• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.20.1-20.1
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• 2011

타이타늄의 내부식 특성은 분해하기 어려운 산화물의 보호피막을 형성 함으로서 무독성의 생체친화적 성질을 가지고 있어 심장밸브, 인공 뼈 등 신체 조직의 이식에 사용될 만큼 인체에 무해한 금속으로 의료용으로 많이 응용되고 있다. 본 강연에서는 생체재료로써 의료용 타이타늄의 적용현황을 소개하고, 이를 통해 타이타늄의 가치를 다시 한번 재고하고자 한다. 타이타늄 임플란트에서 그 표면과 골사이의 골유착(osseointegration)은 성공적인 임상결과를 얻기 위한 중요한 요소 중의 하나이다. 1960년대에는 기계가공 된 매끈한 형태의 타이타늄 표면을 시작으로 골유착을 얻고자 하였다. 이러한 시도를 통해 임플란트가 점차 대중화 되면서 1980년대 부터 타이타늄 표면과 골과의 유착을 조기에 실현하고, 골유착 강도를 강화하기 위해 다양한 표면기술이 개발 되기 시작하였다. 크게는 1. 표면적 증대 기술, 2. 화학적 방식을 통한 표면기술, 3. 생체활성 유도형 표면기술, 4. 서방출 등을 응용한 골유도 및 활성 조절형 표면기술 등이 개발되어 제품화 되거나 그 연구가 진행 중에 있다. 다양한 표면기술에 대한 흐름을 이해하고 이에 대한 장, 단점을 이해함으로써 앞으로 기술적으로 극복해 나가야 할 과제를 제시하고자 한다. 또한 다양한 표면기술에 대한 유효성과 그에 대한 중, 장기 안전성에 대한 중요성을 이해하고 이를 평가하기 위한 여러 가지 절차와 방법 소개를 통해 신뢰성 있는 연구개발이 될 수 있기 바란다.

• Resources Recycling
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• v.11 no.4
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• pp.37-43
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• 2002

As the consumption of galvanized steels in cans and automobiles and the quantity of scraps increase, the recycling problems of EAF dust become a important problem. Valuable metals such as Fe, Zn, Pb are of continued interest to metallurgists. To recover the valuable metal and to remove the toxicity of EAF dust, high temperature smelting process is or researching as a pilot scale. The Reduction kinetics of Zn in EAF dust is so important in a view of the economic consideration of the process. In this study, the kinetics behavior of Zn in EAF dust were measured as a point of application in high temperature smelting process. The rate control step in ZnO and franklinite is revealed to be chemical reaction on the reaction surface.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.9-17
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• 2017

Purpose: The tissue description and electron density indicated by the Computed Tomography(CT) number (also known as Hounsfield Unit) in radiotherapy are important in ensuring the accuracy of CT-based computerized radiotherapy planning. The internal metal implants, however, not only reduce the accuracy of CT number but also introduce uncertainty into tissue description, leading to development of many clinical algorithms for reducing metal artifacts. The purpose of this study was, therefore, to investigate the accuracy and the clinical applicability by analyzing date from SMART MAR (GE) used in our institution. Methode: and material: For assessment of images, the original images were obtained after forming ROIs with identical volumes by using CIRS ED phantom and inserting rods of six tissues and then non-SMART MAR and SMART MAR images were obtained and compared in terms of CT number and SD value. For determination of the difference in dose by the changes in CT number due to metal artifacts, the original images were obtained by forming PTV at two sites of CIRS ED phantom CT images with Computerized Treatment Planning (CTP system), the identical treatment plans were established for non-SMART MAR and SMART MAR images by obtaining unilateral and bilateral titanium insertion images, and mean doses, Homogeneity Index(HI), and Conformity Index(CI) for both PTVs were compared. The absorbed doses at both sites were measured by calculating the dose conversion constant (cCy/nC) from ylinder acrylic phantom, 0.125cc ionchamber, and electrometer and obtaining non-SMART MAR and SMART MAR images from images resulting from insertions of unilateral and bilateral titanium rods, and compared with point doses from CTP. Result: The results of image assessment showed that the CT number of SMART MAR images compared to those of non-SMART MAR images were more close to those of original images, and the SD decreased more in SMART compared to non-SMART ones. The results of dose determinations showed that the mean doses, HI and CI of non-SMART MAR images compared to those of SMART MAR images were more close to those of original images, however the differences did not reach statistical significance. The results of absorbed dose measurement showed that the difference between actual absorbed dose and point dose on CTP in absorbed dose were 2.69 and 3.63 % in non-SMRT MAR images, however decreased to 0.56 and 0.68 %, respectively in SMART MAR images. Conclusion: The application of SMART MAR in CT images from patients with metal implants improved quality of images, being demonstrated by improvement in accuracy of CT number and decrease in SD, therefore it is considered that this method is useful in dose calculation and forming contour between tumor and normal tissues.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.519-534
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• 2019

When the fresh water from the artificial lakes (Ganwolho and Bunamho) were discharged to Cheonsu Bay in summer to prevent the flood over the reclaimed farmland near the lakes, the impact on water qualities (nutrients, organic matters, trace metals) within the bay was investigated through four surveys (June, July, August and October, 2011). Dissolved inorganic nitrogen (DIN) increased about as much as 3-4 times over the whole water column when the freshwater was discharged. And the main species composition of DIN changed from ammonia to nitrate. Dissolved inorganic phosphorus (DIP) decreased as much as 2 times in surface waters, but increased as much as 1.5 times in deep waters, and also silicate concentrations increased as much as 3-4 times in deep waters of the inner bay. The N/P ratios in Chunsu bay seawaters were much higher (2 to 7 times) than the Redfield ratio when the freshwaters were discharged, which indicated the phosphorus limiting in the phytoplankton growth. Dissolved organic carbon (DOC) and nitrogen (DON) increased as much as about 2 times. In addition, particulate organic matters (POC, PON, POP, Bio-Si) increased as much as above 2 times in the surface waters of the inner bay. Trace metals (Fe, Mn, Co, Ni, Cu) increased in the surface waters of the inner bay, but dissolved Cd concentrations decreased as much as 2 times. Therefore, when the contaminated fresh waters from the artificial lakes were discharged into the bay, nutrients, organic matters and trace metals generally increased compared to normal period. Since the phytoplankton bloom occurred in the surface waters of the inner bay, dissolved oxygens at the surface waters were oversaturated and hence hypoxic in the deep waters. Highly enriched nutrients concentrations were found in deep waters of the inner bay, which was accompanied with the hypoxic condition. Finally, the water quality in the inner bay of the Chunsu bay was deteriorated from less than grade 3 in normal periods to grade 5 when the freshwaters from the artificial lakes were discharged in summer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.23-29
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• 2022

To detect harmful chemical substances in seawater, we fabricated a prototype sensor and evaluated its performance. The prototype sensor consisted of a detector, housing, and driving circuit. We built the detector by printing an Indium-Tin-Oxide (ITO) nanoparticle film on a flexible substrate, and it had two detection parts for simultaneous detection of temperature and HNS concentration. The housing connected the detector and the driving circuit and was made of Teflon material to prevent chemical reactions that may affect sensor performance. The driving circuit supplied electric power, and display measured data using a bridge circuit and an Arduino board. We evaluated the sensor performances such as response (ΔR), the limit of detection (LOD), response time, and errors to confirm the specification.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.30-36
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• 2022

A sensor is needed to continuously and automatically measure the change in HNS concentration in industrial facilities that directly discharge to the sea after water treatment. The basic function of the sensor is to be able to detect ppb levels even at room temperature. Therefore, a method for increasing the sensitivity of the existing sensor is proposed. First, a method for increasing the conductivity of a film using a conductive carbon-based additive in a nanoparticle thin film and a method for increasing ion adsorption on the surface using a catalyst metal were studied.. To improve conductivity, carbon black was selected as an additive in the film using ITO nanoparticles, and the performance change of the sensor according to the content of the additive was observed. As a result, the change in resistance and response time due to the increase in conductivity at a CB content of 5 wt% could be observed, and notably, the lower limit of detection was lowered to about 250 ppb in an experiment with organic solvents. In addition, to increase the degree of ion adsorption in the liquid, an experiment was conducted using a sample in which a surface catalyst layer was formed by sputtering Au. Notably, the response of the sensor increased by more than 20% and the average lower limit of detection was lowered to 61 ppm. This result confirmed that the chemical resistance sensor using metal oxide nanoparticles could detect HNS of several tens of ppb even at room temperature.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.1-10
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• 2010

Purpose: The effect of artifact was analyzed, which occurs from fiducial marker during the liver Image Guided Radiation Therapy (IGRT) using the fiducial marker. Materials and Methods: The size of artifact of fixed fiducial marker and length of mobile fiducial marker locus were measured using the On-Board Imager system (OBI) and CT simulator, and 2D-2D matching and 3D-3D matching were carried out, respectively, and at this time, the coordinates transition value of couch was analyzed. Results: The measurement of fixed fiducial marker artifact size indicated CT 4.90, 8.10, 12.90, 19.70 mm and OBI 5.60, 10.60, 14.70, 29.40 mm based on the reference CT slice thickness of 1.25, 2.50, 5.00, and 10.00 mm. Meanwhile, the measurement of mobile fiducial marker locus length indicated CT 42.00, 43.10, 46.50 mm, and OBI 43.40, 46.00, 49.30 mm. The coordinates transition of 1.00, 2.00, and 8.00 mm occurred between 2D-2D matching and 3D-3D matching. Conclusion: It was confirmed that the therapy error increased during IGRT due to the influence of artifact when CT slice thickness increased. Thus, it may be desirable to acquire the image less than 2.50 mm in slice thickness when IGRT is implemented using the fiducial marker.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.15 no.1
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• pp.74-78
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• 2019

Atypical teratoid rhabdoidal tumor(AT/RT) is a rare and fast-growing tumor usually diagnosed in childhood. Routine magnetic resonance imaging(MRI) assessment of AT/RT patients is done to detect metastatic tumors and recurrent lesions. The purpose of this case report is to present a case about caries treatment of a 3-year-8-month old female patient with AT/RT under general anesthesia. A 3-year-8-month old patient with AT/RT visited Seoul National University Dental Hospital for caries treatment. At the first dental visit, she was receiving chemotherapy. Multiple caries were observed from clinical and radiographic examination. The dental procedure was successfully performed under general anesthesia. Patients with brain tumor may take routine MRI to detect metastatic tumors and recurrent lesions. Dentists should take into consideration of possible dislodgement of restoration by ferromagnetic properties and artifact formation on MRI image. Ready-made zirconia crowns can be a good restoration option for such patients.

• Journal of the Korean Society of Radiology
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• v.83 no.5
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• pp.1032-1045
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• 2022

Peripheral arterial disease (PAD) is common in elderly patients. Lower-extremity CT angiography (LE-CTA) can be useful for detecting PAD and planning its treatment. PAD can also be accurately evaluated on reconstructed monoenergetic images (MEIs) from low kiloelectron volt (keV) to high keV images using dual-energy CT. Low keV images generally provide higher contrast than high keV images but also feature more severe image noise. The noise-reduced virtual MEI reconstruction algorithm, called the Mono+ technique, was recently introduced to overcome such image noise. Therefore, this pictorial review aimed to present the imaging findings of PAD on LE-CTA and compare low and high keV images with those subjected to the Mono+ technique. We found that, in many cases, the overall and segmental image qualities were better and metal artifacts and venous contamination were decreased in the high keV images.

• Journal of dental hygiene science
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• v.4 no.3
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• pp.103-109
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• 2004

The present study prepared 72 test samples - 24 made of amalgam alloy, 24 of Verabond (Ni-Cr alloy) for crown and 24 of Talladium $^{TM}alloy$ for denture - according to the manufacturers' manuals and general method in consideration of the width of the mesial-distal dental crown of the lower $1^{st}$ molar and MOD cavity in clinics, put them in a 200 ml beaker containing 80 ml of artificial saliva, and measured their galvanic corrosion at distances of 0 mm, 7 mm and 40 mm after 7 days. Isolated metals in the electrolyte such as Cu, Ag, Ni, Cr, Sn, Zn and Hg were quantitatively analyzed with Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES, JY-50P, VG Elemental Co. France), and from the results were drawn conclusions as follows. First, Cu, Sn, Ag, Hg and Zn were highly advantageous when amalgam contacted gold alloy compared to Ni-Cr alloy for crown and Talladium alloy for denture. In addition, although gold alloy was finest in terms of oral tissue and biocompatibility, it was most disadvantageous when it was with amalgam. Second, when amalgam contacted gold alloy, heavy metals such as Ni and Cr were not isolated at all because gold alloy did not contain such elements but Sn was isolated as much as $227.1{\pm}18.0035{\mu}g/cm^2$ although it was not included in the composition either. Hg was also isolated. These elements are assumed to have been isolated from amalgam itself. Third, when amalgam alloy was apart from gold alloy 0 mm, 7 mm and 40 mm, Cu and Ag showed significance but Hg did not. This suggests that gold alloy must not be used together with amalgam, and must not be used between dissimilar prostheses regardless of distance. Fourth, when amalgam alloy contacted Ni-Cr alloy for crown, Ag was not isolated from the amalgam, but Zn, Ni, Sn, Hg and Cu were isolated in order of quantity. Significance was observed according to distance - 0 mm, 7 mm and 40 mm. Hg was not isolated but heavy metals Ni and Cr were isolated. If amalgam alloy was in the opposite arch or it was apart from Ni-Cr alloy for crown, the isolation Hg was less than that when amalgam alloy contacted Ni-Cr alloy for crown. Fifth, when amalgam alloy contacted Talladium alloy for denture, significance was observed at distances of 0mm, 7 mm and 40 mm. Hg was not isolated but heavy metals Ni and Cr were isolated. If amalgam alloy was in the opposite arch or it was apart from Talladium alloy for denture, the isolation Hg was less than that when amalgam alloy contacted Talladium alloy for denture. Sixth, according to the result of ICPES test on Cu, Sn, Ag, Hg, Zn, Ni and Cr of amalgam alloy, gold ally, Verabond and Talladium alloy when these alloys contacted artificial saliva, significance was observed in Cu and Hg. Seventh, when amalgam alloy contracted two non-precious metals Ni-Cr alloy for crown and Talladium alloy for denture in artificial saliva, significance was observed in the isolated by-products of Hg, Ni and Cr according to distance.