名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成21年3月25日 靍見有史氏の博士論文として提出された

The possibility and feasibility of experimental detection of localized defects in tubes using laser-induced ultrasonic wave approach through Thermo Acousto Photonic Non Destructive Evaluation (TAP-NDE) and Signal processing through wavelet transform is examined in this research. Guided waves in cylindrical surfaces provide solutions for detection of different defects in the material. Several experiments were conducted to this respect. Wave propagation in both axial and circumferential directions was studied. The dispersive wave propagation of ultrasonic waves in hollow cylinders has been investigated experimentally, primarily for use in non-contact and nondestructive inspections of pipes and tubes. The laser ultrasonic waves propagated in cylindrical waveguides are particularly attractive because of their unique characteristics in the applications of nondestructive evaluation (NDE). Contrary to studies making use of only axially symmetric guided waves in hollow cylinders, here are analyzed also nonaxisymmetric waves. The analysis of data is made by using the Gabor wavelet transform. The capability of modeling the guided wave dispersion in hollow cylinders is used in developing guided wave experimental techniques for flaw detection. Good agreement was obtained when comparing the dispersion spectra between theory and experimentation. Measurement of group velocities of guided waves, which are obtained directly from the wavelet transform coefficients, can be used to determine allocation and sizing of flaws.

Pregnancy diagnosis by transrectal ultrasonography (using a 5 MHZ linear probe) presented the maximum sensitivity and negative predictive values at day 26 and day 29 after estrus in heifers and cows, respectively. Palpation per rectum using the fetal membrane slip for pregnancy diagnosis did not increase embryo/fetus mortality when compared with a positive control group of non-palpated females. The use of a controlled randomized block design was a useful approach to study this problem. Blocking for category and number of embryos allowed us to remove these confounding factors. Factors that affected pregnancy loss during the first four months of pregnancy were: period of pregnancy, age of the animal, number of previous lactations and number of embryos. Pregnancy loss was higher during the embryonic than fetal periods. Spontaneous embryo/fetal mortality increased with the age of the animal and lactation number. The risk of spontaneous embryo/fetus mortality was higher in twin than in single pregnancies. Two types of embryo/fetus mortality were noted: Type I and Type II. Type I was characterized by presence of positive fetal membrane slip by palpation per rectum, signs of degeneration by transrectal ultrasonography and persistence of a functional corpus luteum. The uterus took approximately 3 weeks to be noted clean by transrectal ultrasonography and the animals showed estrus one month after the conceptus was diagnosed dead. Type II was characterized by absence of positive signs of pregnancy by palpation per rectum, absence of signs of degeneration by transrectal ultrasonography and absence of a functional corpus luteum. Pregnancy loss in nuclear transfer derived embryos was higher compared to in vivo derived embryos produced by artificial insemination. Pregnancy loss occurred mainly during the transition from the embryonic to the fetal period. Embryo/fetus mortality detected was Type I. Progesterone produced by the corpus luteum was noted at pregnancy levels for approximately two weeks after embryo/fetus death. Protein B, a hormonal placental marker, was maintained at pregnancy levels for approximately 3 weeks after embryo/fetus death. No differences in the levels of the two hormones were noted when comparing females with dead or live conceptuses.

The purpose of this study is to explore the biological effects of ultrasound exposure on growth of Saccharomyces cerevisiae. The result shows the biological effects of ultrasound exposure. The resonance frequencies and a non-resonance frequency were used with different intensities to find the relations between ultrasonic and cell growth. The methods of this study adopted finite element method and Rayleigh-Plesset theory to calculate the resonance frequencies. And then, the study set a diffuse field to exposure the yeast cells. In the experiment, cell growths were analyzed by a 600 nm ultraviolet spectrophotometer measuring the cell mass concentration. The results show that the restrained time under high intensity ultrasonic exposure was longer than low intensity in 0.306 and 11.6625 MHz. However, the restrained effects were the same between high and low irradiation intensity in 2.4079 MHz. By 10 MHz low irradiation intensity, the restrained time was 0.5 hr after sonication. The restrain effects were not obvious under low and high irradiation intensity in 16.124 MHz.

Regenerative medicine is an interdisciplinary field which has advanced with the use of biotechnologies related to biomaterials, growth factors, and stem cells to replace or restore damaged cells, tissues, and organs. Among various therapeutic approaches, cell-based therapy is most challenging and exciting for both scientists and clinicians pursuing regenerative medicine. Specifically, stem cells, including mesenchymal stem cells and adipose-derived stem cells, are promising candidate cell types for cell-based therapy because they can differentiate into multiple cell types for tissue regeneration and stimulate other cells through neovascularization or paracrine signaling. Also, for effective treatment using stem cells, the tissue engineered constructs, such as bioactive degradable scaffolds, that provide the physical and chemical cues to guide their differentiation are incorporated with stem cells before implantation. Also, it was previously demonstrated that tissue-engineered matrices can promote tubulogenesis and differentiation of stem cells to vascular cell phenotypes. Hence, during tissue regeneration after stem cell therapy, there are numerous factors that need to be monitored. As a result, imaging-based stem cell tracking is essential to evaluate the distribution of stem cells as well as to monitor proliferation, differentiation, and interaction with the microenvironment. Therefore, there is a need for a stem cell imaging technique that is not only noninvasive, sensitive, and easy to operate, but also capable of quantitatively assessing stem cell behaviors in the long term with high spatial resolution. Therefore, the overall goal of this research is to demonstrate a novel imaging method capable of continuous in vitro assessment of stem cells as prepared with tissue engineered constructs and noninvasive longitudinal in vivo monitoring of stem cell behaviors and tissue regeneration after stem cell implantation. In order to accomplish this, gold nanoparticles are demonstrated as photoacoustic imaging contrasts to label stem cells. In addition, ultrasound and photoacoustic imaging was utilized to monitor stem cells and neovascularization in the injured rat tissue. Therefore, using these methods, tissue regeneration can be promoted and noninvasively monitored, resulting in a better understanding of the tissue repair mechanisms following tissue injury. / text

Bread owes its appeal to its aerated structure which directly relies on the bubbles entrained into the dough during mixing. If the bubble size distribution (BSD) in the dough can be determined at the end of mixing, then the resulting loaf quality could be predicted before bread is fully manufactured. However, non-invasively monitoring the structure of a fragile opaque soft solid such as dough is challenging. This thesis addressed the challenge by determining dough’s BSD and its evolution using ultrasound and X-ray microtomography. Using a resonant scattering model and the frequency dependence of the ultrasonic parameters measured in the dough, the change in the BSD in dough (made without yeast) with time as a result of disproportionation was determined. At 30 min after mixing, the median radius (R0) of the lognormal BSD was 6.5 microns. Converting the BSD to the radius dependence of bubble volume fraction (BVF(R)), R0V (the median radius of BVF(R)) was 66.4 microns and increased 18 % in the succeeding 90 min. In order to validate the bubble sizes determined ultrasonically, X-rays from a synchrotron source were utilized to examine dough’s microstructure. Large numbers of very small bubbles were discovered and it was apparent that lognormality did not describe the BSDs. Nevertheless, lognormal characterization of the BVF(R) was appropriate. At 30 min after mixing R0V of the BVF(R) was 32.5 microns and it increased by 20 % in the succeeding 90 min, supporting the ultrasonic quantification of bubble volume changes due to disproportionation. Changes in the mode, median and mean of the BVF(R) with time after mixing had the same trend for ultrasound and for X-ray microtomography. The time evolution of the mode of the BVF(R) obtained by ultrasound and X-ray microtomography matched very well; both increasing linearly as a function of time. Ultrasonic assessments of bubble sizes and their changes with time are very encouraging, but the ultrasonic model should use distribution functions that precisely define the empirical data, perhaps not making ‘pre-assumptions’ of lognormality for the BSD data. / February 2015

Intra-cardiac procedures often involve fast-moving anatomic structures with large spatial extent and high geometrical complexity. Real-time visualization of the moving structures and instrument-tissue contact is crucial to the success of these procedures. Real-time 3D ultrasound is a promising modality for procedure guidance as it offers improved spatial orientation information relative to 2D ultrasound. Imaging rates at 30 fps enable good visualization of instrument-tissue interactions, far faster than the volumetric imaging alternatives (MR/CT). Unlike fluoroscopy, 3D ultrasound also allows better contrast of soft tissues, and avoids the use of ionizing radiation. / Engineering and Applied Sciences

The present study examines the acoustic and articulatory features of English onset and coda /l/s as produced by native English and Mandarin Chinese speakers in the vowel contexts of /i/, /ɪ/, /e/, / ɛ/, /u/, /ʊ/, /o/, /ɔ/, /ɑ/, /ʌ/, /ɚ/, and /æ/, and via the elicitation tasks of word list and mini dialogue. Four Mandarin Chinese speakers who had lived in Canada for at least one year by the time of the experiment and four Canadian English speakers who were born and raised on west coast of Canada participated in the research. Both groups of speakers were the graduate students studying at the University of Victoria. The experiment took place at the Phonetics Laboratory in the Department of Linguistics at the University of Victoria. An ultrasound machine together with a synchronized microphone was used to record the speech data for analysis. The results showed that for onset /l/, the tongue position of the Mandarin Chinese speakers was more front than that of the English speakers. For coda /l/s, Mandarin Chinese speakers had lower and more retracted tongue position than their English counterparts. ANOVA tests showed that vowel contexts and task formality had limited impact on the acoustic qualities of the onset and coda /l/s produced by both groups of speakers. The results and conclusions from the present study will contribute to a better understanding of the articulatory features of the English /l/s. Mandarin Chinese learners may also benefit from this study in that they could potentially improve their pronunciations and reduce accent. / Graduate

Objectives Prenatal alcohol exposure can lead to fetal alcohol spectrum disorders (FASD), which include a broad range of cognitive, growth, behavior, and physical abnormalities. Early detection of the teratogenic effects of prenatal alcohol exposure is necessary to identify early interventions. The aim of this study is to identify the effects of prenatal alcohol exposure on growth and infant development, to determine if ultrasound imaging can be used as an early identification tool, and to determine if maternal folate supplementation can mitigate the detrimental effects on growth and infant development. Methods A prospective cohort study and randomized trial from 2008 to 2014 conducted in two sites of Western Ukraine was analyzed. A sample of pregnant women who reported moderate-to-heavy alcohol consumption during pregnancy, and a sample reporting little-to-no alcohol use during pregnancy participated in a comprehensive maternal interview and screening process. Women were further randomized into micronutrient supplementation groups. Standard ultrasound examinations during pregnancy including study specific brain growth measurements, along with blood and urine samples were obtained during follow-up visits. A biometric screening was conducted at birth, along with Bayley Scales of Infant Development-II Mental Development Index (MDI) and Psychomotor Development Index (PDI) assessments at 6 and 12 months of age. Results Estimated fetal weight (EFW), abdominal circumference (AC), biparietal diameter (BPD), transverse cerebellar diameter (TCD), occipitofrontal diameter (OFD), caval-calvarial distance (CCD), and orbital diameter (OD) were significantly reduced by alcohol exposure at third trimester ultrasound (p2(7)=18.044, p=0.012), AC at third trimester (X2(5)=17.955, p=0.003), and birth weight (X2(6)=75.058, p2(11)=63.051, p Conclusions Significant reductions in fetal growth measurements during third trimester ultrasound suggest that the effects of prenatal alcohol exposure may be detectable in late pregnancy. Significant associations between multivitamin supplementation and specific growth measurements suggest that micronutrient supplementation during pregnancy, including high doses of folate, may be an early intervention to reduce the harmful effects of prenatal alcohol exposure. Further studies are needed to identify the specific micronutrients producing these effects, and to assess the appropriate level of these micronutrients necessary to provide the greatest benefit without exceeding the safe limit.

Cancer has been one of main causes of human deaths for many years. Early detection of cancer is essential to provide definitive treatment. Among many cancer treatment methods, nanoparticle-mediated photothermal therapy is considered as one of the promising cancer treatment methods because of its non-invasiveness and cancer-specific therapy. Ultrasound and photoacoustic imaging can be utilized for both cancer detection and photothermal therapy guidance. Ultrasound elasticity imaging can detect cancer using tissue elastic properties. Once cancer is diagnosed, spectroscopic photoacoustic imaging can be used to monitor nanoparticle delivery before photothermal therapy. When nanoparticles are well accumulated at the tumor, ultrasound and photoacoustic-based thermal imaging can be utilized for estimating temperature distribution during photothermal therapy to guide therapeutic procedure. In this dissertation, ultrasound beamforming, elasticity imaging, and spectroscopic photoacoustic imaging methods were developed to improve cancer detection and therapy guidance. Firstly, a display pixel based synthetic aperture focusing method was developed to fundamentally improve ultrasound image qualities. Secondly, an autocorrelation based sub-pixel displacement estimation method was developed to enhance signal-to-noise ratio of elasticity images. The developed elasticity imaging method was utilized to clinically evaluate the feasibility of using ultrasound elasticity imaging for prostate cancer detection. Lastly, a minimum mean square error based spectral separation method was developed to robustly utilize spectroscopic photoacoustic imaging. The developed spectroscopic photoacoustic imaging method was utilized to demonstrate ultrasound and photoacoustic image-guided photothermal cancer therapy using in-vivo tumor-bearing mouse models. The results of these studies suggest that ultrasound and photoacoustic imaging can assist both cancer detection and therapy guidance. / text