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267 Cards in this Set
- Front
- Back
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True/False: Attenuation is ALWAYS a loss. |
True |
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What are the 2 factors of Attenuation? |
path length frequency |
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Which 3 processes are attributed with Attenuation? |
Reflection Scattering Absorption |
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Name the 2 types of reflection. |
Specular reflection Diffuse reflection |
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Which type of reflection has a smooth surface (mirror-like), is strong and angle dependent? |
Specular reflection |
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Which type of reflection is associated with back scatter? |
Diffuse reflection |
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Interaction between the ________________ and the _______________ decides which type of surface it is in regards to reflection. |
wavelength particle |
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The _______________ the wavelength, the rougher things will look. |
shorter |
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The shorter the _________________, the rougher things will look. |
wavelength |
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If you increase the _________________, the surface will look rougher, the diffuse reflection will increase, and the specular reflection will decrease. |
frequency |
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If you increase the frequency, the surface will look _____________, the diffuse reflection will ________________, and the specular reflection will ______________. |
rougher increase decrease |
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If you __________________ the frequency, the surface will look rougher, the diffuse reflection will increase, and the specular reflection will decrease. |
increase the frequency |
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If diffuse reflection increases, then specular reflection will _______________. |
decrease |
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If diffuse reflection _______________, then specular reflection will decrease. |
increases |
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The higher the frequency, the _______________ the specular reflection, and diffuse reflection will ________________. |
lower specular reflection diffuse reflection increases |
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The _________________ the frequency, the lower the specular reflection, and diffuse reflection will increase. |
higher |
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The lower the frequency, the _______________ the specular reflection, and the _________________ the diffuse reflection. |
higher specular reflection lower diffuse reflection |
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The lower the frequency, the specular reflection will _____________, and diffuse reflection will _______________. |
increase specular reflection decrease diffuse reflection |
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The higher the frequency, the specular reflection will ________________, and the diffuse reflection will ________________. |
decrease specular reflection increase diffuse reflection |
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Name the 2 types of Scattering. |
Scattering Rayleigh |
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Which type of scattering moves chaotically in all directions and has some transmission (crosses the boundary/forward)? |
Scattering |
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Which type of scattering is uniform? |
Rayleigh |
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What is the primary Rayleigh scatterer in the body? |
RBC *red blood cells |
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90% of loss is due to __________________. |
absorption |
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True/False: Temperature is average kinetic energy. |
True |
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True/False: The faster the movement of energy, the higher the temperature. |
True |
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True/False: Sound is organized organized kinetic energy. |
True |
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True/False: Sound is longitudinal. |
True |
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True/False: Sound is vibrational temperature. |
True |
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True/False: As sound passes through and bounces off things, it begins to get disorganized. |
True |
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True/False: Sound gets converted into thermal energy (heat) as it passes through and bounces off of things becoming disorganized. |
True |
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True/False: When sound has become disorganized, we can no longer get information from it because it is converted to thermal energy (heat). |
True |
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What is the largest contributor to attenuation? |
absorption |
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The ________________ the frequency, the more rapidly sound converts into thermal energy (heat). |
higher |
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True/False: The longer the path length, the greater the loss. |
True |
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The _______________ the frequency, the greater the loss. |
higher |
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If frequency increases, absorption _______________. |
increases |
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If frequency _______________, absorption increases. |
increases |
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As path length increases, absorption __________________. |
increases |
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True/False: Water (fluid) has a low attenuation. |
True *things will not bounce off of water |
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True/False: Air has a low attenuation. |
False *air has an extremely high attenuation *it's why we use gel to eliminate the air |
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True/False: Reflection + Transmission = 100% |
True *if 20% is reflected, then 80% is transmitted |
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True/False: If the reflection percentage is larger, than the transmission percentage is smaller. |
True |
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Reflection and Transmission are _______________ related. |
inversely |
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True/False: Energy is NEVER conserved. |
False *energy is ALWAYS conserved |
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Equation: Impedance (rayls(Z)) = |
density x propagation speed |
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At a ________________ is where there are impedance differences. |
boundary |
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At a boundary, the larger the impedance difference, the _______________ the reflection, and the _______________ the transmission. |
larger reflection smaller transmission |
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At a boundary, the _______________ the impedance difference, the larger the reflection, and the smaller the transmission. |
larger impedance |
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True/False: If an angle is not perpendicular, than it is called oblique. |
True |
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True/False: The incident beam and reflected beam have the exact same angle. |
True |
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True/False: The incident beam and reflected beam NEVER refract. |
True |
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True/False: Since the reflected beam never refracts, the speed of sound does not change. |
True |
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True/False: If the speed of sound does not change, there will NEVER be refraction. |
True |
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The _______________ beam is the ONLY beam that can refract. |
transmitted |
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True/False: The transmitted beam is the ONLY beam that can refract. |
True |
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True/False: Snell's Law (sine) states that the largest angle ALWAYS goes with the slowest speed. |
False *the largest angle ALWAYS goes with the GREATEST speed (Snell's Law) |
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True/False: According to Snell's Law (sine), the larger angle is on the fast side, and the smaller angle is on the slower side. |
True *fast to slow |
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True/False: The Range Equation, Distance Formula, and 13 Micro-second Rule are the same thing. |
True *they tell us how the machine knows where to put that reflector |
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What do the Range Equation, Distance Formula, and 13 Micro-second Rule tell us? |
How the machine knows where to put that reflector |
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How does the machine know where to put the reflector on the display? |
Range Equation Distance Formula 13 Micro-second Rule |
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True/False: If there is no echo, than there is no image. |
True |
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In regards to the depth of reflector, if sound has gone 13 micro-seconds, then it has gone 1 cm. What is the total distance the sound traveled? |
2 cm *to and from |
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If sound has gone 26 micro-seconds, then the depth of the reflector is 2 cm. What is the total distance the sound traveled? |
4 cm |
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If you are imaging and the reflector is at a depth of 3 cm, What is the total distance the sound has traveled? |
6 cm |
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What is the distance from the transducer to the reflector called? |
depth |
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What is the Piezoelectric Effect? |
pressure to electricity, electricity to pressure sound to electricity, electricity to sound |
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True/False: Send in a voltage, get out a sound pulse is known as the Piezoelectric Effect. |
True |
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Which part of the transducer does the transducing? |
PZT crystal |
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Once the sound pulse is received it is sent through the ______________ ________________. |
Matching Layer |
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Which part of the transducer improves the efficiency of sound transfer in and out and matches the impedance? |
Matching Layer |
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Which part of the transducer stops the ringing? |
Backing material |
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Which part of the transducer has a shorter Pulse Duration, shorter Spatial Pulse Length and better Axial Resolution? |
Backing material |
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In order for the Backing material to stop the ringing, it has to do 3 adverse things, which are? |
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True/False: ALL imaging transducers require us to pulse the sound quickly, therefore ALL imaging transducers have backing material to stop the ringing. |
True |
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True/False: ALL imaging transducers are High Quality transducers. |
False *ALL imaging transducers are Low Q |
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If you raise the temperature of the transducer past it's ___________ ___________, it will depolarize it. |
Curie Point |
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In a Continuous Wave transducer, the frequency of sound is equal to the ______________ frequency. |
voltage frequency |
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What determines the frequency of sound for a Continuous Wave transducer? |
voltage frequency |
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True/False: Whatever the voltage frequency, it is the Continuous Wave transducer frequency (only). |
True |
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What are the 2 factors of Pulsed Wave transducers? |
determined by the ..
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True/False: The speed of sound in the PZT crystal is also referred to as the vibration. |
True |
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The higher the speed of sound in the PZT crystal, the _____________ the frequency in the crystal. |
higher |
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The _______________ the speed of sound in the PZT crystal, the lower the frequency in the crystal. |
lower |
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True/False: In order to oscillate, the thicker the PZT crystal the longer it takes to expand and contract. |
True |
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The thicker the PZT crystal, the ________________ the frequency. |
lower |
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The thinner the PZT crystal, the ____________ the frequency. |
higher |
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The ________________ the PZT crystal, the lower the frequency. |
thicker |
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The _______________ the PZT crystal, the higher the frequency. |
thinner |
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The sound beam ALWAYS converges in the _______ field. |
near field |
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The sound beam ALWAYS diverges in the ______ field. |
far field |
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True/False: The sound beam ALWAYS diverges in the near field. |
False *sound beam always diverges in the far field *sound beam always converges the near field |
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What is the distance from the transducer to the narrowest part of the sound beam called? |
Focal length |
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What is the narrowest part of the sound beam called? |
Focus |
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What is the narrow section that straddles the focus called? |
Focal zone |
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What are Focal length and Divergence determined by? (2) |
diameter of the PZT crystal frequency of the PZT crystal |
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The larger the diameter of the PZT crystal, the ______________ the frequency, the ______________ the Focal length, and the __________ Divergence. |
larger PZT diameter.... higher frequency longer focal length less divergence |
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The smaller the diameter of the PZT crystal, the ____________ the frequency, the _____________ the Focal length, and the _________ Divergence. |
smaller PZT diameter... lower frequency shorter focal length greater divergence |
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True/False: Divergence is ALWAYS in the Far field. |
True |
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The _____________ the Focal length, the less divergence in the Far field. |
longer |
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The longer the Focal length, the _______ divergence in the Far field. |
less |
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Describe Huygens. |
Diffraction (spreading out)(widening) Wavelets (little wavelets into one big wave) |
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The sound pulse that comes off perpendicular to the surface of the transducer (longitudinal), is called? |
Axial Resolution |
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Axial Resolution is ________________ to the beam's main axis. |
parallel |
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True/False: Axial Resolution is lined up Front to Back. |
True |
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Lateral Resolution is _________________ to the beam's main axis. |
perpendicular *long axis |
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Lateral Resolution is lined up Side by Side. |
True |
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Equation: Axial Resoulution = |
axial resolution = 1/2 Spatial Pulse Length |
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True/False: Axial Resolution does not change. |
True *never changes, it is constant |
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True/False: Axial Resolution never changes, it remains constant. |
True |
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Axial Resolution is determined by? |
Spatial Pulse Length |
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True/False: Axial Resolution changes in the Near field and the Far field, and the longest pulse beat is best. |
False *axial resolution never changes *shortest pulse is best |
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Axial Resolution is best with the _____________ frequency, ______________ pulse, and _____________ cycles. |
highest frequency shortest pulse fewest cycles |
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True/False: The shortest pulse is the one with the highest frequency and the fewest cycles. |
True |
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Equation: Lateral Resolution = |
beam width |
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Lateral Resolution is _____________ in the Near field, and the frequency does not matter. |
narrowest *frequency does not matter with lateral resolution |
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True/False: Frequency does not matter with Lateral Resolution. |
True |
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Lateral Resolution is best where the beam is the ______________. |
narrowest (focus) |
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Lateral Resolution is best at the beam's ____________. |
Focus |
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True/False: Lateral Resolution changes constantly. |
True |
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Lateral Resolution changes constantly because the beam ___________ is changing all of the time. |
beam width *converging + diverging |
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What is the best way to describe Lateral Resolution? |
it varies |
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A huge Divergence occurs with a __________ diameter, ____________ beam width, and _____________ Focal length. |
huge divergence... small diameter narrow beam width short focal length |
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In order to get a narrow pulse in the Far field, there needs to be a _____________ diameter and _______ frequency. |
large diameter high frequency (gentle diverging beam) |
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True/False: Phased array means adjustable or multi-focused electronically. |
True |
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True/False: All adjustable focus is done electronically. |
True |
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Every 3 dB change means that the intensity will _____________. |
double |
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Every 10 dB change means that the intensity will _____________ ten times. |
increase ten times |
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A reduction in the intensity of a sound beam to one-half of its original value is ________ dB. |
-3 dB |
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A reduction in the intensity of a sound beam to one-quarter of its original value is _______ dB. |
-6 dB |
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-10 dB means that the intensity is reduced to _________ of its original value. |
One-tenth |
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dB is a mathematical representation with a ____________ scale. a) logarithmic and relative b) division and relative c) longitudinal and relative d) logarithmic and absolute |
a) logarithmic and relative |
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True/False: We need one intensity to calculate decibels. |
False |
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If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is _____________ (+/-). |
positive *beam's intensity is increasing |
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If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is ______________ (+/-). |
Positive *beam's intensity is increasing |
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Name the 3 components of Attenuation. |
Absorption Reflection Scattering |
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As the path length increases, the Attenuation of ultrasound in soft tissue _______________. |
increases |
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Attenuation in lung tissue is __>,=,<__ attenuation in soft tissue. |
greater than (>) |
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Attenuation in bone is __>,=,<__ attenuation in soft tissue. |
greater than (>) |
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Attenuation in air is __>,=,<___ attenuation in soft tissue. |
greater than (>) |
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What are the units of Attenuation? |
decibels (dB) |
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True/False: In a given medium, attenuation is unrelated to the speed of sound. |
True *attenuation and propagation speed are unrelated |
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What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue? |
In soft tissue, the attenuation coefficient in dB per cm is approx 1/2 of the ultrasonic frequency in MHz |
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What are the units of the half-value layer thickness? |
distance (cm) |
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As frequency decreases, depth of penetration ______________. |
increases |
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As path length increases, the half boundary layer ______________. |
remains the same |
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Impedance is associated with? |
ONLY the medium |
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As the path length increases, the attenuation coefficient of ultrasound in soft tissue ________________. |
remains the same |
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Equation: Acoustic impedance = |
=density(kg/m cubed) X propagation speed(m/s) |
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Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance? |
Medium A *impedance = speed x density |
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Impedance is important in _____________ at boundaries. |
reflections |
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Which is better to use while examining a carotid artery, a 7.5 or 3.9 MHz transducer? |
7.5 MHz *higher the frequency produces the better image and the structure is superficial |
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A sound wave with an intensity of 50 W/cm sqd. strikes a boundary and is totally reflected. What is the intensity reflection coefficient? a) 50 W/cm sqd b) 25 W/cm sqd c) 0 W/cm sqd d) 100% e) 0 |
d) 100% |
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A sound wave with an intensity of 50 W/cm sqd strikes a boundary and is totally reflected. What is the reflected intensity? a) 50 W/cm sqd b) 25 W/cm sqd c) o W/cm sqd d) 100% e) 0 |
a) 50 W/cm sqd |
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A pulse of ultrasound is propagating in soft tissue, such as liver. The pulse strikes a boundary with a different soft tissue at normal incidence. What portion of the intensity is reflected back toward the transducer? |
a very small amount (< 1%) |
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Sound is traveling in a medium and strikes a boundary with normal incidence. If 63% of the wave's intensity is reflected back toward the transducer, what percentage is transmitted? |
37% |
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True/False: Reflections only occur when the impedances of two media are different. |
True |
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True/False: A reflection is not created when the impedances of the two mediums are the same. |
True |
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Which of the following terms does not belong with the others? a) orthogonal b) oblique c) normal d) perpendicular |
b) oblique *means other than 90 degrees |
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Sound is traveling from bone to soft tissue. The impedance of the media differ significantly, and 90% of the beam's intensity is reflected. What percentage of the intensity is transmitted? |
10% |
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A pulse of ultrasound propagates in soft tissue. The pulse strikes a soft tissue - sift tissue interface with oblique incidence. Some of the sound energy is transmitted. To what extent is the transmitted beam refracted? |
the transmitted beam undergoes little to know refraction *A transmitted beam is refracted when the incidence is oblique and the propagation speeds are different |
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True/False: A transmitted beam is refracted when the incidence is oblique and the propagation speeds are different. |
True |
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True/False: When the angle of transmission is less than the angle of incidence, sound travels slower in the second medium. |
True |
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True/False: Sound refraction at a boundary is unrelated to the impedances of the media. |
True |
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True/False: Refraction is affected by the speed of sound in the media. |
True |
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True/False: With normal incidence, refraction cannot occur. |
True |
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True/False: Refraction occurs ONLY when there are different speeds and oblique incidence. |
True |
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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) 50% c) 0% d) 25% |
c) 0% *refraction cannot occur with normal incidence |
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What property has units of Rayls? |
Impedance *density x speed |
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What processes occur as the ultrasound passes through all media? |
Attenuation (dB) *absorption, scattering, reflection |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time? |
130 microseconds *time of flight equals depth x 13 microseconds *10 cm x 13 microseconds = 130 |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 microseconds. What is the depth of the reflector? |
2 cm *2 cm x 13 microseconds/cm = 26 |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. the go-return time is 26 microseconds. What is the total distance that the pulse traveled? |
4 cm *total distance traveled is twice the depth of the reflector |
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The maximum imaging depth (depth of view) during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to the Pulse Repetition Period? a) unchanged b) halved c) doubled d) 20 times longer |
c) doubled *PRP is directly related to imaging depth |
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The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to the Pulse Repetition Frequency? a) unchanged b) halved c) doubled d) 20 times longer |
b) halved *PRF is inversely related to imaging depth |
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True/False: The Pulse Repetition Frequency is directly related to imaging depth. |
False *PRF is inversely related to imaging depth *PRP is directly related to imaging depth |
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True/False: The Pulse Repetition Period is inversely related to imaging depth. |
False *PRP is directly related to imaging depth *PRF is inversely related to imaging depth |
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The imaging depth during and ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 5 cm. What happens to the Pulse Repetition Period? a) unchanged b) halved c) doubled d) 20 times longer |
b) halved |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The imaging depth is 10 cm in soft tissue. What is the maximum Pulse Repetition Frequency? a) 7,700 b) 7.7 kHz c) 3,500 Pa d) 7,700 microseconds |
b) 7.7 kHz *because the units are correct |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The maximum imaging depth is 7.7 cm. What is the PRF? a) 7,700 Hz b) 5,000 kHz c) 10,000 Hz d) 100 microseconds |
c) 10,000 Hz *77,000 / 7.7 = 10,000 Hz |
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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 130 microseconds. What is the PRF? a) 7,700 Hz b) 5,000 kHz c) 10 cm d) 100 microseconds |
a) 7,700 Hz |
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Pulse length is ______________ related to Pulse duration. |
directly |
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Q-factor is ________________ related to bandwidth. |
inversely |
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Pulse duration is ______________ related to bandwidth. |
inversely |
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The sensitivity of transducers that create short duration pulses is likely to be _____>=<_____ that of transducers that create long pulses. |
less than (<) |
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All of the following correctly describe an imaging transducer except: a) high sensitivity b) low Q c) wide bandwidth d) damped |
a) high sensitivity *imaging transducers have a low sensitivity |
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True/False: Imaging transducers have a high sensitivity. |
False *imaging transducers have a low sensitivity |
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True/False: Shorter duration events, such as dampened pulses, are more likely to be wide bandwidth. |
True |
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True/False: Longer duration events are more likely to be narrow bandwidth. |
False *longer duration events are more likely to be narrow bandwidth |
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What occurs when a PZT crystal's temperature is elevated above the Curie point? |
depolarization of the PZT crystal |
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True/False: The acoustic impedance of the matching layer is approximately the same as the acoustic impedance of skin. |
False *impedance of the matching layer is greater than the impedance of the skin |
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True/False: Imaging transducers are usually of high rather than low bandwidth. |
True *imaging transducers are broad bandwidth |
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True/False: A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor. |
False *imaging transducers are low Q |
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True/False: A pulse with a long pulse duration is likely to have a narrow bandwidth. |
True *longer pulse has narrow bandwidth *shorter pulse has wider bandwidth |
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True/False: The damping material in a transducer increases the sensitivity. |
False *damping reduces sensitivity |
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True/False: The damping material in a transducer increases the pulse length. |
False *damping shortens pulse length |
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True/False: The damping material in a transducer decreases the pulse duration. |
True |
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True/False: The damping material in a transducer improves the system's longitudinal resolution. |
True |
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True/False: The damping material in a transducer improves the system's lateral resolution. |
False *damping does not affect lateral resolution |
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True/False: Damping does not affect Lateral Resolution. |
True |
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True/False: The damping material in a transducer decreases the bandwidth. |
False *damping increases bandwidth |
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True/False: The damping material in a transducer decreases the quality factor. |
True |
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True/False: If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, then the operating frequency of the transducer is 6 MHz. |
False *with pulsed wave transducers, the frequency of sound is not determined by the electrical signal |
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True/False: With Pulsed Wave transducers, the frequency of sound is not determined by the electrical signal. |
True |
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True/False: If the Pulse Repetition Frequency of a transducer is increased, then the frequency of sound produced by the transducer remains the same. |
True |
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True/False: The diameter of the active element of a transducer helps to determine the frequency of the sound that the transducer creates. |
False *diameter of active element does not determine frequency of sound |
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True/False: If the frequency of the electrical excitation voltage of a Continuous Wave transducer is 6 MHz, then the operating frequency of the transducer is 6 MHz. |
True |
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True/False: Two piezoelectric crystals are made from the same material. The thicker crystal will make a Continuous Wave transducer with a lower frequency. |
False *with a CW transducer, active element thickness does not determine the sound beam's frequency |
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True/False: Two piezoelectric crystals are made from the same material. The thicker crystal will make a Pulsed Wave transducer with a higher frequency. |
False *with PW transducers, thicker active elements create sound with lower frequency |
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True/False: The normal propagation speed in piezoelectric material is about 3.5 times greater than that in soft tissue. |
True |
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The impedance of a transducers active element is 1,900,000 Rayls, and the impedance of the skin is 1,400,000 Rayls. What is an acceptable impedance for the matching layer? a) 1,200,000 Rayls b) 1,400,000 Rayls c) 1,726,000 Rayls d) 1,950,000 Rayls |
c) 1,726,000 Rayls *the impedance of the matching layer is between the active element and the skin |
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Which of the following crystals will produce sound with the lowest frequency? a) thin and with a low speed b) thin and with a high speed c) thick and with a low speed d) thick and with a high speed |
c) thick and with a low speed |
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Which type of transducer has a greater Q-factor: therapeutic or imaging? |
therapeutic transducer |
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Which type of transducer has a greater bandwidth: continuous wave or imaging? |
imaging transducer |
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Which type of transducer has more backing material: therapeutic or imaging? |
imaging transducer |
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In an imaging transducer, what is the purpose of attaching the backing material to the PZT? a) increase bandwidth b) decrease Q-factor c) improve image quality d) decrease transducer sensitivity |
c) improve image quality |
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A Pulsed Wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the bandwidth? |
6 MHz *8 MHz - 2 MHz = 6 MHz |
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A Pulsed Wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz.What is the main(resonant/center) frequency? |
5 MHz |
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A Pulsed Wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the Q-factor? a) 0.8 b) 3 MHz c) 1.5 d) 5 MHz |
a) 0.8 *Q-factor = resonant frequency / bandwidth *5 MHz / 6 MHz = 0.8 (unit-less) *bandwidth has no units |
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A pair of 6 MHz probes are identical except for the active element diameter. The active element diameters are 6 mm and 10 mm. The sound beam of which probe will have a shallower focus? |
6 mm diameter *smaller diameter crystals produce beams with shallower foci |
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A pair of 9 mm diameter probes are identical except for frequency, which is 3 MHz and 6 MHz. Which beam will have a shallower focus? |
3 MHz beam *focal depth increases with increasing frequency |
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Which of the following probes creates a beam with the deepest focus? a) 4 mm diameter, 4 MHz b) 6 mm diameter, 8 MHz c) 6 mm diameter, 2 MHz d) 5 mm diameter, 8 MHz |
b) 6 mm diameter, 8 MHz *higher frequency, larger diameter --> longer focal length |
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Which of the following probes creates a beam with the shallowest focus? a) 4 mm diameter, 4 MHz b) 6 mm diameter, 8 MHz c) 4 mm diameter, 2 MHz d) 5 mm diameter, 8 MHz |
c) 4 mm diameter, 2 MHz *lower frequency, smaller diameter --> shorter focal length |
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Which of the following probes creates a beam with the shallowest focus? a) small diameter, high frequency b) large diameter, high frequency c) small diameter, low frequency d) large diameter, low frequency |
c) small diameter, low frequency |
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True/False: Active element diameter and near zone length are directly related. |
True |
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True/False: Transducer frequency and near zone length are inversely related. |
False *frequency and near zone length are directly related |
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True/False: Wavelength and near zone length are inversely related. |
True |
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A pair of 6 MHz probes are identical except for the active element diameters, which are 6 mm and 10 mm. Which beam will be more compact in the far field? |
the 10 mm probe *larger diameter beams have less divergence in the far field |
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A pair of 9 mm diameter probes are identical except for frequencies, which are 3 MHz and 6 MHz. Which sound beam will spread out more in the far field? |
3 MHz probe (more divergent) *beams are more compact as frequency increases |
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Which of the following probes creates a beam with the least divergence? a) 4 mm diameter, 4 MHz b) 6 mm diameter, 8 MHz c) 6 mm diameter, 2 MHz d) 5 mm diameter, 8 MHz |
b) 6 mm diameter, 8 MHz |
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Which of the following probes creates a beam with the most divergence? a) 4 mm diameter, 4 MHz b) 6 mm diameter, 8 MHz c) 4 mm diameter, 2 MHz d) 5 mm diameter, 8 MHz |
c) 4 mm diameter, 2 MHz |
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Which of the following creates a beam with the most divergence? a) small diameter, high frequency b) large diameter, high frequency c) small diameter, low frequency d) large diameter, low frequency |
c) small diameter, low frequency |
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True/False: Transducer frequency and beam divergence are inversely related. |
True |
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True/False: Active element diameter and beam divergence are inversely related. |
True |
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The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the near zone length? |
increases |
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The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the beam diameter in the far zone? |
decreases |
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The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the wavelength? |
no change |
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The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the beam diameter in the near zone? |
increases |
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At what location is the sound beam diameter three times greater than the transducer diameter? a) end of near zone b) at a depth equal to four focal lengths c) end of far zone d) at the triple diameter depth |
b) at a depth equal to four focal lengths *the only region where the beam diameter exceeds the transducer diameter is at depths exceeding two focal lengths |
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What is the shape of a sound beam created by a tiny piece of PZT? a) hourglass b) V-shaped c) round d) tube shaped |
b) V-shaped *diffraction pattern or Huygens' wavelet |
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Which of the following explains why a sound beam created by a disc-shaped crystal is hour-glass shaped? a) Bernoulli's Principle b) Sheffield's Law c) Ohm's Law d) Huygens' Principle |
d) Huygens' Principle |
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Which of the following location is the deepest? a) end of Fresnel zone b) end of Focal zone c) end of Fraunhofer zone d) end of Near zone |
c) end of Fraunhofer zone *deepest part of the sound beam |
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Which of the following locations is the most shallow? a) beginning of Far zone b) beginning of Focal zone c) Focal depth d) beginning of Fraunhofer zone |
b) beginning of Focal zone |
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What is the ability to accurately distinguish two structures lying close together called? |
resolution |
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The ability to distinguish two structures lying close together front-to-back or parallel to the sound beam is called? |
Axial Resolution *aka longitudinal, range, radial depth |
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Axial Resolution is measured in units of? |
distance (mm, cm) |
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If there are more cycles in a pulse, the numerical value of range resolution is? |
greater |
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If a new pulsed transducer has many more cycles in its pulse, the image accuracy _____________. |
degrades |
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_______ frequency transducers have the best range resolution. |
High |
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Which of the following transducers has the poorest Axial Resolution? a) 1.7 MHz, 4 cycles/pulse b) 2.6 MHz, 3 cycles/pulse c) 1.7 MHz, 5 cycles/pulse d) 2.6 MHz, 2 cycles/pulse |
c) 1.7 MHz, 5 cycles/pulse *longest pulse, lowest frequency, most ringing |
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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 |
c) 2.25 mm *high frequency, few cycles *axial resolution = 1/2 spatial pulse length |
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Which of the following transducers has the best axial resolution? a) 1.7 MHz and 4 cycles/pulse b) 2.6 MHz and 3 cycles/pulse c) 1.7 MHz and 5 cycles/pulse d) 2.6 MHz and 2 cycles/pulse |
d) 2.6 MHz and 2 cycles/pulse *shortest pulse *has the highest frequency and least ringing (fewest cycles/pulse) |
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True/False: A higher frequency transducer creates a shorter pulse thus having a lower numerical value of axial resolution. |
True *lower numbers = improved image quality |
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True/False: Less ringing or fewer cycles in a pulse, generally implies shorter pulses and improved axial resolution. |
True *lower numbers = improved image accuracy |
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True/False: Axial resolution is determined by pulse length. |
True |
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True/False: Shorter pulses have better axial resolution. |
True |
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The ability to distinguish two structures lying close together front-to-back is called? |
Axial resolution *aka longitudinal, range, radial, depth |
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The ability to distinguish two structures lying close together side-by-side is called? |
Lateral resolution *aka angular, transverse, azimuthal |
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Axial resolution and lateral resolution are both measured with units of _______________. |
distance (mm) |
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When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the numerical value of range resolution _____________. |
increases *more cycles in a pulse, the pulse becomes longer |
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When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the image quality _______________. |
degrades *when number of cycles increases, spatial pulse length increases, image quality decreases |
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True/False: When the number of cycles increases, spatial pulse length increases, and image quality decreases. |
True |
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When the number of cycles increases, spatial pulse length ____________, and image quality _____________. |
increases SPL decreases image quality |
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_______ frequency transducers have the best range resolution. |
high |
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Name the 4 synonyms for axial resolution. |
LARRD longitudinal axial range radial depth |
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Name the 3 synonyms for lateral resolution. |
LATA lateral angular transverse azimuthal |
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The length of a pulse is 8 mm. What is the minimum distance between two reflectors, positioned one in front of the other, that still produces two echoes on our image? a) 8mm b) 4 mm c) 16 mm d) cannot be determined |
b) 4 mm *the value is 1/2 the pulse length |
