Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa (RP) or age related macular degeneration (AMD). Recently Korean consortium launched for developing retinal prosthesis. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we performed voltage stimulation experiment both in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). 8x8 grid layout MEA (electrode diameter: 30micrometer, electrode spacing: 200micrometer, and impedance: 50 k omega at 1 kHz) was used to record in-vitro retinal ganglion cell activity. Mono-polar electrical stimulation was applied through one of the 60 MEA channel, and the remaining channels were used for recording. The electrical stimulus was a constant voltage, charge-balanced biphasic, anodic-first square wave pulse without interphase delay, and 50 trains of pulse was applied with a period of 2 sec. Different electrical stimuli were applied. First, pulse amplitude was varied (voltage: 0.5~3.0 V). Second, pulse duration was varied (100~1,200microns). Evoked responses were analyzed by PSTH from averaged data with 50 trials. Charge density was calculated with Ohm's and Coulomb's law. In normal retina, by varying the pulse amplitude from 0.5 to 3 V with fixed duration of 500 microns, the threshold level for reliable ganglion cell response was found at 1.5 V. The calculated threshold of charge density was 2.123 mC/cm2. By varying the pulse duration from 100 to 1,200microns with fixed amplitude of 2 V, the threshold level was found at 300microns. The calculated threhold of charge density was 1.698 mC/cm2. Even after the block of ON-pathway with L-(1)-2-amino-4-phosphonobutyric acid (APB), electrical stimulus evoked ganglion cell activities. In this APB-induced degenerate retina, by varying the pulse duration from 100 to 1200 microns with fixed voltage of 2 V, the threshold level was found at 300microns, which is the same with normal retina. More experiment with APB-induced degenerate retina is needed to make a clear comparison of threshold of charge density between normal and degenerate retina.
Electric Stimulation ; Electrodes ; Fees and Charges ; Ganglion Cysts ; Interphase ; Jurisprudence ; Macular Degeneration ; Microelectrodes ; Prostheses and Implants ; Retina ; Retinal Diseases ; Retinal Ganglion Cells ; Retinaldehyde ; Retinitis Pigmentosa ; Visual Prosthesis

Since the output of retina for visual stimulus is carried by neurons of very diverse functional properties, it is not adequate to use conventional single electrode for recording the retinal action potential. For this purpose, we used newly developed multichannel recording system for monitoring the simultaneous electrical activities of many neurons in a functioning piece of retina. Retinal action potentials are recorded with an extra-cellular planar array of 60 microelectrodes. In studying the collective activity of the ganglion cell population it is essential to recognize basic functional distinctions between individual neurons. Therefore, it is necessary to detect and to classify the action potential of each ganglion cell out of mixed signal. We programmed M-files with MATLAB for this sorting process. This processing is mandatory for further analysis, e.g. poststimulus time histogram (PSTH), auto-correlogram, and cross-correlogram. We established MATLAB based protocol for waveform classification and verified that this approach was effective as an initial spike sorting method.
Action Potentials ; Classification ; Electrodes ; Ganglion Cysts ; Microelectrodes ; Neurons ; Retina ; Retinal Ganglion Cells* ; Retinaldehyde*

Embedded computing and wireless communication technology were used to develop a mobile biotelemetry system, featuring the functions of mobile measurement, wireless transmission, database archival, and internet retrieval of biomedical signals. Two PPCs (Pocket PC) with WLAN (wireless LAN) PC cards were used to simulate the communicating situation of biomedical signals between wireless sensors and a personal monitor. A PPC client program simulated the wireless sensors and a PPC server program simulated the personal medical monitor. Medical PDA was implemented by SBC (single board computer), LCD display, touch screen and Bluetooth module. Windows CE.net was ported as its operating system and the application program was developed using embedded Visual C++ 4. The measured transmission speed of ECG data was 2150 samples per second in the WLAN environment. For wireless internet connection, a Web-based server program was developed, able to display the biomedical signals of remote patients and be remotely monitored by medical doctors in a distant hospital. PDA data, which was archived at the server's database table, was transformed to an XML message and could be displayed on a Web browser as a signal graph. This system would be very useful for patients with chronic illness, especially in an emergent environment, and for containing medical cost in the aged society.
Chronic Disease ; Electrocardiography ; Humans ; Internet ; Web Browser

Obviously, the administration of the prescribed amount of activity to the patient requires proper operation of the dose calibrator, which shall be verified by implementing the required quality control on the instrument. This investigation examined the accuracy and precision of dose calibrator activity measurement of the radiopharmaceutical F-18 FDG. To investigate the status of the nuclear medicine centers in Korea for the performance of dose calibrators, 10 centers providing PET/CT system services in Korea were inspected in 2008. We measured accuracy and precision in 10 equipments in consideration of PET/CT model, installation area, and installation time. According to the results of comparative analysis of 10 dose calibrators used to measure radioactivity of F-18 FDG, accuracy was -5.00~4.50% and precision was 0.05~0.45%, satisfying the international standards, which are accuracy +/-10% and precision +/-5%. This study demonstrated that, for accurate measurements, no adjustment is necessary for a dose calibrator setting when measuring different dose calibrators of F-18 FDG activity prescriptions.
Humans ; Korea ; Nuclear Medicine ; Quality Control ; Radioactivity

Obviously, the administration of the prescribed amount of activity to the patient requires proper operation of the dose calibrator, which shall be verified by implementing the required quality control on the instrument. This investigation examined the accuracy and precision of dose calibrator activity measurement of the radiopharmaceutical F-18 FDG. To investigate the status of the nuclear medicine centers in Korea for the performance of dose calibrators, 10 centers providing PET/CT system services in Korea were inspected in 2008. We measured accuracy and precision in 10 equipments in consideration of PET/CT model, installation area, and installation time. According to the results of comparative analysis of 10 dose calibrators used to measure radioactivity of F-18 FDG, accuracy was -5.00~4.50% and precision was 0.05~0.45%, satisfying the international standards, which are accuracy +/-10% and precision +/-5%. This study demonstrated that, for accurate measurements, no adjustment is necessary for a dose calibrator setting when measuring different dose calibrators of F-18 FDG activity prescriptions.
Humans ; Korea ; Nuclear Medicine ; Quality Control ; Radioactivity

PURPOSE: To report a case of non-glaucomatous retinal nerve fiber layer (RNFL) defect associated with paravascular inner retinal defect (PIRD) in a patient with idiopathic epiretinal membrane (ERM).CASE SUMMARY: A 70-year-old male who was diagnosed with ERM in his right eye and pseudoexfoliative glaucoma in his left eye visited our clinic. His intraocular pressure was 14 mmHg in both eyes while using topical hypotensive medications in both eyes. His right eye showed no glaucomatous change of the optic disc head, and also no glaucomatous visual field defect on standard automated perimetry. Red-free fundus photography and swept-source optical coherence tomography showed an ERM and wedge-shaped RNFL defect starting from the PIRD, not the optic disc head. He was diagnosed with non-glaucomatous RNFL defect in the right eye and was told to stop using topical hypotensive medication for the right eye. After 2 years of discontinuing the medication, the IOP was within the normal range, the RNFL defect showed no progression, and the visual field remained stationary.CONCLUSIONS: A non-glaucomatous RNFL defect can develop in association with PIRD in patients with idiopathic ERM. Examinations for PIRD as well as evaluation of the optic disc head are therefore necessary in patients with ERM and RNFL defect.
Aged ; Epiretinal Membrane ; Glaucoma ; Head ; Humans ; Intraocular Pressure ; Male ; Nerve Fibers ; Photography ; Reference Values ; Retinaldehyde ; Tomography, Optical Coherence ; Visual Field Tests ; Visual Fields

BACKGROUND AND OBJECTIVES: The overriding influence of physical activity and the diurnal variation during ambulatory blood pressure monitoring (ABPM) has been well demonstrated. We prospectively evaluated the usefulness of electronic activity monitoring for deriving the actual physical activity and the diurnal variation of ABPM. SUBJECTS AND METHODS: 24-hour ABPM with using an electronic activity monitor was performed on ten normotensive volunteers and fifteen hypertensive subjects. To interpret the ABPM results of the fifteen hypertensive subjects, we obtained the actual awake/sleep periods of every subject with using an electronic activity monitor. RESULTS: The activity values obtained from the ten normotensive volunteers correlated well with the values of the blood pressure (BP) and the heart rate. In the hypertensives, the nocturnal mean BP derived by the actual period was significantly lower than that derived by the arbitrary period (130+/-16/81+/-13 mmHg versus 124+/-13/77+/-12 mmHg, respectively, p<0.05). The nocturnal BP fall derived by the actual period was significantly larger than that derived by the arbitrary period (14.9+/-8.7/11.6+/-7.5 mmHg versus 21.1+/-8.6/16.2+/-7.4 mmHg, respectively, p<0.01). Four among the 7 non-dippers determined by the arbitrary period were re-classified as dippers when the actual period was used. One among the 13 hypertensives, as determined by the arbitrary period, was also re-classified as a non-hypertensive. CONCLUSION: The electronic activity monitor was able to determine the actual activity level. The interpretation of ABPM may be altered by the use of the electronic activity monitor. These results suggest that the accuracy and reproducibility of the 24-hour ABPM will be improved by using an electronic activity monitor.
Blood Pressure ; Blood Pressure Monitoring, Ambulatory* ; Heart Rate ; Motor Activity ; Prospective Studies ; Volunteers

PURPOSE: Although there are over 40,000 licensed radiological technologists (RTs) in Korea, job competency standards have yet to be defined. This study aims to clarify the job competency of Korean RTs. METHODS: A task force team of 11 professional RTs were recruited in order to analyze the job competency of domestic and international RTs. A draft for the job competency of Korean RTs was prepared. A survey was then conducted sampling RTs and the attitudes of their competencies were recorded from May 21 to July 30, 2016. RESULTS: We identified five modules of professionalism, patient management, health and safety, operation of equipment, and procedure management and 131 detailed job competencies for RTs in Korea. “Health and safety” had the highest average score and “professionalism” had the lowest average score for both job performance and importance. The content validity ratios for the 131 subcompetencies were mostly valid. CONCLUSION: Establishment of standard guidelines for RT job competency for multidisciplinary healthcare at medical institutions may be possible based on our results, which will help educators of RT training institutions to clarify their training and education.
Advisory Committees ; Delivery of Health Care ; Education ; Humans ; Korea* ; Licensure ; Professionalism ; Republic of Korea ; Specialization* ; Technology, Radiologic ; Work Performance

BACKGROUND: IFN-gamma plays an important role in the host response to a mycobacterial infection. A complete IFN-gamma receptor 1 deficiency is a life-threatening condition because it renders patients highly susceptible t o a mycobacterial infection. Several mutations in the IFN-gamma receptor and STAT1 gene have been identified in the rare mycobacterial infections. These mutations have partial function of the IFN-gamma receptor and similar pathologic features to clinical tuberculosis. METHODS: The function of the IFN-gamma receptor was evluated in the patients with clinical tuerculosis. In addition, the DNA coding sequence of the IFNgR1 and STAT1 gene was also analyzed in disseminated tuberculosis patients who might have a defective IFN-gamma receptor. RESULTS: The cell surface expression levels of HLA-DR and CD64 in the PMBC after being stimulation with IFN-gamma (100Imicro/ml, 1000Imicro/ml) were increased in both controls and patients. However, the rate of increase in both groups was similar. The production of TNF-alpha in the response to stimulation with LPS was higher in the both groups (850.7+/-687.8 vs. 836.7+/-564.3 pg/ml). Pretreatment with IFN-gamma prior to LPS stimulation resulted infurther increase in TNF-alpha production in the both groups was similar. The known mutations in the IFNgR1 and STAT1 coding sequences were not found in the genomic DNA of patients wit disseminated tuberculosis. CONCLUSION: The functional and genetic defects of the IFN-gamma receptor were not identified in clinical tuberculosis. This suggests the defective IFN-gamma receptor that predispoe patiens to a BCG or NTM infection can not alone account for the cases of clinical tuberculosis.
Clinical Coding ; DNA ; HLA-DR Antigens ; Humans ; Mycobacterium bovis ; Tuberculosis* ; Tumor Necrosis Factor-alpha

BACKGROUND:In this study, a distribute characteristics on the bispectral coupling of EEG were examined according to the depth of anesthesia by using bispectum analysis a type of nonlinear signal processing. METHODS: 25 patients during the general anesthesia were studied. In the preprocess, base line correction and linear detrend was used. During the awakening state, preoperatively and postoperatively, appearance rate of bispectral coupling was observed that a strong appearance rate was represented in major frequency zone such as (15, 15) Hz but weak appearance rate investigated in the other minor frequency zone. Whilst anesthetized, a strong appearance rate revealed the low frequency range below (10, 10) Hz and a weak appearance rate viewed in the other frequency range. As such was compared with the delta ratio and spectrum edge frequency (SEF). RESULTS: The delta ratio showed significantly lower values at induction (3.60 +/- 0.98) and during the maintenance (5.0+/-1.74) of anaesthesia than preoperatively (10.30 +/- 2.44) and postoperatively (13.03 +/- 2.29)(P < 0.05). These results were consistent with the trend of delta ratio, namely that the index of evaluation for the depth of anesthesia, known as the reflex of the conscious level of patient's during anesthesia. While these results were not consistent with SEF analysis results that the index of evaluation for suppression level of patient's during recovery stage of anesthesia. SEF shows lower values at maintenance (17.00 +/- 1.22) and postoperatively (12.20 +/- 1.53) than preoperatively (22.50 +/- 1.75) and at the induction (22.40 +/- 1.18) of anesthesia(P < 0.05). CONCLUSIONS: The bispectrum analysis method provided useful information about the index of evaluation according to the level of unconsciousness and suppression among other evaluation factor on depth of anesthesia.
Anesthesia* ; Anesthesia, General ; Electroencephalography* ; Humans ; Reflex ; Unconsciousness