Artifacts Flashcards
What can you optimize for attenuation?
Optimize: Gain TGC Filter Scale Appropriate transducer
What do you need in order to have a good Doppler image?
Need a good grey scale image to make a good Doppler image
What is shadowing in vascular?
If the sound beam cannot penetrate through an object during grey scale image the same will be true during color and Doppler imaging
What is an example of shadowing?
Plaque – may need to find a different angle to approach vessel not only for sampling but actual visualization such as compressing a vein posterior to a calcified vessel
What does the beam width do?
Wide beam or large sample gate may pick up more information then is needed. Larger is not always better
What does a small beam do?
Small beam or narrow sample gate may not give you enough information or incorrect information in a very select location (ex. central vessel)
What is spectral boardening?
A wide range of velocities and frequencies
This can be from internal source such as disease processes or lack of optimization
Clean the waveform when necessary – gains, scale, position and angle
What conditions will produce the most accurate velocity measurements?
Sometimes out of our control because inherent in the machine by the configuration of the Doppler equation and construction of the beam
As sonographers we should achieve an angle of 60 degrees or less to the vessel
What is compression of Spectral Display?
Optimizing to produce the optimum grey scale and Doppler images
Appropriate scale - optimizes the time and velocity scales
What is filtering?
Filters out low frequencies
Often used when scanning near the heart to filter out extra frequencies
Careful not to filter out useful information
What is sensitivity?
Some machines have a sensitivity optimization
Some of this is controlled by gain and scale
Decide what should be there and should not
What is aliasing?
Optimizing mostly through scale and less with gain
Sometimes aliasing is diagnostic information
Site of stenosis
Site of bend in the vessel
What is the optimal beam angle?
Less than 60 degrees gives the most accurate velocity (45 – 60 degrees)
60 degrees or less also gives more sensitivity to picking up the signal from blood flow
Often if angle is 90 degrees to the flow no color or Doppler will be detected
Corresponding box angle will also impact color flow, Doppler signal, and possibly information about direction
What will a low scale do?
Too low of scale will cause aliasing
What will a high scale do?
too high of scale may indicate a false positive for thrombosis
