Time filter

Source Type

Cui M.L.,Research Institute of Biomedical Engineering | Ahn H.S.,Research Institute of Biomedical Engineering | Kim J.Y.,Yeungnam University | Lee D.S.,Yeungnam University | And 3 more authors.
Journal of the Korean Surgical Society | Year: 2010

Purpose: Ischemia and reperfusion (I/R) injury is a major cause of hepatic failure after liver surgery, but there is no direct method to monitor it in real-time (like an electrocardiogram in heart disease) during surgery. Recently we found the possible role of bioelectrical impedance (BEI) to monitor I/R injury in liver. But the mechanism responsible for ischemia-related BEI changes has not been clearly determined. Methods: The authors used an LCR meter to quantify BEI changes at 0.12 KHz. Livers were subjected to 70% partial ischemia for 120 minutes, and ATP contents, cation changes in extracellular fluid (ECF; determined using an in vivo intracellular microdialysis technique), hepatocyte sizes, and histological changes were then examined. Results: Liver tissue BEI was found to increase gradually during the first 60 minutes of ischemia and then tended to plateau. During the same period, intracellular ATP contents decreased to below 20% of the baseline level, [Na+] in ECF decreased from 150.4±3.8 to 97.8±10.6 mmol/L, and [K+] in ECF increased from 7.5±0.3 to 34.3±5.5 mmol/L during the first 60 minutes of ischemia. Hepatocyte diameter increased by ∼20% during the first 60 minutes of ischemia. Conclusion: This study suggests that BEI changes during hepatic ischemia are probably caused by sodium and potassium concentration changes in the ECF due to reduced intracellular ATP contents.

Choi M.-H.,Research Institute of Biomedical Engineering | Kim H.-J.,Research Institute of Biomedical Engineering | Kim J.-H.,Research Institute of Biomedical Engineering | Kim H.-S.,Research Institute of Biomedical Engineering | And 6 more authors.
Geriatrics and Gerontology International | Year: 2013

Aim: This study investigated the correlation between response time of the 1-back task and changes of blood oxygen saturation (SpO2) by supplying three different levels of oxygen (21%, 1L/min; 93%, 1L/min; 93%, 5L/min) in the elderly. Methods: A total of 17 older adults (mean age 72.9±4.7years) participated in the experiment. A 1-back task was used as a cognitive task. The experiment consisted of three phases, which included the adaptation phase (3min) after oxygen administration, the control phase (2min) that maintained a stable condition before the task, and the task phase (2min) where the 1-back task was carried out. SpO2 was measured during each phase. Results: As concentration level and supply of oxygen increased, SpO2 increased and response time of the 1-back task decreased. Conclusion: Highly concentrated oxygen administration can increase SpO2 in the elderly and an increase in cognitive performance, such as a decrease in response time, can be observed. © 2012 Japan Geriatrics Society.

Lee B.,Research Institute of Biomedical Engineering | Yoo W.J.,Research Institute of Biomedical Engineering | Jang K.W.,Research Institute of Biomedical Engineering | Cho D.H.,Research Institute of Biomedical Engineering | And 7 more authors.
IEEE Transactions on Nuclear Science | Year: 2010

In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for brachytherapy dosimetry. Organic scintillators are made from a polystyrene base with wavelength-shifting fluors, and they do not disturb the radiation field due to their tissue or water-equivalent characteristics in a wide range of energies. The fiber-optic radiation sensor developed for this study provides a fast real-time response and convenient usage for brachytherapy dosimetry. For more accurate measurement, we have measured Cerenkov light using a dummy fiber and avoided dose measurement errors arising from high dose gradients in brachytherapy dosimetry. The Cerenkov light has been eliminated using a modified subtraction method. Also, the relative depth dose without the dose generated from Cerenkov lights is measured and compared with the results obtained using conventional EBT dosimetry films. © 2010 IEEE.

Yoo W.J.,Research Institute of Biomedical Engineering | Shin S.H.,Research Institute of Biomedical Engineering | Jeon D.,Research Institute of Biomedical Engineering | Hong S.,Research Institute of Biomedical Engineering | And 5 more authors.
Optics Express | Year: 2013

For real-time dosimetry in electron beam therapy, an integrated fiber-optic dosimeter (FOD) is developed using a water-equivalent dosimeter probe, four transmitting optical fibers, and a multichannel lightmeasuring device. The dosimeter probe is composed of two inner sensors, a scintillation sensor and a Cerenkov sensor, and each sensor has two different channels. Accordingly, we measured four separate light signals from each channel in the dosimeter probe, simultaneously, and then obtained the scintillation and Cerenkov signals using a subtraction method. To evaluate the performance of the integrated FOD, we measured the light signals according to the irradiation angle of the electron beam, the depth variation of the solid water phantom, and the electron beam energy. In conclusion, we demonstrated that the pure scintillation and Cerenkov signals obtained by an integrated FOD system based on a subtraction method can be effectively used for calibrating the conditions of high-energy electron beams in radiotherapy. © 2013 Optical Society of America.

Kim K.-A.,Chungbuk National University | Yoo W.J.,Research Institute of Biomedical Engineering | Jang K.W.,Research Institute of Biomedical Engineering | Moon J.,Research Institute of Biomedical Engineering | And 5 more authors.
Radiation Protection Dosimetry | Year: 2013

In this study, a fibre-optic dosemeter (FOD) using an organic scintillator with a diameter of 0.5 mm for photon-beam therapy dosimetry was fabricated. The fabricated dosemeter has many advantages, including water equivalence, high spatial resolution, remote sensing and real-time measurement. The scintillating light generated from an organic-dosemeter probe embedded in a solid-water stack phantom is guided to a photomultiplier tube and an electrometer via 20 m of plastic optical fibre. Using this FOD, the skin dose and the percentage depth dose in the build-up region according to the depths of a solid-water stack phantom are measured with 6- and 15-MV photon-beam energies with field sizes of 10310 and 20320 cm2, respectively. The results are compared with those measured using conventional dosimetry films. It is expected that the proposed FOD can be effectively used in radiotherapy dosimetry for accurate measurement of the skin dose and the depth dose distribution in the build-up region due to its high spatial resolution. © The Author 2012. Published by Oxford University Press. All rights reserved.

Discover hidden collaborations