• 한국음향학회지
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• 제36권4호
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• pp.238-246
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• 2017

고주파수, 고해상도 초음파 영상을 획득하기 위해서는 고주파수 초음파 변환기가 가지는 작은 구경에 따른 낮은 민감도와 침투 깊이에 따른 높은 감쇠량을 극복하여야 한다. 이는 고주파수 초음파 변환기의 본질적인 한계점이므로 수신 시스템을 통하여 그 한계점을 극복하여야 한다. 본 논문은 고주파수, 고해상도 초음파 영상을 위하여 고주파수 초음파 변환기의 본질적인 한계인 낮은 민감도와 높은 감쇠량을 극복할 수 있는 저잡음 광대역 수신 시스템 개발과 특성 평가 결과에 관한 것이다. 개발한 저잡음 광대역 수신 시스템은 80 MHz 이상의 동작 주파수 대역에서 최대 73 dB의 증폭 이득과 48 dB의 가변 이득 범위를 만족하며 ${\pm}1dB$의 증폭 이득 평탄도 성능을 가진다. 또한 개발한 수신 시스템은 상용 리시버에 비하여 8.4 dB 이상의 신호대잡음비 성능과 3.7 dB 이상의 대조도 성능이 우수함을 확인하였다.

• The Journal of the Acoustical Society of Korea
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• 제29권3E호
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• pp.107-110
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• 2010

In this paper, the rationale and contents of the special issue of the Journal of the Acoustical Society of Korea regarding comprehensive reviews on past, present and future of biomedical ultrasound are described. Brief descriptions of invited articles are given, and efforts by all contributing authors are gratefully acknowledged.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.41-45
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• 2006

The fabrication process of fiber placement system of carbon fiber reinforced plastic (CFRP) requires real time process control and reliable inspection to ensure quality by preventing defects such as delamination and void. Therefore, novel non-contact inspection technique is required during the non-destructive evaluation in a fiber placement system. For the inspection of delamination in CFRP, various methods to receive laser-generated ultrasound were applied by using piezoelectric transducer, air-coupled transducer, wavelet transform and scanning laser ultrasonic technique. Laser-generated ultrasound was received with a conventional piezoelectric sensor in contacting manner. Then signal characteristics due to defects were analyzed to find a factor for detecting defects. Air-coupled transducer was used for reception of laser-generated guided wave using linear slit array in order to generate high frequency guided wave. And line scan technique was used to confirm the capability of on-line application. The high frequency component of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled transducer. The first peak of the frequency spectrum under 100kHz in the delamination region is higher than in the sound region. By using this feature, the line scanned frequency data were acquired in fully non-contact generation and reception of ultrasound. This method was proved as useful technique for detecting delamination in CFRP.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1038-1048
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• 2022

Ultrasound is one of the effective methods for skin treatment. The skin penetration depth of the ultrasound depends on the ultrasonic frequency, that is, when the ultrasonic frequency is high, the depth is shallow. We have developed a transducer which can generate effectively 3 different ultrasonic frequencies removing interference between 3 types of frequencies according to impedance matching technology. The generated powers of transducer are 40.67W at 3.MHz, 17.46W at 11.7 MHz, and 14.79W at 21.5 MHz. The signal interference between the three frequencies is designed so that they do not interfere with each other by separating the signals using the SPDT (Single Pole, Double Throw) switch. The developed hybrid ultrasound transducer can be applied in skin care or skin treatment and beauty therapy.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1022-1037
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• 2022

It is important to develop a transducer that generates uniform output power through frequency control of the HIFU at 4 MHz frequency for the high intensity focused ultrasound (HIFU) skin diseases treatment. In this paper, a 4 MHz frequency band HIFU system for skin disease treatment was designed, manufactured and developed. In HIFU, even for the ultrasonic vibrator in the 4 MHz frequency band, the characteristics of the output power of the HIFU are different depending on the difference in the thickness of the PZT material. Through the development of a system amplifier, the sound output of the HIFU transducer was improved to more than 48 W and uniform output power control was possible. And, it is possible to control the output power even in a frequency band of 4.0 to 4.7 MHz, which is wider than 4.0 MHz, and shows the resonance frequency of the transducer. The maximum output power for each frequency was 49.969 W and the minimum value was 48.018 W. The maximum output power compared to the minimum output power is 49.969 W, which is uniform within 4.1%. It was confirmed that the output power of the HIFU through the amplifier can be uniformly controlled in the 4 MHz frequency band.

• Current Optics and Photonics
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• 제2권1호
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• pp.59-68
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• 2018

Opto-acoustic systems provide structural and functional information regarding biological tissues. Conventional opto-acoustic systems typically employ continuous or pulsed lasers as transmission sources. Compared to lasers, light emitting diodes (LEDs) are cost-effective and relatively portable excitation sources but are non, coherent. Therefore, in this study, a relatively low cost lens - a type of Ramsden eyepiece - was specially designed to theoretically calculate the illumination and achieve a constant brightness across the pupil of an eye. In order to verify the capability of the developed light-emitting diode-acoustic (LEDA) systems, we carried out experiments on bovine and bigeye tuna eyeball samples, which are of similar size to the human eye, using low frequency (10 MHz) and high frequency (25 MHz) ultrasound transducers. High frequency ultrasound transducers are able to provide higher spatial resolution compared to low frequency ultrasound transducers at the expense of penetration depth. Using the 10 MHz and 25 MHz ultrasound transducers, acceptable echo signals (3.82, 3.94, and 5.84 mV at 10 MHz and 282, 1557, 2356 mV at 25 MHz) from depth greater than 3 cm and 6 cm from the anterior surface of the eye were obtained. We thereby confirmed that the LEDA system using a pulsed LED with the designed Ramsden eyepiece lens, used in conjunction with low and high frequency ultrasound transducers, has the potential to be a cost-effective alternative method, while providing adequate acoustic signals from bovine and bigeye tuna ocular areas.

• The Journal of the Acoustical Society of Korea
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• 제29권2E호
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• pp.73-85
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• 2010

In the diagnostic ultrasound (US) transducer technology, the high frequency US(HFUS) transducer over 20 MHz is one of the current issues to be pursued for better resolution with the expense of penetration. HFUS single element transducers and the mechanical scanning systems for imaging are reviewed, and HFUS array transducers are also briefly summarized. HFUS applications such as the human applications in ophthalmology and dermatology and small animal applications for research purposes are reviewed with vascular and blood imaging in this paper.

• 한국음향학회지
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• 제18권5호
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• pp.68-77
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• 1999

본 논문에서는 고강도 집속형 초음파의 주파수 특성(파형)에 따른 초음파 공동 현상을 억 제하는 효과를 살펴보았다. 본 연구에서는 세가지 파형, 즉, 정현파(1 MHz, 5 MPa), 주파수 변조파(10 ㎲ 동안 1 MHz에서 6 MHz까지 선형적으로 증가, 5 MPa), 비대칭 충격파(기 본 주파수 1 MHz, 양압 12 MPa, 음압 -4 MPa)를 고려하였다. 동일한 강도(833 W/㎠)를 가지는 각 초음파에 노출된 초기 반경이 1 ㎛인 물 속에 있는 공기 기포의 반응을Gilmore bubble dynamic model 및 Church's rectified gas diffusion equation을 이용하여 예측하였다. 기포 진동의 크기는, 정현파에 노출된 경우와 비교하여, 주파수 변조된 초음파의 경우 현저히 감소하였고, 비대칭 충격파의 경우 약간 감소함을 볼 수 있었다. 흥미롭게도 주파수 변조파에 대한 기포의 반응은 변조된 초음파의 주파수 성분이 기포의 공진 주파수(3 MHz) 이상에서는 거의 동일하게 유지되는 것으로 나타났다. 이 사실은 주파수 변조를 현재의 1 MHz부터 6 MHz까지에서 1 MHz부터 3 MHz까지로 줄여도 유사한 공동 억제 효과를 얻을 수 있음을 암시한다. 실용적으로, 비교적 좁은 밴드 폭을 가지는 범용 초음파 변환기를 이 용하여 초음파의 공동 현상 억제 효과를 얻기 위한 주파수 변조를 구현할 수 있음을 의미한다. 본 연구의 결과는 초음파의 적절한 주파수 성분 조절로 초음파의 공동 현상을 일정 수준 억제할 수 있음을 시사한다.

• The Journal of Korean Physical Therapy
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• 제18권1호
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• pp.83-94
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• 2006

Purpose: This study conducts quantitative evaluation or structural and functional characteristics or normal skeletal muscle with ultrasound image and surface electromyography, and is to provide basic materials for utilizing ultrasound image analysis in physical therapy diagnosis and assessment of skeletal muscle. Methods: Measurement of three stages was conducted with 88 normal adults between their twenties and seventies, correlations and differences using collected data according to age and gender were compared and correlations among measured items were analyzed and then the following conclusions were obtained. Results: Analysis of ultrasound image of normal skeletal muscle showed that density, median frequency had the closest relations with age. In addition, it was found that there were high correlations between density explaining structural characteristics of skeletal muscle and median frequency explaining functional characteristics. Conclusion: Analysis of ultrasound image makes complex evaluation of structure and function of skeletal muscle possible when it is connected with functional evaluation method using physical measurement surface electromyography as well as quantitative evaluation of structural changes of skeletal muscle and is effective in complementing physical therapy diagnosis centering around functionality evaluation.

• The Journal of Korean Physical Therapy
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• 제13권3호
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• pp.719-726
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• 2001

Transdermal drug delivery offers various advantages over conventional drug delivery systems, such as avoidance gastrointestinal degradation and hepatic first-pass effect. encourages patient compliance. and possible sustained release of drugs. However, transdermal transport of drugs is low permeability of the stratum corneum, the superficial layer of the skin. Many physicochemical and biological factors influencing transdermal transport is described together with the corresponding experimental and clinical results. Phonophoresis is medical treatment with drugs introduced into the skin by ultrasound energy. Enhanced drug penetration is through to result from the biophysical alterations of skin structure by ultrasound waves. The frequency used for phonophoresis is usually from 20 kHz to 15MHz. Phonophoresis can be categorized in to three ranges: low-frequency range(below 1 MHz). therapeutic frequency range(1 to 3MHz), and high-frequency range(above 3 MHz). The depth of penetration of ultrasound into skin is inversely proportional to the frequency. Cavitation may cause mechanical stress. temperature elevation, or enhanced chemical reactivity causing drug transport. One theory is that ultrasound affects the permeation of the stratum corneum lipid structure as the limiting step in permeating through the skin. The range of indications for phonophoresis is wide. Aspecific classification of the range of indications is obtained by classification of pathological conditions. The continuous research is needed for many interesting issucs of phonophoretic transdermal delivory in new future.