• The Korean Journal of Nuclear Medicine
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• v.39 no.6
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• pp.413-420
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• 2005

Purpose: Neuroreceptor PET studies require 60-120 minutes to complete and head motion of the subject during the PET scan increases the uncertainty in measured activity. In this study, we investigated the effects of the data-driven head mutton correction on the evaluation of endogenous dopamine release (DAR) in the striatum during the motor task which might have caused significant head motion artifact. Materials and Methods: $[^{11}C]raclopride$ PET scans on 4 normal volunteers acquired with bolus plus constant infusion protocol were retrospectively analyzed. Following the 50 min resting period, the participants played a video game with a monetary reward for 40 min. Dynamic frames acquired during the equilibrium condition (pre-task: 30-50 min, task: 70-90 min, post-task: 110-120 min) were realigned to the first frame in pre-task condition. Intra-condition registrations between the frames were performed, and average image for each condition was created and registered to the pre-task image (inter-condition registration). Pre-task PET image was then co-registered to own MRI of each participant and transformation parameters were reapplied to the others. Volumes of interest (VOI) for dorsal putamen (PU) and caudate (CA), ventral striatum (VS), and cerebellum were defined on the MRI. Binding potential (BP) was measured and DAR was calculated as the percent change of BP during and after the task. SPM analyses on the BP parametric images were also performed to explore the regional difference in the effects of head motion on BP and DAR estimation. Results: Changes in position and orientation of the striatum during the PET scans were observed before the head motion correction. BP values at pre-task condition were not changed significantly after the intra-condition registration. However, the BP values during and after the task and DAR were significantly changed after the correction. SPM analysis also showed that the extent and significance of the BP differences were significantly changed by the head motion correction and such changes were prominent in periphery of the striatum. Conclusion: The results suggest that misalignment of MRI-based VOI and the striatum in PET images and incorrect DAR estimation due to the head motion during the PET activation study were significant, but could be remedied by the data-driven head motion correction.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.199-208
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• 2016

$^{99}mTc-MAG_3$ Renal scan is a method that acquires dynamic renal scan image by using $^{99}mTc-MAG_3$ and dynamically visualizes process of radioactive agent being absorbed to kidney and excreted continuously. Once the test starts, ratio in both kidneys in 1~2.5 minutes was measured to obtain split renal function and split renal function can be expressed in ratio based on overall renal function. This study is based on compares split renal function obtained from data acquired from posterior detector, which is a conventional renal function test method, with split renal function acquired from the geometric mean of values obtained from anterior and posterior detectors, and studies utility of attenuation compensation depending on difference in geometric mean kidney depth. From July, 2015 to February 2016, 33 patients who undertook $^{99}mTc-MAG_3$ Renal scan(13 male, 20 female, average age of 44.66 with range of 5~70, average height of 160.40cm, average weight of 55.40kg) were selected as subjects. Depth of kidney was shown to be 65.82 mm at average for left and 71.62 mm at average for right. In supine position, 30 out of 33 patients showed higher ratio of deep-situated kidney and lower ratio of shallow-situated kidney. Such result is deemed to be due to correction by attenuation between deep-situated kidney and detector and in case where there is difference between the depth of both kidneys such as, lesions in or around kidney, spine malformation, and ectopic kidney, ratio of deep-situated kidney must be compensated for more accurate calculation of split renal function, when compared to the conventional test method (posterior detector counting).

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.237-247
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• 1993

Activity ratio of two radioactive primary fission products which had sufficiently different half-lives was expressed as functions of cooling time and irradiation histories in which average burnup, irradiation time, cycle interval time and the dominant fissile material of the spent fuel were included. The gamma-ray spectra of 36 samples from 6 spent PWR fuel assemblies irradiated in Kori unit-1 reactor were obtained by a spectrometric system equipped with a high purity germanium gamma-ray detector. Activity ratio $^{l44}$Ce $^{l37}$Cs, analyzed from each spectrum, was used for the calculation of cooling time. The results show that the radioactive fission products $^{l44}$Ce and $^{l37}$Cs are considered as useful monitors for cooling time determination because the estimated cooling time by detection of activity ratio $^{l44}$Ce $^{l37}$Cs agreed well with the operator declared cooling time within relative difference of $\pm$5 % despite the low counting rate of the gamma-ray of $^{l44}$Ce (about 10$^{-3}$ count per second). For the samples with several different irradiation histories, the determined cooling time by modeled irradiation history showed good agreement with that by known irradiation history within time difference of $\pm$0.5 year. From this result, it would be expected to be possible to estimate reliably the cooling time of spent nuclear fuel without the exact information about irradiation history. The feasibility study on identification of and/or sorting out spent nuclear fuel by applying the technique for cooling time determination was also performed and the result shows that the detection of activity ratio $^{l44}$Ce $^{l37}$Cs by gamma-ray spectrometry would be usefully applicable to certify spent nuclear fuel for the purpose of safeguards and management in a facility in which the samples dismantled or cut from spent fuel assemblies are treated, such as the post irradiation examination facility.mination facility.

• Progress in Medical Physics
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• v.18 no.2
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• pp.87-92
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• 2007

A thermal neutron beam facility utilizing a typical tangential beam port for Neutron Capture Therapy was installed at the HANARO, 30 MW multi-purpose research reactor. Mixed beams with different physical characteristics and relative biological effectiveness would be emitted from the BNCT irradiation facility, so a quantitative analysis of each component of the mixed beams should be performed to determine the accurate delivered dose. Thus, various techniques were applied including the use of activation foils, TLDs and ionization chambers. All the dose measurements were perform ed with the water phantom filled with distilled water. The results of the measurement were compared with MCNP4B calculation. The thermal neutron fluxes were $1.02E9n/cm^2{\cdot}s\;and\;6.07E8n/cm^2{\cdot}s$ at 10 and 20 mm depth respectively, and the fast neutron dose rate was insignificant as 0.11 Gy/hr at 10 mm depth in water The gamma-ray dose rate was 5.10 Gy/hr at 20 mm depth in water Good agreement within 5%, has been obtained between the measured dose and the calculated dose using MCNP for neutron and gamma component and discrepancy with 14% for fast neutron flux Considering the difficulty of neutron detection, the current study support the reliability of these results and confirmed the suitability of the thermal neutron beam as a dosimetric data for BNCT clinical trials.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.4
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• pp.272-279
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• 2007

Purpose: The aim of this study was to evaluate the discriminating nature of $^{123}I-FP-CIT$ SPECT in patients with parkinsonism. Methods: $^{123}I-FP-CIT$ SPECT images acquired from the 18 normal controls; NC ($60.4{\pm}10.0$ yr) and 237 patients with parkinsonism ($65.9{\pm}9.2$ yr) were analyzed. From spatialIy normalized images, regional counts of the caudate, putamen, and occipital lobe were obtained using region of interest method. Binding potential (BP) was calculated with the ratio of specific to nonspecific binding activity at equilibrium. Additionally, the BP ratio of putamen to caudate (PCR) and asymmetric Index (ASI) were measured. Results: BPs of NC $3.37{\pm}0.57,\; 3.10{\pm}0.41,\; 3.23{\pm}0.48$ for caudate, putamen, whole striatum, respectively) had no significant difference with those of essential tremor; ET ($3.31{\pm}0.64,\; 3.06{\pm}0.61,\; 3.14{\pm}0.63$) and Alzheimer's disease; AD (3.33 $\pm$0.60, 3.29$\pm$0.79, 3.31$\pm$0.70), but were higher than those of Parkinson's disease; PD (1.92$\pm$0.74, 1.39$\pm$0.68, 1.64$\pm$0.68), multiple system atrophy; MSA (2.36$\pm$1.07, 2.16$\pm$0.91, 2.26$\pm$0.96), and dementia with Lewy body; DLB (1.95$\pm$0.72, 1.64$\pm$0.65, 1.79$\pm$0.66)(p<0.005). PD had statisticalIy lower values of PER and higher values of ASI than those of NC (p<0.005). And PD had significantIy lower value of PCR, higher ASI and lower BP in the putamen and whole striatum than MSA (p<0.05). Conclusion: Dopamine transporter image of $^{123}I-FP-CIT$ SPECT was a good value in differential diagnosis of parkinsonism.

• Journal of Radiation Protection and Research
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• v.40 no.2
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• pp.79-86
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• 2015

$^3He$ gas has been used for neutron monitors as the neutron converter owing to its advantages such as high sensitivity, good ${\gamma}$-discrimination capability, and long-term stability. However, $^3He$ is becoming more difficult to obtain in last few years due to a global shortage of $^3He$ gas. Accordingly, the cost of a neutron monitor using $^3He$ gas as a neutron converter is becoming more expensive. Demand on a neutron monitor using an alternative neutron conversion material is widely increased. $^{10}B$ has many advantages among various $^3He$ alternative materials, as a neutron converter. In order to develop a neutron converter using $^{10}B$ (actually $B_4C$), we calculated the optimal thickness of a neutron converter with a Monte Carlo simulation using MCNP6. In addition, a neutron converter was fabricated by the Ar sputtering method and the neutron signal detection efficiencies were measured with respect to various thicknesses of fabricated a neutron converter. Also, we developed a 2-dimensional multi-wire proportional chamber (MWPC) for neutron beam profile monitoring using the fabricated a neutron converter, and performed experiments for neutron response of the neutron monitor at the 30 MW research reactor HANARO at the Korea Atomic Energy Research Institute. The 2-dimensional MWPC with boron ($B_4C$) neutron converter was proved to be useful for neutron beam monitoring, and can be applied to other types of neutron imaging.

• The Korean Journal of Nuclear Medicine
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• v.39 no.1
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• pp.26-33
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• 2005

Purpose: The purpose of this study is to evaluate migration of technetium-99m hexamethylpropylene amine oxime ($^{99m}Tc$-HMPAO) labeled immature and mature dendritic cells (DC) in the mouse. Methods: DC were collected from bone marrow (BM) of tibiae and femurs of mice. Immature and mature DC from BM cells were radiolabeled with $^{99m}Tc$-HMPAO. To evaluate the functional and phenotypic changes of DC from radiolabeling, the allogeneic mixed lymphocyte reaction (MLR) and fluorescence-activated cell sorting (FACS) analysis were performed before and after labeling with $^{99m}Tc$-HMPAO. Migration of intravenously injected DC (iv-DC) was assessed by serial gamma camera images of mice with or without subcutaneous tumor. Percent injected dose per gram (%ID/g) was calculated in lungs, liver, spleen, kidneys, and tumor through dissection of each mice after 24 hours of injection. Results: Labeling efficiency of immature and mature DC were $60.4{\pm}5.4%\;and\;61.8{\pm}6.7%$, respectively. Iv-DC initially appeared in the lungs, then redistributed mainly to liver and spleen. Migration of mature DC to spleen was significantly higher than that of immature DC ($38.3{\pm}4.0%\;vs.\;32.2{\pm}4.1%$ in control group, $40.4{\pm}4.1%\;vs.\;35.9{\pm}3.8%$ in tumor group; p<0.05). Migration to tumor was also significantly higher in mature DC than in immature DC ($2.4{\pm}0.3%\;vs\;1.7{\pm}0.2%$; p=0.034). Conclusion: Assessment of migration pattern of DC in mice was possible using $^{99m}Tc$-HMPAO labeled immature and mature DC. Migration of mature DC to spleen and tumor was higher than that of immature DC when they were i.v. injected.