• Ultrasonography
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• v.32 no.1
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• pp.59-65
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• 2013

Purpose: The purpose of this study is to establish the methodology regarding synthesis of ultrasound contrast agent imaging, and to evaluate the characteristics of the synthesized ultrasound contrast agents, including size or degradation interval and image quality. Materials and Methods: The ultrasound contrast agent, composed of liposome and SF6, was synthesized from the mixture solution of $21{\mu}mol$ DPPC (1, 2-Dihexadecanoyl-sn-glycero-3-phosphocholine, $C_{40}H_{80}NO_8P$), $9{\mu}mol$ cholesterol, $1.9{\mu}mol$ of DCP (Dihexadecylphosphate, $[CH_3(CH_2)_{15}O]_2P(O)OH$), and chloroform. After evaporation in a warm water bath and drying during a period of 12-24 hours, the contrast agent was synthesized by the sonication process by addition of buffer and SF6 gas. The size of the contrast agent was controlled by use of either extruder or sonication methods. After synthesis of contrast agents, analysis of the size distribution of the bubbles was performed using dynamic light scattering measurement methods. The degradation curve was also evaluated by changes in the number of contrast agents via light microscopy immediate, 12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours, and 84 hours after synthesis. For evaluation of the role as an US contrast agent, the echogenicity of the synthesized microbubble was compared with commercially available microbubbles (SonoVue, Bracco, Milan, Italy) using a clinical ultrasound machine and phantom. Results: The contrast agents were synthesized successfully using an evaporation-drying-sonication method. The majority of bubbles showed a mean size of 154.2 nanometers, and they showed marked degradation 24 hours after synthesis. ANOVA test revealed a significant difference among SonoVue, synthesized contrast agent, and saline (p < 0.001). Although no significant difference was observed between SonoVue and the synthesized contrast agent, difference in echogenicity was observed between synthesized contrast agent and saline (p < 0.01). Conclusion: We could synthesize ultrasound contrast agents using an evaporation-drying-sonication method. On the basis of these results, many prospective types of research, such as anticancer drug delivery, gene delivery, including siRNA or microRNA, targeted molecular imaging, and targeted therapy can be performed.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.134-142
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• 2016

In this paper, a method synthesizing speech signal using the 40 kHz ultrasonic signals reflected from the articulatory muscles was introduced and performance was evaluated. When the ultrasound signals are radiated to articulating face, the Doppler effects caused by movements of lips, jaw, and chin observed. The signals that have different frequencies from that of the transmitted signals are found in the received signals. These ADS (Acoustic-Doppler Signals) were used for estimating of the speech parameters in this study. Prior to synthesizing speech signal, a quantitative correlation analysis between ADS and speech signals was carried out on each frequency bin. According to the results, the feasibility of the ADS-based speech synthesis was validated. ADS-to-speech transformation was achieved by the joint Gaussian mixture model-based conversion rules. The experimental results from the 5 subjects showed that filter bank energy and LPC (Linear Predictive Coefficient) cepstrum coefficients are the optimal features for ADS, and speech, respectively. In the subjective evaluation where synthesized speech signals were obtained using the excitation sources extracted from original speech signals, it was confirmed that the ADS-to-speech conversion method yielded 72.2 % average recognition rates.

• Journal of Biomedical Engineering Research
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• v.20 no.4
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• pp.503-513
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• 1999

A general expression for the beam patterns of various synthetic aperture(SA) techniques was derived based on a unified SA model. This model was used to analyze and compare the performance of existing SA methods. Based on the theoretical studies, we propose a new synthetic aperture technique that is best suitable for the linear-scan imaging. The proposed method enables dynamic tow-way focusing in real imaging so that the B-mode image resolution can be greatly improved. Compared to the conventional focusing technique, the focused beam pattern by the proposed shows the mainlobe width reduced by half and comparable sidelobe levels. Computer simulation results demonstrated the validity of the theoretical analysis and the proposed SA method.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.921-927
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• 2001

An effect of ultrasonic irradiation for the extraction and synthesis of alumina from kaolin was investigated by comparing ultrasonic irradiation method and conventional method with the same factors as reaction time, reaction temperature, and acid concentration. The ultrasonic irradiation method accelerated alumina extraction in comparison to conventional method at $60{\sim}80^{\circ}C$ for $1{\sim}6\;h$ in $1{\sim}5\;M$ ${H_2}{SO_4}$. The characteristics of precipitates and calcined samples, synthesized under the ultrasonic irradiation method and the conventional method, were determined by the means of DTA/TG, XRD, SEM, PSA, BET, etc. Especially, the calcined sample synthesized under the ultrasonic irradiation method had smaller particle size and larger surface area than that synthesized under the conventional method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.368-370
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• 2013

본 논문에서는 복부 초음파 영상에서 복부 근육을 추출하고 추출된 근육 영역에서 지방을 분석하는 방법을 제안한다. 복부 초음파 영상에서 밝은 명암도를 가지는 근막 영역과 어두운 명암도를 가지는 근육 영역의 명암 대비를 강조하기 위해서 앤드 인 탐색 스트레칭 방법과 Multiple 연산을 적용한다. 평균 명암도와 명암 대비가 강조된 복부 초음파 영상에서 수직 방향의 명암도가 200이상인 픽셀들은 퍼지 이진화 기법을 적용하여 이진화한다. 이진화된 영상에서 외복사근 상단선을 추출한 후, 퍼지 이진화 기법이 적용된 영상과 합성한다. 합성된 영상에서 최종 근막 영역을 추출한다. 추출된 각각의 복부 근육 영역에 ART2 알고리즘을 적용하여 복부 근육 영역을 양자화한다. 양자화된 복부 근육 내의 영역을 분석하여 최종 지방 영역을 추출한다. 제안된 복부 근육 추출 및 지방 분석 방법을 실제 복부 초음파 영상을 대상으로 실험한 결과, 추출된 복부 근육 영역에 ART2 알고리즘 기반 양자화 기법을 적용하여 지방을 추출하는 것이 복부비만을 분석하는데 도움이 되는 것을 영상 의학과 전문의를 통해 확인하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.395-398
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• 1999

본 연구에서는 초음파현미경에서 다중의 동작주파스를 사용하여 얻어진 영상을 합성하여 깊이분해능이 개선된 초음파영상을 복원하는 방법을 연구하였다. 실험을 위하여 중심주파수가 5MHz이고 비대역폭이 $35\%$인 초음파변환기를 사용하여 초음파현미경을 구성하였다. 시편은 알루미늄을 이용하여 표면에 깊이가 $100{\mu}m$이고 지름이 2mm인 원형결함을 제작하였다. 실험결과, 동작주파수가 5MHz인 단일 주파수를 사용하여 얻어진 영상에서 결함이 존재하는 면과 그렇지 않은 면에 대한 콘트라스트가 0.098로 나타났다. 반면에 동작주파수를 $4.4MHz\~5.6MHz$ 범위에서 200kHz씩 변화시키면서 획득한 데이터를 합성하여 얻어진 영상에서 결함이 존재하는 면과 그러하지 않은 면에 대한 영상 콘트라스트가 0.398로 나타났다. 따라서 초음파현미경에서 다중의 동작주파수를 사용한 경우, 피사체의 깊이 변화에 대한 영상의 콘트라스트가 단일주파수를 사용한 경우에 비하여 개선되어 나타났으며 깊이분해능이 향상되었다. 앞으로의 과제는 초음파현미경에서 음향렌즈의 집속도 변화에 대한 적절한 동작주파수의 동작범위와 영상의 분해능과의 관계에 대한 연구가 계속되어져야 한다고 본다.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.534-544
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• 2022

Medical ultrasound system has been widely used to visualize the lesion for diagnostics in most medical service site including hospitals and clinics thanks to its advantages such as real time operation, ease of use, safety. Among many signal processing blocks of the system, one of the most important part that governs the image quality is the beamformer, and technologies for this part has been continuously developed in long time. The synthetic aperture imaging method, that is one of the major technologies of beamforming, was introduced to maximize utilizing the information delivered from the patient's body through the probe, and contributed to breakthrough of the image quality since it was introduced in around 1990's, and evolved continuously in decades. This paper reviews and surveys the process of development of this technology and expects future evolution.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.185-217
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• 1996

Pb(Mg1/3Nb2/3)O3은 높은 유전율과 전기저항 및 유전율의 온도변화율이 적은 Pb계 relaxor의 대표적인 재료로서 적층 세라믹 콘덴서 재료에의 응용이 크게 기대되고 있다. 그러나 산화물 분말을 이용하는 일반적인 세라믹스 합성방법으로는 Pb(Mg1/3Nb2/3)O3의 단일상의 합성이 어렵고, 합성과정에서 저유전율상인 pyrochlore상이 합성이 어렵고, 합성과정에서 저유전율상인 pyrochlore상이 공존하여 Pb(Mg1/3Nb2/3)O3의 전기적 특성을 저하시킨다. 본연구에서는 용액을 이용하여 Pb(Mg1/3Nb2/3)O3의 단일상을 합성하고자 하였다. 출발물질로는 값싼 금속염인 Niobium Oxalate, magnesium Nitrate 및 Lead Nitrate를 선정하고 증류수에 용해하여 혼합용액을 제좋고, 합성방법으로는 초음파 분무 열분해법과 에멀젼법을 이용하였다. 초음파 분무 열분해법에서는 75$0^{\circ}C$에서 합성한 분말을 다시 75$0^{\circ}C$에서 하소하여 Pb(Mg1/3Nb2/3)O3 단일상을 합성할 수 있었으며, 에멀젼법에서는 80$0^{\circ}C$에서 Pb(Mg1/3Nb2/3)O3 단일상을 합성할 수 있었다.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.521-537
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• 2000

Ultrasonic imaging is the most widely used modality among modern imaging device for medical diagnosis and the system performance has been improved dramatically since early 90's due to the rapid advances in DSP performance and VLSI technology that made it possible to employ more sophisticated algorithms. This paper describes "main stream" digital signal processing functions along with the associated implementation considerations in modern medical ultrasound imaging systems. Topics covered include signal processing methods for resolution improvement, ultrasound imaging system architectures, roles and necessity of the applications of DSP and VLSI technology in the development of the medical ultrasound imaging systems, and array signal processing techniques for ultrasound focusing.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.4
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• pp.20-27
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• 1995

A numerical simulation is carried out on the directivity synthesis of ultrasonic transducers by point source array. Gauss elimination method is practiced by means of a directive method to realize the desired directivity. Desired directivity is chosen to be that of a directivity of line source, a beam width and a direction arbitrary specified. On the numerical result, Gauss elimination method is showed high speed ca- lculative simulation and stability of system more than iterative method(LMS, DFP). Numerical simulations are carried out by PC(CPU:80486 DX2, RAM 16Mbyte).