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205 Cards in this Set
- Front
- Back
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Waves that can propagate through a vacuum are:
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electromagnetic
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If parallel displacement is perpendicular to wave propagation, the wave is:
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transverse
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The period of a sound wave is determined by:
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the source of the sound
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Infrasonic hearing is below:
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16 Hz
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Force per unit area of the sound beam is:
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pressure
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Concentration of energy per unit time is:
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power
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Propagation speed depends on:
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characteristics of the medium
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What is the audible range?
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20 Hz to 20 KHz
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The unit Newton is used for:
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force
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The unit Pascal is used for:
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pressure
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The unit Joule is used for:
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energy
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Wavelength is determined by the ____ & ____.
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source & medium
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What are the 4 acoustic variables?
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pressure, density, temperature, particle motion
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If the freezing point is 32 degrees in fahrenheit, what is it in celsius?
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0 degrees
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If a wave doesn't need a wave to propagate it is considered:
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electromagnetic
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If amplitude decreases by a factor of 2, power will decrease by a factor of ____.
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4
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Pulse duration is expressed in the same unit as ____.
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period
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What transforms echo signals into bright spots?
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video monitor
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Speed of sound in a medium is determined by ____ & ____ of the medium.
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density & stiffness
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Axial resolution is approximately equal to:
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half spatial pulse length
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When the number of pulses increases & pulse duration increases, what happens?
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BW decreases, and axial resolution worsens
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What are the 2 mutually perpendicular (focused) planes?
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lateral & elevation
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The portion of the sound beam used to generate doppler is:
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backscattered portion
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In the franhoffer zone (far field) of the transducer what happens to intensity?
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intensity fades w/ distance
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When imaging depth is increased what happens to DF, PRF & PRP?
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PRF & PRP increase, DF decreases
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When using an annular array transducer there are:
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multiple ring shaped crystals
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SPL is determined by both the ____ & ____.
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source & medium
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The linear phased array real time scanner has a ____ shape.
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rectangle
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What is the shape of an annular scanner?
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sector
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A vector scanner has a ____ shape.
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trapezoid
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The ML(matching layer) is ____ the WL (wavelength)
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1/4
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What is a unit of attenuation coefficient?
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dB/cm
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The length of an ultrasound pulse can be decreased by increasing _____.
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damping
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LARD=
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longitudinal axial radial depth
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LATA=
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lateral azimuthal transverse angular
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Two other classifications of LARD are ____ resolution & ____ resolution.
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range & depth
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How is resolution in the elevation focused?
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by the acoustic lens
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How is lateral resolution improved?
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by focusing the slice thickness
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When transmission occurs with oblique incidence the angle of reflection is = to what?
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angle of incidence
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When constricting the ultrasound transducer, a layer of backing material is used for what?
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to shorten the ultrasound pulse
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Pulse duration is fixed by the ____.
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period
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Giga ---->
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nano
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Mega---->
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micro
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Kilo---->
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milli
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Hecto---->
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centi
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Deca---->
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deci
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1 inch = ____ cm.
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2.54
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1 foot = ____ inches = ____ cm.
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12 inches, 30 cm
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1 Kg = ____ lbs.
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2.204 lbs
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1 liter = ____ ml = ____ cc =____cm3
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1000 ml = 1000 cc = 1000 cm3
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C F - 32
-------- = ---------- 100 180 |
temperature equation
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f = 1/T is the equation for:
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frequency
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T = 1/f is the equation for:
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period
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c= f x wavelength is the equation for:
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propagation speed
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p = mass/volume is the equation for:
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density
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W= work/time is the equation for:
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power
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I= power/beamarea is the equation for:
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intensity
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Z = p x c is the equation for:
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impedance
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With normal incidence, the angle of incidence = ____.
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zero degrees
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With oblique incidence, the angle of reflection is ____.
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Oi = Or
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With oblique incidence, the angle of transmission is ____.
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Ot = Oi (C2/C1)
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What is snell's law?
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Sin Ot = Sin Oi (C2/C1)
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The attenuation coefficient in soft tissue is ____.
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Ac= 0.5 f
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The attenuation coefficient in muscle is ____.
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Ac= 1.0 f
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Total attenuation is:
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A = Ac x l
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The formula for attenuation is:
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dB = 10 log I/Io
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Frame time=
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PRP x LPF
or 1000 msec/FR |
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Color Frame time=
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PRP x Packet size x LPF
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Duty Factor=
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PD/PRP (and has no unit)
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The range equation is used to determine the:
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depth of the reflecting structure
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The depth of the reflecting structure is the distance between the ____ ____ & ____.
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transducer face & reflector (interface)
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Distance to the interface is = to:
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propagation speed of sound in the medium multiplied by the pulses's round trip time divided by 2
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In soft tissue it takes ____ for the transducer to send a pulse & receive an echo from an interface that is 1 cm deep.
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13 usec
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The greater the round trip time, the deeper the ____ ____.
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reflecting structure
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The acoustic line is also called the ____ ____.
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scan line
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What is the acoustic line?
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a line of info produced by a single pulse transmitted in a specific direction
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The display line is also called the ____ ____.
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image line
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What is the display line?
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The data displayed on the screen that corresponds to a single direction within the body.
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T or F. Multiple acoustic lines may be combined to form one display line on the image.
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True
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The complete image generated by transmitting a number of acoustic lines in many directions than reconstructing the recieved data:
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frame
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LPF = the number of ____ needed to generate a frame.
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pulses
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Each pulse generates ____ acoustic line of info.
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1
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What is frame time?
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Time required to generate a frame by transmitting multiple pulses
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PRP (pulse repetition period) is:
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time per acoustic line
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The round trip time is the same as ____ in soft tissue.
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PRP
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What is the unit for frame rate?
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Hz
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What is the average frame rate for US?
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30 frames per second or 30 Hz
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Frame rate & frame time are _____.
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reciprocals
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What are the types of scanned modalities?
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2-D imaging, color flow imaging, and 3-D imaging
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Scanned modality implies that the image is "____ ____" over time by transmitting & receiving in ____ directions.
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"built up", opposite
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Non-scanned modalities acquire data in the ____ direction repeatedly over time.
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same
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What are the different types of non-scanned modalities?
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CW & PW doppler, M-mode, A-mode, and spectral tissue doppler
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The greater the imaging depth, the longer the ____ & lower the ____.
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PRP, PRF
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IF frame time is in sec, frame rate will be in ____.
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Hertz
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If frame time is in msec, frame rate will be in ____.
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KHz
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If frame time is in usec, frame rate will be in ____.
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MHz
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A group of pulses traveling together in a packet generate one ____ ____ ____.
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color display line
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T or F. The frame time is generally greater for color images than 2-D images.
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True
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Color frame rate is ____ than 2-D frame rate.
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lower
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What is temporal resolution?
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The ability of an imaging system to separate events in time (or ability to locate & display position of moving structures)
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The higher the number of frames displayed in one second the better the ____ ____.
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temporal resolution
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_____ resolution is much better than ____ resolution.
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2-D temporal, color temporal
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Why is 2-D temporal resolution better than color temporal resolution?
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because color frame time is longer than 2-D frame time
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Maximum imaging depth & frame rate are ____ related.
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inversely
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Circular waves that travel across the surface when a rock is tossed into the water are called:
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raleigh waves
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What describes the relationship between frequency and period?
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reciprocal
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If particle displacement is parallel to wave propagation the wave is called ____ ____.
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longitudinal wave
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What is the definition of acoustic intensity?
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acoustic power per unit area of the sound beam
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Transducer frequency is dependent on the ____ of ____.
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source of sound
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If a wave needs a medium to propagate it is a _____ wave.
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mechanical
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What will not result in change in wavelength?
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change in amplitude of transmit signal
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If amplitude is decreased by a factor of 4, the power will be ____ by a factor of ____.
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decreased, 16
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If the beam area is increased by a factor of 2, and the power is unchanged, intensity will be ____ by a factor of ____.
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decreased, 2
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The propagation speed of sound at any frequency is determined by:
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elastic properties of the medium
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T or F. Sound waves like light waves travel in vacuums.
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FALSE
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T or F. The peak to peak amplitude is twice the value of amplitude.
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TRUE
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T or F. For a given medium, if wavelength doubles, frequency will be halved.
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TRUE
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T or F. Ultrasound intensity remains constant as sound travels thru tissue.
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FALSE
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T or F. When higher frequencies are used, greater penetration is achieved.
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FALSE
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T or F. Power is proportional to intensity squared.
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FALSE
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T or F. If amplitude is halved, power will be quartered.
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TRUE
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T or F.Simple harmonic motion describes particle motion within a sound wave.
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TRUE
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T or F. If the final intensity of a sound beam is less than the initial intensity, then the change in dB is positive.
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FALSE
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A soundwave strikes a large smooth surface orthogonally. The impedances are identical but densities are different----->
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total transmission
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Axial resolution is approximately equal to:
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half spatial pulse length
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As the # of pulses increases, pulse duration increases, the bandwidth ____ & the axial resolution ____.
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decreases, worsens
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The piezoelectric elements of an annular array transducer are:
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concentric rings
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What are the 2 mutually perpendicular (focused) planes?
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lateral & elevation
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The portion of a sound beam used to generate doppler is the _____ portion.
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backscattered
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In the franhofer zone (far field) of the transducer, intensity ____ with distance.
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fades
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The amplitude of the electrical voltage produced by the transmitter varies between:
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5 - 500 Volts
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The higher the voltage, the higher the ____ ____ of the transducer.
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power output
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What should not be used when referring to power?
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gain
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A higher power wave results in a higher ____ ____ ____.
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intensity sound beam
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What are 5 factors that affect transmit power distribution?
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transducer freq, imaging modality, image size, imaging depth, focus location
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The higher the frequency the greater the ____.
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attenuation
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What are 3 non-scanned modalities?
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pw doppler, cw doppler, m-mode
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Decreasing image size increase the ____ ____.
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frame rate
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Decreasing the imaging depth increases ____ ____ & ____.
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duty factor, power
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What controls the electrical signals sent to the piezoelectric crystals?
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the pulser
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What does the pulser determine?
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PRF, PRP, pulse amplitude, pulse duration, and freq
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What does the beamformer do?
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determines firing patterns of time delays to focus & steer the US beam in phased array systems
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When does the pulser operate?
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during transmission
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The pulser receives timing signals from the ____ ____.
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master synchronizer
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A group of active elements during reception represents the _____.
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aperature
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The pulser applies a constant electrical signal in the form of a continuously alternating current. This is known as ____ ____ ____
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continuous wave mode
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The acoustic frequency generated by the crystal is equal to the ____ ____ frequency.
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drive voltage
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When the pulser applies short duration electrical spikes to achieve elements for US pulse it's known as:
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pulsed wave mode
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2-D imaging has ____ pulses, while doppler & color has ____ pulses.
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short, long
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Most US systems have _____ active receiving channels.
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256 - 512
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What are the 6 receiver functions?
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amplification, compensationm compression, demodulation, rejection, detection of rf signals
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The signals transmitted into the body & echoes received from the body by US are the ____ signals
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analog
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The voltage signals that appear on the transducer's crystals are in the form of ____ ____.
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RF signals
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Overall gain control varies between ____ & ____ db.
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0 db & 100 db
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An overall gain setting of 60db means that the Vo will be amplified ____ times.
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1000
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The TGC is also called ____ ____ ____ & it compensates for ____.
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Receiver Swept Gain, attenuation
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Attenuation is due to what 3 things?
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reflection, scattering, absorption
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What determines the amplitude of the echo received from a reflector?
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the thickness of tissue through which the signal travels
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Echoes returning from greater depths have ____ amplitude than shallow depths.
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lower
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What are the 4 classifications of TGC?
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near gain, delay, slope, and far gain
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TGC curve for color flow is based on ____ ____.
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assumed attenuation
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The process of decreasing the differences b/t the amplitudes of smallest & largest echo signals is:
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compression
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What does compression result in?
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reduction in the range of echo amplitudes, and decreased dynamic range
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The range of echo signal amplitudes that can be processed by a component of US system is:
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dynamic range
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_____ changes the echo signal from an RF signal to a video signal.
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demodulation
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What are the 2 steps of demodulation?
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rectification & smoothing
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The process by which the negative components of signal is converted to positive is ____.
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rectification
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Smoothing causes an _____ signal that can be displayed.
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A-mode
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What does rejection do?
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rejects all echo signal components that fall below a certain level
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A-mode is ____.
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amplitude
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M-mode x- axis represents ____.
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time
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M-mode y-axis represents ____ or ____.
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depth
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A-mode, B-mode, and M-mode is ____ dimensional.
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1
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There is no spectral window with ____ ____ doppler.
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continuous wave
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A mosaic of color is known as ____.
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turbulence
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A-mode is in the form of ____, while B-mode is in the form of ____.
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spikes, grayscale
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Creating a 2-D image from B-mode lines is called a ____.
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B-scan
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The 2 dimensions of 2-D imaging are ____ & ____.
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depth (x plane) & width (y plane)
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What is the third dimension of 3-D imaging?
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brightness
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The time taken to generate a single scan line is ____.
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PRP
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Typical frame rates in US imaging are ___ to ___ Hz.
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30-60 hz
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Flicker rate of the human eye is ____ frames per second.
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15 - 20
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How is a faster frame rate achieved?
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decrease image depth, decrease LPF, use fewer focal zones
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The ability of the system to determine the position of a moving structure is ____ ____.
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temporal resolution
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The higher the frame rate the ____ the temporal resolution.
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better
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Temporal resolution is related to ____ & ____.
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time and motion
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Using multiple transmit foci ____ lateral resolution.
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improves
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The wider the sector size the ____ the frame rate and ____ the temporal resolution.
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lower, worse
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Persistance is used to ____ images and when it decreases, frame rate ____.
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smooth, increases
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Imaging produced by averaging multiple frames formed @ various angles is ____ ____.
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compound imaging
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Temporal resolution is related to ____ & ____.
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time and motion
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Using multiple transmit foci ____ lateral resolution.
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improves
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The wider the sector size the ____ the frame rate and ____ the temporal resolution.
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lower, worse
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Persistance is used to ____ images and when it decreases, frame rate ____.
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smooth, increases
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Imaging produced by averaging multiple frames formed @ various angles is ____ ____.
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compound imaging
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Compound imaging improves ____ ____.
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spatial resolution
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The ability of the US system to show detail on image is ____ ____.
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spatial resolution
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Detail resolution is ____, ____, and ____ combined.
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axial, lateral, and elevation
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Lateral resolution = _____.
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beamwidth
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How is lateral resolution improved?
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by focusing in the lateral dimension or using multiple foci
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Elevation resolution = ____ ____
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slice thickness
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How is elevation resolution improved?
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by focusing in the elevation plane
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The ____ to ____ ratio is a measure of how strong a signal is relative to background noise.
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signal to noise ratio
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What are 3 sources of noise?
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electronic noise, clutter, and haze
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What is used to reduce noise?
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spatial averaging
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