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113 Cards in this Set

  • Front
  • Back
During Doppler exams the u/s system measures the difference between the transmitted and recieved frequencies called
Doppler Shift
Which factor MOST determines axial resolution
Spatial pulse length
The attenuation Coefficient is expressed by which of the following
The alara principel related to
Using min. power and exposure time to u/s
The detected signal amplitude from smallest to largest is equivalent to the system's
Dynamic Range
Which of the following factors MOST affects lateral resolution
beam/transducer diameter
The density of a medium and the propagation speed of sound are
Inversly proportional
The term that describes the size of the transducer surface involved in processing the ultrasound beamand detection of echoes for each beam line is
In order for a refracted wave to be produced which of the following conditions must occur at an interface
Oblique Incidence,
different sound speeds
Which of the following factors determins a transducer resonance frequency
crystal thickness
If a study produced no false positive results it would have 100%
Most color flow systems prosess the color utilizing
According to the AUIM no confirmed bioeffects have been reported on patients or operators, below what intensity for imaging
Impedence is best defined as
The product of the density and the propagation speed
Which term describes the crystals capacity to be excited by an electric impulse to generate a mechanical sound wave as it expands;and conversly transform a detected mechanical soundwave into a electric impulse
Peisoelectric effect
What ratio represents the Higheat Intensity
A slice thickness artifact is Most likely the result of which of the following
Beam diameter larger than the reflector
Which term BEST describes the rate of energy transfer that occurs during a specific period of time
The redirection of sound in many direction by a rough surface or by a heterogeneous media is called
As lateral resolution improves, the beam diameter will be
The axial resolution of the image improves as you
increase the frequency of the transducer
Which of the following will NOT improve frame rate
Using a larger aperature probe
For an U/S system to display 256 shade of gray it would require ____ deep image memory
8 bit
Based upon the doppler equation, the doppler shift is linearly proportional to which of the following
Tranmit doppler frequency
Rank these four media in the increasing order of propagation speed.
bone,fat,air,soft tissue
Air, fat, soft tissue, bone
What is reflection
result of a soundwave being redirected back toward the transducer
Sound wave are
The speed in soft tissue is
what are the acoustic variables
density, pressure, temperature
The effect of soft tissue on US are
acoustic propagation properties
Time for one cycle to occur
Distance covered by one cycle
If the frequency of US is increased from 0.77mhz to 1.54mhz, what happens to the propagation speed
remains the same
The units of pulse repetition frequency are
per minute
Time from the begining of a pulse to its end is
pulse duration
Range resolution is determined by what
Spatial pulse length
If a wave's apmlitude is doubled what happens to the power
Power of sound has units of what
If the Intensity of a sound beam remains unchanged while the beam area is reduced in half, what happens to the power
Put these intensities in decreasing order
The duty factor for continuous wave US is
The units of attenuation are?
What kind of scale?
The rayl is the unit of
What are attenuations 3 compnents
scattering, reflection, absorption
For soft tissue, the approximate attenuation coef. in dB/cm is equal to one-half
Frequency in Mhz
AS the impedance of 2 media become vaslty different the
reflection increses
The angle between an US pulse and the boundry between media is 90degrees
orthononal incidence
The ALARA principle relates to
using min output and exposure
Frequewncy, prp,amplitude,duty factor can be calculated with an PTZ element attached to an oscilloscope instrument called
The 2 mechanisms of bioeffects are thermal and cavitation. T ot F
Small microbubbles that occur as a result of violent molecular agitations are called
The AUIM has issued a statement saying no confirmed biological effects on patients or instrument operators have been reported at intensities below
THe beam profile is measure by what method
acoustic optics
Crystals are utilized to evaluate the total power of the beam by converting energy into heat is called
High reciever gain will increase the intensity of the sound
False high output power
THe method of identifying and measuring the parts of the US that have the potential for producing bioeffects is called
An artifact that appears as multiple reflections equally spaced is called
Grating Lobe artifacts occur with______transducers.
Refraction causes lateral displacement of the reflector and is caused by______ incidence.
Propagations speed errors occur because the equipment assumes a speed of soud in tissue of 1.54 mm/microsec.
T or F
Multipath artifacts are caused by the sound beam interacting with a_____ surface.
2 types of useful artifacts
enhancement, shadowing
Section thickness artiffacts result from a propagation speed error.
T or F
False- beam width
Color mirror image artifacts can be elimanated by reducing the sector size.
T or F
False- color doppler gain
Aliasing occurs when the reflected frequency exceeds ___ the nyquist limit.
Enhancement occurs when the sound beam travels through a medium with an attenuation rate_____ than the surrounding tissue
2 catagories of energy that make up total fluid energy are
potential and kinetic energy
Potential energy is stored energy. T or F
Rule that states that fluid is neither created nor destroyed as it flows through a tube is
As resistance of blood flow through the aartery increases, the pressure drop across the artery will
As the vessel lumen size decreases, blood flow velocity will
When the vessel lumen size increses, blood flow velocity will
If the radius of the blood vessel is decreased by one half, the velocity of the blood flow will
increase four fold
The inverse relationship between pressure and velocity is described by
Bernoulli's equation
A high Reynolds number indicated ____ flow
The primary contributing factor to venous blood flow in the upper and lower extremity include
heart contraction\
intraluminal blood pressure
peripheal resistance in the capillary bed
When colateral blood flow develops, resistance at that level will
When a patient with a stenotic lesion is exercised, the pressure gradient at the site of the stenosis will
Transmural pressure is the difference or gradient between the intramural and tissue pressure
When tissue pressure exceeds intramural pressure, the viens will
If the right atrial pressure or central venous pressure is increased, the veins in the body usually are
Hydrostatic presssure does not have the same value for the arteries as it does for the veins
As venous blood is moved out of the calf veins, intrmural and transmural pressure drops
Factors affecting the blood flow within the body include
Density of blood
velocity of blood
size of vessel
Difference between the transmit frequency and the recieved frequency is called
Doppler shift
What angle provides the max doppler shift
0 degrees
Continuous wave doppler utilized ______elements
Flow towards the transducer is displayed _____ the 0 baseline
The units for the doppler shift are
The nyquist lismit is equal to _____ of PRF
Mirror image artifact occur because of
too much doppler gain
poor doopler angle
PRF is related to depth of pulse travel
Aliasing is a diagnostic parameter for severe disease
Window filling of the spectral tracing is caused by
turbulent flow
sample gate too large
sample volume placed too close to vessel wall
doppler gain too high
The type of flow pattern seen in medium and large size vessels is reffered to as
plug flow
Color flow doppler provides ______ velocity information
The color assigned to flow towards the transducer is
The type of processing utilized with most color flow systems is
A mininmum of 3 pulses per line is required to assign a color
Color aliasing is seen when red and blue are seperated by black. T or F
No flow within a vessel would be indicated by a_____ color.
Color frame rate is affected by all of the following
sector size
color box size
The purpose of the wall filter is to
eliminate high amplitude noise artifacts
On color flow imaging, the best way to overcome aliasing is
use high Prf number
The color priority on color flow instruments is used to
decide the relative contribution of color/echoes in the image
The color map represents the
mean doppler shifts only
the angle corrector is used for
align the u/s beam with the vessel lumen
Aliasing is found in all of the following imaging modes
color doppler
spectral pulsed doppler
Which of the following factors is not dtermined in the doppler equation
a.doppler angle
b.incident frequency
c.reflector speed
d.acoustic information
acoustic information
PWD instruments are characterized because of their ability to do all of the following except:
a.real time spectral doppler
b.gate position
c.velocity estimation
d.velocity limits unrestriction
Velocity limits unrestriction
The method used by CW doppler to discriminate valuable signals is the
zero-crossing detector
In laminar flow, blood is seen to move
in layers
In doppler systems, changing the PRF is equal to changing the
velocity scale