lecture 23 Flashcards
Spectral doppler
Presence, speed, chharacter and direction of blood flow
Quanitification of blood flow
Peak systolic velocity vs end diastolic
Peak systolic is top of highest peak
And diastolic is the smaller peak after the large one
Spectral doppler aka
Pulsed doppler
Pulsed wave doppler
Spectral doppler fires along ____________ at ______ cycles per pulse
Single scan line
5-30 cycles per pulse
Sample volume
Specific area that is being assessed
Aka gate
Range gating
Being able to select information from a speciifc depth
Sample volume made of (2)
Effective sample length and sample width
Effective sample length =
0.5(SPL) + gate length
Sample width =
Beam width
Sample volume is _____defined
User
Larger gate lengths for
Looking for a vessel/ signal
Smaller gate lengths for
More specific info, less noise, better quality of spectral waveform
Samples taken in x and y axis in colour doppler
X axis = time
Y axis = doppler shift/velocity
Then smoothed
Realistically ______________ is obtained at any particular moment in time
A range of velocities
Blood cells _______ are picked up
Moving at different speeds
We are usually concerned with the _____ speeds of the spectra
Fastest
Spectral doppler is all happening within the _____
Signal processor
Quadrature phase detector allows
Detection of bidirectional doppler, meaning we can see positive negative shifts
Mixer in the signal processor
Mixees fR+ fT and fR-fT
Filter in the signal processor get rid of
The sum of fR+fT
Spectrum analyzer determines
Each doppler shift freq and its strength
Fast fourier transform occurs within
The spectrum analyzer
Fast fourier transform is what
A mathmatical technique to figure out the frequency spectrum
Fast fourier transform results sent to
Be displayed on the spectral display
Spectral display shows
Spectral waveforms
The x and y axis on spectral display are
X- time
Y- doppler shift/velocity
On spectral display each point shows (3)
Direction (+/-)
Magnitude (how fast)
Amplitude (brightness)
What factors affect direction on the spectral display
Whether it is coming towards or away from the transducer
Affected by direction of probe/steering
What factors affect magnitude on spectral displau
Speed of blood flow
Doppler angle
Larger doppler angle = _______ doppler shift and ______ velocity calculated
Smaller and slower
What factors can affect amplitude on spectral display
Brightness/ intensity of returning echo
Concentration of RBCs/ reflectors/impedances
Spectral controls (4)
Gate size/ sample volume
Gain
Spectral invert
Baseline
Spectral contols are similar to
colour controls
