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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Biomedical Engineering Research
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Journal DOI :
The Korea Society of Medical and Biological Engineering
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Volume & Issues
Volume 19, Issue 6 - Dec 1998
Volume 19, Issue 5 - Oct 1998
Volume 19, Issue 4 - Aug 1998
Volume 19, Issue 3 - Jun 1998
Volume 19, Issue 2 - Apr 1998
Volume 19, Issue 1 - Feb 1998
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Experimental Considration of Multi-order Sampling for Digital Beamforming
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 105~112
In this paper, several bandwidth sampling methods were compared using experimental result in which contains "multi-order sampling", which was proposed for envelope detections in RF ultrasonic signals. A "Quadrature sampling method" and "Second-order sampling method" were compared with it. The resultant image of second-order sampling method introduces too much error as compared with the result of quadrature sampling. But Multi-order sampling method, specialy 5-th sampling method showed quite good envelope detection property. This means that more economical and quite good performance digital beamforming system can be built by adopting this multi-order sampling method.s multi-order sampling method.
Measurement of Local Motional Characteristics of Cilia in Respiratory Epithelium Using Image Analysis
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 113~118
By their rapid and periodic actions, the cilia of the human respiratory tract play an important role in clearing inhaled noxious particles. Based on the automated image-processing technique, we studied the method analyzing ciliary beat frequency (CBF) objectively and quantitatively. Microscopic ciliary images were transformed into digitized gray ones through an image-grabber, and from these we extracted signals for CBF. By means of a FFT, maximum peak frequencies were detected as CBFs in each partitioned block for the entire digitized field. With these CBFs, we composed distribution maps visually showing the spatial distribution of CBFs. Through distribution maps of CBF, the whole aspects of CBF changes for cells and the difference of CBF of neighboring cells can be easily measured and detected. Histogram statistics calculated from the user-defined polygonal window can show the local dominant frequency presumed to be the CBF of a cell or a crust the region includes.
A Study on Projection Image Restoration by Adaptive Filtering
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 119~128
This paper describes a filtering algorithm which employs apriori information of SPECT lesion detectability potential for the filtering of degraded projection images prior to the backprojection reconstruction. In this algorithm, we determined m minimum detectable lesion sized(MDLSs) by assuming m object contrasts uniformly-chosen in the range of 0.0-1.0, based on a signal/noise model which provides the capability potential of SPECT in terms of physical factors. A best estimate of given projection image is attempted as a weighted combination of the subimages from m optimal filters whose design is focused on maximizing the local S/N ratios for the MDLS-lesions. These subimages show relatively larger resolution recovery effect and relatively smaller noise reduction effect with the decreased MDLS, and the weighting on each subimage was controlled by the difference between the subimage and the maximum-resolution-recovered projection image. The proposed filtering algoritym was tested on SPECT image reconstruction problems, and produced good results. Especially, this algorithm showed the adaptive effect that approximately averages the filter outputs in homogeneous areas and sensitively depends on each filter strength on contrast preserving/enhancing in textured lesion areas of the reconstructed image.
One-Channel Phased-Array Quadrature RF Coil for Spine Magnetic Resonance Imaging
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 129~132
A new one-channel phased-array quadrature RF coil is developed for spine MR imaging. Quadrature RF coils for MRI have been used to improve the signal-to-noise ratio (SNR) by
using two orthogonal RF coils in combination. More recently, the phased-array RF coil has been proposed for more improvement of SNR by using an array of reduced-size RF coil elements. Two schemes proposed for the new phased-array quadrature RF coil are:(1) Proper overlapping of two quadrature RF coils thus removing the mutual inductance and (2) Attaching preamplifiers right after the coil section and combining the signal with proper phase delays. The coil has been implemented for receive-only mode, and tested by phantom and volunteer imaging. The experimental results show the utility of the proposed RF coil.d RF coil.
Quantitative Analysis of Bayesian SPECT Reconstruction : Effects of Using Higher-Order Gibbs Priors
S. J. Lee ;
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 133~142
In Bayesian SPECT reconstruction, the incorporation of elaborate forms of priors can lead to improved quantitative performance in various statistical terms, such as bias and variance. In particular, the use of higher-order smoothing priors, such as the thin-plate prior, is known to exhibit improved bias behavior compared to the conventional smoothing priors such as the membrane prior. However, the bias advantage of the higher-order priors is effective only when the hyperparameters involved in the reconstruction algorithm are properly chosen. In this work, we further investigate the quantitative performance of the two representative smoothing priors-the thin plate and the membrane-by observing the behavior of the associated hyperparameters of the prior distributions. In our experiments we use Monte Carlo noise trials to calculate bias and variance of reconstruction estimates, and compare the performance of ML-EM estimates to that of regularized EM using both membrane and thin-plate priors, and also to that of filtered backprojection, where the membrane and thin plate models become simple apodizing filters of specified form. We finally show that the use of higher-order models yields excellent "robustness" in quantitative performance by demonstrating that the thin plate leads to very low bias error over a large range of hyperparameters, while keeping a reasonable variance. variance.
Volumetric Blood Velocity Measurement on Multigate Pulsed Doppler System based on the Single Channel RF Sampling using the Optimized Sampling Factor
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 143~152
In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at
is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to
/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.
A Study on the Practical Estimation of Nonlinear Hemodynamic Variables for the Moving-Actuator type Total Artificial Heart
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 153~162
It is needless to say that the nonlinear hemodynamic variables estimation is a very important study for the artificial heart. Even though it is important, there have not been satisfactory results which can be applied to the real world situations, In this paper, the problem of hemodynamic variables estimation for the moving-actuator type total artificial heart(MA-TAH) was studed. Multidimensional linear interpolation(MDI)scheme was used for the estimation. Proposed method was verified by in vitro test and showed good performance.
Development and in Vivo Test of an Electrohydraulic Total Artificial Heart at the National Cardiovascular Center in Japan
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 163~170
The ultimate goal of total artificial heart is permanent substitute for a failed heart in a patient without any other therapeutic modality. Until now, infection has been the main problem related to the mechanical circulatory support system. The best way to solve this catastrophic complication and to improve the quality of life of TAH patients in terms of tethering must be implantation of TAH totally. The EH-TAH has been developed in NCVC from 1987 for this purpose. The system consists of an energy converter and pumps, which are designed to be placed in abdomen and pericardial space separately for a good anatomical fit. To evaluate the anatomical fit and hemodynamic performance of the EH-TAH, in vivo test was done. General condition of the animal and hemodynamic status had been stable until the TAH stopped on the 11th pumping day. The estimated cardiac output was about 7.7L/min. The values of mean aortic pressure, left and right atrial pressure were 93
3 and 15
4 mmHg, respectively. The correlation coefficient between left and right atrial pressure was 0.96, which represents the dynamic function of the interatrial shunt in controlling left-right imbalance of cardiac output. During pumping days, the temperature on the surface of actuator had been maintained at 39.7
, less than 1
higher than the rectal temperature. The TAH stopped on the 11th day due to mechanical problems. We concluded that the EH-TAH possessed satisfactory basic performance including anatomic fit and hemodynamic adequacy, although there were several mechanical problems to be solved yet.
Ultrasound Attenuation in the Assessment of Bone Mineral Density and Elastic Modulus of Human Trabecular Bone
Han, S.M. ; Kim, M.S. ;
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 171~176
The objective of this study was to re-evaluate ultrasound attenuation as an indicator of bone properties. Ultrasound attenuation(BUA), were measured in the three orthogonal directions of trabecular bone cubes, Measurements of bone mineral density(BMD) were made using quantitative computed tomography and apparent density by weighing bone specimens and measuring their volume. Ultrasonic modulus was calculated from the standard equation with apparent density and ultrasound velocity. Ultrasound attenuation at a frequency of 0.5 MHz and BUA were correlated with BMD and ultrasonic modulus in the anterior/posterior, medial/lateral, and superior/inferior directions. Analysis of correlations demonstrated that attenuation at 0.5 MHz was superior to BUA in describing both BMD and elastic modulus of trabecular bone. This result may be used to improve current ultrasound diagnostic techniques for assessing bone status.
Effect of Titanium Prosthesis on Computed Tomography Measurements of Bone Mineral Density
Han, S.M. ; Zude Feng ;
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 177~182
This study investigated the effects of a titanium prosthesis, malalignment, field of view, and distal flare of titanium prosthesis on computed tomography( CT) measurements of home mineral density. Eight femora and eight tibiae from fresh male cadavers were used. Fifteen pieces of cancellous bone from the proximal tibiae were milled into rectangular parallelepipeds. Parallelepipeds and femors were scanned with and without titanium prosthesis when centered in the gantry of the CT scanner and malaligned, respectively. Image data were then reconstructed with field of view of 10 and 30 cm. Bone mineral density(BMD) values were obtained from CT images using C-MED software. The effects of titanium prosthesis, malalignmetn, and field of view were investigated. When bone was centered in the gantry of the CT scanner, the mean relative difference of BMD measurements caused by a titanium prosthesis was less than 1% for both cortical and cancellous bone. Field of view had negligible effect on BMD measurements as well. Malalignment and distal flare of prosthesis, however, caused a significant difference in BMD measurements(p<0.0001). The titanium prosthesis did not interfere with malalignment combining the existence of a titnium prosthesis on BMD measurements was significant.
The Effect of the Diameter and Anastomotic Angle on the Compliance and the Stress Distribution of the End-to-side Anastomosis.
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 183~188
Von Mises stress and compliance distribution was evaluated using a finite element analysis on the end-to-side anastomosis of an artery with length of 20-24mm, inner diameter of 4mm, thickness of 0.5mm and a PTFE graft with length of 10mm, inner diameter of 2mm, thickness of 0.2mm when the anastomotic angle was taken from 30
in every 10
and the diameter ratio from 0.1-1 in every 0.1. The inner pressure of 1330 dyne/
was applied inside the 2 conduits. It was found that the compliance whose magnitude is larger on the acute angle anastomotic side than on the abtuse angle side became larger as the anastomotic angle became smaller and the diameter ratio larger and that the equivalent stress on the acute angle anastomotic side was larger than that on the abtuse angle side and became larger as the anastomotic angle and the diameter ratio became larger.
Speed Optimization Design of 3D Medical Image Reconstruction System Based on PC
Bae, Su-Hyeon ; Kim, Seon-Ho ; Yu, Seon-Guk ;
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 189~198
3D medical image reconstruction techniques are useful to figure out complex 3D structures from the set of 2D sections. In the paper, 3D medical image reconstruction system is constructed under PC environment and programmed based on modular programming by using Visual C++ 4.2. The whole procedures are composed of data preparation, gradient estimation, classification, shading, transformation and ray-casting & compositing. Three speed optimization techniques are used for accelerating 3D medical image reconstruction technique. One is to reduce the rays when cast rays to reconstruct 3D medical image, another is to reduce the voxels to be calculated and the other is to apply early ray termination. To implement 3D medical image reconstruction system based on PC, speed optimization techniques are experimented and applied.
Reconstruction of Color-Volume Data for Three-Dimensional Human Anatomic Atlas
Journal of Biomedical Engineering Research, volume 19, issue 2, 1998, Pages 199~210
In this paper, we present a 3D reconstruction method of color volume data for a computerized human atlas. Binary volume rendering which takes the advantages of object-order ray traversal and run-length encoding visualizes 3D organs at an interactive speed in a general PC without the help of specific hardwares. This rendering method improves the rendering speed by simplifying the determination of the pixel value of an intermediate depth image and applying newly developed normal vector calculation method. Moreover, we describe the 3D boundary encoding that reduces the involved data considerably without the penalty of image quality. The interactive speed of the binary rendering and the storage efficiency of 3D boundary encoding will accelerate the development of the PC-based human atlas.