Ultrasound Doppler Instrumentation and Color Flow Imaging

Transcription

1 Ultrasound Doppler Instrumentation and Color Flow Imaging INTODUCTION Ultrasound Doppler Imaging or Medical Applications

2 INTODUCTION Image Example : Spectral Doppler INTODUCTION Image Example : Color Flow Imaging

3 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

4 Ultrasound Doppler Signal Modelling Clutter signal power CD Doppler signal Power DOPPLE PINCIPLE CW DOPPLE SYSTEM CW Doppler Spectrum Example

5 CW DOPPLE SYSTEM Doppler Spectrum CW DOPPLE SYSTEM CW Doppler Probe

6 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

7 Quadrature Demodulator CW DOPPLE SYSTEM A t, t CW DOPPLE SYSTEM Clutter FIlter

8 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

9 CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example.8 Hilbert coeicient plot [3-th order] W/O window with Hamming window magnitude CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example

10 CW DOPPLE SYSTEM Hilbert Transorm Filter Design Example PW Doppler Principle PW DOPPLE SYSTEM

11 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

12 System Block Diagram PW DOPPLE SYSTEM eceived Signal Spectrum PW DOPPLE SYSTEM

13 Aliasing Problem PW DOPPLE SYSTEM Doppler Signal Example : Liver PW DOPPLE SYSTEM

14 PW DOPPLE SYSTEM B-D Simultaneous Mode COLO FLOW IMAGING Spectrum Estimation Display Important Issues : Ensemble Number Limitation

15 .. 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

16 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

17 Clutter Filtering COLO FLOW IMAGING COLO FLOW IMAGING Clutter Filtering

18 Velocity Estimator Block Diagram COLO FLOW IMAGING Σ Σ COLO FLOW IMAGING Overall System Block Diagram

19 Thank You