Bongsoo Lee

Differences in cognitive ability and hippocampal volume between Alzheimer’s disease, amnestic mild cognitive impairment, and healthy control groups, and their correlation

The study investigated differences in cognitive ability and hippocampal volume between groups of patients with Alzheimers disease (AD) and amnestic mild cognitive impairment (aMCI), and healthy control (HC) subjects, and explored the relationship between cognitive ability and hippocampal volume. Among the sub-tests of Korean version of the Consortium to Establish a Registry for Alzheimers Disease (CERAD-K), the Boston naming test score decreased in the order HC, aMCI, and AD. The hippocampal volumes of subjects with AD and aMCI were relatively smaller than those of HC individuals. There were strongly positive correlations between hippocampal volume and the scores for the Boston naming test. Discriminant analysis identified the Boston naming test as having the highest level of discrimination among the variables used to differentiate the three groups (89.9%). In conclusion, the Boston naming test accurately differentiated the three groups and was correlated with hippocampal volume. These results will be helpful for choosing an accurate and economically feasible test method that efficiently differentiates the three groups.

Development of a fiber-optic gamma endoscope to measure both optical and gamma images in a confined space

In nuclear medicine, obtaining information on the exact location, size, and dose of radiopharmaceuticals distributed on lesions is critically important. Therefore, we have fabricated a novel fiber-optic gamma endoscope (FOGE) to measure the shape and size of the radioisotope as well as the gamma-ray distribution simultaneously. To evaluate the performance of the novel FOGE, we obtained optical images and gamma images by using a USAF 1951 target and radioisotope sources, respectively. The experimental results demonstrated that the FOGE could be utilized to obtain both the location and the distribution of the radioactive isotope that emitted gamma-rays. Based on the results of this study, use of a flexible and thin FOGE would be valuable in nuclear medicine and nuclear safety technologies given the advantages of accurate dose-monitoring. Especially, improvements could be achieved in surgery technologies because the FOGE could be used in minimally invasive radioguided surgery owing to its thin form and flexibility.

Characterization of OTDR based fiber-optic humidity sensor

Summary form only given. In this study, the optical time-domain reflectometer (OTDR) based fiber-optic humidity sensor (FOHS) was fabricated to measure humidity in inaccessible hazardous environments. The sensing probe of FOHS consists of a single mode optical fiber and a moisture-sensitive material (mixture of HEC and PVDF) which varies its refractive index according to the relative humidity [1, 2]; here, the end of fiber was coated with the moisture-sensitive material by using the dip coating method. By Fresnel reflection between the sensing material and the single mode fiber, the optical power of the OTDR varies with the relative humidity. To optimize the FOHS, we evaluated the variation of optical power according to the contents (0.23, 0.33, 0.43, 0.53, and 0.63 g) of PVDF in the moisture-sensitive material and wavelengths (1310 and 1550 nm) of the laser source. As the result, the moisture-sensitive material containing 0.43 g of PVDF had the highest sensitivity with 1310nm laser source.

Feasibility study on remote gamma spectroscopy system with fiber-optic radiation sensor

In this study, we developed a remote gamma spectroscopy system based on fiber-optic radiation sensor (FORS) to detect species of gamma-emitting sources at large distances. In order to evaluate the performance of the gamma spectroscopy system, we measured the scintillating light intensity and gamma energy spectra as a function of the length of the plastic optical fiber (POF) and radioactivity of the gamma-ray source. Using the obtained experimental results, we selected the optimal inorganic scintillator as the FORS sensing material and measured the energy spectra. In addition, the photopeaks of the gamma-emitting sources were detected for different lengths of the POF and radioactivity of the 137Cs gamma-ray source. It is expected that the remote gamma spectroscopy system based on FORS can be an effective and convenient tool that can detect gamma-emitting sources at large distances, and can identify species of radioactive sources by measuring gamma energy spectra in nuclear facilities.

A simulation study on the effects of neuronal ensemble properties on decoding algorithms for intracortical brain–machine interfaces

BackgroundIntracortical brain–machine interfaces (BMIs) harness movement information by sensing neuronal activities using chronic microelectrode implants to restore lost functions to patients with paralysis. However, neuronal signals often vary over time, even within a day, forcing one to rebuild a BMI every time they operate it. The term “rebuild” means overall procedures for operating a BMI, such as decoder selection, decoder training, and decoder testing. It gives rise to a practical issue of what decoder should be built for a given neuronal ensemble. This study aims to address it by exploring how decoders’ performance varies with the neuronal properties. To extensively explore a range of neuronal properties, we conduct a simulation study.MethodsFocusing on movement direction, we examine several basic neuronal properties, including the signal-to-noise ratio of neurons, the proportion of well-tuned neurons, the uniformity of their preferred directions (PDs), and the non-stationarity of PDs. We investigate the performance of three popular BMI decoders: Kalman filter, optimal linear estimator, and population vector algorithm.ResultsOur simulation results showed that decoding performance of all the decoders was affected more by the proportion of well-tuned neurons that their uniformity.ConclusionsOur study suggests a simulated scenario of how to choose a decoder for intracortical BMIs in various neuronal conditions.

Dual type fiber-optic radiation sensor for measuring alpha and beta particles

In this study, we fabricated a dual type fiber-optic radiation sensor (DFORS) system using a spectroscopic technique to measure alpha and beta particles simultaneously and separately. The DFORS is composed of a sensing probe, a plastic optical fiber (POF), a photomultiplier tube (PMT)-amplifier system, and a multichannel analyzer (MCA). As sensing probes, a ZnS(Ag) film and CaF2(Eu) crystal were used for alpha and beta spectroscopy. And, we measured the alpha and beta energy spectra using the proposed DFORS system to discriminate species of the radioisotopes emitting alpha or beta particle. From the experimental results, we demonstrated that the small-sized, flexible, and insertable DFORS system can measure and discriminate the alpha and beta successfully with the spectral information of each radioisotope.