URR part 2 Flashcards
Non specular reflector increases with increasing ______
frequency
______ relies on Rayleigh scattering from red blood cells to demonstrate the flow on the image
Doppler imaging
System sensitivity should be ______ for all types of Doppler imaging.
increased
Although higher frequency transducers result in greater amounts of ______, penetration of the beam must still be adequate to properly demonstrate flow in deeper structures
Rayleigh scattering
Time of flight or go-return time refers to the time sound travels to and from the transducer
range equation
total time for the pulse to reach a reflector and return to the transducer
range equation
used to calculate distance to the transducer
range equation
US system uses this reflector information to locate pixel placement on the screen
range equation
d = c x 1/2
range equation
in soft tissue, every 13 us of time of flight, the reflector is 1 cm deeper
13 us rule
Cosine of 0 degrees=
1
cosine of 60 degrees =
0.5
cosine of 90 degrees =
0
A CW probe is not limited by the ____ and _____ because the beam is not pulsed
PRF
Nyquist limit
What is the primary factor that determines the resistance characteristics of the arterial signal displayed by PW Doppler?
part it is supplying
Which of the following is a limitation of Analog Doppler?
a. cannot detect flow velocities over 300 cm/s
b. cannot detect flow velocities less than 60 cm/s
c. overestimates high velocities and underestimates low velocities
d. unable to detect post stenotic turbulence and spectral broadening
d
Which of the following will improve a color Doppler image by averaging previous frames to create a new image?
a. sensitivity
b. gain
c. priority
d. persistence
d
If the peak systolic velocity is 3 m/s, what is the peak pressure gradient?
36 mm/Hg
Bernoulli equation
pressure gradient = 4(velocity) squared
When evaluating a focal stenosis of an artery, where should you place the cursor to obtain the highest velocity related to the stenosis?
at the narrowest point in the vessel or immediately distal to the focal point of the stenosis
occurs with slow moving bloow flow and the reflections from the congregated red blood cells
Rouleaux formation
Blood flow at a focal stenosis will demonstrate:
increased resistance
How is the PRP reduced in Doppler imaging?
decreasing imaging depth
Decreased imaging depth = _______ PRP
decreased