Ulrasound Doppler Insrumenaion and Color Flow Imaging 한림대학교정보통신공학부배무호
TABLE OF CONTENT Inroduion Doppler Priniple CW Doppler Sysem PW Doppler Sysem Color Flow Imaging Doppler Measuremen Examples Oher Doppler Imaging Mehods
INTRODUCTION Ulrasound Doppler Imaging or Medial Appliaions 초음파를이용, 인체내의혈류를계측, 또는영상화심장, 주변혈관계질환등의진단 Non-invasive, real-ime : 편리하고저비용의효과적인진단수단 Speral Doppler 관심있는지점의혈류정보계측혈류의시간에따른변화정량적계측 : 속도, 방향등. Doppler Sperum 과 Audio 로표현 Color Doppler 관심있는평면의혈류를단층영상으로표현정성적영상화평균속도, 방향, 난류 (Turbulene), Power 등을색상으로표현
INTRODUCTION Image Example : Speral Doppler
INTRODUCTION Image Example : Color Flow Imaging
General Doppler Ee DOPPLER PRINCIPLE
DOPPLER PRINCIPLE Chrisian Andreas Doppler Born: 29 Nov 183 in Salzburg, Ausria Died: 17 Marh 1853 in Venie, Ialy
DOPPLER PRINCIPLE General Doppler Ee Reeiver A Frequeny o ransmied wave = Saionary soure Reeived wave requeny by Reeiver A Reeiver B Reeiver C = by Reeiver B < by Reeiver C Moving soure o 1 = + d = d vs + v v v s o > : Doppler shi requeny : Sound Speed : Speed o Sound Soure : Speed o Observer
DOPPLER PRINCIPLE Ulrasound Doppler Ee in Flowing Blood Cells (3MHz) θ +d (3.3896MHz) Transduer low v Doppler shi requeny: where 2v d = osθ : ulrasound speed v :low speed : Transmi requeny Example : = 3MHz =154m/s v =1m/s os θ = 1 d = 3896Hz 가청주파수범위!
DOPPLER PRINCIPLE General Doppler Ee : Formulaion 거리 z 이동속도 v s 송신수신음속이 인경우, 출발 ~ 도착까지걸린시간 : 즉, 송신기에서시각의현상은수신기에서시각에관측됨. 송신신호를, 수신신호를라하면 Le Then hus I hen where v z s = v z s + () s ) r( ( ) s v z r s = + z v v z s s + = + 1 v z s / 1 / = = v z s r s / 1 / ) ( ) os(2 ) ( s π = ( ) 1 1 2 os 1 2 os ) ( φ π π + = = v z r s v v s s = = 1 1
DOPPLER PRINCIPLE General Doppler Ee : Formulaion 이동속도 v o 송신 거리 z 수신 z vo 음속이 인경우, 출발 ~ 도착까지걸린시간 : = 즉, 수신기에서 시각의현상은송신기에서 z vo 시각에출발됨. 송신신호를 s (), 수신신호를 r() 라하면 r ) = s z v = s + o ( 1 vo z v I s( ) os(2π) hen ( ) = os 2π 1 + o z r = os 2π 1 + φ1 where vo + vo 1 = 1+ = + vo 송 / 수신이다움직이면 1 = + d = v = ( ) s
General Doppler Ee : Formulaion DOPPLER PRINCIPLE 송신수신프로브송신 이동속도 v 거리 z 반사적혈구동일한상황이동속도 v 수신 즉, 초음파진단기에서는송 / 수신기가서로마주보고같은속도로다가가는 ( 멀어지는 ) 상황과같음. 즉 1 = + 따라서 d = + v v 2v d 2v + 거리 z 수신 프로브 그대로재송신 적혈구
Ulrasound Doppler Signal Modelling Doppler Signal Cluer CDR 주로적혈구에서반사 d : 가청주파수대역 DOPPLER PRINCIPLE 혈관벽, 연조직등거의정지해있는 arge 으로부터의신호 d : 낮음. (DC 부근 ) Doppler Signal 에비해진폭이매우큼 Cluer-o-Doppler Raio Cluer signal power CDR = Doppler signal Power 일반적으로 CDR > 4dB
CW DOPPLER SYSTEM CW Doppler Sperum Example
CW DOPPLER SYSTEM CW Doppler Sperum Example : Real-Time
CW DOPPLER SYSTEM Doppler Sperum 의표현 [m/s] 5 4 3 2 1-1 -2 어느한순간 일반적초음파 Doppler sperum 표현 시간 5 4 3 2 1-1 -2 [m/s] 속도 순시 Sperum 크기 이속도의적혈구가비교적많음 이속도의적혈구는거의없음
CW DOPPLER SYSTEM CW Doppler Probe Seering Type 일반적 phased array Aperure 절반은 Tx, 절반은 Rx로사용 송수신빔이동가능 2D image 위에서조작 : 편리 Tx Beam Rx Beam Sai CW Probe (Penil Type) CW 전용 : 2-elemen 한 elemen는 Tx, 나머지는 Rx로사용 빔방향및교차점고정 Tx Beam 저가형 Rx Beam 2D image 없이감각적으로혈류찾아야함.
Sysem Blok Diagram r() CW DOPPLER SYSTEM Tx Amp. CW Osillaor s() Rx Amp. -9 o LPF LPF Quadraure Demodulaor i() q() HPF HPF Cluer iler i 1 () ADC q 1 () ADC + a () FFT Sperum Analysis o Display Forward low Transmi Probe Transmi Beam Paern low Reeive Beam Paern Reeive Probe -9 o Hilber Transorm + + - Audio Amp a r () Audio Speaker Reverse low
CW : Frequeny, Phase, Magniude CW DOPPLER SYSTEM Re Re θ θ =9 o = o T =1/T Im A θ A A os( 2π ) θ =18 o 반지름 A인원주를등속으로돌고있는점을 Re축상으로투영한길이 : A os( 2π ) A : 진폭 (ampliude), T : 주기 (period), =1/T : 주파수, θ : insananeous phase
CW DOPPLER SYSTEM CW : Relaive Phase, Quadraure Base Band Signal 기준 phasor Re Re T T =1/T =1/T A os( 2π ) A Im 불변 (-45 o ) A A os(2π 45 O ) 계속변화 Im A Re Quadraure base band signal : 기준 phasor signal 에대한상대적위상과진폭을복소수로표시. Quadraure base band signal o o = A os( 45 ) + ja sin( 45 ) = I + jq =.77 j.77 Quadraure Base Band Signal I : inphase, Q: Quadraure
CW DOPPLER SYSTEM Quadraure Base Band Doppler Signal I () Q() A os( 2π ) ( 2π ( ) A os + ) d Doppler Signal : 기준 phasor signal( 송신신호 ) 과주파수가만큼차이남. Quadraure base band Doppler signal : = I( ) + jq( ) = A os(2π ) + jasin(2π ) = A exp( j2π ) d 이신호의주파수가바로 Doppler shi 주파수임. 허수부의역할 : 이동방향을알려줌. ( 물체접근 : d >, 멀어짐 : d < ) d d d Forward Flow I() Reverse Flow I() Q() Q()
Quadraure Demodulaor CW DOPPLER SYSTEM r() s() -9 o i () LPF q () LPF i() q() r( ) s( ) = = os(2π ) A( )os(2π ( + d ) + φ( )) i q ( ) = Quadraure Demodulaor A( )os(2π ( 1 2 + A( )sin(2π (2 d ) + φ( )) os(2π ) 1 1 = A( )os(2π (2 + d ) + φ( )) + A( )os(2π d + φ( )) 2 2 ( ) = A( )os(2π ( + ) + φ( )) sin(2π ) = 1 i( ) = A( )os(2π d + φ( )) 2 1 q( ) = A( )sin(2π d + φ( )) 2 d + d ) + φ( )) 1 2 A( )sin(2π d + φ( ))
CW DOPPLER SYSTEM Cluer FIler Magniude Cluer iler Charaerisis Magniude Cluer iler Charaerisis Quadrarure demodulaor oupu signal i()+jq() requeny Cluer Filering Cluer Filer oupu signal i ()+jq () requeny
PW DOPPLER SYSTEM PW Doppler Priniple CW Doppler : Almos no range inormaion Range inormaion 위해송신 : burs 수신 : range-gaing Frequeny resoluion 위해일정주기반복송 / 수신 Disree-ime signal Transmiing Signal Example 'h Tx 1's Tx 2'nd Tx T T = PRI : Pulse Repeiion Inerval [s]. PRF = Pulse Repeiion requeny [Hz] =1/T [s] Cener Frequeny [Hz] = 1/
PW DOPPLER SYSTEM PW Doppler Priniple : Range Inormaion Transduer issue vessel Transmi Burs pulse Range gae Sampled signal
PW DOPPLER SYSTEM PW Doppler Priniple : Range Inormaion T 2T Moving Range gae Reeived Signal Example Single Targe Consan veloiy moving oward probe Doppler 효과로이해할수도있지만, arge의위치이동 초음파왕복시간변화 수신신호위상변화로이해할수도있음. T = 1/PRF k Sampled Daa
Sysem Blok Diagram PW DOPPLER SYSTEM CW Osillaor r() -9 o LPF i() S/H ADC i 1 (k) HPF i 2 (k) Burs s() LPF q() Range Gae S/H Cluer iler q 1 (k) ADC HPF q 2 (k) FFT Sperum Analysis o Display Tx Amp. low Probe Rx Amp. Quadraure Demodulaor Hilber Transorm -9 o a + (k) DAC + + - DAC a r (k) LPF LPF Audio Amp Forward low Audio Speaker Reverse low
Aliasing Problem Real Imaginary a b d e a b d e Real Imaginary a b d e a b d e Real Imaginary a b d e a b d e Real Imaginary Couner -lokwise! a b d e a b d e Imaginary Real Couner -lokwise! Imaginary Real a b d e???? PW DOPPLER SYSTEM
Doppler Signal Example : Liver 1 PW DOPPLER SYSTEM CDR =37[dB] 1 1 DNR = 21[dB] 1 1 -.5 -.25.25.5 Sperum a an insane *PRF Aual Image 3 25 2 15 1 5 1 11 21 31 41 51 61 71 81 91 11 111 121 i & q daa k i(k) q(k)
PW DOPPLER SYSTEM B-D Simulaneous Mode Live B-mode image와동시에 Live Doppler Sperum Sanline Sequene Probe 7 1 7 2 7 7 12 7 매두번의송신에하나의 Doppler daa 를얻음 PRF 가실질적으로반으로줄어듦. 12 11 1 9 8 7 6 5 4 3 2 1 Sanline number Doppler San line
PW DOPPLER SYSTEM PW Doppler Real-Time Image Example
COLOR FLOW IMAGING Sperum Esimaion Esimaes mean and variane o he Doppler sperum in Every Pixel in he ROI Veloiy Only Veloiy +Max Veloiy + Turbulene Veloiy +Max Display Mean veloiy : Towards : Red, Away : Blue Fas : Ligh, Slow : Dark Turbulene : Add Yellow -Max -Max Turbulene Max Imporan Issues : Ensemble Number Limiaion Eiien luer ilering Noise insensiive esimaion
COLOR FLOW IMAGING Image ormaion and Tx/Rx sequene...... Sanline index 12 L Pixel index 1 2... vessel 혈류 x... M.. ZM Transmi Burs 2-D ROI 한 sanline 당 N 회반복송 / 수신 o Sanline 1 o Sanline 2 1 2 3 N 1 2 3 N Ensemble index
Sysem Blok Diagram COLOR FLOW IMAGING i,q Inpu Corner urning Cluer Filer Auo -orrelaor an -1 () veloiy Inpu Corner Turning Daa 순서재정돈, 각 pixel 에필요한 daa 끼리모음 'h Tx 1,1 1,2 1,3 1,4 1,M 1's Tx 2,1 2,2 2,3 2,4 2,M 2'nd Tx 3,1 3,2 3,3 3,4 3,M N'h Tx N,1 N,2 N,3 N,4 N,M or pixel 1 or pixel 2 or pixel 3 or pixel 4 or pixel M
Cluer Filering COLOR FLOW IMAGING Problem : Small Ensemble Number N ap FIR Filer IIR Filer N ransien oupu daa : M-N oupu daa available Large N needed or si ransien band haraerisis Inheren ransien response problem Regression Filer Some ways o sae variable iniializaion o minimize i. Example : E.S. Chornoboy, Iniializaion or improved IIR iler perormane, IEEE Transaions on Signal Proessing, Vol. 4, No. 3, pp543-55, Mar. 1992. Cluer 를 ensemble daa 의 regression 으로추정, 제거. No loss o oupu daa number : requeny esimaion 에유리 Example : A. P. Kadi and T. Loupas, On he perormane o regression and sep iniialized IIR lier ilers or olor Doppler sysems in diagnosi medial ulrasound, IEEE Transaions on UFFC, vol. 42, no. 5, pp. 927-937, Sep. 1995
COLOR FLOW IMAGING Cluer Filering Example : Regression Filer 1 s Order : Linear Regression 2 15 1 5 i q regression o i regression o q ilered i ilered q 1 3 5 7 9 11 13 15-5
Veloiy Esimaor Blok Diagram COLOR FLOW IMAGING i(k) Z -1 i(k-1) + - + + A = Σ[i(k-1)q(k) - i(k)q(k-1)] Z -1 Z -1 an -1 (y,x) v q(k) Z -1 q(k-1) + + + + B = Σ[i(k)i(k-1) + q(k)q(k-1)]
COLOR FLOW IMAGING Overall Sysem Blok Diagram Tx Amp. Eho Proessor B-mode image Array Transduer Rx Amp. Beam -ormer BPF LPF LPF Quadraure Demodulaor i q Doppler Proessor CF Proessor Doppler Sperum Audio Color Flow Image Digial San Converer o Display Audio Speaker
Real-Time Image Examples COLOR FLOW IMAGING 경동맥 Aliasing 발생한경우
Real-Time Image Examples COLOR FLOW IMAGING 심장, Regurgiaion
DOPPLER MEASUREMENT EXAMPLES Sroke Volume Flow rae = CSA Flow veloiy CSA : Cross-seional area CSA Volume o Flow = CSA Flow veloiy ime Flow veloiy가시간에따라변화하는경우 Flow veloiy ime ( Flow vloiy) d Volume o Flow = 밑면적 높이 = CSA ( Flow veloiy ime) Flow veloiy ime Veloiy-ime inegral (VTI) or Time-veloiy inegral (TVI) 한주기동안적분따라서 Sroke Volume = CSA TVI 또 2 D CSA = π = D 2 따라서 2 SV = D. 785 TVI 2.785
DOPPLER MEASUREMENT EXAMPLES PISA (Proximal Isoveloiy Sure Area) Mehod (Color Doppler) Regurgian Volume = ERO Regurgian TVI ERO : Eeive Regurgian Oriie area Flow rae onservaion : Isoveloiy surae Flow rae a any shell surae = low rae a he oriie 계산의편의상 surae 는 isoveloiy surae 특히, aliasing 이생기는면 반구의표면적이 2 2π r 이므로 2 Flow rae = 6.28 r aliasing = ERO regurgian 2 ERO = 6.28 r veloiy aliasing veloiy MR veloiy veloiy a surae a Oriie r low 즉 2 aliasing veloiy regurgian volume = ERO MR TVI = 6.28 r MR TVI MR veloiy
Oher Doppler Imaging Mehods Power Doppler Imaging Color Doppler에서평균속도, 분산등을계산하지않고 Doppler signal의 power만을계산혈관분포등을관찰시간적으로평균을많이취할수있으므로 SNR 유리. Engio mode 등으로부르기도. Tissue Doppler Imaging (TDI) 적혈구로부터의신호대신 wall로부터의 luer를이미징. PW, Color, Color M-mode 등으로관찰 Cardia에서 valve 등의 moion관찰, 진단.
B-Flow Imaging B-Flow : B-Mode Blood Flow Convenional B-mode image : Very small releion rom he RBC Blood is almos blak level To visualize he dark blood in he B-mode, Coded ransmission o improve SNR Ex; Golay Code : Long pulse(=high power) bu an be ompressed (Good Resoluion) Tissue Equalizaion (similar o luer iler) Suppress Tissue brighness Emphasize moving blood brighness Beneis : Fas, Inuiive Visualizaion o blood low Drawbak : poor peneraion, poor sensiiviy
Reen Researhs- SFP in HFUS VXD Yang (Torono Univ) e al, 24 Ulrasoni Symposium SFP : Spekle Flow Proessing, HFUS : High Frequeny Ulrasound Over 4MHz : Very high resoluion (<1um), very poor peneraion (4~5mm) RBC releion oeiien dramaially inreased Spekle rom RBC an be observed Flow an be esimaed by spekle variaion a a pixel. Angle independen! Experimenal Resuls : Imaging o developing leg region o a adpole
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