The object detection capabilities of ultrasonic imaging systems are limited by the ability of the detection process to distinguish the resolved object signals from backscattered speckle noise. It has been shown that the phase component of the Fourier transform of the speckle noise is random. Based on this property. we propose a new algorithm for distinguishing between speckle and specular targets. The proposed algorithm is implemented by taking the Fourier transform of the received signal, low-pass filtering the phase, and taking the inverse Fourier transform of the filtered phase to enhance specular reflectors and reduce speckle in the image. Simulations and experiments using phantoms confirm the algorithm yielding significant reduction of speckle noise.

The detection of pulmonary blood vessels is very difficult owing to their complex tree structures and different widths. In this paper, We propose a new detection algorithm. The motivation of this algorithm is that Han is the best detector. So, this algorithm is developed to imitate the human searching process. To realize it, the algorithm consist of two components. One is Pyramid Images whose one pixel is median value of four pixels of the previous low level. Searching gradually from high level to low level, We concentrate on global and main information of structure at the first. Then based on it, We search the detailed data in low level. The other is fuzzy logic which makes it easy to convert searching process expressed as human language into numeric multi_value. This algorithm showes speedy and robust results. But the more study on both human searching process and the detection of small part is needed.

In abdominal NMR imaging the respiratory ordering techniques have been successfully used to remove the ghosting artifacts arising from the respiratory motion. In the existing respiratory ordering schemes, however, it is generally accepted that blurring of the moving parts still remains as in the signal averaging technique. A new optimal respiratory ordering scheme which can correct the blurring as well as the ghosting artifacts is theoretically derived through the analysis of the phase encoding directional motion effects in Fourier imaging. The performance of the optimal respiratory ordering scheme is experimentally confirmed together with a suboptimal ordering scheme which is suggested as a compromise for the practicality.

A new technique for reducing the susceptibility artifact in gradient echo imaging which uses a tailored RF pulse is proposed. It is applied to the case of imaging where artifacts and distortions arise due to the high local magnetic field inhomogeneity i. e., the susceptibility. The signal loss and void phenomena due to susceptibility in a voxel are studied and a correction method using a tailored RF pulse is proposed. Applications of this method in imaging are given and experimental results obtained using an human volunteer with a 2.0 T KAIS NMR system are presented.

We tested the ability of two-dimensional echocardiograms of complete heart cycle in closed-chest human to discriminate between normal and infarcted myocardium using fixed window, Inter- and Intra-frame analysis. The results show that statistical parameter, MEAN, second order gray level statistics parameter, ASM and proposed parameter, HGE, I.T, can quantitatively distinguish between normal and Infarcted regions. The manner in which these parameters vary over the cardiac cycle is also a good indicator of the state of myocardium. The infarcted areas yield regions of higher Intensity throughout the cardiac cycle. Whereas, normal tissue demonstrates greater variability throughout the cardiac cycle.

The method for enhancing the edges from medical images is described. The various methods are tested for the medical Images contaminated by noises, such as weighted averaging based on local probabilities, unsharp masking techniques, and proposed combined techniques. As a result, the combined technique using the median filtering and edge masks in six directions is well suited to remove the noises as to as to preserve the edges. Experimental results and computational procedures are presented.

Endoscope system is the device that observe interior the body. It has some demerits because it use of optical fibers. The resolution of images depends on the number of optical fibers, it is impossible that several people observe at the same time and it needs special camera in order to record images. In order to overcome these demerits, electro endoscope system using CCD(Charge Coupled Device) has been developed recently. If the diameter of insertion tube is thinner, it is easier to be examined by thin endoscope system. At the present time, we develope these type of electro endoscope system in the department of SNU biomedical engineering. Moreover, we are researching an algorithm of the 3D-reconstruction of interior of the gaster. In this paper, a method for 3D information detection using electroendoscopic image sequence has been presented.

A new spline function for resampling discrete signal adaptively is proposed. In general, B-spline function is used for an image interpolation because of its smoothness and continuity, but accompanies a large amount of blurring effect. Hence, we developed a new spline function to remedy this effect, with two procedures ; deblurring of Gaussian blurring and diminishing of aliasing effect caused by deblurring procedure. The proposed function has a parametric expression with $\alpha$ which is related to the variance of Gaussian blurring model. Locally adaptive resampling scheme is obtained by changing a according to statistical characteristics of an image. The proposed, interpolation function shows edge-sharpening effect as well as noise smoothing, with comparison to the conventional schemes.

In this paper, a new adaptive image processing method based on human visual system has been presented. The basic idea behind the proposed method is to improve the efficiency of the information transfer channel regionally by manipulating the displayed image in order to compensate the regional inefficiency of the information transfer channel. The proposed method consists of two parts; the first part reallocates pixel values corresponding to high X-ray attenuation to that of more intense X-ray exposure by multiplying the pixel values with the local adaptive multiplcation factor, and the second part adjusts the pixel values of dark area of displayed image such as overexposed lung area to be more bright. The processed image with the proposed method shows significantly increased visibility of mediastinal and subdiaphramatic area, and also the lung area of over exposed case without any artifact.

A new in vivo high resolution imaging method which is performed with a newly developed three channel surface gradient coil (SGC) is described. The surface gradient coil can produce more than an order of magnitude stronger gradient fields with good linearity within a limited imaging region. To increase the signal to noise ratio (SNR), we have developed an RF coil integrated surface gradient coil set. In this paper, the geometrical structures and characteristics of the proposed surface gradient coil are discussed and experimentally obtained high resolution images ($50\;{\mu}m$ to $100\;{\mu}m$) of a water filled phantom and a human volunteer's knee using the new surface RF coil integrated SGC set are presented for the demonstration of the in vivo high resolution imaging capability of the new imaging method.

To develop better blood compatibility of commercial polyurethane(PU), PU surface was chemically modified wi th a hydrophobic perfluorocarhon or a hydrophilic polyethylene oxide(PEO) and/or sulfonated groups, respectively. The water contact angle of modified PUs varied from $110^{\circ}$ to $0^{\circ}$. All the modified PUs were more blood compatible than untreated PU. In particular, PEO-sulfonate grafted PUs showed a very enhanced antithrombogenicity due to the synergistic effect of PEO and $SO_3$ groups. Therefore more hydrophobic and hydrophilic PU surfaces are promising for improving the blood compatibility.

Bending strength, bending elastic modulus ,and fracture toughness of different types of dental composite resins were deter mined. The relationship between bending strength, fracture toughness and filler volume fraction of dental composite resin was understood. In Acoustic Emission(AE) behavior during fracture toughness test, characteristic generation patterns of each type were understood. The fracture toughness values, AE generation patterns, and the nature of fracture surface were analyzed to understand fracture behavior of dental composite resin.

반도체 및 전자공업의 급속한 발달에 힘입어 압력센서가 소형, 경량, 대량 생산화됨으로써 의료용으로의 사용이 최근 급속히 늘고 있다. 따라서 본 논문은 현재 가장 활발히 개발되고 있는 압저항형 압력 센서의 원리인 압저항 효과에 대해 이론적인 분석을 상세히 소개하였다. 그리고 기존에 많이 소개된 바 있는 정사각형 모양의 박막모서리 중앙 부분에 위치한 압저항체의 설계 보다 직사각형 박막 중심에 위치한 압저항체의 설계가 우수한 특성을 보일 수 있는 이론적 근거를 설명한다.

혈중 산소농도는 의료 분야에 기초적인 간으로 쓰이고, 이의 측정법은 오랜 역사를 가지고 있다. 현재까지 인체의 혈액 중 산소 포화도는 혈액을 직접 추출하여 조사할 수 있었으나, 이러한 직접추출 방법은 생리학적인 제조건의 변화에 따라 변할 수 있어서, 인공심장 등의 응용으로 사용될 때에는 신속한 정보를 알아야 하므로 부적합하다. 본 연구에서는 비추출식 산소 포화도를 광학적인 방법으로 연구하는데 필요한 자료 조사 및 기본 이론 분석에 있다.

Cross correlation method was newly applied for the calculation of latency of evoked otoacoustic emission. The latency was calculated from the main peak of cross correlation function, which is one of possible definition of latency. The output was also compared with those of conventional autocorrelation method. The results show that cross correlation method has better performance than that of conventional method.

Nowadays, the amounts of cells and tissues in the field of pathology is being increased rapidly due to the increasing number of peoples and growing medical well fares. But, unfortunately the number of professional pathologist is not enough to deal with the great inspection amounts and there are several difficult problems in processing the inspections with naked eyes. To process a lot of inspections rapidly and solve difficults in inspections, the need of the inspection automation come appears. With this study the primarily cells and tissues can be sorted using image processing technics. As a result, the normal cells are separated from the abnormal cells and the abnormal cells can be distinguished through screening of abnormal cell's image with reference data to judge abnormal cells. Owing to this study the number of inspections which the pathologists should examine will be decreased and the time for inspection will be shortened.

A new approach to impulsive noise rejection and background normalization of digitized electrocardiogram signals is presented using mathematical morphological operators that incoporate the shape information of a signal. A brief introduction to these nonlinear signal processing operators, as well as detailed description of the new algorithm, is presented. Empirical results show that the new algorithm has good performance in impulsive noise rejection and background normalization.

EEG signal is analyzed by two methods, analysis by visual inspection of EEG recording sheets and analysis by quantative method. Generally visual inspection method is used in the clinical field. But this method has its limitation because EEG signal is random signal. Therefore it is necessary to analyze EEG signals quantatively to obtain more precise and objective information of neural and brain. In this paper, power spectrum of EEG signal was estimated by AR(AutoRegressive) model in the frequency domain. This process is useful as a preprocessing stage for tomographic brain mapping (TBM) at each frequency, band. As a method for estimating power spectral density of EEG signals, periodogram method, autocorrelation method. covariance method, modified covariance method, and Burg method are tested in this paper.

This paper describes development of an implantable power switching system for biotelemetry system. This system is designed and manufactured to achieve as small size and low power dissipation as possible, using pulse powered circult and CMOS technology. The function of the power switching system is to connect the implantable battery to implanted sensors and, electronics systems by receiving intermittent command signals from external circuits. The power dissipation of this system was about $15{\mu}W$ for a stand-by operation.