別紙41 (課程博士(英文))Date of submission (month day, year)

Na01〕iro Hozumi

Depaltm引]t ofElectrical and EleC仇'onic

Sluden11D Numbel

D189202

Infonnation Engineelin号
へPI〕11Cal〕1'S I〕an〕eJuly、 51h,2021

Yoshinobu MUTakami
Supelvlsors

Edo Ba牙Us prastika

Abst"act (Doctor)
Ti11e of TI〕esis

DeveloP1ηenl ofa]1'ee・dim引〕sional physica1 即'operty hnaging method fm'1ayel'ed materials
Using ultl、asoundApprox.80o words
A tl〕ree、din)ensional (3D) PI)ysical property ima牙il〕g using ultrasound is proposed. Afocused transducer scans the layered object along x and ydirection and the cross、sectional viewOf the object is obtained. The reaection coefficient is then calculated by deconvoluting a11 thereaected waveforn〕S. unlike the conventional B、n)ode ech0宮raphy wl)ere each re曾ion (1ayers) of
the object 訊7as only indicated by the intensity of the reaected signal(bri容htness), this study
1)roposes a quantitative observation by convertin宮 each tlme、dependent reflection coefficient into
its physicalproP飢'ty such as acoustic ln〕pedanceConventionaⅡy deconvolution is perforn〕ed by division in 丘equency domain. However,inPractice, the deconvoluted waveform suffers from the instability of baseline. This can be caused

by impropef spectruln division (noise divided by noise) which wi11 Create a spuTious in
10W'frequency components, resultin晉 il〕 a wavy waveform when the result is broU牙ht back into
time domain. since the process of acoustic impedance conveYsion is similar to the inte晉rationalon牙 time axis, any instability in baseline wi111ead to the accumulation of error as inte牙ration
牙oes deeper, which wi11 appear as an a主tifact in acoustic impedance image.1n addition, as thedepth ofmeasurementtar号et 牙ets deepeT, the instability in baseline afteT deconvolution wi11also
become stron牙er.1t can be concluded that deconvolution process becomes an essential aspect inacoustic impedance ima号ing.

In conjunction with the above problems, this study proposes an improvement in thedeconvolution process.1nstead of performin目 deconvolution only in frequency domain, theCalculation is also P飢'formed in time domain because spectral division is not reqU辻ed and the晉eneration ofspurious in low'frequency parts after deconvolution can be avoided. However, since
the calculation speed of time domain deconvolution is directly proportionalto the number ofSamples in the waveform, a down'sampling is performed to speed up the calculation process,With the consequence of the waveform havin牙 its high'frequency components reduced, The
Spurious in low、frequency components as the result of frequency domain deconvolution is thenreplaced by that calculated by time domain deconvolution by specifyin牙 a threshold value. This
Way of calculation wiH retain the stability of low'6'equency components in the spectrum,resulting in a waveform with stable baseline
The first chapter of this study wiH discuss about the background and history ofn)icroscopic in〕a琴in牙 by usin牙 Ultrasound. The tar牙et and motivation as we11 as the contTibution
Ofthe thesis wi11 also be described.

The second chapter wi11 discuss about the theoretical prepafation of tl〕e proposed
quantitative acoustic in〕aging n〕etl〕od includln晉 the process of acoustic lmpedance

inteTpretation and the concept of conventional and the proposed un〕e'frequency (duaD don〕ain〔1econvolution method.

TI)e third chapter wi11 discuss about the application of tl〕e proposed si宮nal processin曾mcl,1)od t0 1〕ulnan cheek skin observation. As the result, each layer of human cheelく Slan wasYisible and could be contrasted by its acoustic parameters, which can be correlated to elasticity

The fourth chapter wil] discuss about tl〕e requiYelnent to perforn〕 a 3D calculation (byPeTforn〕ing many tilnes of deconvolution process) so that tl〕e calculated acoustjc in〕pedance
data can be sliced in a11 Cross'sect,ional direction. The in〕provement and optn〕〕al condition ofdual don〕ain deconvolution 訊7hen calculating a stack of acoustlC 11npedance 11〕〕ages ln order toincrease the robustness and quic]ロ〕ess of tl)e calculation w】11 be discussed. As a result,3D
1、econstruction of human cheeR SIQn and a quantitative skln observation based on thediffeYence of ages and 北S cofrelation 、、'jth the gene]'ation of wrlnkleS 訊d11 be discussed

The fi丑h chapter of u〕js study wiⅡ discuss about the pfoposed slgnal processlng for
Observing tl〕e dynamisln of cujtu〕'ed cel】S (clial ce11S and Fibroblast ceHS). As a result, the area
Of culture liquid, ce11 and substrate could be distin目Uished based on lts acoustic nnpedance
Value.1n addition, by stacldng a11the calculated cross'sectional acoustlc lmpedance ln〕a牙es, thedynamism of tlie ce11 SUCI) as the change in height and s}〕ape befの'e and after the treatment(fixation by aldehyde) could be tracked.

The sixth chapter ofthis study wi11 discuss about the application ofthe proposed acousticin〕aging method for coating film n)onltorln牙 in automotive industry, as an alternative to theConventional observation by usin牙 Terahertz li冨ht wl)icl〕 is expensive. As a result, not only thetl)ickness but tl〕e unif01.mity of eacl) 1ayer could also be assessed by means of its acousticil〕〕pedance distribution.1n another section of the chapter, the application of the proposed si宮nal
Processing to the space char曾e measurementin 仇'OSS、1inked polyethylene (XLPE) cable by using
Pulsed electro・acoustic (PEA) device 訊7i11 also be discussed. since the stability of each 訊7aveform
Can be maintained by dual domain deconvolution, the char晉e intensity, electric field andPotential distribution could then be calculated by inte目rating aⅡ the calculated 訊7aveform
It can be concluded that from the above'mentioned applications, the proposed signal

Processing method is believed to be advanta今eous and applicable to many uHrasound'based
research fields because many of the applications require an integration process along time

axis and when stabi1北y and quickness of the calculation can be maintained, the analysis
Tesult can be interpreted into solnethin牙 more lnformative and quantitative.