Kang-sik Kim

2K-1 A Hand-Held Ultrasound Imaging System for Point-of-Care Applications

As demands for point-of-care (POC) services have increased in and out of hospitals, more and more attention has been drawn to developing portable medical diagnosis systems with imaging capability. We have recently developed a prototype of PDA-type hand-held device which is designed to have the functions and portability required for POC applications by combining an ultra small ultrasound scanner and a full custom PDA using Linux as its OS. The prototype now only supports a phased array but was designed to support various probe types. It is powered by a Lithium polymer battery to achieve the maximum scanning time of about one and half hours. We will present the images obtained with the system and application results of other features. The images will be compared to images obtained from a commercial product using 32 channels in both transmit and receive

Column-based micro-beamformer for improved 2D beamforming using a matrix array transducer

In a 3-D medical ultrasound imaging system, a matrix array probe with 2-D positioning of the elements allows high resolution of ultrasound images due to its capability of two-dimensional dynamic focusing. However, the hundreds (up to thousands) of elements in the matrix array make the fabrication of the transducers and cables challenging. In this paper, to achieve high quality of 3-D ultrasound images with low hardware complexity, we introduce a column-based micro-beamformer (CMB) in which a column in the matrix array is considered as a sub-array and then elevational and lateral beamformings are sequentially conducted in the analog and digital stages, respectively. For the performance evaluation of the proposed beamformer, the beam pattern simulations are conducted and point-spread-functions are obtained. In addition, root-mean-square-errors (RMSEs) in round-trip time delays were measured over the depths. Compared to a conventional micro-beamformer, the CMB produced more tightly focused beam patterns and showed almost equivalent performance to that of fully sampled array. In the near field, the mean RMSEs of the proposed and conventional beamformers were 274 ns and 18.1 ns (improved 93.4% of delay accuracy), respectively.

Barker-sequence-modulated golay coded excitation technique for ultrasound imaging

In medical ultrasound imaging, Signal-to-noise ratio (SNR) is an important factor for imaging quality. Coded excitation methods have been widely used such as Golay codes and Barker codes to achieve higher SNR without degradation of axial resolution. The improvement of SNR is determined by code length. However, because conventional Golay codes and Barker codes are limited to specific known sequences, it is only allowed to select one of the known sequences for ultrasound imaging. In this paper, we propose a new Barker-sequence-modulated Golay (BMG) coded excitation technique for ultrasound imaging. The sequences of proposed BMG technique are generated by modulating Golay code with Barker code, which can lead to additional improvement in signal intensity and flexibility for code length compared with conventional Golay code. From the phantom study, the intensity of BMG technique is 28.9dB higher than 1C-pulse. We demonstrate that BMG technique has a higher contrast than the others. To perform a quantitative evaluation, contrast-to-noise ratio (CNR) values were computed from the cyst images. The 6C-BMG method are improved in terms of the CNR value of 4.19.

Context modeling based lossless compression of radio-frequency data for software-based ultrasound beamforming

Abstract A new lossless compression method using context modeling for ultrasound radio-frequency (RF) data is presented. In the proposed compression method, the combination of context modeling and entropy coding is used for effectively lowering the data transfer rates for modern software-based medical ultrasound imaging systems. From the phantom and in vivo data experiments, the proposed lossless compression method provides the average compression ratio of 0.45 compared to the Burg and JPEG-LS methods (0.52 and 0.55, respectively). This result indicates that the proposed compression method is capable of transferring 64-channel 40-MHz ultrasound RF data with a 16-lane PCI-Express 2.0 bus for software beamforming in real time.

A feasibility study for arbitrary waveform generation using on-off pulses and modified PWM waveforms in the front-end circuit integrated with transducers

It is a challenge to implement the arbitrary waveform generator (AWG) with high performance devices such as digital to analog converters (DACs) and linear power amplifiers (LPAs) in the front-end circuits which should be integrated with array transducers due to its issue in size and power consumption. Over the past several decades, a number of approaches using only on-off pulses have been proposed to transmit an arbitrary waveform. A pulse width modulation (PWM) technique is one of the approaches to simplify the implementation of AWG into the transmitter. In this paper, a preliminary study for an arbitrary waveform generation, which is essential for the coded excitation imaging, using only on-off pulses is introduced. In this study, we propose a proof of concept of an adapted PWM waveform using uni-polar and bi-polar pulses. In theoretical and simulation studies, transmission signals using uni-polar and bi-polar pulses, and the PWM waveforms are analyzed and investigated in terms of a frequency characteristic and a transmission power efficiency (TPE) that indicates the pulse-shaping performance of the generated waveform by defining the ratio of its output and input power through a given transducer. The results demonstrate the possibility to perform the arbitrary waveform generation with the transmitter architecture using only on-off pulses and the PWM waveforms without any DAC and LPA.