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188 Cards in this Set
- Front
- Back
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Scan conversion is a function of the ____ ____ of the US machine.
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back end
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A B-scan displays ____ scan line at a time.
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one
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A raster scan shows a series of ____ ____ lines.
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horizontal raster
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A raster scan can be either ____ or ____.
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interlaced or non-interlaced
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Standard TV monitors operate using alternating current w/ a frequency of ____ Hz.
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60
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With an interlaced display, there is a frame rate of ____ Hz.
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30
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What type of monitors have more raster lines?
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higher resolution (spatial) monitors (1024 lines)
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HD broadcasts use ____ monitors.
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non-interlaced
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There is no ____& ____ field to interlace w/ non-interlaced display
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odd & even
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Non-interlaced displays are produced in ____ the time & the ____ ____ is doubled.
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half, frame rate
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What is the frame rate for non-interlaced displays?
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60 Hz
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The human eye cannot perceive motion changes occurring at a rate faster than ____.
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60 cycles/second
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What is PAL?
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Phase alternate line
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PAL is a format higher in ____ ____ but lower ____ ____.
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spatial resolution (625 raster lines), temporal resolution (FR 25 Hz)
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SECAM was a color TV system used in ____.
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france
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The very first ultrasound systems used ____ that were not able to display various ____.
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oscilloscopes, brightnesses
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With bistable display the bright spot was either ____ or ____.
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there or not there (on or off)
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Grayscale imaging seen on the monitor is made possible by the ____ ____.
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scan converter
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Early ultrasound systems used ____ scan converters.
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analog
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In gray scale display, different echo amplitudes are presented as different ____ of ____.
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shades of gray
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The resulting range of echo amplitudes after the RF signals are amplified & demodulated is called ____ ____.
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dynamic range
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If dynamic range is 40 dB than there are ____ different echo amplitudes.
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100 (shades of gray)
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What is the smallest picture element?
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a pixel
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A digital scan converter is a block of digital memory w/ a ____.
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CPU (central processing unit)
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What are 5 other functions of the back end of the US system?
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analog to digital conversion & vice versa, preprocessing, memory storage, postprocessing
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The gray shade of each pixel is determined by the ____.
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apmlitude
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The ultrasound system's main memory is directly or indirectly connected to the central processing unit via a ____ ____.
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memory bus
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The memory bus is actually 2 buses. A ____ bus & a ____ bus.
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address, data
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Voltage levels are processed as ____ ____.
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binary numbers
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The binary system uses 2 digits. What are they?
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0 & 1
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The decimal system uses ____ digits.
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10
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A ____ is a unit of info in a digital system. It is the smallest amount of digital storage.
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bit
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A bit is ____.
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bistable
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What is a byte?
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a group or sequence of bits assigned to each pixel
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The number of bits in each byte is determined by the number of ____ found in the ____ ____.
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planes, memory matrix
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The ____ stores the location & the amplitude of the echoes acquired.
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RAM (random access memory)
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The greater the number of shades, the lower the ____ ____.
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image contrast
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The ability of the US system to distinguish differences b/t echo strengths is ____ ____.
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contrast resolution
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The term ____ ____ is used to describe the overall quality of the image.
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spatial resolution
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If the dynamic range of echo amplitudes is 40 dB, than there are ____ shades of gray.
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100
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What are the 6 factors affecting contrast/spatial resolution?
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number of bits per pixel & DR, matrix size, pixel density, number of display raster lines, size of the field of view
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What are the 5 monitor controls that affect the display image?
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brightness control, contrast and sharpness/focus, polarity switch, and display subdivisions
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Increasing the contrast ____ the gray scale.
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decreases
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What does the polarity switch do?
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display white spots on a black background or vice versa.
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What is the dynamic range of the transducer?
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120 dB
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A preprocessing function which affects dynamic range is called ____ ____.
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single compression
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Increasing single compression ____ the dynamic range.
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decreases
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A wide dynamic range means ____ shades of gray and ____ contrast images.
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more, low
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A narrow dynamic range means ____ shades of gray and ____ contrast images.
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fewer, high
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Edge enhancement is achieved by ____ ____ also called ____ ____.
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pixel interpolation, spatial averagng
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What are 2 different forms of zoom used?
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write/acoustic zoom, or read/non-acoustic zoom
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Write zoom is a ____ function applied during ____ ____.
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preprocessing, date acquistion
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Read zoom is a ____ function where magnification occurs ____ image date is stored.
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postprocessing, after
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A unique US technique that analyzes tissue motion by tracking pixels/speckles is ____ ____.
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speckle tracking
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What are the 4 major components of PACS?
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imaging modalities, secured LAN, workstations, and archives for storage & retrieval
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What are used to transmit data for teleradiology?
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coaxial cables
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Doppler techniques use ____ ____ ____ from moving RBC's.
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backscattered acoustic pressure
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One of the most prevalent applications of doppler is ____.
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radar
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What is the doppler effect?
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an apparent change in frequency as a result of a change in wavelength caused by motion
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If the reflector is moving at a velocity than the ____ frequency and ____ frequency are NOT the same.
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transmitted, and reflected
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T or F. When the reflector is not moving the transmitted & reflected frequency are not the same.
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TRUE
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When the reflector moves toward the sound source the ____ frequency is greater & the doppler shift will be ____.
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reflected, positive
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When the reflector moves away from the source the ____ frequency is greater & the doppler shift will be ____.
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transmitted, negative
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The change of frequency is in the range of ____.
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0 - 10 KHz
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The higher the transmitted frequency the higher the ____ frequency will be and the pitch heard is ____.
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reflected, higher
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Also the higher the velocity, the greater the change in ____ and the pitch heard is ____.
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frequency, higher
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What is the change in frequency due to?
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a change in wavelength of the propagating sound wave in the medium
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The angle between the direction of the sound beam and direction of blood flow is called ____ of ____.
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angle of interrogation
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The doppler shift is directly related to the ____ of the angle of interrogation.
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cosine
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As the doppler insonification angle increase, the ____ ____ decreases.
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doppler shift
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Doubling the frequency increase scattering by ____ times.
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16
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In reality, using higher frequencies produces ____ doppler signals due to ____.
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weaker, attenuation
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For depths greater than 5 cm the optimal frequency is ____ MHz.
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1.8
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The simplest technology for the detection of flow w/ ultrasound is ____ ____ doppler.
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continuous wave
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CW doppler uses ____ crystals, ____% of the time.
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2, 100%
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A voltage generator which modifies the alternating signal is called the ____.
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oscillator
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The frequency of a CW ultrasound wave is = to the frequency of the ____ ____.
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drive voltage
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The unit where the doppler signal is extracted from transmitted & reflected frequencies is the ____.
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mixer
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The unit where undesired frequency components are removed is called the ____ ____ ____.
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high pass filter
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What are 2 examples of CW doppler instruments?
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fetal heart rate monitor, and vascular directional doppler
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What doppler uses a single crystal?
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PW doppler
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The PW doppler sample volume is a ____ ____ volume that changes its size w/ ____.
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three dimensional, location
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When the transducer is placed in the far field the PW sample volume becomes very ____.
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large
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PW doppler sample volume is smallest in the ____ zone.
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focal
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Above the baseline means the direction of flow is ____ the transducer.
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towards
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The maximum doppler shift that can be measured is called the ____ ____.
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nyquist limit
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What is the formula for myquist limit NL?
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NL= PRF/2
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If the doppler shift detected exceeds the nyquist limit, ____ occurs.
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aliasing
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What is aliasing?
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an ambiguous plotting of velocities which are too high & wrap around the display spectrum
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With CW doppler the frequency of sound is determined by the ____ of the ____ ____
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frequency, drive voltage
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CW doppler doesn't have ____ ____.
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depth resolution
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CW doppler has the ability to measure very high ____ w/o ____.
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velocites, aliasing
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CW doppler has a ____ maximum focus, while PW doppler has a ____ maximum focus.
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shallower, deeper
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What is the frequency of PW sound determined by?
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the thickness of the crystal & pulser
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T or F. PW doppler has good depth resolution.
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TRUE
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What are 2 doppler methods used to measure higher doppler shifts w/ less aliasing?
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high PRF doppler & multi-gate doppler
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High PRF doppler uses at least 1 ____ gate in addition to the main gate set at the ____ ____.
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shallower, beam focus
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Multi-gate doppler uses ____ gates set at equally spaced ____.
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multiple, depths
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What leads to graphic display of blood flow velocities plotted over time?
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spectral analysis of doppler shift info
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An algorithm used to generate the discrete fourier transform for spectral analysis is the:
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chirp Z transform
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What does the discrete fourier transform do?
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converts the complex waveform from the time to the frequency domain
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An algorithm that can identify the various frequency shifts present in a complex waveform is:
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fast fourier transform
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The intensity of each velocity bin is directly related to the number of ____.
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RBC's
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What information is contained w/in the doppler spectrum?
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velocity, direction of flow, amplitude, and timing of events
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The ____ velocity represents the velocity at which most of the RBC's are moving at an instant.
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modal
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What does modal velocity correspond to?
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the most intense (brightest) display point at the peak.
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A distance measurement obtained by tracing the doppler spectrum is called ____.
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VTI (velocity time integral)
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VTI is obtained ____ the curve.
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under
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VTI represents the ____ traveled by RBC's while moving at the ____ velocity.
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distance, mean
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A spectral window indicates ____ ____.
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laminar flow
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A CW doppler spectrum has very little or no ____ ____.
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spectral window
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When does laminar flow occur?
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when the sample volume (in the center of vessel) is small relative to the diameter of the vessel
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Color flow imaging or mapping is a ____ ____ doppler technique.
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multigated pulsed
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Every pixel of the color box acts as a separate ____ ____ and requires a separate ____.
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sample volume (gate), pulse
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The number of pulses per line is the ____ ____.
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packet size
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The + direction of the color bar indicates that flow is ____ the transducer and the doppler isonification anlge is < ____.
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towards, 90 degrees
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The - direction of the color bar indicates that flow is ____ the transducer and the doppler isonification anlge is > ____.
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away from, 90 degrees
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A positive doppler shift = a positive ____.
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velocity
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The highest detectable mean velocity (nyquist) towards or away from the transducer is ____.
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63.6 cm/sec
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Higher saturation represents ____ flow.
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slower
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What are 2 types of map arrangements?
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velocity mode & variance mode
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When is aliasing useful?
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when identifying proximal flow convergence & measuring PISA radius
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Turbulence displays as a mosaic of ____.
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colors
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In spectral doppler the ____ ____ is used to eliminate high amplitude, and low velocity signals.
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wall filter
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If the color wall filter is set too low, the color will appear to ____ through vessel walls.
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bleed
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Color doppler display is ____ dependent.
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angle
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If the insonification angle is 90 degrees the color will be ____.
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black
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T or F. Color frame rate is slower than 2D frame rate.
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TRUE
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Decreasing the color box width decreases the ____ & ____ ____ but increases the ____ ____.
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LPF & frame time, frame rate
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Decreasing the color box depth decreases ____ & ____ ____ and increases ____ & ____ ____.
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PRP & frame time,
PRF & frame rate |
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Decreasing the packet size decreases the ____ ____ & increases the ____ ____ improving ____ ____.
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frame time, frame rate, temporal resolution
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Color persistance if a technique in which color frames are ____ over time.
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averaged
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Color persistence is used to improve signal to noise ratio but reduces ____ ____.
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temporal resolution
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With low color persistence there is a higher ____ ____.
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temporal resolution
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Power doppler identifies presence of a doppler shift but does not evaluate ____ or ____ of flow.
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velocity, direction
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Power doppler processes the ____ of the ____ signals.
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amplitude, backscattered
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What are the advantages of power doppler?
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hgih sensitivity to low venous flow, unaffected by doppler angle, no aliasing
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What are the disadvantages of power doppler?
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no velocity or direction info, reduced temporal resolution, and it susceptible to motion artifact
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What are the 4 factors that influence blood flow?
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cardiac function, compliance/capacitance, cardiac muscle & vessel stiffness, vessel diameter change
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Energy is always ____ never ____.
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conserved, lost
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Energy relating to motion is known as ____ energy.
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kinetic
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Energy is lost in what 3 ways?
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viscous, frictional, and inertial loss
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Viscosity is a measure of the ____ of a fluid to flow.
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resistance
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Viscosity is measured in units of ____.
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poise
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As viscosity increases ____,decreases.
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flow
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Normal hematocrit value is ____%.
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40%
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With high hematocrit blood behaves like a ____.
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solid
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What is newtonian fluid?
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a fluid w/ a constant viscosity at any given temp
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When does blood viscosity change?
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when vessel diameter changes, temp, chemical comp, and metabolic changes
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When does frictional energy loss occur?
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when energy is converted to heat as blood rubs against vessel walls
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Friction causes ____ flow to develop.
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laminar
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The ____ the vessel radius the more the friction & less flow.
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smaller
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Inertia relates to the tendency of fluid to resist a change in ____ or ____.
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velocity or direction
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A form of potential energy determined by the weight of a column of fluid above a reference pt due to gravity is:
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hydrostatic pressure
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What is the formula for hydrostatic pressure?
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P x G x H
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When a patient is supine the hydrostatic pressure is ____ mmHG.
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0
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If someone is upright, the hydrostatic pressure anywhere above the heart is ____ & below the heart is ____.
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negative, positive
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The volume of blood which moves past a point per unit time is the ____ ____.
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volumetric flow
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Normal human adult CO ranges b/t ____ & ____ liters/min.
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4.0 - 8.0
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Capacitance is the change in ____ per change in ____.
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volume, time
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High capacitance means a ____ change in volume over a ____ time.
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large, short
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What is compliance?
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the change in volume per change in pressure
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High compliance means a ____ increases in volume for a ____ increase in pressure.
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large, small
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What are the determinants of resistance?
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length and radius of vessel & viscosity of fluid/blood
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As blood flows away from the heart pressure ____, resistance ____ & velocity of flow ____.
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decreases, increases, decreases
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Stable flow that occurs in unobstructed, straight vessels is called ____ flow.
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laminar
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What are the 2 forms of laminar flow?
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plug & parabolic flow
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When does plug flow occur?
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when all blood cells travel at the same velocity
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Parabolic laminar flow has a ____ shape.
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bullet
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Blood flows in ____ as a series of concentric ____ w/ parabolic laminar flow.
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streamlines, layers
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Velocity of flow ____ w/in a stenosis.
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increases
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A term that describes the tendency for turbulence to occur is the ____ ____.
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reynold's number
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If the reynolds number is < 2000 the trend is for ____ flow. If it's above than the trend is for ____ flow.
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laminar, turbulent
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If velocity, diameter, or density increase than turbulence ____.
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increases
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If ____ increases than turbulence decreases.
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viscosity
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The ____ principle describes the relationship between pressure & velocity of blood flow.
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bernoulli's
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Potential energy is energy that is ____.
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stored
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The area of a normal vessel diameter has the highest ____ energy.
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potential
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The area of stenosis has the highest ____ energy.
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kinetic
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Segmental pressure will show a drop of more than ____ mmHg b/t segments if there is a ____.
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20 mmHg, stenosis
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The ____ velocity is always lower than the ____ velocity.
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mean, max
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What are varicose veins caused by?
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valves that are congenitally defective
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Low pulsatility waveforms have ____ ____ peaks and forward flow throughout the ____.
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broad systolic, diastole
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High pulsatiliy waveforms have ____ ____ systolic peaks and low, absent or reversed ____.
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tall sharp, diastole
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Acceleration is the change in ____ over the change in ____.
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velocity, time
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Acceleration decreases w/ ____.
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stenosis
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The presence of a ____ ____ indicates laminar flow in a healthy vessel.
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spectral window
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Absence of a spectral window occurs in ____ vessels due to ____.
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diseased, turbulence
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