• IEIE Transactions on Smart Processing and Computing
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• 제3권3호
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• pp.153-159
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• 2014

As the number of treatments in the therapeutic ultrasound field targeted at fat tissue increase, the performance of the equipment should be evaluated for safety using a fat phantom. In this study, a fat phantom was fabricated using olive oil and a tissue-mimicking material (TMM) phantom. To evaluate the acoustic properties of the TMM phantom according to the changes in the olive oil, the composition ratio of a liquid mixture of olive oil with a surfactant was adjusted from 5-20% in 5% steps. The acoustic properties of the phantom were evaluated using the sound velocity, attenuation coefficient, density, and acoustic impedance. The experimental results showed that the sound velocity decreased with increasing amount of olive oil but the other acoustic properties did not change. In addition, the phantom using an olive-oil mixture with a 15% composition ratio was most similar to the acoustic characteristics of fat tissue with a sound velocity of 1477.35 m/s, an attenuation coefficient of 0.514 dB/MHz-cm, a density of $1.07g/cm^3$, and an acoustic impedance of 1.575 MRayl. These experimental results are expected contribute to the accuracy of the results using a TMM phantom and will be useful for the therapeutic ultrasound field targeted at subcutaneous fat tissue.

• 대한의용생체공학회:의공학회지
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• 제14권3호
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• pp.273-282
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• 1993

This study is concerned with the temperature dependence characteristics of ultrasound parameters in biological tissues, which are basic on the noninvasive deep body temperature estimation. Used parameters are ultrasonic attenuation coefficient and sound velocity In order to accomplishment our purpose, several signal processing methods were used. Attenua4iorl coefficient was estimated by spectral difference method and sound velocity was estimated by P-P method. And we also examined these methods through a series of IN VITRO experi mentis that used tissue-mimicking phantom samples and biological tissue samples. In order to imitate the biological soft tissue two kinds of phantom samples are used, one is agar phantom sample which is composed of agar, graphite, N-propyl alcohol and distilled water, and the other is fat phantom sample which is composed of pure animal fat. And the ultrasound transmission mode and reflection mode experiments are performed on the pig's spleen, kidney and fat. As a result, it is found that the temperature characteristics are uniform in case of phan- tom samples but not in biological tissues because of complicate wave propagation within them. Consequently, the possibility of temperature measurement using ultrasound on biological tissue is confirmed and its results may contribute to the establishment of reference values of internal temperature measurement of biological tissues.

• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.53-60
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• 2018

The purpose of this study was investigating the effect of 3D printing technology that changes the speed of sound (SOS) and the broadband ultrasound attenuation (BUA) by controlling the density of the media phantom. We used 3D printers which called additive manufacturing (AM) by using material with polylactic acid (PLA). The inside of the medium phantom was filled crossly with 100%, 90%, 80%, 70%, 60%, and 50% of the material. The ultrasonic instrument measured the SOS and the BUA using a 0.55 MHz ultrasound output in opposing mode with a pair of transducers. As a result, the density of the medium phantoms with the SOS showed very high correlation (r = 0.944), but the SOS showed very low correlation (r = 0.500). It is expecting that the manufacturing and measurement method of the medium phantom using 3D printing technology will be used as basic data for ultrasonic bone mineral density.

• 대한의용생체공학회:의공학회지
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• 제2권2호
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• pp.141-144
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• 1981

This paper descirbes about effects of refraction of ultrasonic beam on B-mode tomogram. Both compution based on Snell's law and the experiments performed using B-mode scanner and schlieren optical method are discussed on a circular phantom immersed in water. In these results, if the discrepancy of sound velocity is more than 0. 6%, the distortion of the B-mode image becomes conspicuous and a target beyound the phantom may disappear or displayed as two targets depending on the velocity of the phantom.

• 대한전자공학회논문지SP
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• 제47권5호
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• pp.9-17
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• 2010

이 연구는 다양한 라우드 스피커 구성인 2-horizontal, 2-vertical, triplet 라우드 스피커 구성에서 UHD TV를 위한 가상 음상의 인지 위치 결과를 제시한다. 비등간격 라우드 스피커 구성에서 가상 음상을 생성하기 위해 잘 알려진 vector-based amplitude panning 알고리즘을 수정하여 적용하였다. 실제 상황에서의 위치 인지 성능을 평가하기 위해, 청취 평가는 일반적인 청취환경에서 TV의 on-axis와 off-axis에서 수행되었다. 인지 각도의 모호함에 의한 오차를 줄이기 위해 각도 조정 테스트 방법이 옥타브 밴드 신호의 각도 평가에 이용되었다. 피실험자는 실제 음원과 가상 조정된 음원의 각도가 일치할 때까지 조정각도를 변화하였다. 공간적 블러링은 각 밴드에서 인지된 조정 각도의 차이를 비교하여 측정되었다. 청취 평가 결과는 triplet panning 방법이 vertical panning 방법보다 on-axis와 off-axis 둘 다, 인지 위치와 공간적 블러링 관점에서 더 나은 성능을 보여주었다.

• 대한의용생체공학회:의공학회지
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• 제30권3호
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• pp.233-240
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• 2009

Using a spatial compound imaging technique in a medical ultrasound imaging system, the average speed of sound in a medium of interest is measured, and imaging of its distribution is implemented. When the brightness reaches the highest level in an ultrasonic image obtained as the speed of sound used in focusing is varied, it turns out that the focusing has been accomplished satisfactorily and that the speed of sound which has been adopted becomes the sought-after average speed of sound. Because spatial compound imaging provides many different views of the same object, the adverse effect of erroneous speed-of-sound estimation tends to be more severe in compound imaging than in plain B-mode imaging. Thus, in compound imaging, the average speed of sound even in the case of speckled images can be accurately estimated by observing the brightness change due to different speeds of sound employed. Using this new method that offers spatial diversity, we can construct an image of the speed of sound distribution in a phantom embedded with a 10-mm diameter plastic cylinder whose speed of sound is different from that of the background. The speed of sound in the cylinder is found to be different from that of the surrounding medium.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.447-450
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• 2005

Multi-channel artificial reverberation algorithm to control perceived direction and distance is described in this paper. In conventional algorithms using IIR filters, reverberation time is the only parameter to be controlled. Moreover, since the convolution-based conventional algorithms apply only same impulse responses, but not considering sound localization, it was not realistic enough. The new algorithm proposed in this paper utilizes early reflections segmented according to the azimuth from which direct sound comes and controls perceived direction by panning the direct sound, and controls perceived distance by adjusting Energy Decay Curve (EDC) of reverberation and gain of the direct sound. In addition, the algorithm enhances Listener Envelopment(LEV) to make late reverberation incoherent among channels.

• 한국방사선학회논문지
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• 제9권7호
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• pp.509-513
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• 2015

본 연구에서는 재사용이 가능한 NIPAM 팬텀의 열적 민감도를 측정하여 조직유사 팬텀의 열변성 특성을 평가하였으며, 초음파 재사용 횟수와 재사용 기간에 따른 음향학적 특성 및 열 변성 형태 특성을 관찰하였다. 측정 결과조사 횟수가 증가함에 따라 NIPAM 팬텀의 음속은 100 m/s 정도 감소하고 감쇠계수는 조금 증가하는 경향을 보였다. 반면에 재사용 기간에 따른 변화는 관찰되지 않았다. 초음파 조사에 따른 열변성의 형태 및 크기는 유효할 정도의 변화는 확인되지 않았다. 본 연구를 통하여 NIPAM 팬텀이 반복 조사를 통한 초음파 치료 평가에도 적합한 것으로 판단되었다.

• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.302-306
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• 2008

Plastic hardener and softener based ultrasound phantoms were made in various constitutions and their acoustic properties were measured. Speed of sound is approximately $1.4\;mm/{\mu}sec$ in all the phantoms, which is about 7% less than that of in soft tissue. Attenuation coefficient is strongly dependent on the ratio between hardener and softener. In order to achieve the tissue level attenuation (0.5 dB/cm/MHz), 60% of hardener or less is required. The synthesized phantoms can be preserved for more than 6 months without structural degradation.

• 대한의용생체공학회:의공학회지
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• 제19권3호
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• pp.321-325
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• 1998

일반적으로 현재의 초음파 의료영상시스템에서 지연시간의 계산에 사용하는 음속도는 인체의연조직에서의 평균속도인 1540m/s 의 값을 이용한다. 그러나 사람마다 혹은 매질의 특성에 따라 초음파의 속도가 크게 차이가 나서 고정된 속도를 이용한 집속 지연시간 계산에는 오차가 발생한다. 이는 해상도의 저하를 가져올 뿐만 아니라, 매질의 기하학적인 크기나 거리정보가 필요한, 심장이나 신장의 용적을 계산과 같은 경우에는 큰 오차를 가져온다. 따라서 매질의 속도를 정확히 구하는 것이 해상도 향상의 중요한 관건의 하나임을 알 수가 있다. 본 논문에서는 이를 위해 매질내의 관심영역에서의 밝기를 최대화시켜주는 접속지연시간 프로파일을 구해 매질 내에서의 옴파의 속도를 측정하여 실제 초음파 팬텀에 적응하여 좋은 결과를 얻을 수 있었다.