• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.187-190
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• 2001

A new ultrasound imaging technique based on simultaneous multiple transmit focusing using orthogonal modified Golay codes is presented. modified Golay codes are used to increase signal-to-noise-ratio(SNR) and maximize the transmit power efficiency(TPE). Conventional Golay codes consist of a pair of complementary codes with same length and can be compressed into a delta-like signal due to their complementary property. In the present work, two modified Golay codes focused at different depths are transmitted at the same time, which are mutually orthogonal. On receive, these orthogonal modified Golay codes are separately compressed into two short pulses and individually focused. These two focused beam are combined to form a frame of image with improved lateral resolution. Computer simulations are performed to verity the proposed method improves the lateral resolution of image compared with the conventional echo system.

• Progress in Medical Physics
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• v.27 no.1
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• pp.37-45
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• 2016

In proton therapy, in vivo proton beam range verification is very important to deliver conformal dose to the target volume and minimize unnecessary dose to normal tissue. For this purpose, a multi-slit prompt-gamma camera module made of 24 scintillation detectors and 24-channel signal processing system is under development. In the present study, we have developed and tested a dual-mode signal processing system, which can operate in the energy calibration mode and the fast data acquisition mode, to process the signals from the 24 scintillation detectors. As a result of performance test, using the energy calibration mode, we were able to perform energy calibration for the 24 scintillation detectors at the same time and determine the discrimination levels for the detector channels. Further, using the fast data acquisition mode, we were able to measure a prompt-gamma distribution induced by a 45 MeV proton beam. The measured prompt gamma distribution was found similar to the proton dose distribution at the distal fall-off region, and the estimated beam range was $17.13{\pm}0.76mm$, which is close to the proton beam range of 16.15 mm measured by an EBT film.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.21-30
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• 2018

A passive time-reversal technique can improve error performance of the underwater communication system by reducing influence of inter-symbol interferences, which is caused by a multipath channel response. The passive time-reversal communication system equipped with numerous receivers generally can obtain superior error performance since larger diversity gain can be obtained as the number of available received signal increased. In this paper, we analyze the optimal number and combination of receivers that can approximately achieve the best error performance when using the limited number of receivers. For this analysis, we use communication data collected during SAVEX15 (Shallow-water Acoustic Variability Experiment 2015) carried out in the south-western part of Jeju Island from May 14 to May 28, 2015. Analysis results show that there are depths of energy concentration due to the channel characteristics in which the underwater sound channel are present, and the passive time-reversal technique using the limited number of the receivers can derive near-optimal communication performance if the receivers for time-reversal processing are located at the depths where energy is concentrated.