Ultrasound Doppler Instrumentation and Color Flow Imaging INTODUCTION Ultrasound Doppler Imaging or Medical Applications
INTODUCTION Image Example : Spectral Doppler INTODUCTION Image Example : Color Flow Imaging
DOPPLE PINCIPLE General Doppler Eect eceiver A Frequency o transmitted wave Stationary source eceived wave requency by eceiver A eceiver B eceiver C by eceiver B < by eceiver C Moving source > DOPPLE PINCIPLE Ultrasound Doppler Eect in Flowing Blood Cells Transducer + d θ low v Doppler shit requency: where v d c cosθ c : ultrasound speed v :low speed : Transmit requency
Ultrasound Doppler Signal Modelling Clutter signal power CD Doppler signal Power DOPPLE PINCIPLE CW DOPPLE SYSTEM CW Doppler Spectrum Example
CW DOPPLE SYSTEM Doppler Spectrum CW DOPPLE SYSTEM CW Doppler Probe
System Block Diagram CW DOPPLE SYSTEM Quadrature Demodulator CW DOPPLE SYSTEM r t cosπ t s t A tcosπ + t + t d i t A tcosπ + t + t cosπ t d A tcosπ + d t + t + A tcosπ dt + t q t A tcosπ + t + t sinπ t d A tsinπ + d t + t A tsinπ dt + t i t A tcosπ dt + t q t A tsinπ dt + t
Quadrature Demodulator CW DOPPLE SYSTEM A t, t CW DOPPLE SYSTEM Clutter FIlter
CW DOPPLE SYSTEM Typical Clutter Filter Implementation Example Audio : Forward & everse Flow Discrimination Hilbert transorm g t g x t H x dt dt g x π x t π t πx F H x F F g x πx F sgn w sgn w πx CW DOPPLE SYSTEM i w otherwise
CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example.8 Hilbert coeicient plot [3-th order] W/O window with Hamming window magnitude.6.4. -. -.4 -.6 -.8-5 5 5 3 CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example
CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example PW Doppler Principle PW DOPPLE SYSTEM
PW DOPPLE SYSTEM PW Doppler Principle : ange Inormation Transducer tissue vessel Transmit Burst pulse ange gate Sampled signal PW DOPPLE SYSTEM PW Doppler Principle : ange Inormation
System Block Diagram PW DOPPLE SYSTEM eceived Signal Spectrum PW DOPPLE SYSTEM
Aliasing Problem PW DOPPLE SYSTEM Doppler Signal Example : Liver PW DOPPLE SYSTEM
PW DOPPLE SYSTEM B-D Simultaneous Mode COLO FLOW IMAGING Spectrum Estimation Display Important Issues : Ensemble Number Limitation
.. M L.......... Scanline index. x ZM vessel Image ormation and Tx/x sequence COLO FLOW IMAGING Mean Frequency Estimation using Autocorrelator d e S d e S dt t z t z π π d S d S d S d S π / π ' ' ' ' t t dt t z t z dt t z t z + + ' - A A A e A e A e A ' ' ' ' π π π + e A e A e A where COLO FLOW IMAGING
COLO FLOW IMAGING Mean Frequency Estimation using Autocorrelator T Fp ' T π π T π Fp Im[ T ] tan π e[ T ] F P PF / T T E[ z k z k ] E[{ i k + q k}{ i k q k }] E[{ i k i k + q k q k } + { q k i k i k q k }] J { q k i k i k q k } Fp tan k π J { i k i k + q k q k } k tan F p F π x π p var S d T { } S d T System Block Diagram COLO FLOW IMAGING Input Corner Turning
Clutter Filtering COLO FLOW IMAGING COLO FLOW IMAGING Clutter Filtering
Velocity Estimator Block Diagram COLO FLOW IMAGING Σ Σ COLO FLOW IMAGING Overall System Block Diagram
Thank You