Ch. 1 Physical Principles/ Doppler Imaging Flashcards
___: the difference between transmitted frequency and received frequency
Doppler shift
What are some factors that can cause spectral broadening?
-disease
-large sample volume
-can occur in normal vessels
Will PW or CW Doppler will always have spectral broadening and why?
CW because of the large sample volume (remember CW samples the whole length of the beam)
___: the filling in of the spectral window
Spectral broadening
___: number of cycles per second
Frequency
___: the number of pulses the US beam sends into the body each second
Pulse repetition frequency (PRF)
___: the time it takes the US beam to travel 1cm into the body and back
13 microsecond rule
What is the Doppler equation when solving for velocity
If this is the Doppler equation when solving for velocity what does each part represent and what is directly related
V= velocity
C= speed of sound in soft tissue (1540)
Fo= transducer freq
Cos 0= angle of incidence
Df= Doppler shift freq
Df and C are directly related with velocity
What is the Doppler equation when solving for Doppler freq
___: digital technique used to process both PW and CW Doppler
Fast Fourier transfer (FFT)
when the transducer has increased freq what happens to pen and res
increases freq= increased res, decreased pen
decreased freq= ___ res and ___ pen
decreased freq= decreased res, increased pen
what is the optimal angle of incidence for gray scale imaging
90 degrees
what is the optimal angle of incidence for doppler imaging
60 or less
which of the following has spectral broadening
the bottom one
how are frame rate and depth related
inversely, meaning increased depth = decreased frame rate
what artifact does this image show
aliasing
___: the ability of the system to properly display flow
Nyquist limit
what happens when PRF is greater than 1/2 the nyquist limit
aliasing
what are some things you can do to fix aliasing
-increase scale
-lower baseline
-lower freq
-use CW doppler (doesn't alias)
what is the speed of US through soft tissue
1540 m/sec
what are the two types of CW doppler
-analog
-digital or spectral
what are the benefits of CW doppler
does not alias