• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.25-31
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• 2019

Purpose: Metals induce metal artifact during CT-image for therapy planning, and it occurs images distortion, which affects the volumetric measurement and radiation calculation. In the case of using megavoltage computed tomography(MVCT), the volume of metals can be measured as similar to true volume due to minimal metal artifact outcome. In this study, radiation assessment was conducted by comparing teeth volume from images of kVCT and MVCT of head and neck cancer patients, then assigning to kVCT image to calculate radiation after obtaining the similar volume of true teeth volume from MVCT. Also, formal IR image was able to verify the accuracy of radiation calculation. Material and method: 5 head and neck cancer patients who had intensity-modulated radiation therapy from Radixact^® Series were of the subject in this study. Calculations of radiation when constraining true teeth volume out of kVCT image(A-CT) and when designated specific HU after teeth assigned using MVCT image were compared with formal IR image. Treatment planning was devised at the same constraints and mean dose was measured at the radiation assess points. The points were anterior of the teeth, between PTV and the teeth, the interior of PTV near the teeth, and the teeth where 5cm distance from PTV. Result: A difference of metals volume from kVCT and MVCT image was mean 3.49±2.61cc, maximum 7.43cc. PTV was limited to where the internal teeth were fully contained. The results of PTV dose evaluation showed that the average CI value of the kVCT treatment planning without the artifact correction was 0.86, and the average CI value of the kVCT with the artifact correction using MVCT image was 0.9. Conclusion: When the Treatment Planning was made without correction of metal artifacts, the dose of PTV was underestimated, indicating that dose uncertainty occurred. When the computerized treatment plan was made without correction of metal artifacts, the dose of PTV was underestimated, indicating that dose uncertainty occurred.

• Proceedings of KOSOMES biannual meeting
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• 2008.05a
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• pp.159-164
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• 2008

In order to understand the spatio-temporal distribution of geochemical parametrs in surface sediments of the artificial Lake Shihwa in the vicinity of Kyunggi Hay in Korea, surface sediments were sampled at 14 sites in July 2007 and analyzed by CHN analyzer and ICP/MS. Metal concentrations in the sediments tended to be decreasing from the head to the mouth of the Lake Shihwa because of extreme pollutant discharge from various kinds of anthropogenic sources such as the Banweol and Shihwa Industrial Complex and cities. With the deposition of fine-grained sediments, high metal concentrations were also observed in the central part of lake. Although various programs(improvement of wastewater collection and treatment system, sea-lake water exchange etc) to improve the environmental conditions around the Lake Shihwa after dike construction were carried out, it was not dear to reach a good environmental quality. Therefore, further environmental programs should be conducted continuously for environmental improvement.

• Journal of Digital Contents Society
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• v.12 no.1
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• pp.49-55
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• 2011

Because of causing the geometrical transformation of the magnetic field, the patient implementing the fixation using the nonmagnetic metal screw causes the magnetic susceptibility artifact at an image. Thus, in this research, the distortion measure of the image according to the frequency oblique direction conversion tried to be compared in the magnetic susceptibility artifact occurence. First, the itself phantom inserting the nonmagnetic metal screw of the titanium component was made and the region of interest was set up and the frequency oblique direction the anterior - back side was converted to the right-to-left direction in the axial image and a right-to-left was converted to the upper side - bottom side in the coronal plane and the upper - bottom side was converted to the anterior - back side in the sagittal plane and the distortion measure of the region of interest was compared, it observed. In a result, when converting the frequency oblique direction, the distortion difference of the region of interest could be confirmed and it is considered to enhance the diagnostics efficiency changing the oblique direction appropriately.

• The Science & Technology
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• v.32 no.7 s.362
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• pp.71-75
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• 1999

몇해 전만 해도 대부분의 과학자들은 신장이나 심장과 같은 인간의 조직은 장기제공자로부터 직접 이식을 받거나 또는 플라스틱, 금속 그리고 컴퓨터칩으로 만든 완전 인공부붚므오만 대체할 수 있다고 믿고 있었다. 또 많은 사람들은 생세포와 인공폴리머의 혼성물인 바이오인공장기는 결코 제작할 수 없으며 이식용 인간장기의 부족을 충당할 수 있는 유일한 길은 동물의 장기를 사용하는 것 뿐이라고 생각했다. 그러나 앞으로는 조직공학이라는 새로운 생명과학기술의 진보로 간질환 환자가 자기의 간세포와 플라스틱섬유로 만든 '네오(신)장기' 이식으로 병을 치유할 수 있고 인슐린에 의존하던 당뇨병환자가 대체용 췌장 덕에 인슐린주사를 자주 맞을 필요가 없게 되며 신장병환자는 누구든지 자기의 세포로 키운 새로운 신장을 이식할 수 있게 되어 신장투석기의 모습이 세상에서 사라지게 되는 시대를 기대할 수 있게 되었다. 또 우리 몸을 형성하는 육체의 '부품'을 사고 팔 수 있는 시대가 뜻밖에도 빨리 다가올지 모른다고 생각하고 있는 과학자들도 있다.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.35-43
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• 2012

Purpose : PET/CT performed CT-based attenuation correction generates the beam hardening artifact by metallic implant. The attenuation correction causes over or underestimate of the area adjacent to metallic hip prosthetic material and change of $^{18}F$-FDG uptake. Also, the image quality and the diagnosability on genitourinary disease are reduced. Therefore, this study will evaluate the usefulness of MAR (Metal Artifact Reduction) algorithm method to improve the image quality on PET/CT. Materials and Methods : PET/CT was performed by fixing hip prosthesis in SPECT/PET phantom. In PET images with and Without MAR algorithm, the Bright streak, Dark streak, Metal region and Background area that appeared on CT were confirmed, and the change of each SUV (standardized uptake value) was analyzed. Also, in 15 patients who underwent total hip arthroplasty, each MAR algorithm and Without MAR algorithm and non attenuation correction was evaluated. Results : In PET image Without MAR algorithm, SUV of Bright streak region was $0.98{\pm}0.48$ g/ml; Dark streak region was $0.88{\pm}0.02$ g/ml; Metal region was $0.24{\pm}0.16$ g/ml, Background area was $0.91{\pm}0.18$ g/ml. In SUV of PET image with MAR algorithm, Bright streak region was $0.88{\pm}0.49$ g/ml, Dark streak region was $0.63{\pm}0.21$ g/ml, Metal region was $0.06{\pm}0.07$ g/ml, Background was $0.90{\pm}0.02$ g/ml. SUV generally decreased when applying MAR algorithm. In PET image Without MAR algorithm, SUVs of Bright region were higher than those measured in the Background, and it was false positive uptake. But, in PET image with MAR algorithm, SUVs of Bright region were similar to the Background, and false positive uptake disappeared. Conclusion : MAR algorithm could reduce an increase of $^{18}F$-FDG uptake due to attenuation correction in the hip surrounding tissue. However, decrease of SUV in Dark streak region should be considered in the future. Therefore, this study propose that the diagnostic accuracy can be improved in genitourinary diseases adjacent to metallic hip prosthesis, if provided PET images with and Without MAR algorithm, and non attenuation correction images at the same time.

• Journal of the Korean Society of Radiology
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• v.16 no.2
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• pp.131-139
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• 2022

The purpose of this study was to insert a pedicle screw into a pig thoracic vertebrae, a general CT scan(Non MAR), and a thoracic axial image obtained with the Metallic Artifact Reduction for Orthopedic Implants (O-MAR) to reduce artifacts. The image obtained by reconstructing the algorithm (Standard, Soft, Bone, Detail) was used using the image J program. Signal to noise ratio(SNR) and contrast to noise ratio(CNR) were compared and analyzed by obtaining measured values based on the given equation. And this study was to investigate tube voltage and algorithm suitable for CT scan for thoracic pedicle screw insertion. As a result, when non-MAR was used, the soft algorithm showed the highest SNR and CNR at 80, 100, 120, and 140 kVp, On the other hand, when MAR was used, the standard algorithm showed the highest at 80 kVp, and the standard and soft algorithms showed similar values at 100 kVp. At 120 kVp, the Soft and Standard algorithms showed similar values, and at 140 kVp, the Soft algorithm showed the highest SNR and CNR. Therefore, when comparing Non-MAR and MAR, even if MAR was used, SNR and CNR did not increase in all algorithms according to the change in tube voltage. In conclusion, it is judged that it is advantageous to use the Soft algorithm at 80, 100, 120, and 140 kVp in Non MAR, the Standard algorithm at 80 and 100 kVp in MAR, and the Soft algorithm at 120 and 140 kVp. This study is expected to serve as an opportunity to further improve the quality of images by using selective tube voltage and algorithms as basic data to help evaluate images of pedicle screw CT scans in the future.

• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.545-549
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• 2020

Although rare, the treatment options for a medial collateral avulsion fracture during total knee arthroplasty (TKA) range from conservative management using a cast and orthosis to internal fixation using metal screws. Bioabsorbable suture anchors have been used to replace metal fixators with distinct advantages, such as biocompatibility, radiolucency, and unnecessary second removal surgery, but complications, such as osteolysis, have been reported. This paper reports a potential risk of an extensive osteolysis-related suture anchor fixation of a medial collateral ligament (MCL) avulsion fracture during TKA in conjunction with a literature review.

• Journal of Biomedical Engineering Research
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• v.23 no.2
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• pp.119-130
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• 2002

The nonlinear finite element program has been developed to analyze the design performance of an artificial hip prosthesis and long term behavior of a treated femur with stems made of composite material after cementless total hip arthroplasty(THA). The authors developed the three dimentional FEM models of femoral bone with designed composite stem which was taken with elliptic cross section of 816 brick elements under hip contact load and muscle farce in simulating single leg stand. Using the program, density changes, stress distributions and micromotions of the material femoral bone were evaluated by changing fiber orientation of stems for selected manufacturing method such as plate cut and bend mold. The results showed that the composite materials such as AS4/PEEK and T300/976 gave less bone resorption than the metallic material such as cobalt chrome alloy, titanium alloy and stainless steal. It was found that increasing the long term stability of the prosthesis in the femur could be obtained by selecting the appropriate ply orientation and stacking sequence of composite.

• Journal of Dental Rehabilitation and Applied Science
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• v.40 no.2
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• pp.82-90
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• 2024

It often happens that a removable partial denture needs to be repaired due to tissue changes in the remaining alveolar ridge, fracture of the denture, or fracture of the abutment tooth. There are several advantages to retrofitting a customized surveyed crown under the existing RPD. Retrofitting a crown to the RPD decreases the economic burden to the patient and avoids the need for several appointments to fabricate a new RPD. It is difficult for artificial teeth used to repair dentures due to fractured natural teeth to have a shape similar to that of natural teeth, and to repair aesthetic artificial teeth, it is necessary to manufacture customized artificial teeth similar to the shape of each patient's teeth. Recently, CAD/CAM technology has been used to fabricate customized prosthetics on existing RPD to achieve high retention and fitness accuracy, and by manufacturing customized artificial teeth, more aesthetic and harmonious artificial tooth repair is possible. This is a case in which a denture was repaired using a digital method to fabricate a customized prosthesis on an existing partial denture and customized artificial teeth that mirrored the adjacent dentition, saving time and cost, simplifying the process, and achieving aesthetically and functionally satisfactory results.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.349-349
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• 2011

인공관절은 노인성 질환이나 자가 면역질환, 신체적인 외상 등으로 인하여 발생하는 관절의 손상 부위를 대체하기 위해 고안된 관절의 인공 대용물이다. 인공 관절 중 인공 고관절의 경우 관절 운동을 하는 라이너(Liner)와 헤드(Head) 부분이 인공관절의 수명을 결정하게 되는데, 헤드 부분에 메탈소재와 라이너 부분에 고분자 소재를 사용하는 MOP(metal on polymer) 구조의 인공관절은 충격흡수의 장점이 있는 반면 wear debris에 의한 골용해로 인하여 관절이 느슨해지는 문제점이 발생하여 재 시술의 주요 원인이 되고 있다. 현재 인공관절의 수명을 늘리기 위해 DLC, ZrO, TiN 등의 높은 경도 값을 갖는 박막을 금속헤드 위에 증착하여 상대재인 인공관절용 고분자 소재의 마모량을 줄이고자 하는 연구가 활발하게 진행되고 있다. 따라서 본 연구에서는 PIII&D(Plasma Immersion Ion Implantation & Deposition)공정을 이용하여 Co-Cr-Mo 합금 소재에 질소 이온을 주입 한 후 NbN 박막을 증착하여 상대재인 초고분자량 폴리에틸렌(UHMWPE)의 마모량을 줄이고자 하였다. NbN 박막의 특성을 평가하기 위해 XRD, XPS, AFM 등의 분석을 수행하였으며, 상대재인 초고분자량 폴리에틸렌의 마모량을 측정하기 위해 Pin-on-disk tribometer를 이용하여 마모 실험을 진행하였다. 마모 실험 결과, NbN 박막을 단순 증착한 경우, 현재 인공관절용 헤드(Head) 소재로 가장 널리 사용되고 있는 Co-Cr-Mo 합금에 비하여, 상대재인 초고분자량 폴리에틸렌의 마모량을 약 20% 감소시키는 것을 알 수 있었다. 또한, Co-Cr-Mo 합금 소재에 질소 이온주입을 하여 표면을 개질한 후, NbN 박막을 증착한 경우, 마모량이 최대 50%까지 감소하는 것을 확인할 수 있었다.