• Bulletin of the Korean Space Science Society
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• 1993.10a
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• pp.17-17
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• 1993

The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70${\pm}$1.32mmHg/min)compared to CF dialyzers(4.32${\pm}$0.55mmHg/min)(p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHe/min)on the reused dialyzers(2 out of 40 CP and S out 26 C-DAK) were attributed to the Possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD is a more sensitive test than UFR test to evaluate the integrity of the fibers. 30527 T00401030527 ^x For quantitative measurement of reflected light from a clinical diagnostic strip, a prototype old reflectance photometer was designed. The strip loader and cassette were made to obtain more accurate reflectance parameters. The strip was illuminated at 45˚c through optical fiber and the intensity of reflected light was determined at rectanguLat angle using a photodiode. The kubelka-munk coefficient and reflection optical density were determined ar four different wavelengths(500,550,570 and 610nm) for blood glucose strip. For higher concentration than 300mg/41 about glucose, a saturation state of abforbance was observed at 500,550 and 570nm. The correlation between glucose concentration and parameters was the best at 610nm. 30535 T00401030535 ^x Radiation-induced fibrosarcoma tumors were grown on the flanks of C3H mice. The mice were divided into two groups. One group was injected with Photofrin II, intravenously (2.5mg/kg body weight). The other group received no Photofrin II. Mice from both groups were irradialed for approximately 15 minutes at 100,300, or 500 mW/cm2 with the argon (488nm/514.5 nm), dye(628nm) and gold vapor (pulsed 628 nm) laser light. A photosensitizer behaved as an added absorber. Under our experimental conditions, the presence of Photolfrin II increased surface temperature by at least 40% and the temperature rise due to 300 mW/cm2 irradiation exceeded values for hyperthermia. Light and temperature distributions with depth were estimated by a computer model. The model demonstrated the influence of wavelength on the thermal process and proved to be a valuable tool to investigate internal temperature rise. 30536 T00401030536 ^x We investigated the structural geometry of thirty-eight Korean femurs. The purpose of this study is to identify major geometrical differences between Korean femurs 3nd others that we believe belong to Caucasians so that we would be able to get insights into the femoral component design that fits Asians including Koreans. We utilized computerized tomography (CT) images of femurs extracted from cadavers. The CT images were transformed into bitmap data by using a film scanner, and then analyzed by using a commercially available software called Image v.1.0 and a Macintosh IIci computer.The resulting data were compared with already published data. The major results show that the geometry of the Korean femurs is significantly different from that of Caucasians: (1) the anteversion angle and the canal flare index are greater by the amount of approximately 8˚ and 0.5, respectively, (2) the shape of the isthmus cross section is more round, and (3) the distance between the teaser trochanter and the proximal border of the isthmus is shelter by about 15 mm. The results suggested that the femoral component suitable for Asians should be different from the currently-used components designed and manufactured mostly by European or American companies. 30537 T00401030537 ^x It is well known that nonlinear propagation characteristics of the wave in the tissue may give very useful information for the medical diagnoisis. In this paper, a new method to detect nonlinear propagation characteristics of the internal vibration in the tissue for the low frequency mechanical vibration by using bispectral analysis is proposed. In the method, low frequency vibration of f0( = 100Hz) is applied on the surface of the object, and the waveform of the internal vibration x (t) is measured from Doppler frequency modulation of silmultaneously transmitted probing ultrasonic waves. Then, the bispectra of the signal x (t) at the frequencies (f0, f0) and (f0, 2f0) are calculated to estimate the nonlinear propagation characteristics as their magnitude ratio, w here since bispectrum is free from the gaussian additive noise we can get the value with high S/N. Basic experimental system is constructed by using 3.0 MHz probing ultrasonic waves and the several experiments are carried out for some phantoms. Results show the superiority of the proposed method to the conventional method using power spectrum and also its usefulness for the tissue characterization. 30541 T00401030541 ^x This paper describes the implementation of a computerized radial pulse diagnosis by aids of a clinical expert. On this base, we composed of the radial pulse diagnosis system in korean traditional medicine. The system composed of a radial pulse wave detection system and a radial pulse diagnosis system. With a detection system, we detected Inyoung and Cheongu radial pulse wave and processed it. Then, we have got the characteristic parameters of radial pulse wave and also quantified that according to the method of Inyoung-Cheongu Comparison Radial Pulse Diagnosis. We defined the jugement standard of radial pulse diagnosis system and then we confirmed the possibility for realization of automatic radial pulse diagnosis in korean traditional medicine. 30545 T00401030545 ^x Microspheres are expected to be applied to biomedical areas such as solid-phase immunoassays, drug delivery systems, immunomagnetic cell separation. To synthesize microspheres for biomedical application, "two stage shot growth method" was developed. The uniformity ratio of synthesized microspheres was always smaller than 1.05. And the surface charge density (or the number of ionizable functional groups) of the microspheres synthesized by "two stage shot growth method" was 6~13 times higher than that of the microspheres synthesized by conventional seeded batch copolymerization. As a previous step for biomedical application, adsorption experiments of bovine albumin on microspheres were carried out under various conditions. The maximum adsorbed amount was obtained in the neighborhood of pH 4.5. Isoelectric point of bovine albumin is pH 5.0, so experimental result shows that it shifted to acid area. The adsorption isotherm was obtained, the plateau region was always reached at 2.Og/L (bulk concentration of bovine albumin).The effect of the kind and the amount of surface functional group was also examined. 30575 T00401030575 ^x A medical image workstation was developed using multimedia technique. The system based on PC-486DX was designed to acquire medical images produced by medical imaging instruments and related audio information, that is, doctors' reporting results. Input information was processed and analyzed, then the results were presented in the form of graph and animation. All the informations of the system were hierarchically related with the image as the apex. Processing and analysis algorithms were implemented so that the diagnostic accuracy could be improved. The diagnosed information can be transferred for patient diagnosis through LAN(local area network). 30592 T00401030592 ^x In the conventional infrared imaging system, complex infrared lens systems are usually used for directing collimated narrow infrared beams into the high speed 2-dimensional optic scanner. In this paper, a simple reflective infrared optic system with a 2-dimensional optic scanner is proposed for the realization of medical infrared thermography system. It has been experimentally proven that the intfrared thermography system composed of the proposed optic system has the temperature resolution of 0.1˚c under the spatial resolution of lmrad, the image matrix size of 256 X 240, and tile imaging time of 4 seconds. 30593 T00401030593 ^x In this paper, MIIS (Medical Image Information System) has been designed and implemented using INGRES RDBMS, which is based on a client/server architecture. The implemented system allows users to register and retrieve patient information, medical images and diagnostic reports. It also provides the function to display these information on workstation windows simultaneously by using the designed menu-driven graphic user interface. The medical image compression/decompression techniques are implemented and integrated into the medical image database system for the efficient data storage and the fast access through the network. 30594 T00401030594 ^x In this paper, computerized BEAM was implemented for the space domain analysis of EEG. Trans-formation from temporal summation to two-dimensional mappings is formed by 4 nearest point inter-polaton method. Methods of representation of BEAM are two. One is dot density method which classify brain electrical potential 9 levels by dot density of gray levels and the other is colour method which classify brain electrical 12 levels by red-green colours. In this BEAM, instantaneous change and average energy distribution over any arbitrary time interval of brain electrical activity could be observed and analyzed easily. In the frequency domain, the distribution of energy spectrum of a special band can easily be distinguished normality and abnormality. 30608 T00401030608 ^x Laboratory information system (LIS) is a key tool to manage laboratory data in clinical pathology. Our department has developed an information system for routine hematology using down-sized computer system. We have used an IBM 486 compatible PC with 16MB main memory, 210 MB hard disk drive, 9 RS-232C port and 24 pin dot printer. The operating system and database management system were SCO UNIX and SCO foxbase, respectively. For program development, we used Xbase language provided by SCO foxbase. The C language was used for interface purpose. To make the system use friendly, pull-down menu was used. The system connected to our hospital information system via application program interface (API), so the information related to patient and request details is automatically transmitted to our computer. Our system interfaced with fwd complete blood count analyzers(Sysmex NE-8000 and Coulter STKS) for unidirectional data tansmission from analyzer to computer. The authors suggests that this system based on down-sized computer could provide a progressive approach to total LIS based on local area network, and the implemented system could serve as a model for other hospital's LIS for routine hematology. 30609 T00401030609 ^x To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed a composite that is consisted of calcium phosphate and collagen. To use as the structural matrix of the composite, collagen was purified from human umbilical cord. The obtained collagen was treated by pepsin to remove telopeptides, and finally, the immune-free atelocollagen was produced: The cross linked atelocollagen was highly resistant to the collagenase induced collagenolysis. The cross linked collagen demonstrated an improved tensile strength. 30618 T00401030618 ^x This paper is a study on the design of adptive filter for QRS complex detection. We propose a simple adaptive algorithm to increase capability of noise cancelation in QRS complex detection with two stage adaptive filter. At the first stage, background noise is removed and at the next stage, only spectrum of QRS complex components is passed. Two adaptive filters can afford to keep track of the changes of both noise and QRS complex. Each adaptive filter consists of prediction error filter and FIR filter The impulse response of FIR filter uses coefficients of prediction error filter. The detection rates for 105 and 108 of MIT/BIH data base were 99.3% and 97.4% respectively. 30619 T00401030619 ^x To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed and produced a composite that is consisted of calcium phosphate and collagen. Human umbilical cord origin pepsin treated type I atelocollagen was used as the structural matrix, by which sintered or non-sintered carbonate apatite was encapsulated to form an inorganic-organic composite. With cross linking atelocollagen by UV ray irradiation, the resistance to both compressive and tensile strength was increased. Collagen degradation by the collagenase induced collagenolysis was also decreased. 30620 T00401030620 ^x We have developed a monoleaflet polymer valve as an inexpensive and viable alternative, especially for short-term use in the ventricular assist device or total artificial heart. The frame and leaflet of the polymer valve were made from polyurethane, To evaluate the hemodynamic performance of the polymer valve a comparative study of flow dynamics past a polymer valve and a St. Jude Medical prosthetic valve under physiological pulsatile flow conditions in vitro was made. Comparisons between the valves were made on the transvalvular pressure drop, regurgitation volume and maximum valve opening area. The polymer valve showed smaller regurgitation volume and transvalvular pressure drop compared to the mechanical valve at higher heart rate. The results showed that the functional characteristics of the polymer valve compared favorably with those of the mechanical valve at higher heart rate. 30621 T00401030621 ^x Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd:YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as Br.), and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased.To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained. 30622 T00401030622 ^x N1 and N2 gross neural action potentials were measured from the round window of the guinea pig cochlea at the onset of the acoustic stimuli. N1-N2 audiograms were made by means of regulating stimulant intensities in order to produce constant N1-N2 potentials as criteria for different input tone pip frequencies. The lowest threshold was measured with an input tone pip I5 dB SPL in intensity and 12 KHz in frequency when the animal was in normal physiological condition. The procedure of experimental measurements is explained in detail. This experimental approach is very useful for the investigation of the Cochlear function. Both noN1inear and active functions of the Cochlea can be monitored by N1-N2 audiograms. 30623 T00401030623 ^x In electrical impedance tomography(EIT), we use boundary current and voltage measurements toprovide the information about the cross-sectional distribution of electrical impedance or resistivity. One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.77 NMR machine. We implemented a resistivity mage reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the mage reconstruction algorithm and furture direction of the research. 30624 T00401030624 ^x A new method of digital image analysis technique for discrimination of cancer cell was presented in this paper. The object image was the Thyroid eland cells image that was diagnosed as normal and abnormal (two types of abnormal: follicular neoplastic cell, and papillary neoplastic cell), respectively. By using the proposed region segmentation algorithm, the cells were segmented into nucleus. The 16 feature parameters were used to calculate the features of each nucleus. A9 a consequence of using dominant feature parameters method proposed in this paper, discrimination rate of 91.11% was obtained for Thyroid Gland cells. 30625 T00401030625 ^x An electrical stimulator was designed to induce locomotion for paraplegic patients caused by central nervous system injury. Optimal stimulus parameters, which can minimize muscle fatigue and can achieve effective muscle contraction were determined in slow and fast muscles in Sprague-Dawley rats. Stimulus patterns of our stimulator were designed to simulate electromyographic activity monitored during locomotion of normal subjects. Muscle types of the lower extremity were classified according to their mechanical property of contraction, which are slow muscle (msoleus m.) and fast muscle (medial gastrocneminus m., rectus femoris m., vastus lateralis m.). Optimal parameters of electrical stimulation for slow muscles were 20 Hz, 0.2 ms square pulse. For fast muscle, 40 Hz, 0.3 ms square pulse was optimal to produce repeated contraction. Higher stimulus intensity was required when synergistic muscles were stimulated simultaneously than when they were stimulated individually. Electrical stimulation for each muscle was designed to generate bipedal locomotion, so that individual muscles alternate contraction and relaxation to simulate stance and swing phases. Portable electrical stimulator with 16 channels built in microprocessor was constructed and applied to paraplegic patients due to lumbar cord injury. The electrical stimulator restored partially gait function in paraplegic patients. 30626 T00401030626 ^x Two-Dimensional modelling of the Cochlear biomechanics is presented in this paper. The Laplace partial differential equation which represents the fluid mechanics of the Cochlea has been transformed into two-dimensional electrical transmission line. The procedure of this transformation is explained in detail. The comparison between one and two dimensional models is also presented. This electrical modelling of the basilar membrane (BM) is clearly useful for the next approach to the further. Development of active elements which are essential in the producing of the sharp tuning of the BM. This paper shows that two-dimension model is qualitatively better than one-dimensional model both in amplitude and phase responses of the BM displacement. The present model is only for frequency response. However because the model is electrical, the two-dimensional transmission line model can be extended to time response without any difficult. 30627 T00401030627 ^x A method has been proposed for the fully automatic detection of left ventricular endocardial boundary in 2D short axis echocardiogram using geometric model. The procedure has the following three distinct stages. First, the initial center is estimated by the initial center estimation algorithm which is applied to decimated image. Second, the center estimation algorithm is applied to original image and then best-fit elliptic model estimation is processed. Third, best-fit boundary is detected by the cost function which is based on the best-fit elliptic model. The proposed method shows effective result without manual intervention by a human operator. 30628 T00401030628 ^x The intelligent trajectory control method that controls moving direction and average velocity for a prosthetic arm is proposed by pattern recognition and force estimations using EMG signals. Also, we propose the real time trajectory planning method which generates continuous accelleration paths using 3 stage linear filters to minimize the impact to human body induced by arm motions and to reduce the muscle fatigue. We use combination of MLP and fuzzy filter for pattern recognition to estimate the direction of a muscle and Hogan's method for the force estimation. EMG signals are acquired by using a amputation simulator and 2 dimensional joystick motion. The simulation results of proposed prosthetic arm control system using the EMf signals show that the arm is effectively followed the desired trajectory depended on estimated force and direction of muscle movements. 30638 T00401030638 ^x A new neural network architecture for the recognition of patterns from images is proposed, which is partially based on the results of physiological studies. The proposed network is composed of multi-layers and the nerve cells in each layer are connected by spatial filters which approximate receptive fields in optic nerve fields. In the proposed method, patterns recognition for complicated images is carried out using global features as well as local features such as lines and end-points. A new generating method of matched filers representing global features is proposed in this network. 30659 T00401030659 ^x An implementation scheme of the magnetic nerve stimulator using a switching mode power supply is proposed. By using a switching mode power supply rather than a conventional linear power supply for charging high voltage capacitors, the weight and size of the magnetic nerve stimulator can be considerably reduced. Maximum output voltage of the developed magnetic nerve stimulator using the switching mode power supply is 3,000 volts and switching time is about 100 msec. Experimental results or human nerve stimulations using the developed stimulator are presented. 30768 T00401030768 ^x In this paper, we describe the design methodology and specifications of the developed module-based bedside monitors for patient monitoring. The bedside monitor consists of a main unit and module cases with various parameter modules. The main unit includes a 12.1" TFT color LCD, a main CPU board, and peripherals such as a module controller, Ethernet LAN card, video card, rotate/push button controller, etc. The main unit can connect at maximum three module cases each of which can accommodate up to 7 parameter modules. They include the modules for electrocardiograph, respiration, invasive blood pressure, noninvasive blood pressure, temperature, and SpO2 with Plethysmograph.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.3
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• pp.192-200
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• 2008

To evaluate the hemodynamic changes and the predictive factors of the clinical outcome in pediatric patients with moyamoya disease, we analyzed pre/post basal/acetazolamide stress brain perfusion SPECT with automated volume of interest (VOIs) method. Methods: Total fifty six (M:F = 33:24, age $6.7{\pm}3.2$ years) pediatric patients with moyamoya disease, who underwent basal/acetazolamide stress brain perfusion SPECT within 6 before and after revascularization surgery (encephalo-duro-arterio-synangiosis (EDAS) with frontal encephalo-galeo-synangiosis (EGS) and EDAS only followed on contralateral hemisphere), and followed-up more than 6 months after post-operative SPECT, were included. A mean follow-up period after post-operative SPECT was $33{\pm}21$ months. Each patient's SPECT image was spatially normalized to Korean template with the SPM2. For the regional count normalization, the count of pons was used as a reference region. The basal/acetazolamide-stressed cerebral blood flow (CBF), the cerebral vascular reserve index (CVRI), and the extent of area with significantly decreased basal/acetazolamide- stressed rCBF than age-matched normal control were evaluated on both medial frontal, frontal, parietal, occipital lobes, and whole brain in each patient's images. The post-operative clinical outcome was assigned as good, poor according to the presence of transient ischemic attacks and/or fixed neurological deficits by pediatric neurosurgeon. Results: In a paired t-test, basal/acetazolamide-stressed rCBF and the CVRI were significantly improved after revascularization (p<0.05). The significant difference in the pre-operative basal/acetazolamide-stressed rCBF and the CVRI between the hemispheres where EDAS with frontal EGS was performed and their contralateral counterparts where EDAS only was done disappeared after operation (p<0.05). In an independent student t-test, the pre-operative basal rCBF in the medial frontal gyrus, the post-operative CVRI in the frontal lobe and the parietal lobe of the hemispheres with EDAS and frontal EGS, the post-operative CVRI, and ${\Delta}CVRI$ showed a significant difference between patients with a good and poor clinical outcome (p<0.05). In a multivariate logistic regression analysis, the ${\Delta}CVRI$ and the post-operative CVRI of medial frontal gyrus on the hemispheres where EDAS with frontal EGS was performed were the significant predictive factors for the clinical outcome (p =0.002, p =0.015), Conclusion: With probabilistic map, we could objectively evaluate pre/post-operative hemodynamic changes of pediatric patients with moyamoya disease. Specifically the post-operative CVRI and the post-operative CVRI of medial frontal gyrus where EDAS with frontal EGS was done were the significant predictive factors for further clinical outcomes.

• Journal of Chest Surgery
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• v.31 no.5
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• pp.472-480
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• 1998

We reviewed the surgical results of intracardiac lateral tunnel Fontan procedure for the repair of functional single ventricles. Between 1990 and 1996, 104 patients underwent total cavopulmonary anastomosis. Patients' age and body weight averaged 35.9(range 10 to 173) months and 12.8(range 6.5 to 37.8) kg. Preoperative diagnoses included 18 tricuspid atresias and 53 double inlet ventricles with univentricular atrioventricular connection and 33 other complex lesions. Previous palliative operations were performed in 50 of these patients, including 37 systemic to pulmonary artery shunts, 13 pulmonary artery bandings, 15 surgical atrial septectomies, 2 arterial switch procedures, 2 resections of subaortic conus, 2 repairs of total anomalous pulmonary venous connection and 1 Damus-Stansel-Kaye procedure. In 19 patients bidirectional cavopulmonary shunt operation was performed before the Fontan procedure and in 1 patient a Kawashima procedure was required. Preoperative hemodynamics revealed a mean pulmonary artery pressure of 14.6(range 5 to 28) mmHg, a mean pulmonary vascular resistance of 2.2(range 0.4 to 6.9) wood-unit, a mean pulmonary to systemic flow ratio of 0.9(range 0.3 to 3.0), a mean ventricular end-diastolic pressure of 9.0 (range 3.0 to 21.0) mmHg, and a mean arterial oxygen saturation of 76.0(range 45.6 to 88.0)%. The operative procedure consisted of a longitudinal right atriotomy 2cm lateral to the terminal crest up to the right atrial auricle, followed by the creation of a lateral tunnel connecting the orifices of either the superior caval vein or the right atrial auricle to the inferior caval vein, using a Gore-Tex vascular graft with or without a fenestration. Concomitant procedures at the time of Fontan procedure included 22 pulmonary artery angioplasties, 21 atrial septectomies, 4 atrioventricular valve replacements or repairs, 4 corrections of anomalous pulmonary venous connection, and 3 permanent pacemaker implantations. In 31, a fenestration was created, and in 1 an adjustable communication was made in the lateral tunnel pathway. One lateral tunnel conversion was performed in a patient with recurrent intractable tachyarrhythmia 4 years after the initial atriopulmonary connection. Post-extubation hemodynamic data revealed a mean pulmonary artery pressure of 12.7(range 8 to 21) mmHg, a mean ventricular end-diastolic pressure of 7.6(range 4 to 12) mmHg, and a mean room-air arterial oxygen saturation of 89.9(range 68 to 100) %. The follow-up duration was, on average, 27(range 1 to 85) months. Post-Fontan complications included 11 prolonged pleural effusions, 8 arrhythmias, 9 chylothoraces, 5 of damage to the central nervous system, 5 infectious complications, and 4 of acute renal failure. Seven early(6.7%) and 5 late(4.8%) deaths occured. These results proved that the lateral tunnel Fontan procedure provided excellent hemodynamic improvements with acceptable mortality and morbidity for hearts with various types of functional single ventricle.

• Journal of Chest Surgery
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• v.35 no.10
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• pp.712-723
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• 2002

Substantial alterations in cerebral blood flow(CBF) are known to occur during cardiopulmonary bypass(CPB). Many investigators have speculated that these changes may be responsible for both minor and major cerebral damages after CPB. More recently, these changes in CBF have been observed to be intimately related to the arterial carbon dioxide tension(Pa$CO_2$) maintained during CPB. The present study was prospectively designed to investigate the clinical effects of normocapnic and hypercapnic CPB on the cerebral oxygen metabolism in cardiac surgery Material and Method: Thirty-six adult patients scheduled for elective cardiac surgery were randomized to either normocapnic group (Pa$CO_2$35~40 mmHg, n＝18) or hypercapnic group(Pa$CO_2$, 45~55 mmHg, n＝18) with moderately hypothermic nonpulsatile CPB(nasopharyngeal temperature of 29~3$0^{\circ}C$). In each patient, middle cerebral artery blood flow velocity( $V_{MCA}$), cerebral arteriovenous oxygen content difference (C(a-v) $O_2$), cerebral oxygen extraction(COE), cerebral metabolic rate for oxygen(CMR $O_2$), cerebral oxygen transport( $T_{E}$ $O_2$), $T_{E}$ $O_2$/CMR $O_2$ ratio, cerebral desaturation(internal jugular bulb blood oxygen saturation $\leq$ 50%), and arterial and jugular bulb blood gas were evaluated throughout the operation. Postoperative neuropsychologic complications were assessed in all patients. All variables were compared between the two groups. Result: VMCA(169.13 $\pm$ 8.32 vs 153.11 $\pm$8.98%), TE $O_2$(1,911.17$\pm$250.14 vs 1,757.40$\pm$249.56), $T_{E}$ $O_2$,/CMR $O_2$ ratio(287.38$\pm$28.051 vs 246.77$\pm$25.84), $O_2$ tension in internal jugular bulb (41.66$\pm$9.19 vs 31.50$\pm$6.09 mmHg), and $O_2$saturation in internal jugular bulb(68.97$\pm$10.96 vs 58.12$\pm$12.11%) during CPB were significantly lower in normocapnic group(p＝0.03), whereas hypercapnic group had lower C(a-v) $O_2$(3.9$\pm$0.3 vs 4.9$\pm$0.3 mL/dL), COE(0.3$\pm$0.03 vs 0.4$\pm$0.03), CMR $O_2$(5.8 $\pm$0.5 vs 6.8$\pm$0.6), and arterial blood pH(7.36$\pm$0.09 vs 7.46$\pm$0.07, p＝0.04) during CPB. Hypercapnic group had lower incidence of cerebral desaturation than normocapnic group(3 vs 9 patients, p=0.03). Duration of the neuropsychologic complication(delirium) were shorter in hypercapnic group than in normocapnic group(36 vs 60 hrs, p＝0.009). Conclusion: These findings suggest that hypercapnic CPB may have salutary effects on the cerebral oxygen metabolism and postoperative neurologic outcomes in cardiac surgery.surgery.

• Tuberculosis and Respiratory Diseases
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• v.41 no.5
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• pp.504-512
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• 1994

Background: It is well known that severe hypoxemia is often associated with liver cirrhosis without preexisting cardiac or pulmonary diseases. Pulmonary vascular impairments, more specifically, intrapulmonary shunting have been considered as a major mechanism. Intrapulmonary shunting arises from pulmonary vascular dilatation at the precapillary level or direct arteriovenous communication and has relationship with the characteristic skin findings of spider angioma. However, these results are mainly from Western countries where alcoholic and primary biliary cirrhosis are dominant cuases of cirrhosis. It is uncertain that the same is true in viral hepatitiss associated liver cirrhosis, which is dominant causes of liver cirrhosis in Korea. We investigated the incidences of hypoxemia and orthodeoxia in Korean cirrhotic patients dominantly composed of postnecrotic cirrhosis and the significance of intrapulmonary shunting as the suggested mechanism of hypoxemia, Method: We performed the arterial blood gas analysis separately both at the supine and errect position in 48 stable cirrhotic patients without the evidences of severe complications such as ascites, variceal bleeding, and hepatic coma. According to the results of arterial blood gas analysis, all patients were divided into hypoxemic and normoxemic group. In each group, pulmonary function test and Tc-99m-MAA whole body scan were performed. The shunting fraction was calculated based on the fact that the sum of cerebral and bilateral renal blood flow is 32% of the systemic blood flow. Results: The hypoxemia of $PaO_2$ less than 80 mmHg was observed in 9 patients(18.8%) and Orthodeoxia more than 10 mmHg was observed in 8 patients(16.7%). But there was no patient with significant hypoxemia of $PaO_2$ less than 60 mmHg. $PaO_2$ was significantly decreased in the patients with spider angioma than the pathients without spider angioma and showed no correlation with the serologic type and severities of liver function test findings. Any parameters of pulmonary function test did not demonstrate the difference between normoxemic and hypoxemic group. But hypoxemic group showed significantly increased shunt fraction of $11.4{\pm}4.1%$ than normoxemic group of $4.1{\pm}2.0%$ (p<0.05). Conclusions: Hypoxemia is not infrequently observed complication in liver cirrhosis and intrapulmonary shunting is suggested to p1ay a major ro1e in the development of hypxemia. But there was no great likelihood of clinically significant hypoxemia in our domestic cirrhotic patients predominantly composed of postnecrotic type.

• Health Policy and Management
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• v.27 no.4
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• pp.273-275
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• 2017

It has been forty years since the implementation of National Health Insurance (NHI) in South Korea. Following the 1977 legislature mandating medical insurance for employees and dependents in firms with more than 500 employees, South Korea expanded its health insurance to urban residents in 1989. Resultantly, total expenses of the National Health Insurance Service (NHIS) have greatly increased from 4.5 billion won in 1977 to 50.89 trillion won in 2016. With multiple insurers merging into the NHI system in 2000, a single-payer healthcare system emerged, along with separation policy of prescribing and dispensing. Following such reform, an emerging financial crisis required injections from the National Health Promotion Fund. Forty years following the introduction of the NHI system, both praise and criticism have been drawn. In just 12 years, the NHI achieved the fastest health population coverage in the world. Current medical expenditure is not high relative to the rest of the Organization for Economic Cooperation and Development. The quality of acute care in Korea is one of the best in the world. There is no sign of delayed diagnosis and/or treatment for most diseases. However, the NHI has been under-insured, requiring high-levels of out-of-pocket money from patients and often causing catastrophic medical expenses. Furthermore, the current environmental circumstances of the NHI are threatening its sustainability. Low birth rate decline, as well as slow economic growth, will make sustainment of the current healthcare system difficult in the near future. An aging population will increase the amount of medical expenditure required, especially with the baby-boomer generation of those born between 1955 and 1965. Meanwhile, there is always the problem of unification for the Korean Peninsula, and what role the health insurance system will have to play when it occurs. In the presidential election, health insurance is a main issue; however, there is greater focus on expansion and expenditure than revenue. Many aspects of Korea's NHI system (1977) were modeled after the German (1883) and Japanese (1922) systems. Such systems were created during an era where infections disease control was most urgent and thus, in the current non-communicable disease (NCD) era, must be redesigned. The Korean system, which is already forty years old, must be redesigned completely. Although health insurance benefit expansion is necessary, financial measures, as well as moral hazard control measures, must also be considered. Ultimately, there are three aspects that we must consider when attempting redesign of the system. First, the health security system must be reformed. NHI and Medical Aid must be amalgamated into one system for increased effectiveness and efficiency of the system. Within the single insurer system of the NHI must be an internal market for maximum efficiency. The NHIS must be separated into regions so that regional organizers have greater responsibility over their actions. Although insurance must continue to be imposed nationally, risk-adjustment must be distributed regionally and assessed by different regional systems. Second, as a solution for the decreasing flow of insurance revenue, low premium level must be increased to an appropriate level. Likewise, the national reserve fund (No. 36, National Health Insurance Act) must be enlarged for re-unification preparation. Third, there must be revolutionary reform of benefit package. The current system built a focus on communicable diseases which is inappropriate in this NCD era. Medical benefits must not be one-time events but provide chronic disease management. Chronic care models, accountable care organization, patient-centered medical homes, and other systems that introduce various benefit packages for beneficiaries must be implemented. The reimbursement system of medical costs should be introduced to various systems for different types of care, as is the case with part C (Medicare Advantage Program) of America's Medicare system that substitutes part A and part B. Pay for performance must be expanded so that there is not only improvement in quality of care but also medical costs. Moreover, beneficiaries of the NHI system must be aware of the amount of their expenditure through a deductible payment system so that spending can be profiled and monitored. The Moon Jae-in Government has announced its plans to expand the NHI system; however, it is important that a discussion forum is created so that more accurate analysis of the NHI, its environments, and current status of health care system, can take place for reforming NHI.

• Journal of Chest Surgery
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• v.38 no.9 s.254
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• pp.601-608
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• 2005

Background: To maximize the histological advantage and minimize the physiological disadvantage, we have been using the skeletonized gastroepiploic artey (GEA) as a free graft for total arterial revascularization. The aims of the current study was to assess the efficacy of the skeletonized GEA as a composite or extended graft for total arterial revascularization. Material and Method: Between January 2000 and Feburary 2005, 133 patients (43 female, mean age=61.8 yrs) undergoing coronary artery bypass grafting (CABG) with a skeletonized GEA as free graft (22 extended, 107 composite and 4 others) were enrolled in this study. Coronary angiograms were performed in the immediate (median 44 days, n=86), early (median 366 days, n=56) and midterm (median 984 days, n=29) postoperative periods. Result: There were 3 ($2.2\%$) early and 4 ($3.3\%$) late cardiac-related deaths. The mean number of distal anastomoses per patient was 3.34 for total graft and 1.92 for GEA graft. The immediate, early, and midterm GEA patency were 157/159 ($98.7\%$), 106/142 ($94.6\%$), and 53/56 ($94.6\%$), respectively. During follow-up, four patients required percutaneous intracoronary intervention because of GEA and target coronary artery stenosis or competitive flow. Conclusion: These data demonstrate satisfactory clinical and angiographic results in the skeletonized GEA as free graft for total arterial revascularizatioh. Although we need a careful longer follow-up, the skeletonized GEA as a free graft will be a valuable option 'to be' for CABG.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.114-118
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• 1997

Purpose: Functional MR imaging is the method of demonstrating changes in regional cerebral blood flow produced by sensory, motor, and any other tasks. Functional MR of visual cortex is performed as a patient stares a photic stimulation, so adaptable photic stimulation is necessary. The purpose of this study is to evaluate whether the size of photic stimulator can affect the degree of visual cortex activation. Materials and Methods: Functional MR imaging was performed in 5 volunteers with normal visual acuity. Photic stimulator was made by 39 light-emitting diodes on a plate, operating at 8Hz. The sizes of photic stimulator were full field, half field and focal central field. The MR imager was Siemens 1.5-T Magnetom Vision system, using standard head coil. Functional MRI utilized EPI sequence (TR/TE= 1.0/51. Omsec, matrix $No.=98{\times}128$, slice thickness=8mm) with 3sets of 6 imaging during stimulation and 6 imaging during rest, all 36 scannings were obtained. Activation images were obtained using postprocessing software(statistical analysis by Z-score), and these images were combined with T-1 weighted anatomical images. The activated signals were quantified by numbering the activated pixels, and activation a index was obtained by dividing the pixel number of each stimulator size with the sum of the pixel number of 3 study using 3 kinds of stimulators. The correlation between the activation index and the stimulator size was analysed. Results: Mean increase of signal intensities on the activation area using full field photic stimulator was about 9.6%. The activation index was greatest on full field, second on half field and smallest on focal central field in 4. The index of half field was greater than that of full field in 1. The ranges of activation index were full field 43-73%(mean 55%), half field 22-40 %(mean 32%), and focal central field 5-24%(mean 13%). Conclusion: The degree of visual cortex activation increases with the size of photic stimulator.

• Tuberculosis and Respiratory Diseases
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• v.66 no.4
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• pp.288-294
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• 2009

Background: A lung hyperinflation, or air trapping, caused by expiratory flow-limitation contributes to dyspnea in patients with chronic obstructive pulmonary disease (COPD). Forced expiratory volume in 1 second ($FEV_1$) has served as an important diagnostic measurement of COPD, but does not correlate with patient-centered outcomes such as dyspnea. Therefore, this study was performed to investigate the role of radiologic quantity in evaluating the dyspnea in patients with COPD by measuring lung hyperinflation in chest x-ray and high resolution chest tomography (HRCT). Methods: Fifty patients with COPD were enrolled in this study. Their subjective dyspnea score (modified Borg scale dyspnea index), spirometry, and lung volume were measured. Simultaneous hyperinflations of chest x-ray score ("chest score") and degree of emphysema of HRCT ("HRCT score") were measured. The "chest score" were composed of lung length, retrosternal space width, and height of the arc of the diaphragm and "HRCT score" were composed of severity and extent of emphysema. Results: The mean age of patients was 69 years old and their mean $FEV_1$ was 51.7%. The Borg score significantly correlated with parameters of spirometry and lung volume, including FVC, $FEV_1$, $FEV_1$/FVC, RV, RV/TLC, and DLCO. The Borg score correlated well with "HRCT score", but did not correlate with "chest score". Also, the Borg scale correlates inversely with body mass index. Conclusion: The quantity of emphysema on chest HRCT may serve as an objective marker of dyspnea in patients with COPD.

• The Korean Journal of Nuclear Medicine
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• v.36 no.3
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• pp.155-165
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• 2002

Purpose: The aim of this study was to identify the brain areas whose regional cerebral blood flow (rCBF) was changed in medial temporal lobe epilepsy (mTLE) using ${H_2}^{15}O-PET$. Materials and Methods: 12 patients with mTLE (6 left, 6 right mTLE) and 6 normal controls were scanned during a fixation baseline period and a sensory-motor condition where subjects pressed a button to an upward arrow. A voxel-based analysis using SPM99 software was peformed to compare the patient groups with the normal controls for the rCBF during fixation baseline period and for relative changes of rCBF during the sensory-motor task relative to fixation. Results: During the fixation baseline, a significant reduction of rCBF was found posterior insula bilaterally and right frontopolar regions in right mTLE patients compared to the normal controls. In left mTLE patients, the reduction was found in left frontopolar and temporal legions. During the sensory-motor task, rCBF increase over the fixation period, was reduced in left frontal and superior temporal legions in the right mTLE patients whereas in various areas of right hemisphere in left mTLE patients, relative to normal controls. However, the increased rCBF was also found in the left inferior parietal and anterior thalamic/fornix regions in both right and left mTLE patients compared to normal controls. Conclusion: Epilepsy induced changes were found not only in relative increase/decrease of rCBF during a simple sensory-motor control condition relative to a fixation rest condition but also in the relative rCBF distribution during the rest period.