Physics Knobology Flashcards
The Nyquist frequency AKA Nyquist Limit is what
the highest Doppler frequency or velocity that can be measured without the appearance of aliasing
What is the correct way to set color gain?
increase the gain until noise speckle just becomes apparent THEN decrease the color gain until the color speckle disappears
for a color doppler exam, what are the MAIN (there are others) tools for maintaining the frame rate?
Doppler box size and two-dimensional image width
FRAME RATE IS VERY IMPORTANT! DON’T PRODUCE HUGE ASS ULTRASOUNDS
Power maps?
also called ENERGY MODE also called COLOR ANGIO is good only for showing the strength (amplitude) of a reflected signal without regard to velocity - great for looking for flow in small
how to adjust ALIASING in pulsed wave?
adjust the baseline, decrease scale
Pulsed Wave settings are the SAME on every machine TRUE OR FALSE
TRUE
if using respiratory variation to illustrate pathology, would you want a LOWER or HIGHER sweep speed?
LOWER!
you’ll get a lot more waveforms displayed so you can see overall what is going on in relation to respiratory variation
what is the purpose of a higher sweep speed?
displays fewer waveforms but provides GREATER DETAILS OF INDIVIDUAL WAVEFORMS
on some systems this is called “low velocity reject” but is mainly referred to as
Doppler Wall Filter or wall filter
what is Doppler wall filter usually used for in US
usually used to filter out very low frequencies that may add noise to a spectral Doppler waveform
general tips for wall filter
use less wall filter to accurately measure low velocity flows
use more wall filters when looking at high velocity flows
Removing the low frequency reverberation of an arterial wall would be an example of what
wall filter
The best angle to evaluate an artery would be at ________ degrees or ________ to the vessel. Because this isn’t possible, what control should be used?
zero degrees
parallel
use DOPPLER ANGLE / ANGLE CORRECT
Try to get between 45-60 degrees with the probe (ideal) then use doppler angle *rarely used in cardiac unless cannot get parallel to flow
Tissue Doppler imaging measures what and what does diastolic tissue Doppler measure
myocardial velocities
Diastolic tissue Doppler velocities reflect myocardial relaxation used to estimate LV filling pressure
Placement for TDI?
No farther than 1 cm below the MV annulus
Observe your mitral valve inflow, place TDI 1 cm below on septal annulus. Measure. Then place 1 cm below on lateral annulus. Measure.
What is Continuous Wave Doppler (CW) BEST used for?
best for HIGH VELOCITY jets! Doppler should always be parallel to flow
*remember TOWARDS probe is ABOVE baseline and AWAY from probe is BELOW baseline
