Module 3 Self Test Flashcards
Briefly explain the principle of the doppler shift as it relates to sonography
Sound emitted from the transducer will reflect off of moving RBCs and return to the probe with slightly different frequency than what was emitted. IF the RBCs are moving towards the probe the received frequency will be high and if the RBCs are moving away then the frequency returned will be lower
List the axis used in spectral doppler
X: time
Y: Velocity
Z: power
Why is angle correct not utilized in most venous doppler studies?
- There is no velocity criteria for veins, therefore there is no need for an angle correct.
- The velocity of venous flow can vary for many reasons in different patients.
- The presence, direction, and quality of flow are more important indicators of normal than velocity
How can a sonographher ensure that the colour gain is set appropriately
To set the gain, it should be increased until there is a flash artifact seen on the screen. The gain is then reduced until the flash disappears. This will ensure the gain to compensate for the amount of attenuation occurring at the area of interest
Aliasing in the spectral trace is often corrected for adequate analysis. When is aliasing appropriate in venous duplex?
Aliasing should be demonstrated in the spectral tracing during augmentation of the calf when assessing the veins of the leg. If aliasing is not present and the augment is reduced, it indicates either poor technique or pathology of the lower limb
Explain why mirror imaging artifacts occur with spectral doppler
Mirror imaging occurs when the angle of intonation is too close to 90 degrees or when the spectral gain is set to high
What are the potential advantages to using power colour doppler?
- No aliasing since the amplitudes of the RBCs are interrogated as opposed to doppler shifts.
- More sensitive to low flow states
- Less angle dependent
