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Reduced Effect of kV-CBCT Dose by Use of Shielding Materials in Radiation Therapy
Hyeonjong Jo(조현종),Euntae Park(박은태),Junghoon Kim(김정훈) 한국방사선학회 2018 한국방사선학회 논문지 Vol.12 No.4
CBCT is useful for improving the accuracy of the treatment site, but Repeated use increases the exposure dose. In this study, we aimed to provide basic data for dose reduction in CBCT implementation by dataization the simulating and dose reduction effect using shielding substance. Material in this study, Analyzation the photon beam by simulate the CBCT Through MCNPX and then calculate the absorption dose of body organ at shooting moment of thoracic abdominal position as target UF-Revise simulated body. At this time. Dose reduction effects at this time were evaluated according to the texture of materials and presence of shielding materials( lead, antimony, barium, sulfate, tungsten, bismuth). When CBCT was taken without shielding, the dose was calculated to be high in the breast and spine, and the dose in the esophagus and lung was calculated to be low. The doses according to the shield material were calculated as barium sulfate, antimony, bismuth, lead, and tungsten. The shielding rate was the highest in the thymus (73.6%) and the breast (59.9%) compared with the dose reduction according to presence or absence of the shield. However, it showed the lowest shielding rate in lung (2.1%) and spine (12.6%). CBCT는 치료부위의 정확도 향상에 유용하지만, 반복적인 사용으로 피폭선량이 높아지는 단점이 있다. 이에 본 연구에서는 차폐체를 사용한 모의실험과 선량감소 효과를 데이터화하여 CBCT 시행 시 선량 저감화를 위한 기초자료를 제공하고자 한다. 본 연구에서는 MCNPX를 통해 CBCT를 모사하여 광자선을 분석한 후, UF-revised 인체 모의 피폭체를 대상으로 흉복부 촬영 시 장기의 흡수선량을 계산하였다. 이 때, 차폐체(납, 안티몬, 황산바륨, 텅스텐, 비스무스) 유무와 차폐 재질에 따른 장기선량을 평가하였다. 차폐를 하지 않고 CBCT 촬영을 하였을 경우 유방과 척추에서 선량이 높게 계산되었으며, 식도와 폐에서 선량이 낮게 계산되었다. 차폐체 재질에 따른 선량은 황산바륨, 안티몬, 비스무스, 납, 텅스텐 순으로 선량이 높게 계산되었다. 차폐체 유무에 따른 선량 감소율을 평가해 보면 흉선(73.6%), 유방(59.9%)에서 가장 차폐율이 높고, 폐(2.1%), 척추(12.6%)에서 가장 낮은 차폐율을 보였다.
방사선 치료 시 차폐물질 사용에 따른 kV-CBCT 선량감소 효과
조현종 ( Hyeonjong Jo ),박은태 ( Euntae Park ),김정훈 ( Junghoon Kim ) 한국방사선학회 2018 한국방사선학회 논문지 Vol.12 No.4
CBCT는 치료부위의 정확도 향상에 유용하지만, 반복적인 사용으로 피폭선량이 높아지는 단점이 있다. 이에 본 연구에서는 차폐체를 사용한 모의실험과 선량감소 효과를 데이터화하여 CBCT 시행 시 선량 저감화를 위한 기초자료를 제공하고자 한다. 본 연구에서는 MCNPX를 통해 CBCT를 모사하여 광자선을 분석한 후, UF-revised 인체 모의 피폭체를 대상으로 흉복부 촬영 시 장기의 흡수선량을 계산하였다. 이 때, 차폐체(납, 안티몬, 황산바륨, 텅스텐, 비스무스) 유무와 차폐 재질에 따른 장기선량을 평가하였다. 차폐를 하지 않고 CBCT 촬영을 하였을 경우 유방 과 척추에서 선량이 높게 계산되었으며, 식도와 폐에서 선량이 낮게 계산되었다. 차폐체 재질에 따른 선량 은 황산바륨, 안티몬, 비스무스, 납, 텅스텐 순으로 선량이 높게 계산되었다. 차폐체 유무에 따른 선량 감소율을 평가해 보면 흉선(73.6%), 유방(59.9%)에서 가장 차폐율이 높고, 폐(2.1%), 척추(12.6%)에서 가장 낮은 차폐율을 보였다. CBCT is useful for improving the accuracy of the treatment site, but Repeated use increases the exposure dose. In this study, we aimed to provide basic data for dose reduction in CBCT implementation by dataization the simulating and dose reduction effect using shielding substance. Material in this study, Analyzation the photon beam by simulate the CBCT Through MCNPX and then calculate the absorption dose of body organ at shooting moment of thoracic abdominal position as target UF-Revise simulated body. At this time. Dose reduction effects at this time were evaluated according to the texture of materials and presence of shielding materials( lead, antimony, barium, sulfate, tungsten, bismuth). When CBCT was taken without shielding, the dose was calculated to be high in the breast and spine, and the dose in the esophagus and lung was calculated to be low. The doses according to the shield material were calculated as barium sulfate, antimony, bismuth, lead, and tungsten. The shielding rate was the highest in the thymus (73.6%) and the breast (59.9%) compared with the dose reduction according to presence or absence of the shield. However, it showed the lowest shielding rate in lung (2.1%) and spine (12.6%).
Biomechanical analysis of 4 types of short dental implants in a resorbed mandible
Lee, Hyeonjong,Park, Soyeon,Noh, Gunwoo Elsevier 2019 The Journal of prosthetic dentistry Vol.121 No.4
<P><B>Abstract</B></P> <P><B>Statement of problem</B></P> <P>Short implants have been increasingly used in the aging society. However, studies which explain the difference of stress distribution according to different connections in short implant treatment are scarce.</P> <P><B>Purpose</B></P> <P>The purpose of this finite element (FE) analysis was to evaluate the stress and strain distribution of short implants and surrounding bone under static and cyclic loading conditions with 4 different connections.</P> <P><B>Material and methods</B></P> <P>Three-dimensional models of 4 types of implant systems were considered: internal tissue level, internal tissue level wide, internal bone level (IB), and external bone level. Each system had different types of abutment, implant, and screw with the resorbed mandibular segment of the bone block. Static FE analysis was performed under external loads of 200 N (vertical or 30-degree oblique) to each cusp tip. The strain distributions of the peri-implant bone and von Mises stress fields in the abutment, implant, and screw were evaluated. Based on the static FE results, a computational fatigue analysis was performed to predict the risk of fracture caused by fatigue accumulation of repetitive mastication.</P> <P><B>Results</B></P> <P>Bone tissues in fatigue failure level (greater than 4000 με) were observed in the alveolar ridge and the plateaus close to the implant apex in all situations. Under the oblique loading condition, the total volume of the bone tissue in hypertrophy and fatigue failure levels (greater than 2500 με) was the largest at IB and the smallest at external bone level. Among the 4 situations, the highest stress occurred in the abutment (506.9 MPa) and implant (311 MPa) of IB. In fatigue analysis, fracture was only predicted in the IB abutment model (588 301 cycles), and cracking occurred in the lingual direction, where stress concentration occurred when the oblique load was applied.</P> <P><B>Conclusions</B></P> <P>The abutment of IB showed the highest stress of the implant component, and internal tissue level model showed the highest strain of bone. In all groups, the bone strain values mostly appeared within physiologic capacity (under 4000 με). Various mechanical situations should be considered when using internal bone-level connections in short implants for replacing posterior teeth.</P>
Jeongjin Park,HyeonJong Jung,YoungGab Kim 대한인간공학회 2015 대한인간공학회 학술대회논문집 Vol.2015 No.10
Objective: The aim of this development is to improve the human performance of employee in nuclear power plant each group and to internalize human performance tools in early stage. Background: Human error caused severe events and issued in NPP. So, most nuclear power plants are using human performance tools to enhance human performance. Human performance tools consisted of following 16 tools; Task Review, Job Site Review, Questioning Attitude, Stop When Unsure, Self-Checking, 3-Way Communication, Phonetic Alphabet, Procedure Use and Adherence, Pre-Job Briefing, Concurrent Verification, Independent Verification, Peer Checking, Flagging, Placekeeping, Turnover, Post-Job Critique. Lecture material includes these all tools. However, prior lecture material of human performance tools is too difficult and boring because they are text-oriented and not systematic. Especially, there is no classification by lecture group (such as new employee, operation team, maintenance team and etc.) Method: The lecture material needs to be customized by training target group. So, we divide following 5 groups; new employee, operation team, maintenance team, maintenance partner companies and experts. Because there is different about understanding level and application method in each group, we use video clip and actual examples to help that they can be easily understanding human performance tools. Results: To effective learning of human performance tools, video clip and actual examples will be helpful. But human performance tools are not trained once. So, Periodic update of video clip and actual examples is required. Conclusion: Human performance tools are powerful technique to prevent human error in NPP. So, effective learning program and lecture material must be developed consistently. Application: The standard lecture material will be distributed to each training center and NPP and used in human performance enhancement training course.
Kim, Amy,Lee, Jung-Bok,Ko, Yousun,Park, Taeyong,Jo, Hyeonjong,Jang, Jin Kyoo,Lee, Kyoungsuk,Kim, Kyung Won,Lee, In-Seob The Korean Gastric Cancer Association 2022 Journal of gastric cancer Vol.22 No.2
Purpose: Weight loss and deterioration in body composition are observed in patients with gastric cancer (GC) following gastrectomy. This study aimed to investigate the impact of residual stomach volume (RSV) on the nutritional status and body composition of patients with GC treated with distal gastrectomy. Materials and Methods: In total, 227 patients who underwent minimally invasive distal gastrectomy with Billroth 1 anastomosis for stage I GC between February 2015 and May 2018 were enrolled. Clinicodemographic and laboratory data were collected from the GC registry. The RSV, abdominal muscle area, and subcutaneous/visceral fat areas were measured using computed tomography data. Results: A larger RSV was associated with a lower decrease in the nutritional risk index (P=0.004) and hemoglobin level (P=0.003) during the first 3 months after surgery, and better recovery at 12 months. A larger RSV demonstrated an advantage in the preservation of abdominal muscle area (P=0.02) and visceral fat (P=0.04) after surgery, as well as less reduction in weight (P=0.02) and body mass index (P=0.03). Conclusions: Larger RSV was associated with improved nutritional status and better preservation of muscle and fat after distal gastrectomy.