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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 23, Issue 6 - Dec 2002
Volume 23, Issue 5 - Nov 2002
Volume 23, Issue 4 - Aug 2002
Volume 23, Issue 3 - Jun 2002
Volume 23, Issue 2 - Apr 2002
Volume 23, Issue 1 - Feb 2002
Volume 24, Issue 6 - 00 2002
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Efficient Implementation of Synthetic Aperture Imaging with Virtual Source Element in B-mode Ultrasound System Based on Sparse Array
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 419~430
In this paper. we propose an efficient method for implementing hi-directional pixel-based focusing(BiPBF) based on a sparse array imaging technique. The proposed method can improve spatial resolution and frame rate of ultrasound imaging with reduced hardware complexity by synthesizing transmit apertures with a small number of sparsely distributed subapertures. As the distance between adjacent subapertures increases, however. the image resolution tends to decrease due to the elevation of grating lobes. Such grating lobes can be eliminated in conventional synthetic aperture imaging techniques. On the contrary, grating lobes arisen from employing sparse synthetic transmit apertures can not be eliminated, which has been shown analytically in this paper. We also propose the condition and method for suppressing the grating lobes below -40dB, which is generally required in practical imaging. by placing the transmit focal depth at a near depth and properly selecting the subaperture distance in Proportion to receive aperture size. The results of both the Phantom and in vivo experiments show that the proposed method implements two-wav dynamic focusing using a smaller number of subapertures, resulting in reduced system complexity and increased frame rate.
Development of Integration Protocol of Nuclear Medicine Image with A Commercial PACS
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 431~436
The purpose of this study was to develop an integration protocol of Nuclear Medicine image with a commercial PACS. Two independent local networks. PACS network and Nuclear Medicine network, were connected using a Nuclear Medicine DICOM gateway A DICOM converter Program was developed to convert Interfile 3.3. which is used in nuclear medicine scanners in our hospital. to DICOM 3.0. The Program converts Interfile format images to those of DICOM format and also transfers converted DICOM files to PACS DICOM gateway. PACS DICOM gateway compares and matches the DICOM image information with patient information in Hospital Information System and then saves to PACS database. The transfer protocol was designed to be able to transfer Interfile. screen dumped file. and also scanned file. We successfully transferred Nuclear Medicine images to PACS. Images transferred by Interfile transfer protocol could be further processed using various tools in PACS. The graphs, numerical information and comments could be conveniently transferred by screen dumped file. The image in a hard copy can be transferred after scanning using an ordinary scanner. The developed protocol can easily transfer Nuclear Medicine images to PACS in various forms with low cost.
Influence of Cardiac Contraction and its Phase Angle with Coronary Blood flow on Atherosclerosis of Coronary Artery
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 437~449
Coronary arteries are subjected to very different flow conditions compared to other arteries in systemic blood circulation. We Performed a computational fluid dynamic research to investigate influence of such flow conditions in coronary arteries on development and progress of atherosclerosis in the same. The results showed big differences in the flow field of the coronary artery compared to the abdominal and femoral arteries. The coronary artery showed higher wall shear stresses due to the small vessel diameter. On the other hand, it showed only one vortex distal to the stenosis throat during a whole pulse cycle. However. several vortices were observed in the abdominal and femoral arteries in both proximal and distal sides of the stenosis throat The wall shear stresses and extent of recirculation area were increased with impedance phase angle increasing toward more negative values. Therefore, cardiac contraction and the negative impedance phase angle as large as -110。 may induce a flow field that accelerates atherosclerosis.
A Micro Finite Element Analysis on Effects of Altering Monomer-to-Powder ]Ratio of Bone Cement During Vertebroplasty
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 451~458
Osteoporosis is a systemic skeletal disease caused by low bone mass and the decrease of bone density in the microstructure of trabecular bone. Drug therapy(PTH Parathyroid hormone) may increase the trabecular thickness and thus bone strength. Vertebroplasty is a minimally invasive surgery foy the treatment of osteoporotic vertebral compression fracture. This Procedure includes Puncturing vertebrae and filling with Polymethylmethacrylate(PMMA). Although altering recommended monomer-to-Powder ratio affects material properties of bone cement, clinicians commonly alter the mixture ratio to decrease viscosity and increase the working time. The Purposes of this study were to analyze the effect of 4he monomer-to-powder ratio on the mechanical characteristics of trabecular. In this paper, the finite element model of human vertebral trabecualr bone was developed by modified Voronoi diagram, to analyze the relative effect of hormone therapy and vertebroplasty at the treatment of osteoporotic vertebrae. Trabeuclar bone models for vertebroplasty with varied monomer-to-Powder ratio(0.40∼1.07 ㎖/g) were analyzed. Effective modulus and strength of bone cement-treated models were approximately 60% of those of intact models and these are almost twice the values of hormone-treated models. The bone cement models with the ratio of 0.53㎖/g have the maximum modulus and strength. For the ratio of 1.07㎖/g, the modulus and strength were minimum(42% and 49% respectively) but these were greater than those for drug therapy. This study shows that bone cement treatment is more effective than drug therapy. It is found that in vertebroplasty, using a monomer-to-powder ratio different from that recommended by manufacturer nay significantly not only reduce the cement's material Properties but also deteriorate the mechanical characteristics of osteoporotic vertebrae.
Communication Aid System For Dementia Patients
Sung-Ill Kim ; Byoung-Chul Kim ;
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 459~465
The goat of the present research is to improve the quality of life of both the elderly patients with dementia and their caregivers. For this Purpose, we developed a communication aid system that is consisted of three modules such as speech recognition engine, graphical agent. and database classified by a nursing schedule. The system was evaluated in an actual environment of nursing facility by introducing the system to an older mail patient with dementia. The comparison study was then carried out with and without system, respectively. The occupational therapists then evaluated subject"s reaction to the system by photographing his behaviors. The evaluation results revealed that the proposed system was more responsive in catering to needs of subject than professional caregivers. Moreover we could see that the frequency of causing the utterances of subject increased by introducing the system.
The Effects of Warm and Cold Stimulations on the Temperature Distribution in the Prostate
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 467~475
Hyperthermia using transrectal thermal probes has been used for a noninvasive treatment of prostate diseases. However it is known that heating the rectal wall at excessively high temperature can lead to destruction of the rectal mucous membrane. and it is difficult to maintain an optimum temperature over the entire prostate. Thus, a more accurate understanding of the heat transfer mechanism between prostate and hyperthermia system is needed Numerical analysis was performed to investigate how the cold/warm stimulations on the prostate surface affect the temperature distribution in the prostate model. The general purpose software "FLUENT" was used for obtaining a finite volume solution to the unsteady conduction equation and to calculate the time-varying temperature in the prostate. Effects of the warm/cold stimulations and the stimulation frequency on the temperature distribution were simulated. and we visualized how hyperthermia affected the inside of the prostate. It was found that the effect of hyperthermia by using a typical heating method is limited due to the low thermal conductivity of the prostate. Consecutive repetitions of warm and cold stimulations were considered to provide the thermal irritations inside a prostate. The effects of temperature difference and duration of warm/cold stimulations were investigated, and basic data for the optimum period and effective patterns of stimulations were obtained. A simplified bioheat equation was also solved to describe effects of the blood flow on the blood-tissue heat transfer. The effect of blood flow was not dominant compared to that of warm/cold stimulations. These results might be used as data for design of prostate treating probe, prostatic therapy and thermal stimulation effects on the prostate.
A Pacemaker AutoSense Algorithm with Dual Thresholds
Kim, Jung-Kuk ; Huh, Woong ;
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 477~484
A pacemaker autosense algorithm with dual thresholds. one for noise or tachyarrhythmia detection (noise threshold, NT) and the other for intrinsic beat detection (sensing threshold. ST), was developed to improve the sensing performance in single pass VDD electrograms. unipolar electrograms, or atrial fibrillation detection. When a deflection in an electrogram exceeds the NT (defined as 50% of 57), the autosense algorithm with dual thresholds checks if the deflection also exceeds the ST. If it does, the autosense algorithm calculates the signal to noise ratio (SNR) of the deflection to the highest deflection detected by NT but lower than ST during the last cardiac cycle. If the SNR 2, the autosense algorithm declares an intrinsic beat detection and calculates the next ST based on the three most recent intrinsic peaks. If the SNR
2, the autosense algorithm checks the number of deflections detected by NT during the last cardiac cycle in order to determine if it is a noise detection or tachyarrhythmia detection. Usually the autosense algorithm tries to set the 57 at 37.5% of the average of the three intrinsic beats, although it changes the percentage according to event classifications. The autosense algorithm was tested through computer simulation of atrial electrograms from 5 patients obtained during EP study, to simulate a worst sensing situation. The result showed that the ST levels for autosense algorithm tracked the electrogram amplitudes properly, providing more noise immunity whenever necessary. Also, the autosense algorithm with dual thresholds achieved sensing performance as good as the conventional fixed sensitivity method that was optimized retrospectively.
Respiratory Effort Monitoring Using Pulse Transit Time in Human
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 485~489
In this study. respiratory efforts were monitored by the change of pulse transit time (PTT) which is related with the arterial pressure PTT is the time interval between the peak of R wave in ECG and the maximal slope point of photoplethysmogram(PPG). Biosignals, ECG and finger photoplethysmogram(PPG), were converted to digital data, and PTT was evaluated in personal computer with every heart beat. Results were presented as a graph using spline interpolation. The software was implemented in C
++/ as a window-based application program. PTT was periodically changed according to airflow in resting respiration. In the resting respiration, PTT was changed according to the respiratory cycle. The amplitude of PTT fluctuation was increased by deep respiration, and increased by partial airway obstruction. These results suggest that PTT is responsible to respiratory effort which could be evaluated by the pattern of PTT change. And it is expected that PTT could be applied in the monitoring of respiratory effort by noninvasive methods, and is very useful method for the evaluation of respiratory distress.
An Efficient Rendering Method for Anisotropic Volume Data in 3D Medical Imaging
Journal of Biomedical Engineering Research, volume 23, issue 6, 2002, Pages 491~498
In medical visualization fields, anisotropic volume data are more common than isotropic ones. In this paper, we propose an efficient rendering method for anisotropic volume data, which directly computes the intensity of intermediate samples by interpolating the intensity of two corresponding voxels on consecutive slices. Unlike conventional rendering method, it does not require a preprocessing step for generating intermediate slices or additional memory for storing them. In order to evaluate the validity and performance of our method, we applied the method to shear-warp rendering algorithm. Experimental results show that this method improves rendering speed without significantly sacrificing the image quality.