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56 Cards in this Set
- Front
- Back
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Damping (improves/degrades) the quality of the sound
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degrades
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The Q-factor is the (unitless) ____ of the pulse, measured using either SPL or PD.
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length
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A damped sound will have a (higher/lower) Q-factor than an undamped sound
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lower
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What is bandwidth?
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The difference between the highest and lowest frequency in the pulse
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What is the relationship between Q-factor and damping?
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They are inversely related
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Is a low Q-factor or high Q-factor transducer preferred for imaging purposes?
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Low Q-factor
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Does a high Q-factor produce a higher quality image?
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No, it produces a lower quality image
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Is a pulse a pure frequency?
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No
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A pulse produces a ____ of frequencies
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range
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Bandwidth is the ___ of frequencies within the ___ ___ ___.
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range
main operating frequency |
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The shorter the pulse, the _____ the bandwidth
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greater
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The longer the pulse, the ____ the bandwidth
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lesser
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What effect does increasing damping have on:
1) Ringing? 2) SPL? 3) PD? 4) Q-factor? 5) Axial resolution? 6) Bandwidth? |
1) Decreases
2) Decreases 3) Decreases 4) Decreases 5) Increases 6) Increases |
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What is Q-factor equal to?
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operating frequency / bandwidth
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Frame Rate = ?
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PRF / scan lines
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How is compressibility related to propagation speed?
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Compressibility is inversely related to propagation speed (the more compressible the material, the slower the propagation speed)
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How is density related to propagation speed?
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Density is inversely related to propagation speed (the denser the material, the slower the propagation speed)
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Bulk modulus is a negative ratio of _____ and ____.
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stress
strain |
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How is compressibility related to bulk modulus?
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Compressibility is inversely related to bulk modulus
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What is the bulk modulus, for practical purposes?
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Stiffness
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How is bulk modulus related to propagation speed?
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They are directly related
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How is elasticity related to propagation speed?
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They are inversely related
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What is propagation speed, in terms of elastic bulk modulus and density?
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Propagation speed = SQRT (bulk modulus / density)
For practical purposes, this also = SQRT (stiffness / density) |
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What % of the sound beam is reflected when the beam passes from soft tissue into:
1. soft tissue 2. bone 3. air |
1. 1%
2. 50% 3. 90% |
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The extent of sound transmission between two mediums is determined by the ____ of the ______ _____ of the two mediums.
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ratio
acoustic impedances |
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What is a specular reflection?
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A reflection which belongs to the same medium as the transmitted beam
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What is the difference between speed and velocity?
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Speed is directionless, while velocity has a specified direction
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How is compressibility related to elasticity?
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They are directly related
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What is meant by a "normal" angle of incidence?
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An angle of 90 degrees
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The angle of incidence = ?
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the angle of reflection
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What is another term for "scattering"?
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Non-specular reflection
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Is absorption higher in bone or soft tissues?
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Bone
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Where in bone is absorption highest?
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At the surface of the bone
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What is "back scattering"?
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Scattering which occurs when a beam strikes an irregular surface
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What is Rayleigh scattering?
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A type of scattering which occurs when the structure's dimensions are much smaller than the beam's wavelength
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How is Rayleigh scattering related to frequency?
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Rayleigh scattering is proportional to (frequency)**4
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What is the fundamental difference between reflection and refraction?
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Refraction occurs after the beam crosses the interface into the 2nd medium
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What 2 conditions must be met for refraction to occur?
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1. There must be a non-perpendicular angle of incidence.
2. The two media must have different propagation speeds. |
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What is the term for the % of the intensity that bounces back when a sound beam strikes a boundary between two media?
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Intensity Reflection Coefficient (IRC)
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What is the term for the % of the intensity that passes in the forward direction when a sound beam strikes a boundary between two media?
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Intensity Transmission Coefficient (ITC)
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IRC + ITC = ?
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1 (or 100%)
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Under what conditions will the transmission angle be greater than the incident angle?
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When the speed of medium 2 is greater than the speed of medium 1
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Under what conditions will the transmission angle be less than the incident angle?
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When the speed of medium 2 is less than the speed of medium 1
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What is the "go-return" time?
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The time from pulse creation to pulse reception, aka "time of flight"
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What is the critical angle of refraction?
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The angle of incidence which causes the angle of refraction to be 90 degrees - in other words, the beam no longer enters media 2.
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What value represents the intensity of the beam at the time of its maximum value?
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ITP = Intensity at Temporal Peak
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What value represents the average intensity of the beam during the most intense half-cycle?
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IMax = Intensity Max
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What value represents the average intensity of the beam during pulse duration?
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IPA = Intensity Pulse Average
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What value represents the average intensity of the beam during the entire pulse repetition period, including transmit and receive times?
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ITA = Intensity Temporal Average
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What are the temporal values, in order from highest to lowest?
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1. ITP
2. IMax 3. IPA 4. ITA |
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What is the formula for duty factor, in terms of temporal values?
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Duty Factor = ITA / IPA
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What is the PRP dependent on?
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The depth, which is operator-dependent
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What is the relationship between PRP and PRF?
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PRP = 1 / PRF
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The PRF affects ____ resolution, but not ____ resolution
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temporal
lateral |
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What is the difference between PRP and go-return time?
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PRP = go-return time x depth (because go-return time is a coefficient, per unit of depth)
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What is Snell's law?
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(Speed of medium 2 / Speed of medium 1) = ((sin (transmission angle) / (sin (incident angle))
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