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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 28, Issue 6 - Dec 2007
Volume 28, Issue 5 - Oct 2007
Volume 28, Issue 4 - Aug 2007
Volume 28, Issue 3 - Jun 2007
Volume 28, Issue 2 - Apr 2007
Volume 28, Issue 1 - Feb 2007
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Dynamic Quasi-Elastic Light Scattering Measurement of Biological Tissue
Youn, Jong-In ; Lim, Do-Hyung ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 169~173
During laser irradiation, mechanically deformed cartilage undergoes a temperature dependent phase transformation resulting in accelerated stress relaxation. Clinically, laser-assisted cartilage reshaping may be used to recreate the underlying cartilaginous framework in structures such as ear, larynx, trachea, and nose. Therefore, research and identification of the biophysical transformations in cartilage accompanying laser heating are valuable to identify critical laser dosimetry and phase transformation of cartilage for many clinical applications. quasi-elastic light scattering was investigated using Ho : YAG laser
and Nd:YAG Laser
for heating sources and He : Ne
laser, high-power diode pumped laser
, and Ti :
for light scattering sources. A spectrometer and infrared radiometric sensor were used to monitor the backscattered light spectrum and transient temperature changes from cartilage following laser irradiation. Analysis of the optical, thermal, and quasi-elastic light scattering properties may indicate internal dynamics of proteoglycan movement within the cartilage framework during laser irradiation.
Choice of Thresholding Technique in Micro-CT Images of Trabecular Bone Does Not Influence the Prediction of Bone Volume Fraction and Apparent Modulus
Kim, Chi-Hyun ; Kim, Byung-Gwan ; Guo, X. Edward ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 174~177
Trabecular bone can be accurately represented using image-based finite element modeling and analysis of these bone models is widely used to predict their mechanical properties. However, the choice of thresholding technique, a necessary step in converting grayscale images to finite element models which can thus significantly influence the structure of the resulting finite element model, is often overlooked. Therefore, we investigated the effects of thresholding techniques on micro-computed tomography (micro-CT) based finite element models of trabecular bone. Three types of thresholding techniques were applied to micro-CT images of trabecular bone which resulted in three unique finite element models for each specimen. Bone volume fractions and apparent moduli were predicted for each model and compared to experimental results. Our findings suggest that predictions of apparent properties agree well with experimental measurements regardless of the choice of thresholding technique in micro CT images of trabecular bone.
Compensation of Error in Noninvasive Blood Pressure Measurement System Using Optical Sensor
Ko, J.I. ; Jeong, I.C. ; Lee, D.H. ; Park, S.W. ; Hwang, S.O. ; Park, S.M. ; Kim, G.Y. ; Joo, H.S. ; Yoon, H.R. ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 178~186
This study is attempted to correct an error of electronic blood pressure meter with an optical sensor. In general, for a hospitalized patient, ECG, blood pressure, oxygen saturation, and respiration are basically measured to monitor the patient's condition. Opening of a blood vessel after it is occluded by pressurizing the cuff influences the blood flow of peripheral blood vessels as well as oscillation changes in the cuff. Blood vessels are occluded and peripheral blood flow disappears at cuff pressure above the examinee's blood pressure, while blood vessels are opened and peripheral blood flow appears again at cuff pressure under the examinee's blood pressure. Then Disappear-Appear Point Length(DAPL) of peripheral blood flow can be judged with the signal of peripheral blood flow, thus is available as a factor of error correction for electronic blood pressure meter. Also, systolic or diastolic blood pressure can be corrected with Appear-Point-Pressure(APP) of cuff pressure at a point where blood flow occurs and Appear-Maximum Pressure(AMP) of cuff pressure at the maximum amplitude point of peripheral blood flow after peripheral blood flow appears again. For verification, 27 examinees were selected, and their blood value was obtained through experimental procedure of 4 stages including induction of blood pressure change. The examinees were divided into two groups of experimental group and control group, regression analysis was conducted for experimental group, and correction of a blood pressure error was verified with optical signal by applying the regression equation calculated in experimental group to control group. As an experimental result, mean of the whole measurement errors was 5mmHg or more, which did not meet the standard fur blood pressure meter. As a result of correcting blood pressure measurements with data of DAPL, APP, and AMP as drawn out of PPG signal, systolic blood pressure, mean blood pressure, and diastolic blood pressure were
, respectively, indicating that mean of the whole measurement errors was greatly improved, and standard deviation was decreased.
The Analysis of GRF during Golf Swing with the Slopes
Moon, G.S. ; Choi, H.S. ; Hwang, S.H. ; Kim, Y.H. ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 187~194
The purpose of this study is to determine the characteristics of ground reaction force(GRF) in golf swing for various slopes of flat lie and uphill lies of 5 and 10 degrees. Five right-handed professional golfers were selected for the experiment and the 7 iron club was used. We used four forceplates to measure GRF and synchronized with the three-dimensional motion analysis system. Results showed that slope did not affect the total time for golf swing, but the time until the impact had a tendency to slightly increase for the uphill lie(p<0.05). The medial-lateral GRF of the right foot increased toward the medial direction during back swing, but less increases were found with the angle of uphill lie(p<0.05). The GRF of the left foot increased rapidly toward the medial direction at the uncocking and the impact during down swing, but decreased with the increase in the angle of uphill lie(p<0.05). The anterior-posterior GRF of both feet showed almost the same for different slopes. With the slopes, the vertical GRF of the right foot increased, but the vertical GRF of left foot decreased(p<0.05). Uphill lies would have negative effect to provide the angular momentum during back swing, restricting pelvic and trunk rotations, and to provide the precise timing and strong power during down swing, limiting movements of body's center of mass. The present study could provide valuable information to quantitatively analyze the dynamics of golf swing. Further study would be required to understand detailed mechanism in golf swing under different conditions.
Digital Color Imaging Systems for Quantitative Evaluation of Skin Lesions
Han, Byung-Kwan ; Jung, Byung-Jo ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 195~198
In this paper, we introduce a digital cross-polarization and fluorescent color imaging system for quantitative evaluation of skin lesions. We describe the characterization of the imaging systems and the quantitative image analysis methods to show the feasibility for quantitative evaluation of skin lesions. The polarization color image was used to compute erythema and melanin index image which are useful for quantitative evaluation of pigmentation and vascular skin lesions, respectively. The fluorescent color image was used to quantitatively evaluate "sebum" and "vitiligo". In quantitative evaluation of various skin lesions, we confirmed the clinical efficacy of the imaging systems for dermatological applications. Finally, we sure that the imaging systems can be utilized as important assistant tools for the evaluation of skin lesions by providing reproducible quantitative result for widely distributed skin lesions.
DR Image Enhancement Using Multiscale Non-Linear Gain Control For Laplacian Pyramid Transformation
Shin, Dong-Kyu ; Lee, Jin-Su ; Kim, Sung-Hee ; Park, In-Sung ; Kim, Dong-Youn ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 199~204
In digital radiography, to improve the contrast of digital radiography image, the multi-scale nonlinear amplification algorithm based on unsharp masking is one of the major image enhancement algorithms. In this paper, we used the Laplacian pyramid to decompose a digital radiography(DR) image. In our simulation, the DR image was decomposed into seven layers and the coefficients of the each layer was amplified with nonlinear function. We also imported a noise containment algorithm to limit noise amplification. To enhance the contrast of image, we proposed a new adaptive non-linear gain amplification coefficients. As a result of having applied to some clinical data, a detail visibility was improved significantly without unacceptable noise boosting. Images that acquired with the proposed adaptive non-linear gain coefficients have shown superior quality to those that applied similar gain control method and expected to be accepted in the clinical applications.
A Simulation Study on Improvements of Speech Processing Strategy of Cochlear Implants Using Adaptation Effect of Inner Hair Cell and Auditory Nerve Synapse
Kim, Jin-Ho ; Kim, Kyung-Hwan ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 205~211
A novel envelope extraction algorithm for speech processor of cochlear implants, called adaptation algorithm, was developed which is based on a adaptation effect of the inner hair cell(IHC)/auditory nerve(AN) synapse. We achieved acoustic simulation and hearing experiments with 12 normal hearing persons to compare this adaptation algorithm with existent standard envelope extraction method. The results shows that speech processing strategy using adaptation algorithm showed significant improvements in speech recognition rate under most channel/noise condition, compared to conventional strategy We verified that the proposed adaptation algorithm may yield better speech perception under considerable amount of noise, compared to the conventional speech processing strategy.
Estimation of Visual Stimulus Intensity From Retinal Ganglion Cell Spike Trains Using Optimal Linear Filter
Ryu, Sang-Baek ; Kim, Doo-Hee ; Ye, Jang-Hee ; Kim, Kyung-Hwan ; Goo, Yong-Sook ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 212~217
As a preliminary study for the development of electrical stimulation strategy of artificial retina, we set up a method fur the reconstruction of input intensity variation from retinal ganglion cell(RGC) responses. In order to estimate light intensity variation, we used an optimal linear filter trained from given stimulus intensity variation and multiple single unit spike trains from RGCs. By applying ON/OFF stimulation(ON duration: 2 sec, OFF duration: 5 sec) repetitively, we identified three functional types of ganglion cells according to when they respond to the ON/OFF stimulus actively: ON cell, OFF cell, and ON-OFF cell. Experiments were also performed using a Gaussian random stimulus and a binary random stimulus. The input intensity was updated once every 90 msec(i. e. 11 Hz) to present the stimulus. The result of reconstructing 11 Hz Gaussian and binary random stimulus was not satisfactory and showed low correlation between the original and reconstructed stimulus. In the case of ON/OFF stimulus in which temporal variation is slow, successful reconstruction was achieved and the correlation coefficient was as high as 0.8.
The Development and Evaluation of the Active Gait Training System for the Patients with Gait Disorder
Hwang, S.J. ; Tae, K.S. ; Kang, S.J. ; Kim, J.Y. ; Hwang, S.H. ; Kim, H.I. ; Park, S.W. ; Kim, Y.H. ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 218~228
Modem concepts of gait rehabilitation after stroke favor a task-specific repetitive approach. In practice, the required physical effort of the therapists limits the realization of this approach. Therefore, a mechanized gait trainer enabling nonambulatory patients to have the repetitive practice of a gait-like movement without overstraining therapists was constructed. In this study, we developed an active gait training system for patients with gait disorder. This system provides joint movements to patients who cannot carry out an independent gait. It provides a normal stance-swing ratio of 60:40 using an eccentric configuration of two gears. Joint motions of the knee and the ankle were evaluated with using the 3D motion analysis system and compared with the results from the multi-body dynamics simulation. In addition, clinical investigations were also performed for low stroke patients during the 6-week gait training. Results from the dynamics simulation showed that joint movements of the knee and the ankle were affected by the gear size, the step length and the length of the foot plate, except the radius of curvature of the foot guide plate. Also, the 6-week gait training revealed relevant improvements of the gait ability in all low subjects. Functional ambulation category levels of subjects after training were 2 in three patients and 1 in a patient. The developed active gait trainer seems feasible as an adjunctive tool in gait rehabilitation after stroke.
Optical Property Measurements of Optical Phantoms and Honan Tissues Using Frequency-Domain Diffuse Optical Tomography
Ho, Dong-Su ; Kwon, Ki-Woon ; Eom, Gi-Yun ; Lee, Seung-Duk ; Kim, Beop-Min ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 229~234
Diffuse optical tomography (DOT) is a relatively new medical imaging modality which uses near infrared light to image large-sized tissues noninvasively. We constructed a frequency-domain DOT system to measure the optical properties of optical phantoms and human tissues. The FD-DOT uses the intensity-modulated infrared light source that illuminates the biological tissues. The phase shift and modulation changes at each detector site are separately processed to measure the optical properties. The absorption and scattering coefficients are separately estimated using inverse algorithms.
A Study For Optimizing Input Waveforms In Radiofrequency Liver Tumor Ablation Using Finite Element Analysis
Lim, Do-Hyung ; NamGung, Bum-Seok ; Lee, Tae-Woo ; Choi, Jin-Seung ; Tack, Gye-Rae ; Kim, Han-Sung ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 235~243
Hepatocellular carcinoma is significant worldwide public health problem with an estimated annually mortality of 1,000,000 people. Radiofrequency (RF) ablation is an interventional technique that in recent years has come to be used for treatment of the hepatocellualr carcinoma, by destructing tumor tissues in high temperatures. Numerous studies have been attempted to prove excellence of RF ablation and to improve its efficiency by various methods. However, the attempts are sometimes paradox to advantages of a minimum invasive characteristic and an operative simplicity in RF ablation. The aim of the current study is, therefore, to suggest an improved RF ablation technique by identifying an optimum RF pattern, which is one of important factors capable of controlling the extent of high temperature region in lossless of the advantages of RF ablation. Three-dimensional finite element (FE) model was developed and validated comparing with the results reported by literature. Four representative Rf patterns (sine, square, exponential, and simulated RF waves), which were corresponding to currents fed during simulated RF ablation, were investigated. Following parameters for each RF pattern were analyzed to identify which is the most optimum in eliminating effectively tumor tissues. 1) maximum temperature, 2) a degree of alteration of maximum temperature in a constant time range (30-40 second), 3) a domain of temperature over
isothermal temperature (IT), and 4) a domain inducing over 63% cell damage. Here, heat transfer characteristics within the tissues were determined by Bioheat Governing Equation. Developed FE model showed 90-95% accuracy approximately in prediction of maximum temperature and domain of interests achieved during RF ablation. Maximum temperatures for sine, square, exponential, and simulated RF waves were
, respectively. While the maximum temperatures were decreased in the constant time range, average time intervals for sine, square, exponential, and simulated RE waves were
seconds, respectively. Average magnitudes of the decreased maximum temperatures in the time range were
for sine wave,
for square wave,
for exponential wave, and
for simulated RF wave. Volumes of temperature domain over
IT for sine, square, exponential, and simulated RF waves were 1480mm3, 1440mm3, 1380mm3, and 395mm3, respectively. Volumes inducing over 63% cell damage for sine, square, exponential, and simulated RF waves were 114mm3, 62mm3, 17mm3, and 0mm3, respectively. These results support that applying sine wave during RF ablation may be generally the most optimum in destructing effectively tumor tissues, compared with other RF patterns.
Phase-Separation Properties of Poly(Ethylene Glycol) had Dextran Solutions In Microfluidic Device
Choi, Joo-Hyung ; Chang, Woo-Jin ; Lee, Sang-Woo ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 244~249
Fluidic conditions for the separation of phases were surveyed in a microfluidic aqueous two-phase extraction system. The infusion ratio between polyethylene glycol (PEG) and dextran solution defines the concentrations of each polymer in micro-channel, which determine the phase-separation. The appropriate ratio between PEG (M.W. 8000, 10%, w/v) and dextran T500 (M.W. 500000, 5%, w/v) in order to perform the separation of phases of both polymers was observed as changing the mixed ratio of both polymers. Based on the fluidic conditions, stable two-phase solutions were obtained within 4% to 8% and 3% to 1% of PEG and dextran, respectively. In addition, the characteristics of the two-phase were discussed. The separation technique studied in the paper can be applied for the implementation of a lab-on-a chip which can detect various biological entities such cells, bacterium, and virus in an integrated manner using built in a biosensor inside the chip.
Design of Gastrointestinal Diagnosis System based on Ultrasonic Response Characteristics
Lim, Do-Hyung ; Kim, Eun-Geun ; Lee, Gyoun-Jung ; Park, Won-Pil ; Kim, Han-Sung ; Shin, Tae-Min ; Choi, Seo-Hyung ; Lee, Yong-Heum ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 250~257
Functional gastrointestinal disorders affect millions of people of all age regardless of race and sex. There are, however, rare diagnostic methods for the functional gastrointestinal disorders because functional disorders show no evidence of organic and physical causes. Our research group identified recently that the gastrointestinal tract well in the patients with the functional gastrointestinal disorders becomes more rigid than healthy people when palpating the abdominal regions overlaying the gastrointestinal tract. The aim is, therefore, to develop a diagnostic method for the functional gastrointestinal disorders based on quantitative measurement of the rigidity of the gastrointestinal tract well using ultrasound technique. For this purpose, a preliminary ultrasound diagnostic system was developed and verified through phantom tests. The system consisted of transmitter, ultrasonic transducer, receiver, TGC, and CPLD, and verified via a phantom test. For the phantom test, ten soft-tissue specimens were harvested from porcine. Five of them were then treated chemically to mimic a rigid condition of gastrointestinal tract well, which was induced by functional gastrointestinal disorders. Additionally, the specimens were tested mechanically to identify if the mimic was reasonable. The customized ultrasound system was finally verified through application to human subjects with/without functional gastrointestinal disorders(Normal and Patient Groups). It was identified from the mechanical test that the chemically treated specimens were more rigid than normalspecimen. This finding was favorably compared with the result obtained from the phantom test. The phantom test also showed that ultrasound system well described the specimen geometric characteristics and detected an alteration in the specimens. The maximum amplitude of the ultrasonic reflective signal in the rigid specimens
at the interface between the fat and muscle layers was explicitly higher than that in the normal specimens
(p<0.05). Clinical tests using our customized ultrasound system for human subject showed that the maximum amplitudes of the ultrasonic reflective signals nea. to the gastrointestinal tract well for the patient group
were generally higher than those in normal group
(p<0.05). These results suggest that newly designed diagnostic system based on ultrasound technique may diagnose enough the functional gastrointestinal disorders.
Feasibility Study of EEG-based Real-time Brain Activation Monitoring System
Chae, Hui-Je ; Im, Chang-Hwan ; Lee, Seung-Hwan ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 258~264
Spatiotemporal changes of brain rhythmic activity at a certain frequency have been usually monitored in real time using scalp potential maps of multi-channel electroencephalography(EEG) or magnetic field maps of magnetoencephalography(MEG). In the present study, we investigate if it is possible to implement a real-time brain activity monitoring system which can monitor spatiotemporal changes of cortical rhythmic activity on a subject's cortical surface, neither on a sensor plane nor on a standard brain model, with a high temporal resolution. In the suggested system, a frequency domain inverse operator is preliminarily constructed, considering the individual subject's anatomical information, noise level, and sensor configurations. Spectral current power at each cortical vertex is then calculated for the Fourier transforms of successive sections of continuous data, when a single frequency or particular frequency band is given. An offline study which perfectly simulated the suggested system demonstrates that cortical rhythmic source changes can be monitored at the cortical level with a maximal delay time of about 200 ms, when 18 channel EEG data are analyzed under Pentium4 3.4GHz environment. Two sets of artifact-free, eye closed, resting EEG data acquired from a dementia patient and a normal male subject were used to show the feasibility of the suggested system. Factors influencing the computational delay are investigated and possible applications of the system are discussed as well.
Development of Multi-Purpose Variable Polarization Imaging System for Clinical Diagnosis
Bae, Young-Woo ; Jung, Byung-Jo ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 265~270
Polarization imaging systems have been widely used to selectively characterize skin lesions. Nevertheless, current systems are used in single-mode due to the limitations of a fixed polarization mode and a single-working distance of light source, in which uniform light distribution is achieved on target area. To address such limitations, we developed a variable polarization imaging system based on multi-working distance of light source for various clinical diagnoses. In this study, we characterize the imaging system and present experiment results demonstrating its clinical usefulness. The imaging system consists of a CCD color camera, linear polarization filters, and a single-layered LED ring light source which provides uniform light distribution at multi-working distances. The first polarizer was placed on the light source and the second polarizer placed on objective lens provides continuous linear polarization angle from
. The clinical efficacy of the imaging system was investigated by acquiring and analyzing clinical images of skin wrinkle and dental plaque. With the experiments, we verified the potential usefulness of the imaging system for other clinical applications.
Performance Evaluation of Cochlear Implants Speech Processing Strategy Using Neural Spike Train Decoding
Kim, Doo-Hee ; Kim, Jin-Ho ; Kim, Kyung-Hwan ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 271~279
We suggest a novel method for the evaluation of cochlear implant (CI) speech processing strategy based on neural spike train decoding. From formant trajectories of input speech and auditory nerve responses responding to the electrical pulse trains generated from a specific CI speech processing strategy, optimal linear decoding filter was obtained, and used to estimate formant trajectory of incoming speech. Performance of a specific strategy is evaluated by comparing true and estimated formant trajectories. We compared a newly-developed strategy rooted from a closer mimicking of auditory periphery using nonlinear time-varying filter, with a conventional linear-filter-based strategy. It was shown that the formant trajectories could be estimated more exactly in the case of the nonlinear time-varying strategy. The superiority was more prominent when background noise level is high, and the spectral characteristic of the background noise was close to that of speech signals. This confirms the superiority observed from other evaluation methods, such as acoustic simulation and spectral analysis.
Implementation of the Wearable Sensor Glove Using EDA Sensor and Conducting Fabric
Lee, Young-Bum ; Lee, Byung-Woo ; Choo, Young-Min ; Kim, Jin-Kwon ; Jung, Wan-Jin ; Kang, Dae-Hoon ; Lee, Myoung-Ho ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 280~286
The wearable sensor glove was developed using EDA sensors and conducting fabric. EDA(Electro-dermal Activity) signal is an electric response of human skin. There are SIL(Skin Impedance Level) and SIR(Skin Impedance Response) in EDA. SIL consists mostly of a DC component while SIR consists of an AC component. The relationship between drowsiness and the EDA signal is utilized. EDA sensors were made using a conducting fabric instead of AgCl electrodes, for a more suitable, more wearable device. The EDA signal acquisition module was made by connecting the EDA sensor gloves through conductive fabric lines. Also, the EDA signal acquisition module can be connected to a PC that shows the results of the EDA signal processing analysis and gives proper feedback to the user. This system can be used in various applications to detect drowsiness and prevent accidents from drowsiness for automobile drivers.
The Estimation of the Depth of Anesthetic Using Higher-Order Spectrum Analysis of EEG Signals
Park, Jong-Duk ; Ye, Soo-Young ; Jeon, Gye-Rok ; Huh, Young ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 287~293
The researchers have studied for a long time about the depth of anesthesia but they don't make criteria for the depth of anesthesia. Anesthetists can't make a prediction about patient's reaction. Therefore, patients have potential risk such as poisonous side effect, late-awake, early-awake and strain reaction. In this study, the distributed characteristics on the bispectrum and bicoherence, the type of nonlinear signal processing, as a result of the coupling of EEG were presented according to depth of anesthesia. These results were consistent with a trend of delta ratio that the index of evaluation for the depth of anesthesia. The higher-order spectrum (HOS), the bispectrum and bicoherence, gives the useful information about depth of anaesthesia than other indexes.
Ultrasound Image Enhancement Based on Automatic Time Gain Compensation and Dynamic Range Control
Lee, Duh-Goon ; Kim, Yong-Sun ; Ra, Jong-Beom ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 294~299
For efficient and accurate diagnosis of ultrasound images, appropriate time gain compensation(TGC) and dynamic range(DR) control of ultrasound echo signals are important. TGC is used for compensating the attenuation of ultrasound echo signals along the depth, and DR controls the image contrast. In recent ultrasound systems, these two factors are automatically set by a system and/or manually adjusted by an operator to obtain the desired image quality on the screen. In this paper, we propose an algorithm to find the optimized parameter values far TGC and DR automatically. In TGC optimization, we determine the degree of attenuation compensation along the depth by dividing an image into vertical strips and reliably estimating the attenuation characteristic of ultrasound signals. For DR optimization, we define a novel cost function by properly using the characteristics of ultrasound images. We obtain experimental results by applying the proposed algorithm to a real ultrasound(US) imaging system. The results verify that the proposed algorithm automatically sets values of TGC and DR in real-time such that the subjective quality of the enhanced ultrasound images may be sufficiently high for efficient and accurate diagnosis.
Performance Evaluation of a Selenium(a-Se) Based Prototype Digital Radiation Detector
Park, Ji-Koon ; Kang, Sang-Sik ; Cho, Sung-Ho ; Shin, Jung-Wook ; Kim, So-Yeong ; Son, Dae-Woong ; Nam, Sang-Hee ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 300~305
In this study, we have studied the fabrication and the performance evaluation of digital radiation detector of the based on selenium (a-Se) prototype which is widely researched about recently. The detector was fabricated using amorphous selenium in the specification of active area size
, pixel pitch
, and 12 bit ADC. In order for the performance evaluation of the fabricated detector, we used radiation quality RQA 5 that is suggested by the International Electrotechnical Commission (IEC), and evaluated modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Concerning MTF measurement, we used slit camera (Nuclear Associates, Model : 07-624-2222), and evaluated in the slit method. Also so as to compare the performance evaluation on the detector fabricated in this study, we used Hologic Direct-Ray (DR-1000) and GE Revolution XQ/I system, and evaluated and compared in the same method MTF, NPS, and DQE which are image quality factors. And as a result, the MTF of each detector In Nyquist frequency were evaluated to be 58% (at 3.5 lp/mm) in the case of DR-1000 and 65% (at 2.5 lp/mm) in the case of XQ/I, and that for the detector fabricated in this study was evaluated to be 36% (at 3.51 lp/mm). Also in the case of DQE(0), the detector fabricated in this study, DR-1000 of Hologic company, and XQ/I system of GE company respectively were evaluated as 36%, 32%, and 50%.
Characterization of the a-Se Film for Phosphor based X-ray light Modulator
Kang, Sang-Sik ; Park, Ji-Koon ; Cho, Sung-Ho ; Cha, Byung-Youl ; Shin, Jung-Wook ; Lee, Kun-Hwan ; Mun, Chi-Woong ; Nam, Sang-Hee ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 306~309
PXLM(Phosphor based x-ray light modulator) has a combined structure by phosphor, photoconductor, and liquid crystal and it can realize x-ray image of high resolution in clinical diagnosis area. In this study, we fabricated a photoconductor and investigated electrical and optical properties to confirm application possibility of radiator detector of PXLM structure. As photoconductor, amorphous selenium(a-Se), which is used most in DR(Digital radiography) of direct conversion method, was used and for formation of thin film, it was formed as
by using thermal vacuum evaporation system. For a produced a-Se film, through XRD(X-ray diffraction) and SEM(Scanning electron microscope), we investigated that amorphous structure was uniformly established and through optical measurement, for visible light of 40
, it had absorption efficiency of 95 % and more. After fabricated a-Se film on the top of ITP substrate, hybrid structure was manufactured through forming
on the bottom of the substrate. As the result to confirm electrical property of the manufactured hybrid structure, in the case of appling
, leakage current of
and x-ray sensitivity of
were investigated. Finally, we manufactured PXLM structure combined with hybrid structure and liquid crystal cell of TN(Twisted nematic) mode and then, investigated T-V(Transmission vs. voltage) curve of external light source for induced x-ray energy. PXLM structure showed a similar optical response with T-V curve that common TN mode liquid crystal cell showed according to electric field increase and in appling
, it showed linear transmission efficiency of
. This result suggested an application possibility of PXLM structure as radiation detector.
A Development of Eddy Current Sensor System for An Axial-flow type Blood Pump with The Magnetic Bearing
Ahn, C.B. ; Moon, K.C. ; Jeong, G.S. ; Nam, K.W. ; Lee, J.J. ; Sun, K. ;
Journal of Biomedical Engineering Research, volume 28, issue 2, 2007, Pages 310~315
The axial-flow type blood pump(XVAD) which has been developed in our group consists of mechanical parts (an impeller, a diffuser and a flow straightener) and electrical parts (a motor and a magnetic bearing). The magnetic bearing system fully levitates the impeller to remove mechanical coupling with other parts of the pump with constant gap, which needs non-contact type gap sensing. Conventional gap sensors are too large to be adopted to the implantable axial -flow type blood pump. Thus, in this paper, the compact eddy current type gap sensor system proper for the implantable axial-flow type blood pump was developed and its performance was evaluated in vitro. The developed eddy current type gap sensor system is a transformer type and has a differential probe. Sensor coil(probe) has small dimensions(6 mm diameter, 2 mm thickness) and its optimal inductance was determined as 0.068 mH for the measurement range of
. It could be manufactured with 130 turns of the 0.04 mm diameter copper coil. The characteristics of the developed eddy current type gap sensor system was evaluated by in vitro experiment. At experiment, it showed satis(actory performance to apply to the magnetic bearing system of the XVAD. It could measure the gap up to 3mm, but the linearity was decreased at the range of
. Moreover, it showed no difference in different media such as the water and the blood at the temperature range of