Hak-Yeol Sohn

Sogang University, Sŏul, Seoul, South Korea

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Publications (6)2.03 Total impact

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    ABSTRACT: Coded excitation can improve the signal-to-noise ratio (SNR) in ultrasound tissue harmonic imaging (THI). However, it could suffer from the increased sidelobe artifact caused by incomplete pulse compression due to the spectral overlap between the fundamental and harmonic components of ultrasound signal after nonlinear propagation in tissues. In this paper, three coded tissue harmonic imaging (CTHI) techniques based on bandpass filtering, power modulation and pulse inversion (i.e., CTHI-BF, CTHI-PM, and CTHI-PI) were evaluated by measuring the peak range sidelobe level (PRSL) with varying frequency bandwidths. From simulation and in vitro studies, the CTHI-PI outperforms the CTHI-BF and CTHI-PM methods in terms of the PRSL, e.g., -43.5dB vs. -24.8dB and -23.0dB, respectively.
    Ultrasonics 05/2010; 50(6):613-9. · 2.03 Impact Factor
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    ABSTRACT: In this paper, a PC-based fully-programmable medical ultrasound imaging system is presented where a high performance graphics processing unit (GPU) is utilized to perform entire ultrasound processing. In the proposed architecture, ultrasound signal and image processing algorithms were divided into four modules and efficiently implemented on the NVIDA's Computer Unified Device Architecture (CUDA) platform (GeForce GTX285, NVIDA, Santa Clara, CA, USA). To evaluate the real-time performance of the proposed architecture, 64-channel, 128-scanline pre-beamformed radio-frequency (RF) data were captured with a commercial ultrasound machine (G40, Siemens Healthcare, Mountain View, CA, USA). The execution time was measured by examining the time stamp produced by a CIDA timer. For generating a 800×600 ultrasound B-mode image, it takes 18.32 ms for single-beam based ultrasound processing with the acquisition time of 19.7 ms. These results indicate that the GPU-based fully-programmable system architecture can support real-time ultrasound signal and image processing.
    Ultrasonics Symposium (IUS), 2010 IEEE; 01/2010
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    ABSTRACT: Due to improved portability and patient acceptability, a recently-developed hand-held ultrasound machine has been tested in various emerging clinical applications, e.g., ambulatory healthcare. For miniaturization, in a hand-held ultrasound machine, application specific integrated circuits (ASICs) have been widely used. However, since the clinical utility of a hand-held ultrasound machine is continuously evolving, it would be appropriate to have improved functional flexibility, especially in mid and back-end processing. In this paper, we present a software-based hand-held ultrasound system where a single digital signal processor (DSP) is utilized to support color Doppler imaging in real time.
    01/2009;
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    ABSTRACT: Software implementation of a medical ultrasound imaging system using commercial DSPs (Digital Signal Processor) has advantages over FPGA- or ASIC-based system in development cost and time. The authors have developed a full software-based ultrasound scanner consisting of a typical analog front-end block and a DSP system. In this work, we present efficient methods for software realization of an echo processor to perform all the ultrasound signal processing functions following the receive beamforming. For implementation with a single TMS320C6416 DSP, the most computationally demanding functions such as dynamic filtering, quadrature demodulation, decimation, magnitude calculation, and log compression are implemented using modified algorithms and structures optimized to best match the DSP architecture for fast computation. The DSC (digital scan converter) is realized with an LUT for generating memory addresses and interpolation coefficients for each display point. The LUT table is stored in a single external SDRAM so that the internal DSP memory can be fully utilized by the DSP core to maximize the processing speed. The possible memory stall that can be caused by the external memory access is removed by properly employing the enhanced direct memory access channels. Experimental results show that the proposed implementation can support up to 4 kHz PRF (pulse repetition frequency) when the input data rate is 40 MHz.
    Proc SPIE 03/2008;
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    ABSTRACT: We present a software-based ultrasound beamformer to build a fully software-based ultrasound scanner which performs real-time delay-sum beamforming using fractional delay filters using ADSP-TS201 DPSs (Analog Device Inc.). Receive dynamic focusing generally requires fast transfer of a large amount of data for inter-channel summation and for delay control. The DSPs are connected in pipelined network architecture without a glue logic using the DPS's parallel ports, which allows the connection of unlimited DSPs. Each DSP has a small input FIFO which takes as input the data samples from each ADC and can take delay values either from a memory (to use pre-calculated delay values) or an external FPGA (for real-time delay calculation) via its LVDS channel. Two fractional delay beamformer (FDBF) schemes are implemented on the DSP system. Each scheme is programmed in assembly code optimized for speed; instruction level parallelism is secured to maximally utilize the four execution units of each DSP, pipeline scheduling is employed to avoid pipeline stall, and instruction reordering techniques are used to prevent memory contention while preserving the program semantics. It is found that dynamic focusing is carried out faster when delay filtering is performed prior to interchannel summation, whereas hardware implementation of the FDBF favors performing delay filtering after interchannel summation. The frame rate achievable with 16 DSPs is up to 28Hz when the sampling rate is 40MHz, the view depth is 20cm, the number of scanline is 128, and the number of channel is 64.
    Proc SPIE 01/2008;
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    ABSTRACT: A software-based ultrasound system using commercial DSP processors has the advantages of easy reconfiguration and reuse of previous designs, offering reduced development cost and time. In general, however, software implementation of major signal processing blocks of ultrasound imaging systems requires a much higher computational power than that of the most advanced DSP processors currently available. Therefore, it is very important to find a method for optimally mapping the existing algorithms to a target DSP system. In this paper, we will show the results of software implementation of the echo processor block of a conventional ultrasound imaging system and propose a new echo processing algorithm optimized for implementation with the TMS320C6202 processor.
    Ultrasonics Symposium, 2004 IEEE; 09/2004