Ch. 17-20 Final Exam Review Flashcards
The energy at the beginning of the vessel must be __ than the energy at the end of the vessel for blood to flow.
Greater
Contrast agents are used to improve image quality by changing the __ properties of the tissue that it resides in.
Acoustic
What is characterized by chaotic flow patterns in many different directions and at many different speeds?
Turbulent flow
Blood flows from regions of __ energy to __ energy.
High; low
What imaging technique sends a positive and then a negative pulse down each scan line?
Pulse inversion harmonics
Where are harmonics generated?
In tissue
Resistance to blood flow is primarily controlled by __.
The radius of the vessel
MI is proportional to ___ pressure.
Rarefactional
MI is inversely proportional to __.
Frequency
What uses the amplitude of the Doppler shift and the intensity of the red blood cells to be able to generate color on the image independent of the angle of insonation.
Power Doppler
What form of Doppler has a large sample volume that obtains signals from all vessels within?
CW Doppler
What is the best obtainable angle of insonation to produce the most accurate Doppler shift information?
60 degrees
When is Doppler shift the highest?
When the beam angle is parallel to the direction of flow
What is the smallest number of crystals a PW Doppler device may have?
One
According to Bernoulli Principle, where will you find the highest velocity in a vessel with stenosis?
At the site of stenosis
If blood pressure increases with no change in resistance, what happens?
Increased flow rate
What is the type of blood flow typically visualized in arteries?
Pulsatile
What type of blood flow is normally associated with veins?
Phasic
A Reynolds number __ indicates turbulent flow on color Doppler evaluation.
Greater than 2000
Resistance increases in a vessel:
Smaller vessels, increased viscosity, longer vessels, and closer to the vessel wall
What happens when spectral Doppler gain is too high?
Overmeasurement of the velocities
Which controls affect the amount of color fill in a vessel evaluated with color Doppler?
Color Doppler scale settings, sample size, and sample angle
Does aliasing occur with color Doppler?
Yes
The brightness of the reflection on the Doppler tracing represents __.
The number of red blood cells moving at each velocity displayed
What type of blood flow is predicted with a Reynold’s number less than 1500?
Laminar flow
Which mathematical processing technique is used to analyze the data and produce a spectral waveform?
Fast Fourier Transform
What does increasing the PRF/scale setting on spectral Doppler do?
Decreases the potential for aliasing