• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.306-309
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• 2007

PXLM(Phosphor based x-ray light modulator) has a combined structure by phosphor, photoconductor, and liquid crystal and it can realize x-ray image of high resolution in clinical diagnosis area. In this study, we fabricated a photoconductor and investigated electrical and optical properties to confirm application possibility of radiator detector of PXLM structure. As photoconductor, amorphous selenium(a-Se), which is used most in DR(Digital radiography) of direct conversion method, was used and for formation of thin film, it was formed as $20{\mu}m-thick$ by using thermal vacuum evaporation system. For a produced a-Se film, through XRD(X-ray diffraction) and SEM(Scanning electron microscope), we investigated that amorphous structure was uniformly established and through optical measurement, for visible light of 40 $0\sim630nm$, it had absorption efficiency of 95 % and more. After fabricated a-Se film on the top of ITP substrate, hybrid structure was manufactured through forming $Gd_2O_3:Eu$ phosphor of $270{\mu}m-thick$ on the bottom of the substrate. As the result to confirm electrical property of the manufactured hybrid structure, in the case of appling $10V/{\mu}m$, leakage current of $2.5nA/cm^2$ and x-ray sensitivity of $7.31nC/cm^2/mR$ were investigated. Finally, we manufactured PXLM structure combined with hybrid structure and liquid crystal cell of TN(Twisted nematic) mode and then, investigated T-V(Transmission vs. voltage) curve of external light source for induced x-ray energy. PXLM structure showed a similar optical response with T-V curve that common TN mode liquid crystal cell showed according to electric field increase and in appling $50\sim100V$, it showed linear transmission efficiency of $12\sim18%$. This result suggested an application possibility of PXLM structure as radiation detector.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.65.1-65.1
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• 2013

The 2011 August 09 Flare is one of the largest X-ray flares of Sunspot Cycle 24 to attract a lot of attention for its various activities detected in coronal images. In this study we concern ourselves mostly on information of high energy electrons produced during this flare provided by hard X ray data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and radio data from the Korean Solar Radio Burst Locator (KSRBL) and Ondrejov. EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory are used to provide the context of magnetic reconnection. In our results, (1) HXR spectra have a rich spectral morphology. Initially it could be fit by one thermal component (T~30MK) and one single power law nonthermal spectrum, but later a better fit could be made by introducing an additional thermal component (T~55 MK). (2) Time delays between the KSRBL burst and the RHESSI hard X-ray emission were found which are more obvious at low frequencies and insignificant at high frequencies. (3) The HXR source lies in the core of the quadrupolar active region. In our interpretation based on AIA 94 A images, the outer part of the active region erupted to be blown out, leaving the intense hard X-ray emission concentrated in the core. We relate the appearance of the second thermal component to the evolution of the AIA 171 and 94 A images. The time delays of microwave peaks to HXR peaks are interpreted as indicating presence of trapped electrons in larger closed magnetic loops. With these result we conclude that the hard X ray and microwaves are due to impulsive acceleration in the low and high heights and a sigmoidal reconnection scenario.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.223-226
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• 1997

X-Ray Angiography has been gold standard for imaging of blood flow. However, patients have to take many risks such as catheterization procedure, iodine contrast agent and ionizing X-rays. MR Angiography has been suggested as a substitute for its non-hazard to patient. But the resolution and contrast was inferior to that of X-ray Angiography. Recently the resolution and the contrast have been much improved due to the development of fast imaging technique. Here we report some preliminary results of the MR Angiography we have implemented on 1 Tesla MRI unit.

• Imaging Science in Dentistry
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• v.38 no.1
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• pp.49-56
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• 2008

Purpose: Diagnostic estimation of destruction and formation of bone has the typical limit according to capacity of x-ray generator and image detector. So the aim of this study was to find out how much it can reproduce the shape and the density of bone in the case of using recently developed dental type of cone beam computed tomography, and which image is applied by new detector and mathematic calculation. Materials and Methods: Cone beam computed tomography (PSR 9000N, Asahi Roentgen Ind. Co., Ltd., Japan) and soft x-ray radiography were executed on dry mandible that was already decalcified during 5 hours, 10 hours, 15 hours, 20 hours, and 25 hours. Estimating and comparing of those came to the following results. Results: The change of inferior border of mandible and anterior border of ramus in the region of cortical bone was observed between first 5 and 10 hours of decalcification. The reproduction of shape and density in the region of cortical bone and cancellous bone can be hardly observed at cone beam computed tomography compared with soft x-ray radiography. The difference of decrease of bone density according to hours of decalcification increase wasn't reproduced at cone beam computed tomography compared with soft x-ray radiography. Conclusion: CBCT images revealed higher spatial resolution. However, contrast resolution in region of low contrast sensitivity is the inferiority of images' property.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.282-293
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• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• Journal of Korean Neurosurgical Society
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• v.59 no.5
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• pp.466-470
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• 2016

Objective : To determine imaging features that may separate adamantinomatous and papillary variants of craniopharyngiomas given that tumors with adamantinomatous signature features are associated with higher recurrence rates, morbidity, and mortality. We specifically reviewed calcification on CT, T1 bright signal intensity, and cystic change on T2 weighted images for differentiating these two types. Methods : We retrospectively reviewed the MRI and CT studies in 38 consecutive patients with pathologically proven craniopharyngiomas between January 2004 and February 2014 for the presence of calcification on CT scans, bright signal intensity on T1 weighted images, and cystic change on T2 weighted images. Results : Of the 38 craniopharyngiomas, 30 were adamantinomatous type and 8 were papillary type. On CT scans, calcification was present in 25 of 38 tumors. All calcified tumors were adamantinomatous type. Twenty four of 38 tumors had bright signal intensity on T1 weighted images. Of these 24 tumors, 22 (91.7%) were adamantinomatous and 2 were papillary type. Cystic change on T2 weighted images was noted in 37 of 38 tumors; only 1 tumor with papillary type did not show cystic change. Conclusion : T1 bright signal intensity and calcification on CT scans uniformly favor the adamantinomatous type over papillary type of craniopharyngioma in children. However, these findings are more variable in adults where calcification and T1 bright signal intensity occur in 70.6% and 58.8% respectively of adult adamantinomatous types of craniopharyngiomas.

• Imaging Science in Dentistry
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• v.34 no.1
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• pp.49-54
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• 2004

Primary intraosseous carcinoma (PIOC) is a rare odontogenic carcinoma defined as a squamous cell carcinoma arising within a jaw having no initial connection with the oral mucosa, and presumably developing from residues of the odontogenic epithelium. A 56-year-old patient who complained of delayed healing after extraction of upper left central incisor visited our department. The conventional radiographs showed a bony destructive lesion with ill-defined margin and moth-eaten appearance. On the computed tomographic images, the lesion perforated the labial cortex of alveloar bone, elevated the left nasal floor superiorly, and perforated partially both nasal floor. The magnetic resonance images showed low signal intensity at T2 and Tl weighted images at the area and adjacent soft tissue. Histologically, there were irregular epithelial islands with cell atypia, nuclear hyperchromatism, pleomorphism, atypical mitosis. The final diagnosis was PIOC.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.48-48
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• 2006

• Imaging Science in Dentistry
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• v.34 no.4
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• pp.199-202
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• 2004

The odontogenic myxoma is an benign, slow growing neoplasm which is of ectomesenchymal origin. This neoplasm occurs almost exclusively in the jaw bones and comprises 0.2% to 17.7% of odontogenic tumors. The odontogenic myxoma may show a wide spectrum of radiographic appearances, unilocular, multilocular radiolucency and a distinct or diffuse border, making the differential diagnosis difficult. We present a case of the odontogenic myxoma in the maxilla with conventional and recent image modalities. Occlusal film revealed a medially extended multilocular lesion with intralesional fine and straight trabeculations from the scalloped margin and buccal expansion and thinning of cortical bone. Computed tomogram revealed lesion showed equivalent density to the muscles in the left maxillary sinus with partial cortical discontinuity of medial wall and the tennis-racket pattern with internal straight trabeculations. MRI revealed intermediate signal intensity on Tl weighted image and high signal intensity on T2 weighted image. In Gd enhanced MR image, the peripheral portions of the lesion were enhanced.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.3
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• pp.26-35
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• 1980

The degradation of image due to the finite size of sensing devices has been one of the problems in all digital imaging systems. The basic study on the improvement of the spatial resolution was carried out in both spatial and frequency domains by the resolution recovery techniques which have been used in optics. Here, the techniques were applied to CT (Computerized Tomography) system, and image with finer resolution was obtained by these techniques. The basic theory is described and the results of the simulation are shown.