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90 Cards in this Set

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  • Back
Which of the following human tissues demonstrates the highest rate of attenuation of the ultrasound wave? Liver, Fat, Fulid, Lung, or Blood Vessels?
Lung
What property would result in increased propigation speed of a medium?
Increased stiffness
If sound waves of 3Mhz, 5Mhz, and 10Mhz are transmitted through the same section of liver, which frequency would reach the transducer first?
Reflections from all three frequencies would have identical transmit times
While preforming an ultrasound of the thyroid gland, you adjust the acoustic power by -3 dB, what would happen to the intensity?
It would be halved
What detrermines acoustic impedance?
Density and propagation speed of the medium
Which of the following is true regarding the half value (HVL) thickness for a 10Mhz transducer in soft tissue? It represents a 3dB decrease in signal intensity, it occurs at a shallower dpth than the HVL for a 5Mhz transducer, It represents the point at which the beam intensity is reduced by one half, B & C, or A & B& C
A & B& C
With absorption, acoustic energy is converted into what?
Heat
What term is used to describe the hyperechoic region region seen below a cyst?
Acoustic enhancement
The attenuation os ultrasound propigating through soft tissue is approx what?
0.5 dB/cm/Mhz
As acoustic pressure increases, so does what?
Intensity
As a general observation about media of concern in diagnostic ultrasound, sound propaggates faster in materials with greater what?
Stiffness
With specular reflection the strength of the received signal depends on what 2 factors?
Difference in acoustic impedance and angle of incidence
How is a longitudinal wave characterized?
Particle motion occurring in the same direction as propagation
You are imaging a structure that is highly attenuating, WHat effect would you expect to encounter?
Shadowing
Bulk modulus refers to what quality?
Stiffness
When your patient asks you how much longer the exam will take, his voice is in the audible frequency range. What is an audible frequency range?
10kHz
Which of the following frequencies is considered to be ultrasound? 2,000Hz, 20Hz, 2MHz, 200Hz, or 2Hz?
2MHz
What does Snell's law describe?
The angle of sound transmission as an interface with oblique incidence and different propagation speeds
Describe Diffuse reflection?
A reflected beam that is scattered in all directions
During an ultrasound examination of the aorta, a 45degree beam to vessel angle would be called what?
Oblique incidence
What is the period of 5MHz frequency?
.0000002s
What is the sped of sound defined as?
The Speer at which the sound wave propagates through the medium
What interaction of ultrasound and tissue is primarily respnsible for imaging the internal structure of organs?
Scattering
When the sound beam is refracted during an ultrasound examination, which of the following will you detect on the ultrasound image?
Lateral Misregistration
Which of the following terms denotes the time it takes for one cycle to occur? Frequency, Amplitude, Wavelength, Period, or Pressure?
Period
For distance measurement to be accurate in an ultrasound tissue phantom, the phantom sound propagation speed must be waht?
1540m/s
The hyperechoic region under a cycst results from what?
Decreased attenuation through a fluid filled structure
While preforming an abdominal ultrasound examination, you encounter the following interfaces. Which will produce the strongest reflected signal? Spleen/kidney, Liver/pancreas, Liver/Bowel gas, Liver/bile duct, Renal cortex/ renal sinus
Liver/bowel gas
The regions of low pressure and density that are formed during sound propagation are termed waht?
Rarefractions
During an abdominal ultrasound exam, you encounter all of the following interactions of ultrasound and tissue. Which of the following will not cause redirection of ultrasound energy? Reflection, Scattering, Divergence, Absorption, Refraction
Absorption
Which prefix equals 10-3?
Milli
Frequency of the ultrasound wave is defined as what?
Number of cycles per second
You are scanning a patient with suspected gallstones using a 3.5MHz transducer. You do not ditect shadowing distal to the suspected gallstone. What can you do to enhance the visibility of the acoustic shadow distal to a gallstone?
Increase the transducer frequency
According to Snell's law, the angle of transmission is related to the incident beam angle and what?
The relative velocities of sound in the two media
What is another term for nonspecular reflection?
Scattering
During the performance of an abdominal ultrasound examinatioin, you would most expect to encounter refraction in what view?
Transverse view of the gallbladder
What would be the result of inaging the aorta at an angle of 45?
Tha angle of reflection will be oriented away from the transducer resulting in decreased visuaalization of the aorta
Wavelength depends on what two factors?
Frequency and propagation speed
If the propgation speed is unchanged at the interface, which most correctly describes the sound tissue interaction that will take place when the ultrasound wave strikes the interface? Specular reflection, Dcattering, Diffraction, Refraction, or None
Scattering
When you switch from a 2.5MHz to a 5MHz transducer, what happens to the wavelength?
It halves
You are scanning an interface at normal incidence in which the acoustic impedance is unchanged from one media to the other. WHat will occur?
There will be no sound reflected
Describe sound propagation in a medium
Molecules oscillating back and forth to propagate sound waves but does not move frorm one end of the medium to another
For pulsed ultrasound, the following factors determine the frequency of the sound wave: Pulse repitition frequency, propagation speed of the piezoelectric material, thickness of the piezoelectric material, B & C, or A & B & C
B propagation speed of the piezoelectric material & C Thickness of the piezoelectric material
You have increased the transmit power while performing a pelvic ultrasound. Which actions does this increase?
Penetration, Acoustic power, Image brightness, and the voltage applied to the crystals
While imaginag a breast cyst, you notice shadowing posterior to each lateral border of the cyst. Wjat is the source of the shadow?
Redirection of the sound beam at an interface with diefferent propagation speeds and a curved surface
For soft tissue, which one of the following is responsible for determining acoustic impedance: Attenuation, Frequency, Absorption, Density, or Amplitude?
Density
What two conditions must be present to cause refraction of a sound wave?
Oblique incidence and different media propagation speeds
If the number of cycles in a pulse is increased but the wavelength remains the same, what happens to the pulse duration?
It is increased
The maximum cyclical change in a quantity is known as what?
Amplitude
What sound tissue interaction is necessary to form an ultrasound image?
Reflection
The transducer you are using to image the liver transmits a wide beam of 3-5MHz. Describe the beam after it has transversed the liver?
The reflected bandwith will be shifted down in frequency due to the increased attenuation of higher frequencies
Increasing the frequency on a multifrequency transducer from 3.5 to 5.0 MHz will do what to what wavelength?
Decrease it
What term is used to describe the reduction in the intensity of sound as it propagates through tissue?
Attenuation
Sound may be attenuated by all of the following Except: Reflection, Scattering, Conversion of sound to heat, Absorption, or Compression?
Compression
In sound wave propagation, the region of elevated pressure is termed what?
Compression
During the performance of an ultrasound exam, you decide to adjust the system parameters to improve the image. Which of the following parameters is not adjustable by operator control on ultrasound system: Frequency, Prop speed, power, intensity, or echo signal amplificaiton?
Prop speed
Which of the following is an example of a rayleigh scatter: Renal capsule. arterial wall, red blood cells, bowel gas, or femur?
Red blood cells
An echo from which of the following sound reflectors is most dependent on the angle of incidence: Rayleigh, Diffuse, Specular, Acoustic, or Nonspecular?
Specular
The following adjustment would decrease beam intensity: Increasing acoustic output, Decreasing receiver gain, increasing focusing, Increasing beam area, increasing amplitude
Increasing beam area
You are scanning a large abdominal mass that is comprised primarily of fat. What are you most likely to encounter?
Axial misregistration of the mass on the screen caused by the slower propagation speed through fat
What is the relationship of frequency to absorption?
If frequency is doubled, absorption is doubled
Which of the following tissues would have the slowest propagation speeds for sound? Fat, Blood, Muscle, Bone or Liver?
Fat
Relative measurement of intensity based on a logarithmic scale is expressed how?
In decibels
An interation of echoes that leads to reinforcement rather than to partial or total cancellation is known as what?
Constructive interference
WHat is the velocity of an ultrasound wave in bone?
4080 m/s
What is the algebraic summation of waves called?
Interference
What interaction is associated with divergence of the sound beam after passing through a small aperature?
Diffraction
During abdominal US, you image the following structures: Blood bile, Liver parenchyma, Gallstone, Spleen, which is most attenuating?
Gallstone
As frenquency increases what else increasees?
Absorption, Scattering, Attenuation
What system control should you adjust to account for sound attenuation with depth?
TGC
you are imaging the interface between two abdominal structures at normal incidence. They have the same acoustic impedance. What will occur at the boundary of the two structures?
All of the sound will be transmitted
The intensity coefficient at the interface between two structures equals 1%, What is the intensity reflection coefficient
99%
You are imaging an irregular round mass in the liver that has a much slower propagation speed than liver tissue, what sound tissue interaction will be encountered as the ultrasound propagates through this interface?
Refraction, Reflection, Absoprtion, Scattering
Which of the following factor does not affect impedance: Stiffness, Density Prop speed, Frequency or all of the above?
Frequency
13kHz can also be expressed as what?
13,000 Hz
Which of the following adjustments would reduce sound attenuation in the body most? Increasing receiver gain, Decreasing transmit power, Increasing dynamic range, Decreasing frequency, or Decreasing focus?
Decreasing frequency
Why is diagnostic US limited in its diagnostic application to the adult brain?
Because the great acoustic impedance mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface
Reflection of the sound beam from a large interface wilth a rough surface is called what?
Diffuse reflection
Which of the followinf interactions of sound and tissue decreases the intensity of the transmitted beam? Absorption, Reflection, Scattering, Conversion to heat, or all of them?
All of them
What must be present for sound reflection to occur at the interface of two structures?
A difference in the acoustic impedance of the media
Which of the following statements is true regarding the effect of frequency on Rayleigh scattering; The amount of scattering is not affected by frequency, Scattering intensity doubles if frequency is doubled, Doubling the freq results in halving the scattering intensity, Doubling the freq results in quartering the scattering intensity, or Scattering intensity is proportional to freq raised to the fourth power
Scattering intensity is proportional to frequency raised to the fourth power
What can be done to enhance visibility of a specular reflector?
Acan with an incident angle of 90
What is an example of a specular reflector?
Renal capsule
While performing a hepatic sonogram on a patient with a fatty liver, you are unable to visualize the posterior right lobe of the liver. Which of the following solutions would be most likely to enable visualization of this area: Decrease dynamic range, Decrease nearfield DGC, Choose a lower freq transduce, Increase the scan line density, Change the gray scale map?
Choose a lower freq transducer
If you choose a lower freq transducer to image a highly attenuating liver, what tradeoff are you making?
Decreased Spatial resolution
What sound interaction would produce shadows posterior to a fetal head?
Refraction
Attenuation increases with increasing what?
Path lenght, absorption, frequency, acoustic impedance
What is the unit of impedance?
Rayl
What sound parameter is determined only by the medium?
Propagation speed
As you perform an abdominal ultrasound exam, you switch from a 3.5 to 7.0 MHz transducer to image a pancreatic mass. Compared to those of the previous transducer, what will the new attenuation rate and the wavelength be?
Double attenuation rate, on-half wavelength