• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3943-3948
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• 2022

Single-photon emission computed tomography is one of the reliable pin-by-pin verification techniques for spent-fuel assemblies. One of the challenges with this technique is to increase the total fuel assembly verification speed while maintaining high verification accuracy. The aim of the present study, therefore, was to develop an artificial intelligence (AI) algorithm-based tomographic image analysis technique for partial-defect verification of fuel assemblies. With the Monte Carlo (MC) simulation technique, a tomographic image dataset consisting of 511 fuel-rod patterns of a 3 × 3 fuel assembly was generated, and with these images, the VGG16, GoogLeNet, and ResNet models were trained. According to an evaluation of these models for different training dataset sizes, the ResNet model showed 100% pattern estimation accuracy. And, based on the different tomographic image qualities, all of the models showed almost 100% pattern estimation accuracy, even for low-quality images with unrecognizable fuel patterns. This study verified that an AI model can be effectively employed for accurate and fast partial-defect verification of fuel assemblies.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1527-1532
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• 2023

The noise reduction algorithm using the non-local means (NLM) approach is very efficient in nuclear medicine imaging. In this study, the applicability of the NLM noise reduction algorithm in single-photon emission computed tomography (SPECT) images with a brain phantom and the optimization of the NLM algorithm by changing the smoothing factors according to various reconstruction methods are investigated. Brain phantom images were reconstructed using filtered back projection (FBP) and ordered subset expectation maximization (OSEM). The smoothing factor of the NLM noise reduction algorithm determined the optimal coefficient of variation (COV) and contrast-to-noise ratio (CNR) results at a value of 0.020 in the FBP and OSEM reconstruction methods. We confirmed that the FBP- and OSEM-based SPECT images using the algorithm applied with the optimal smoothing factor improved the COV and CNR by 66.94% and 8.00% on average, respectively, compared to those of the original image. In conclusion, an optimized smoothing factor was derived from the NLM approach-based algorithm in brain SPECT images and may be applicable to various nuclear medicine imaging techniques in the future.

• The Korean Journal of Nuclear Medicine
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• v.32 no.3
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• pp.211-224
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• 1998

The role of scintigraphic imaging has moved from the detection of lesions to the tissue-specific characterization of lesions over the past 2 decades. Major advances in nuclear medicine imaging include: 1) positron imaging, 2) improved instrumentation, such as the use of multidetector (dual or triple head) gamma cameras for single photon emission computed tomography, and 3) development of numerous new radiopharmaceuticals for positron or single photon imaging (labeled glucose analogue, amino acids, fatty acids, hormones, drugs, receptor ligands, monoclonal antibodies, etc). These advances have resulted in a significantly improved efficacy of radionuclide techniques for the evaluation of various tumors, including those within the liver. The current role of nuclear medicine in the evaluation of focal hepatic tumors is reviewed in this article with an emphasis on the clinical applications of various tracer studies and imaging findings.

• Journal of Biomedical Engineering Research
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• v.18 no.2
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• pp.113-120
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• 1997

This paper presents an optimal design for the SPECT reconstruction filter, based on a physical limit of SPECT lesion detection capability. To increase the performance of the filter on lesion detectability, the filter design was focused on increasing the local SyW ratio of a threshold lesion, that was determined by minimum detectable lesion size (MDU) from SPECT lesion detectabllity contrast-detail curve. The proposed filter showed flexible window characteristics of resolution recovery and noise smoothing for MDLSs in the resolution-limited and photon-limited regions, respectively, compennting for the relative impact of the main limitation factors on threshold detectability. The simulated results showed good adaptability of the proposed filter to the changes in physical parameters of photon counts, object contrast, and detector system resolution.

• Polymer(Korea)
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• v.24 no.2
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• pp.211-219
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• 2000

Fluorene-based light emitting polymer blends with liquid crystalline characteristics were studied on effective energy transfer and dichroic characteristics. Incorporating 0.5 wt% of the non-liquid crystalline into the liquid crystalline polymer suppressed the PL emission at 420 nm on photoexcitation at 360 nm, but generated a new PL emission of the non-liquid crystalline polymer at 480 nm. The highest PL intensity at 480 nm, which was 13 times stronger than those of the two polymers before blending, was observed for a blend with 2.0 wt% of the non-liquid crystalline polymer. When the molecules of the blends were aligned on a rubbed polyimide surface by a heating-cooling process, the dichroic ratio and the order parameter were 2.0 and 0.25, respectively. Time-correlated single photon counting (TCSPC) study revealed that the time required for energy transfer between the two chromophores was shortened by 93 ps when the blends were aligned on the rubbed polyimide surface by the heating-cooling process. The thermal treatment also enhanced the energy transfer efficiency by 9%.

• Clinical and Experimental Pediatrics
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• v.52 no.7
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• pp.804-810
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• 2009

Purpose : We investigated whether ictal single-photon emission computed tomography (SPECT) with prolonged injection of technetium-99m (99mTc) ethyl cysteinate dimer during repeated spasms can localize the epileptogenic foci in children with infantile spasms. Methods : Fourteen children with infantile spasms (11 boys, 3 girls; mean age, $2.2{\pm}1.3$ years) were examined. When a cluster of spasms was detected during video electroencephalography (EEG) monitoring, $^{99m}Tc$ ethyl cysteinate dimer was slowly and continuously injected for 2 minutes to determine the presence of ictal SPECT. For 7 children, the ictal and interictal SPECT images were visually analyzed, while for the remaining 7 children, the SPECT images were analyzed using the subtraction ictal SPECT coregistered to magnetic resonance imaging (MRI) (SISCOM) technique. Subsequently, we analyzed the association between the ictal SPECT findings and those of other diagnostic modalities such as EEG, MRI, and positron emission tomography (PET). Results : Increase in cerebral blood flow on ictal SPECT involved the epileptogenic foci in 10 cases6 cases analyzed by visual assessment and 4 analyzed by the SISCOM technique. The ictal SPECT and video-EEG findings showed moderate agreement (Kappa=0.57; 95% confidence interval, 0.18-0.96). Conclusion : Ictal SPECT with prolonged injection of a tracer could provide supplementary information to localize the epileptogenic foci in infantile spasms.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.61-67
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• 2011

The confocal laser scanning microscopy and two-photon microscopy was implemented based on a single laser source and an objective lens. We imaged and compared the morphology of identical sites of ex vivo human skin using both microscopes. The back-scattering emission from the sample provided the contrast for the confocal microscopy. The intrinsic autofluorescence and the second harmonic generation were used as the luminescence source for the two-photon microscopy. The wavelength of the Ti:Sapphire laser was tuned at 710 nm, which corresponds to the excitation peak of NADH and FAD in skin tissue. The various cell layers in the epidermis and the papillary dermis were clearly distinguished by both imaging modalities. The two-photon microscopy more clearly visualized the intercellular region and the nucleus of the cell compared to the confocal microscopy. The fibrous structures in the dermis were more clearly resolved by the confocal microscopy. Numerous cells in papillary dermal layer, as deep as $100\;{\mu}m$, were observed in both CLSM and two-photon microscopy. While most previous studies focused on fibrous structure imaging (collagen and elastin fiber) in the dermis, we demonstrated that the combined imaging with the CLSM and two-photon microscopy can be applied for the non-invasive study of the population, distribution and metabolism of papillary dermal cells in skin.

• Annals of Clinical Neurophysiology
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• v.10 no.1
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• pp.13-24
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• 2008

Functional neuroimaging, especially positron emission tomography (PET) and functional magnetic resonance imaging (MRI), is the main tool that allows the unveiling of the neurovascular events during a migraine attack. In migraine with aura, functional neuroimaging has contributed greatly to the understanding of the fundamental pathophysiology of the visual aura, whereas in migraine without aura, the PET findings of brainstem activation suggest a pivotal role of brainstem in the generation of migraine headache. In addition, voxel-based morphometry (VBM) method has provided an insight into the morphometric changes of the brain, which might be considered as a consequence of repeated migraine attacks. In this article, I will briefly discuss the main neuroimaging findings pertaining to the pathophysiology of migraine.

• Toxicological Research
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• v.29 no.1
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• pp.1-6
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• 2013

The process of drug discovery and development requires substantial resources and time. The drug industry has tried to reduce costs by conducting appropriate animal studies together with molecular biological and genetic analyses. Basic science research has been limited to in vitro studies of cellular processes and ex vivo tissue examination using suitable animal models of disease. However, in the past two decades new technologies have been developed that permit the imaging of live animals using radiotracer emission, X-rays, magnetic resonance signals, fluorescence, and bioluminescence. The main objective of this review is to provide an overview of small animal molecular imaging, with a focus on nuclear imaging (single photon emission computed tomography and positron emission tomography). These technologies permit visualization of toxicodynamics as well as toxicity to specific organs by directly monitoring drug accumulation and assessing physiological and/or molecular alterations. Nuclear imaging technology has great potential for improving the efficiency of the drug development process.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.10-14
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• 1997

Single pulse laser excitation at 656 nm and successive pulse excitation at 635.2 and 648.4 nm produced blue emission at 480 nm by two-step upconversion process in Tm/sup 3+/:LaF/sub 3/. The excited-state absorption cross-section of the /sup 3/F/sub 4/ to /sup 1/G/sub 4/ transition was estimated by a looping mechanism with cross-relaxation processes. The dynamics of up-conversion andthe possibility of the photon avalanche by a pulse laser excitation were studied by numerical simulation with the rate equation model.