Attenuation refers to
a. the density of tissues and the propagation speed
b. the changing of direction through an interface
c. the gradual weakening of the beam as it transmits through the medium
d. the redirection back toward the transducer
C
The attenuation coefficient usually varies
a. inversely to frequency
b. directly to frequency
c. logarithmically to frequency
d. with frequency squared
B
Absorption in a medium is from
a. conversion to friction
b. conversion to harmonic frequencies
c. conversion to heat
d. conversion to artifacts
C
the usual value of attenuation in soft tissue is
a. 2 dB/cm2/Hz
b. 1 dB/cm/Hz
c. 2 dB/cm2/MHz
d. 0.5 dB/cm/MHz
D
Attenuation is determined by
a. density and stiffness
b. frequency and propagation speed
c. PRF and path length
d. path length and frequency of the beam
D
Which of the following does NOT contribute to attenuation?
a. reflection
b. focusing
c. absorption
d. redirection in multiple directions
B
What type of reflection occurs from a smooth boundary when the reflectors are much smaller than the wavelength?
a. partial
b. Rayleigh
c. specular
d. backscatter
C
An irregular boundary between two media creates which type of reflection?
a. specular
b. backscatter (also called diffuse)
c. Rayleigh
d. refraction
B
Which of the following apply to diffuse reflections?
a. they come from smooth boundaries
b. they are created by larger reflectors
c. the echoes return in many directions
d. the echoes spread in a sunburst pattern
C
When the beam is reflected in multiple directions from very small particles, the reflection is probably
a. specular
b. Rayleigh
c. Backscatter
d. diffuse
B
Which of the following are related to Rayleigh scattering?
a. half the wavelength
b. have the propagation speed
c. frequency to the fourth power
d. half of PRF
C
When attenuation is reported as an amount per cm of path length it is called
a. attenuation
b. absorption coefficient
c. attenuation coefficient
d. duty factor
C
If the attenuation coefficient is 3 dB/cm and the path length is 9 cm, what is the total attenuation?
a. 9 dB
b. 3 dB
c. 27 dB
d. 19 dB
C
Attenuation through bone is ________ through soft tissue.
a. greater than
b. less than
c. the same as
A
Attenuation through lung tissue is ________ through soft tissue
a. greater than
b. lesser than
c. same as
A
A 3 MHz sound beam travels through two media. It attenuates 5 dB in medium A and 6 dB in medium B. What is the total attenuation that the sound beam undergoes as it travels through both media?
a. 6 dB
b. 11 dB
c. 3 dB
d. 15 dB
B
A 10 MHz sound beam travels through two media. It attenuates 5 dB in medium A and 1 dB in medium B. What is the total attenuation that the sound beam undergoes as it travels through both media?
a. 6 dB
b. 10 dB
c. 16 dB
d. 15 dB
A
A 3 MHz sound beam travels 10 cm, 6 cm in medium A and 4 cm in medium B. The total attenuation is 14 dB. If the sound beam attenuated 4 dB in medium A, then how much attenuation occurred in medium B?
a. 2 dB
b. 14 dB
c. 10 dB
d. cannot be determine
C
Which of the following is the best estimate for the attenuation coefficient of sound traveling in soft tissue?
a. 1.8 dB/cm/MHz
b. 0.77 dB/cm/MHz
c. 0.45 dB/cm/MHz
d. 1.0 dB/cm/MHz
C
A 10 dB increase in intensity is equivalent to a difference of
a. two times the intensity
b. ten times the intensity
c. one hundred times the intensity
d. one thousand times the intensity
B
Amplitude is measured in
a. W/cm2
b. distance of displacement such as mm
c. powers of 10
d. decibels
D
A decibel is
a. the absolute value of a sound level
b. a range of values
c. a relationship between two levels
C
Decibel notation is
a. a sum of the initial and final levels
b. the difference between the initial and final levels
c. a ratio between the two levels
d. a product of the initial and final levels
C
Decibel notation uses which scale?
a. linear’
b. logarithmic
c. discrete
d. divisive
B
If the intensity decreases from 1.5 W/cm2 to 0.75 W/cm2, how many decibels is this change?
a. 3 dB
b. -3 dB
c. 0.75 dB
d. 2 dB
e. -2 dB
B
If the power increases two times the original value, how many decibels is this change?
a. 3
b. 6
c. 10
d. 20
A
Which of these media has the greatest attenuation and the slowest speed?
a. bone
b. tendon
c. fat
d. air
D
Which of these media has the greatest attenuation and the fastest speed?
a. bone
b. tendon
c. lung
d. fat
e. air
A
Which of the following describes the physics of refraction mathematically?
a. Bernoulli’s Principle
b. Snell’s Law
c. Pouiseulle’s Law
d. Murphy’s Law
e. Bernoulli’s Law
B
Which of the following terms does not belong with the others?
a. oblique
b. normal
c. perpendicular
d. orthogonal
e. ninety degrees
A
Which of the following terms best describes a reflection arising from a rough boundary?
a. non-diffuse
b. absolute
c. Rayleigh
d. smooth
e. non-specular
E
A sound wave strikes a boundary between two media with different impedances. The angle of incidence is non-orthogonal. Which of the following statements is most correct?
a. all of the sound will be reflected
b. some of the sound will be reflected
c. some of the sound may be reflected
d. some of the sound will be refracted
e. none of the sound will be refracted
C
A sound pulse is produced by a transducer and travels in an ultrasound phantom. The pulse travels from the transducer to pin “D”, reflects off of it and returns to the transducer in 130 μs. How deep is pin “D”?
a. 5 cm
b. 10 cm
c. 15 cm
d. 20 cm
B
A sound pulse emitted from a transducer travels in an ultrasound phantom, reflects off of pin “A”, and returns to the transducer in 52 μs. How deep is pin “A”? What is the total distance that the pulse traveled?
a. 8 cm
b. 6 cm
c. 4 cm
d. 2 cm
C
A sound wave is created by a transducer, reflects off of an object and returns to the transducer. The depth of the reflector is 10 cm. The round-trip time is 2 seconds. What is the speed of sound in the medium?
a. 5 cm/s
b. 10 cm/s
c. 20 cm/s
d. 2 cm/s
B
