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A Study on Automated Identification of Heart Wall Using Multiple
Features Extracted from Ultrasound Backscattered Signals

Hiroki TAKAHASHISupervisor: Hiroshi KANAI,

Research Advisor: Hideyuki HASEGAWA

In most methods for evaluation of cardiac function based on echocardiography, the heart wall is currently
identified manually by an operator. However, this task is time consuming and causes inter- and intraobserver variability. To overcome this problem, this study proposes a method which uses multiple features ofultrasonic echo signals for automated identification of the heart wall region throughout an entire cardiac
cycle. In the proposed method, the multiple features were extracted to reduce influences of undesirable echocharacteristics (a low echogenicity inside the heart wall and stationary components owing to echoes frommainly ribs) which would degrade the accuracy of identification of the heart wall. Furthermore, the optimal
cardiac phase to accurately identify the heart wall region based on these features was determined. In thepresent study, the heart wall region at a frame of interest in the optimum cardiac phase was identified by theexpectation-maximization (EM) algorithm, and heart wall regions in the following frames were identified bytracking each point classified in the initial frame as the heart wall region using the phased tracking method.
The results for several subjects indicate the feasibility of the proposed method.

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S 1 *Ó=yVu`no©Hgf2XeÜHzggeat´«:kmno7 S<F©H
Vª=a3 \¸¹pArä\3=_U` 1.44mm (ÑÒ%òéD=E) \¼* \ RF ÒÖSTU`;ú©Hz2)

3)

interventricular
septumright ventricle(the distance from the probe)

direction of frame (time)

sector probe
direction of xdepth&'()*+,-./:=>IAEHPQRSTUV*W
XYZ[\]^=_U`abcde\fghaYZ
ijfkH*lm\nopqrs=tu`vwex
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©Hv[epaÏ 1 =ÐAEHt¯=*l=PQRSÑÒ©Hgfe 1 *ÓÔÕ\e/:{VPQR RF ÒÖ×ØÙÚÛ=¼{`aÜHÝÞ (¼*ßàá) \ RF ÒÖ|âãäaåæçàèé¼· (MSC) a_tê ë |\=ìdEHíîïð\@§SYZ©HVª= moving-target indicator (MTI) ßñòØóè1.

nn −1n +1n+ kframe No.

ii+1left ventricle
sampling ∆xinterval

left ventricular
Nj posterior wall
j1 0 scan line No.

? 1: *lPQRC[=_U`PQRáSAr©Hgf=t´FEHCL\Ïf/:AEH RF ÒÖz
3. 4Ä!B)$Ä ÉÍ¼*ßàá\mno\«¬paÔ9\3ß
measured RF signals at j−th scan lineàá\no7 =­^16SM$He=MeÜHz°gea7>s|/:{V*l\PQ
R RF ÒÖ×ØÙÚÛ=_U`a3Þemf* ëSvw@o{a@o{V eùúAEH¸¹|§ÂX<¬ J S;ú©Hz;
úAEH§ÂXSTU`a 3ÿk4|±v[\¼*ßàáAB=_HÀõk*=U`9;©Hz4)ΙΙ ΙΙΙ

IVcutoff frequancy [Hz]

ECG
PCG

criterion ofseparability

300(a)

250
150

8100650

4012MSC5)(b)0.80.60.4
0.200(c)−20IVS
LVPW
LV

2nd heart soundassigned area in heart wall
for classification
assigned area in lumen
for classification(a)

1st heart sound 2nd heart soundR−wave

ECG
PCG
0.2 s

10

normalized
magnitude [dB]

1210200mm

Ι

R−wave­HzgEpa5NF¾=_H:*\\2=H¯:m\5k?{Vgfem¤ (éÛà%èàÛ) ¦A^k´a0JeaíN¬µUS{`UHVªa*lmf*ë\ MSC \C=­k©HVªeÜ
Hf9$EHz
4. ÄÅÆÇÈÉ 1 Ä )!" ÌÍ23 #&7>s\:D'(=_U` 1 *Ó\*lmSno{VzÏ 3(a) p5NF¾|NF¾\øx¾|AB{V¼*ßàá=_H B )*(fno7 eÜ´aÏ 3(b) p¼*ßàá=_U`mfnoAEVS0ÛÚ èô[ =t´D+©HgfeFEV
3*=_Hno7 a_têno7S B )*(==,V7 SÐ©zggeaEMûòüóýá\-´.{/;=_H%/Ø\8¾Cf{`a3|vweAB{VS¿*f©H½I |;úAEHCSTUVz−40(b)−60−80

strain rate [(m/s)/m]velocity [mm/s]

heart wall

−150−100−50050100150
1050−5−10−15−20lumen(d)isovolumic
contraction phase(e)

00.2

0.4

0.60.8

11.2

time from R−wave [s]? 2: (a) §ÂX<¬ J a(b) MSC _tê (c) âãä\ Ca*lm\ (d) ¬_tê (e) Õf®\éÛà%èàÛ (IVS: *¿3maLVPW: :ömaLV: : ë)zÏ 2(a)a(b)a(c)a(d)a(e) p°EE3Þ\§ÂX<¬aMSC _têâãä\ Ca_tê0ÛÚ èô[=tu`/:AE
VÜHArä=_Hm¬féÛà%èàÛSÐ©zggea0÷ø\ùú\Vª\ MTI ßñòØ\ ÚÛ ß½R·S 25 Hz 3e¤ {a3ÚÛ ß½R·=_U`§ÂX<¬S;ú{VzÏ¿\¾ I, II, III, _tê IV pa°EE ú¾aE¾a5NF¾a_têNF¾SIy©zÏ 2(a) |a5NF¾|NF¾\øx¾=_U`§ÂXÀfkHgfSGe

earlyejection phaselateejection phaseisovolumic
relaxation phase? 3: (a) ¼*ßàá\ B )*(fno7z(b) kH*\no7 z
5. KO±v[=tu`noAEVmf B )*(SLP{V7 |a±v[=tH*lm\ 1 *Ó=yVHþwno\2XÐAEVzdVaEM ûòüóýá\t¯k%/ÛóÚQkQé§Âv[m\no=RSeÜHgfSÐ{VzTUVW
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