• Journal of Biomedical Engineering Research
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• v.26 no.1
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• pp.31-35
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• 2005

A novel synthetic aperture method for real-time three-way dynamic focusing is proposed, which provides lateral beam patterns represented as the product of Fourier transforms of transmit subaperture, receive subaperture, and a synthetic window function. In the proposed method, all array elements are fired individually and for each firing echo signals are recorded from all elements of a receive subaperture moving along an array with the transmit element. The three-way dynamic focusing is then achieved by employing a synthetic aperture algorithm for two-way dynamic focusing and a synthetic focusing method for transmit dynamic focusing. Both theoretical analysis and computer simulation results show that the proposed method produces ultrasound beams with improved lateral resolution at all depths compared to the conventional phased array imaging and synthetic aperture focusing methods.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.559-562
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• 1997

In this paper, we propose the method that reduce the grating lobe in the ultrasound synthetic focusing images. synthetic focusing images have more larger and closer grating lobe than conventional phased array images and more lower signal to noise ratio. so, we represent the method that reduce the grating lobe by using multi element receive focusing. experimental results are showed that the proposed multi element receiving method reduce the grating lobe and increase the signal to noise ratio.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.798-802
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• 2007

The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.803-810
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• 2007

Although synthetic aperture focusing techniques can improve the spatial resolution of ultrasound imaging, they have not been employed in a commercial product because they require a real-time N-channel beamformer with a tremendously increased hardware complexity for simultaneous beamforming along M multiple lines. In this paper, a hardware-efficient beamformer architecture for synthetic aperture focusing is presented. In contrast to the straightforward design using NM delay calculators, the proposed method utilizes only M delay calculators by sharing the same values among the focusing delays which should be calculated at the same time between the N channels for all imaging points along the M scan lines. In general, synthetic aperture beamforming requires M 2-port memories. In the proposed beamformer, the input data for each channel is first upsampled with a 4-fold interpolator and each polyphase component of the interpolator output is stored into a 2-port memory separately, requiring 4M 2-port memories for each channel. By properly limiting the area formed with the synthetic aperture focusing, the input memory buffer can be implemented with only 4 2-port memories and one short multi-port memory.

• Journal of Biomedical Engineering Research
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• v.22 no.4
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• pp.321-330
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• 2001

In this paper, we propose a new synthetic aperture focusing scheme for improving the lateral resolution which is one of the most important factors determining the quality of ultrasound imaging. The proposed scheme enables full round-trip dynamic focusing with approximately limited property. This properties are obtained through transmitting plane waves of which the traveling angle varies with the receive subaperture position, as opposed to stepping the spherical wave source across an array in other synthetic aperture focusing schemes, and employing dynamic focusing in receive. In this paper, the properties of the proposed scheme is analyzed in which a hypothetical infinite line source is used to transmit the plane waves and verified through computer simulation results. Also, we show that the proposed scheme is realizable with an array transducer with a finite aperture size. In summary, it is shown through comparison between the field contours of the proposed scheme and the conventional scheme that the proposed scheme can improve greatly the lateral resolution of ultrasound imaging.

• Journal of Biomedical Engineering Research
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• v.23 no.3
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• pp.243-251
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• 2002

Synthetic zinc wave employs Pulsed plane wave as transmit beam with linear time delay curve. The received echoes in different transmit directions at different transmit times are superposed at imaging Points with Proper time delay compensation using synthetic focusing scheme. This scheme. which uses full aperture in transmit, obtains a high SNR image, and also features high lateral resolution by using two way dynamic focusing at all imaging depths. In this Paper, we consider the Problems in realization of synthetic zinc wave. Also. we have applied the scheme to obtain phantom and in-vivo images using a linear array of 5 MHz. In phantom test. experimental images show high resolution over a more extended imaging depth than conventional fixed Point transmit and receive dynamic focusing schemes In-vivo images show that the resolution could not overcome conventional focusing systems because of motion blurring and(or) aberration of tissue. but the frame rate tan be increased by a factor of more than 5 compared to conventional focusing schemes. with competitive resolution at all imaging depths .

• 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.

• The Journal of the Acoustical Society of Korea
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• v.33 no.3
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• pp.200-209
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• 2014

In this paper, we present a general model for synthetic transmit focusing method using plane waves (STF-PW) of which the properties are investigated through mathematical analysis and compared with those of the conventional focusing method. The analysis results show that STF-PW produces non-diffracting beams in the sense that their main lobe widths do not change with depth. We also present a method for synthesis of plane waves to obtain a desired main lobe width while preventing grating lobe generation and a method for broadening the region over which the non-diffracting property is maintained. The proposed model and analysis results were validated through computer simulations.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.215-216
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• 1998

The ultrasonic imaging systems using synthetic aperture beamforming has been formed in the way that one element transmits and then receives a pulse. Because the amplitude of a pulse from one element is too small to propagate a long distance, the SNR(Signal to Noise Ratio)is low. This paper proposes the method to make a circular wave almost equal to one generated by one element using several elements. The amplitude of the wave made up of several elements is much larger than that of one element. And we can improve the SNR.

• The Journal of the Acoustical Society of Korea
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• v.17 no.6
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• pp.14-22
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• 1998

기존의 널리 사용되는 초음파 영상진단기에서는 수신집속은 모든 점에 대해 행하는 것이 가능하지만 송신접속은 미리 정해진 수 개의 점에 대해서만 행하는 한계가 있다. 본 논문에서는 영상화할 대상이 정지해 있거나 매우 느리게 움직이는 경우에 한하여, 송신음장 의 집속은 합성집속방법(synthetic focusing)을 사용하고, 수신집속은 동적 집속(dynamic receive focusing)을 이용함으로써 모든 영상점에서 송수신 집속하여 측방향 해상도를 향상 시키는 방법을 제안하였다. 컴퓨터 시뮬레이션 결과 초점깊이에서와 같은 해상도를 유지하 는 음장거리(fields of depth)가 기존의 방법에 비하여 월등히 우수하였으며, 3.5MHz의 선형 배열변환기를 이용하여 펜텀 영상에 대한 실험 결과도 모든 영상 깊이에서 측방향 해상도가 기존의 B-mode의 영상보다 우수하였다.