• 대한방사선기술학회지:방사선기술과학
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• 제41권2호
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• pp.141-148
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• 2018

This study examined the properties of photons and the dose distribution in a human body via a simulation where the total body irradiation(TBI) is performed on a pediatric anthropomorphic phantom and a child size water phantom. Based on this, we tried to find the optimal photon beam energy and material for beam spoiler. In this study, MCNPX (Ver. 2.5.0), a simulation program based on the Monte Carlo method, was used for the photon beam analysis and TBI simulation. Several different beam spoiler materials (plexiglass, copper, lead, aluminium) were used, and three different electron beam energies were used in the simulated accelerator to produce photon beams (6, 10, and 15 MeV). Moreover, both a water phantom for calculating the depth-dependent dosage and a pediatric anthropomorphic phantom for calculating the organ dosage were used. The homogeneity of photon beam was examined in different depths for the water phantom, which shows the 20%-40% difference for each material. Next, the org an doses on pediatric anthropomorphic phantom were examined, and the results showed that the average dose for each part of the body was skin 17.7 Gy, sexual gland 15.2 Gy, digestion 13.8 Gy, liver 11.8 Gy, kidney 9.2 Gy, lungs 6.2 Gy, and brain 4.6 Gy. Moreover, as for the organ doses according to materials, the highest dose was observed in lead while the lowest was observed in plexiglass. Plexiglass in current use is considered the most suitable material, and a 6 or 10 MV photon energy plan tailored to the patient condition is considered more suitable than a higher energy plan.

• 한국초전도ㆍ저온공학회논문지
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• 제17권2호
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• pp.36-40
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• 2015

Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2-4]. In this paper three simulation models with 3, 4 and 6 solenoid system were built, but it's not considered anything else except the number of coils. Two groups of optimization analysis are presented, and the evolution strategy (ES) is adopted as an optimization tool which is a technique based on the ideas of mutation, adaptation and annealing [5]. In this research, the volume of ECR zone was calculated approximately, and optimized designs for ECR solenoid magnet system were presented. Firstly it is better to make the volume of ECR zone large to increase the intensity of ion beam under the specific confinement field conditions. At the same time the total volume of superconducting solenoids must be decreased to save material. By considering the volume of ECR zone and the total length of solenoids in each model with different number of coils, the 6 solenoid system represented the highest coil performance. By the way, a certain case, ECR zone volume itself can be essential than the cost. So the maximum ECR zone volume for each solenoid magnet system was calculated respectively with the same size of the plasma chamber and the total magnet space. By comparing the volume of ECR zone, the 6 solenoid system can be also made with the maximum ECR zone volume.

• Radiation Oncology Journal
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• 제2권2호
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• pp.271-280
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• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• 한국의학물리학회지:의학물리
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• 제17권2호
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• pp.123-129
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• 2006

최근 발표된 EGS5 몬테칼로 코드의 방사선치료 응용을 위한 시험코드를 작성하였다. 본 시험코드는 점선원 모델과 원통형 팬텀에 대하여 깊이선량을 계산하도록 작성되었다. 시험코드의 평가를 위하여 6, 9, 12, 15 MeV 전자선 그리고 Co-60, 10 MV 광자선에 대한 깊이선량을 계산하고 DOSRZ/EGS4의 결과와 비교하였다. 시험코드와 DOSRZ 코드와의 깊이선량 계산결과의 차이는 전자선에서 약 ${\pm}1.5%$ 이내, 광자선에서 약 ${\pm}3.0%$ 이내를 보였다.

• 대한기계학회논문집A
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• 제31권5호
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• pp.550-555
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• 2007

The effective fracture toughness testing of materials intended for application in Micro Electro Mechanical Systems (MEMS) devices is required in order to improve understanding of how micro sized material used in device may be expected to perform upon the micro scale. ${\gamma}$-TiAl based materials are being considered for application in MEMS devices at elevated temperatures. Especially, in Alloy 4, both ${\alpha}_2$ and ${\gamma}$ lamellae were altered markedly in 3,000 h, $700^{\circ}C$ exposure. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. The materials were examined 2 types Alloy 4 on heat exposed specimen($700^{\circ}C$, 3,000 h) and no heat exposed one. Micro sized cantilever beams were prepared mechanical polishing on both side at $25{\sim}30{\mu}m$ and electro final stage polishing to observe lamellar orientation of same colony with EBSD (Electron Backscatter Diffraction Pattern). Through lamellar orientation as inter-lamellae or trans-lamellae, Cantilever beam was fabricated with Focused Ion Beam(FIB). The directional behavior of the lamellar structure was important property in single material, because of the effects of the different processing method and variations in properties according to lamellar orientation. In MEMS application, it is first necessary to have a reliable understanding of the manufacturing methods to be used to produce micro structure.

• 한국진공학회지
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• 제18권5호
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• pp.384-389
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• 2009

ZnO는 육방정계결정구조의 물질로서 3.37 eV의 넓은 띠 간격과 60 meV의 큰 exciton 결합에너지에 따른 높은 효율의 자외선발광으로 짧은 파장의 빛 (녹, 청, 자외선)을 내는 LED (Light Emitting Diode) 분야에서 관심을 기울이고 있는 물질이다. LED제작을 위해서는 n형의 ZnO와 p형의 ZnO가 필요하지만 기본적으로 ZnO은 n형이므로 신뢰성 있는 p형 ZnO박막을 제작하기 위한 노력이 기울여지고 있다. 본 연구에서는 ALD (Atomic Layer Deposition)로 제작된 ZnO박막에 20 keV의 에너지를 갖는 질소이온을 $10^{13}{\sim}10^{15}ions/cm^2$로 조사한 후 Hall 효과 측정장치를 이용하여 질소이온 조사에 따른 전기적 특성변화를 조사하였다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2410-2414
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• 2020

Heavy ions have a high potential for destroying deep tumors that carry the highest dose at the peak of Bragg. The peak caused by a single-energy carbon beam is too narrow, which requires special measures for improvement. Here, carbon-12 (¹²C) ion with different energies has been used as a source for calculating the dose distribution in the water phantom, soft tissue and bone by the code of Monte Carlobased FLUKA code. By increasing the energy of the initial beam, the amount of absorbed dose at Bragg peak in all three targets decreased, but the trend for this reduction was less severe in bone. While the maximum absorbed dose per bone-mass unit in energy of 200 MeV/u was about 30% less than the maximum absorbed dose per unit mass of water or soft tissue, it was merely 2.4% less than soft tissue in 400 MeV/u. The simulation result showed a good agreement with experimental data at GSI Darmstadt facility of biophysics group by 0.15 cm average accuracy in Bragg peak positioning. From 200 to 400 MeV/u incident energy, the Bragg peak location increased about 18 cm in soft tissue. Correspondingly, the bone and soft tissue revealed a reduction dose ratio by 2.9 and 1.9. Induced neutrons did not contribute more than 1.8% to the total energy deposited in the water phantom. Also during ¹²C ion bombardment, secondary fragments showed 76% and 24% of primary 200 and 400 MeV/u, respectively, were present at the Bragg-peak position. The combined treatment of carbon ions with neutron or electron beams may be more effective in local dose delivery and also treating malignant tumors.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2195-2207
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• 2024

To enhance skeletal dosimetry in conjunction with the adult mesh-type reference Korean phantoms (MRKPs), Korean/Asian photon fluence-to-skeletal dose response functions (DRFs) were established utilizing an updated version of micro-CT-based detailed bone models from Tsinghua University. These bone models were incorporated into the MRKPs using the parallel geometry feature of Geant4. We calculated bone-site-specific electron absorbed fractions and used them to generate DRFs, following a similar methodology employed for ICRP-116 DRFs that have been used with the ICRP reference phantoms for skeletal dosimetry. To assess dosimetric implications of the Korean/Asian DRFs, we calculated RBM and BE doses for the MRKPs exposed to photon beams in the antero-posterior direction using the Korean/Asian and ICRP-116 DRFs. For energies ≥200 keV, the Korean/Asian DRFs-based skeletal doses exhibited excellent agreement with the ICRP-116 DRFs-based skeletal doses, attributed to the existence of charged particle equilibrium across the bone site. Conversely, significant differences of up to ~2.3 times were observed at lower energies, due to differences in the skeletal tissue distributions of bone models used to derive the Korean/Asian and ICRP-116 DRFs. The DRFs established in this study are expected to yield more accurate skeletal doses for Korean and Asian populations compared to the ICRP-116 DRFs.

• Radiation Oncology Journal
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• 제26권2호
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• pp.113-117
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• 2008

목적: 노령의 피부암에서 방사선치료 후 국소 제어률, 생존율, 실패양상, 부작용을 알아보기 위해 이 연구를 시행하였다. 대상 및 방법: 1990년 1월부터 2002년 10월까지 계명대학교 동산의료원 방사선종양학과에서 방사선치료를 받은 노령 환자 15명을 대상으로 하였다. 연령 분포는 72세에서 95세로 평균 78.8세였다. 병리학적으로 10명은 편평상피암이었고 3명은 기저세포암이었고 1명은 사마귀상암, 1명은 피부부속기원암이었다. 종괴의 위치로는 두부가 13명으로 대부분을 차지하였다. 종괴의 장경은 평균 4.9cm($2{\sim}9cm$)이었다. 방사선치료는 $6{\sim}15$ MeV의 전자선을 종괴의 크기와 깊이에 맞추어 사용하였으며 80% 등선량곡선에 하루에 2 Gy 씩 주 5회 사용하였으며 총방사선량은 $50{\sim}80$ Gy(평균 66 Gy)를 조사하였다. 림프절전이가 있었던 1명은 6 MV X-선으로 치료한 후 전자선으로 추가 조사하였다. 추적기간은 10개월에서 120개월로 중앙값 48개월이었다. 결과: 모든 환자에서 완전관해를 얻었으며 5년 무병생존율은 80%이었다. 전체 15명 중 12명은 재발이 없었다. 3명은 재발없이 평균 90개월($68{\sim}120$개월)동안 생존하고 있으며 방사선치료 후 20%(3/15)에서 재발하였고 9명은 재발이나 전이없이 평균 55.8개월 살다가 다른 병으로 사망하였다. 방사선치료 중 방사선 피부염 외에는 특별한 부작용은 없었으며 방사선피부염은 치료 종료 후 보존적 치료로 회복 되었다. 결론: 노령의 피부암의 방사선치료는 매우 효과적이며 안전하며 좋은 생존율을 보인다고 사료된다.

• 대한방사선치료학회지
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• 제26권2호
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• pp.163-170
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• 2014

목 적 : 표재성 종양 치료를 위하여 선택한 전자선은 bolus와 동시에 사용할 경우 표면선량에 급격한 변화를 보이게 되며 이는 치료결과의 중요한 변수로 작용할 수 있다. 이에 본 논문에서는 전자선 치료에서 bolus가 적용될 경우 표면선량을 좌우할 수 있는 4 가지 변수에 따른 치료계획시스템(Treatment Planning System, TPS)의 표면선량 계산 값과 실제 측정값을 비교 분석하였다. 대상 및 방법 : 치료계획시스템(Pinnacle 9.2, philips, USA)과 실제 측정값을 비교하기 위하여 실제 치료 시 주로 발생되는 4가지 변수(A: bolus 두께 - 3, 5, 10 mm, B: 조사야 크기 - $6{\time}6$, $10{\time}10$, $15{\time}15cm2$, C: 에너지 - 6, 9, 12 MeV, D: 겐트리 각도 - 0, $15^{\circ}$)를 설정하였다. 16 cm 두께의 solid water phantom을 이용하여 bolus(Action Products, USA) 없이 전산화단층촬영(lightspeed ultra 16, General Electric, USA)을 시행하였고 치료 계획은 TPS 상에서 각각 3, 5, 10 mm bolus를 생성하여 A, B, C, D를 조합한 총 54개의 beam으로 계획하였다. 이때 SSD 100 cm, 300 MU를 조사하였고 TPS와 실제 측정값을 비교 분석하기 위해 EBT3 film(International Specialty Products, NJ, USA)을 이용해 iso-center에 위치시켜 2회 반복 측정하였다. 측정된 film은 디지털 평판 스캐너(Expression 10000XL, EPSON, USA)와 선량 농도 분석시스템(Complete Version 6.1, RIT, USA)을 사용하여 각각의 평균값과 표준편차 값으로 분석하였다. 결 과 : bolus 두께에 따른 값은 3, 5, 10 mm에서 실제 측정된 값이 TPS의 계산 값보다 각각 101.41%, 99.58%, 101.28%, 표준편차는 각각 0.0219, 0.0115, 0.0190 으로 나타났다. 조사야 크기에 따른 실제 측정값은 $6{\time}6$, $10{\time}10$, $15{\time}15cm2$ 각각 계산 값에 비해 99.63%, 101.40%, 101.24%, 표준편차는 0.0138, 0.0176, 0.0220 으로 나타났다. 에너지에 따른 값은 상대적으로 6, 9, 12 MeV 각각 99.72%, 100.60%, 101.96%, 표준편차는 0.0200, 0.0160, 0.0164로 나타났다. 빔 각도에 따른 실제 측정값은 계산된 값에 비하여 0, $15^{\circ}$에서 각각 100.45%, 101.07%, 표준편차는 0.0199, 0.0190 으로써 $15^{\circ}$에서 $0^{\circ}$보다 0.62% 높게 측정되었다. 결 론 : 본 논문에서 사용한 변수에 따른 계산 값과 측정값을 분석한 결과 5 mm bolus, $6{\time}6cm2$ 조사야, 저 에너지 전자선, $0^{\circ}$ 겐트리 각도에서 TPS로 계산한 값이 측정값에 더 가까웠지만 다른 변수를 적용한 비교에서도 최대 2% 오차범위 내에 포함되는 결과를 보였다. 전자선과 bolus를 동시에 사용하는 경우 본 논문에서 선택된 변수의 범위를 벗어난다면 각각의 변수에 따라 실제 측정값이 TPS와 달라질 수 있기 때문에 정확한 표면선량에 대한 QA를 반드시 실시해야 한다.