LPE법에 의한 ZnO co-doped Er :$ LiNbO_3$, 박막의 성장 및 구조적 특성

심장보,전원남,윤석규,윤대호 한국결정성장학회 2002 韓國結晶成長學會誌 Vol.12 No.1

Liquid phase epitaxy(LPE)법을 이용하여 ZnO co-doped Er:$LiNbO_3$, 단결정 박막을 $LiNbO_3$ (001) 기판 위에 성장시켰다. ZnO co-doped Er:$LiNbO_3$박막 성장의 초기 융액은 첨가제 $Er_2O_3$ 농도를 1 mol%로 고정시키고 ZnO 농도를 3,5 mol%로 조절하였다. ZnO co-doped Er :$LiNbO_3$박막의 결정성은 $LiNbO_3$ 기판보다 더 우수하였다. ZnO 5mol% 첨가한 경우 박막의 표면에는 수직한 방향과 평행한 방향으로 모두 압축응력이 작용하고 있었다. 또한 ZnO 3mol% 첨가된 Er :$LiNbO_3$박막의 표면은 원래의 $LiNbO_3$기판보다 더 평탄하였다 ZnO co-doped Er:$LiNbO_3$ single crystal thin films have been grown on $LiNbO_3$ (001) substrate by liquid phase epitaxy (LPE) method. The melts of ZnO co-doped Er:$LiNbO_3$ was fixed $Er_2O_3$, concentration (1 mol%) and different ZnO concentrations 3 and 5 mol%. The crystallinity of ZnO co-doped Er :$LiNbO_3$ films became better than the $LiNbO_3$ substrate. At ZnO 5 mol% concentration, the surface of ZnO co-doped Er:$LiNbO_3$ film is affected by compressive stress along both the perpendicular and the parallel direction. Also the surface of ZnO 3 mol% co-doped Er:$LiNbO_3$film is smoother than the original $LiNbO_3$ substrate surface.

Basic 암모노써멀 방법에 의한 벌크 GaN 단결정의 성장 및 특성

심장보,이영국,Shim, Jang Bo,Lee, Young Kuk 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.2

Basic 암모노써멀 방법을 사용하여 벌크 GaN 단결정을 성장시켰다. 종자 결정은 Hydride vapor phase epitaxy법으로 성장한 c면의 GaN 템플릿을 사용하고 광화제는 sodium metal, amide, azide를 사용하였다. 결정 성장 온도는 $500{\sim}600^{\circ}C$, 성장 압력은 2~3 kabr에서 실시하였다. c 축의 결정 성장 속도는 운용 압력이 증가함에 따라 선형적으로 증가하였다. Cathodoluminescence로 측정한 평균 전위 밀도는 $1{\times}10^5/cm^2$였다. Double Crystals X-ray Diffraction로 측정한 (002)면의 반치폭은 Ga 면에 대해서는 약 270 arcsec, N 면에 대해서는 약 80 arcsec이었다. Bulk GaN crystals were grown by the basic ammonothermal method. The c-plane GaN templates grown by hydride vapor phase epitaxy were used as seed crystals and sodium metal, amide, and azide were added as a mineralizer. The growth conditions are at temperatures from $500{\sim}600^{\circ}C$ and pressures from 2~3 kbar. The growth rate for the c-axis was increased with increasing the operating pressure. Average dislocation density was measured $1{\times}10^5/cm^2$ by the cathodoluminescence measurement. The full-width at half-maximum of the X-ray diffraction rocking curve for (002) reflection was approximately 270 arcsec for Ga face and 80 arcsec for N face.

Czochralski 법으로 성장된 Yb³⁺ doped Y₃Al₅O₁₂ 단결정의 성장 분위기 및 도핑 농도에 따른 광학적 특성

심장보,이영진,강진기,이영국,Shim, Jang Bo,Lee, Young Jin,Kang, Jin Ki,Lee, Young Kuk 한국결정성장학회 2015 韓國結晶成長學會誌 Vol.25 No.2

Single crystals of $Yb^{3+}$ doped $Y_3Al_5O_{12}$ up to 25 at.% were grown by the Czochralski method. Using the pulling rate of 0.8 mm/h and the rotation rate of 10 rpm, single crystals with diameters of up to 40 mm and lengths up to 160 mm were obtained. The growth atmosphere was either pure nitrogen or the mixture of nitrogen and oxygen. The crystal was bluish green when using pure nitrogen and the crystal was colorless when using the mixture of 99 % nitrogen and 1 % oxygen. The concentration of $Yb^{3+}$ ions decreased with increasing the length of the crystal and $Yb^{3+}$ concentration of core area was slightly higher than the other areas in the compositional analysis. The fluorescence lifetime decreased with increasing the doping concentration of $Yb^{3+}$ ions. $Yb^{3+}$ 이온이 25 at.%까지 치환된 $Y_3Al_5O_{12}$ 단결정을 Czochralski 법으로 성장시켰다. 0.8 mm/h의 인상속도와 10 rpm의 회전 속도로 40 mm의 결정 직경과 160 mm의 결정 길이를 가진 단결정을 얻었다. 결정 성장 분위기는 순수한 질 소 혹은 질소와 산소를 혼합한 가스 분위기였다. 순수한 질소 분위기에서는 청록색을 띤 결정이 성장되었고 99 %의 질소와 1 %의 산소를 혼합한 가스 분위기에서 성장한 결정은 무색이었다. 농도 분석결과를 보면, 결정의 길이가 길어짐에 따라 $Yb^{3+}$의 농도는 감소하고, core 영역의 $Yb^{3+}$ 농도는 core 없는 영역보다 다소 높게 검출되었다. $Yb^{3+}$ 이온의 도핑 농도가 증가함에 따라 형광 수명은 감소하였다.

화학적 polishing 및 etching을 통한 RE : YAG (RE = Nd³⁺, Er³⁺, Yb³⁺) 단결정의 표면 결함 분석

심장보,강진기,이영국,Shim, Jang Bo,Kang, Jin Ki,Lee, Young Kuk 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.4

The conditions for chemical polishing and etching technique were investigated to reveal surface defects in RE : YAG ($RE=Nd^{3+},\;Er^{3+},\;Yb^{3+}$) single crystals grown by Czochralski method. The optimal condition for chemical polishing was in 85 % $H_3PO_4$ solution at $330^{\circ}C$ for 30 minutes with a specimen fixed in the vertical direction. In addition, the optimal condition for chemical etching was in 85 % $H_3PO_4$ solution at $260^{\circ}C$ for 1 hour, and $70{\sim}80{\mu}m$ sized triangular etch pits were observed on (111) face. As a result of defect density analysis, $1.9{\times}10^3/cm^2$ for Nd(1 %) : YAG, $4.3{\times}10^2/cm^2$ for Er(7.3 %) : YAG, and $5.1{\times}10^2/cm^2$ for Yb(15 %) : YAG were measured. Czochralski 법으로 성장한 RE : YAG ($RE=Nd^{3+}\;,Er^{3+}\;,Yb^{3+}$) 단결정의 표면 결함을 측정하는 chemical polishing 및 etching 조건에 대하여 조사하였다. 최적의 chemical polishing 조건은 시편을 수직 방향으로 고정하고 85 % $H_3PO_4$ 용액에서 $330^{\circ}C$, 30분 동안 진행한 것이었다. 또한 최적의 chemical etching 조건은 85 % $H_3PO_4$ 용액에서 $260^{\circ}C$, 1시간 동안 진행한 것이었고, (111) 면에 $70~80{\mu}m$ 크기의 삼각형 etch pit들이 관찰되었다. 결함 밀도 분석 결과, Nd(1 %) : YAG는 $1.9{\times}10^3$개/$cm^2$, Er(7.3 %) : YAG는 $4.3{\times}10^2$개/$cm^2$, Yb(15 %) : YAG는 $5.1{\times}10^2$개/$cm^2$로 측정되었다.

Er³⁺ doped Y₃Al₅O₁₂ 단결정의 core 영역 및 광학적 특성

심장보,이영진,강진기,이영국,Shim, Jang Bo,Lee, Young Jin,Kang, Jin Ki,Lee, Young Kuk 한국결정성장학회 2015 韓國結晶成長學會誌 Vol.25 No.3

$Er^{3+}$ 이온이 5, 7.3, 8, 10 at.% 치환된 $Y_3Al_5O_{12}$ 단결정을 Czochralski법으로 질소 분위기에서 성장시켰다. 1.0 mm/h의 인상속도와 10 rpm의 회전 속도로 50 mm의 결정 직경을 가진 <111> 방향의 $Er:Y_3Al_5O_{12}$ 단결정을 얻었다. 두꺼운 직경의 core 영역은 주로 결정 성장 중 직경 변화가 있는 영역에서 발생되었다. 결정 내에서 $Er^{3+}$의 농도는 융액 내의 농도와 같았다. Core 영역의 $Er^{3+}$ 농도는 core가 없는 영역보다 다소 높게 검출되었다. $Er^{3+}$ 이온의 도핑 농도가 증가함에 따라 형광 수명은 포화되었다. $Er^{3+}$ doped $Y_3Al_5O_{12}$ (Er:YAG) single crystals, in which the concentrations of $Er^{3+}$ ion were 5, 7.3, 8, and 10 at.%, were grown by the Czochralski method under nitrogen atmosphere. The <111> oriented Er:YAG single crystals with diameters of up to 50 mm were grown at a pulling rate of 1.0 mm/h and rotation rate of 10 rpm. The thick part of the core region was generated mainly when there was a diameter change during the crystal growth. The concentrations of $Er^{3+}$ ion in the crystals were the same as it was in the melt. $Er^{3+}$ concentration of core region was slightly higher than the other regions in the compositional analysis. The fluorescence lifetime was saturated according to the increase of $Er^{3+}$ doping concentrations.

Quality Assurance of Volumetric Modulated Arc Therapy for Elekta Synergy

심수정,심장보,이상훈,민철기,조광환,신동오,최진호,박성일,조삼주,Shim, Su-Jung,Shim, Jang-Bo,Lee, Sang-Hoon,Min, Chul-Kee,Cho, Kwang-Hwan,Shin, Dong-Oh,Choi, Jin-Ho,Park, Sung-Ill,Cho, Sam-Ju Korean Society of Medical Physics 2012 의학물리 Vol.23 No.1

최근 환자맞춤형방사선치료를 위해 임상에서 활용하고 있는 입체적세기조절회전방사선치료의 정도관리를 수행하고자 기존의 세기조절방사선치료에서 수행하는 정도관리 프로그램을 본 원의 실정에 맞게 치료계획단계 정도관리(Treatment planning QA), 치료전 전달단계 정도관리(Pretreatment delivery QA), 치료단계 정도관리(Treatment QA)인 세 가지 단계로 나누어 설정하였다. 각 정도관리 단계에서는 정도관리 프로그램에 따라 점검할 항목과 측정하여 평가할 항목을 설정하여 문서화를 위해 서식화 하였다. 본 원에서는 서식화한 정도관리 프로그램에 따라 실제 치료환자에 적용하였으며 본원의 치료전 전달 정도관리의 임상 허용기준을 위해 국소적 신뢰수준(confidence limit, CL)을 평가하였다. 그 결과 고선량 영역 점선량 측정, 저선량영역 점선량 측정의 CL는 모두 기존의 IMRT 수준과 유사한 결과를 얻었으며 이를 토대로 본원의 임상허용 기준은 고선량영역은 3%, 저선량 영역은 5%로 설정하였다. 입체적세기조절회전방사선치료의 특성상 Intensity map 평가는 360도 전 방향에서 Intensity map을 측정할 수 있는 ArcCheck 기기를 사용 하여 감마 지표(Gamma Index) 평가를 하였으며 그 결과는 IMRT의 개별적 intensity map 평가와 유사한 결과를 얻었으며 본원의 CL은 93%로 설정하였다. 등선량분포 평가는 2D detector array인 Mapcheck을 사용하였으며 95% 이상의 일치도를 보여 본원의 CL은 95%로 설정하였다. 방사선치료 정도관리에서 임의의 불확도와 계통 오차를 줄이려면 실제 환자 적용에 앞서 다 기관이 참여하는 팬톰을 이용한 국소적 CL 평가를 권장하고 있다. 국내 여건상 다 기관이 참여하는 연구가 여의치 않다면 본 연구와 같이 개별 기관에서 자체적으로 허용검사가 끝난 후에 실제 임상에서는 환자 치료 부위별로 세분화 하여 국소적 CL을 평가하는 방법이 유용할 것으로 사료된다. For applying the quality assurance (QA) of volumetric modulated arc therapy (VMAT) introduced in Eulji Hospital, we classify it into three different QA steps, treatment planning QA, pretreatment delivering QA, and treatment verifying QA. These steps are based on the existing intensity modulated radiation therapy (IMRT) QA that is currently used in our hospital. In each QA step, the evaluated items that are from QA program are configured and documented. In this study, QA program is not only applied to actual patient treatment, but also evaluated to establish a reference of clinical acceptance in pretreatment delivering QA. As a result, the confidence limits (CLs) in the measurements for the high-dose and low-dose regions are similar to the conventional IMRT level, and the clinical acceptance references in our hospital are determined to be 3 to 5% for the high-dose and the low-dose regions, respectively. Due to the characteristics of VMAT, evaluation of the intensity map was carried out using an ArcCheck device that was able to measure the intensity map in all directions, $360^{\circ}$. With a couple of dosimetric devices, the gamma index was evaluated and analyzed. The results were similar to the result of individual intensity maps in IMRT. Mapcheck, which is a 2-dimensional (2D) array device, was used to display the isodose distributions and gave very excellent local CL results. Thus, in our hospital, the acceptance references used in practical clinical application for the intensity maps of $360^{\circ}$ directions and the coronal isodose distributions were determined to be 93% and 95%, respectively. To reduce arbitrary uncertainties and system errors, we had to evaluate the local CLs by using a phantom and to cooperate with multiple organizations to participate in this evaluation. In addition, we had to evaluate the local CLs by dividing them into different sections about the patient treatment points in practical clinics.

Qualitative Evaluation of 2D Dosimetry System for Helical Tomotherapy

마선영,정태식,심장보,임상욱,Ma, Sun Young,Jeung, Tae Sig,Shim, Jang Bo,Lim, Sangwook Korean Society of Medical Physics 2014 의학물리 Vol.25 No.4

본 연구의 목적은 새로 개발된 2차원 토모테라피 선량측정 시스템의 가능성을 알아보는 것이다. 방사선이 조사되면 가시광성을 내보내는 인광판을 원통형 물팬텀에 삽입하였다. 치료계획장치에서 원 모양, C자 모양, 다중표적 3종류의 가상의 표적을 만들고 각 표적에 10 Gy의 방사선을 전달하도록 하였다. 원통형 팬텀을 토모테라피 치료테이블위에 올려놓고 치료계획대로 방사선을 조사하였다. CCD카메라로 쵤영된 모든 프레임은 누적되었고 각 픽셀은 선량으로 변환되었다. 인광판으로부터 나온 영상은 치료계획장치에서 계산된 선량분포와 비교하였다. 선량기울기(dose rate)와 픽셀값의 관계그래프는 선량기울기 900 MU/min 까지 포화(saturated)되지 않았다. 인광판의 선형성 보정이 개선된다면 인광판과 CCD카메라를 이용한 토모테라피의 2차원 선량측정이 유용할 것으로 기대한다. The purpose of this study is to see the feasibility of the newly developed 2D dosimetry system using phosphor screen for helical tomotherapy. The cylindrical water phantom was fabricated with phosphor screen to emit the visible light during irradiation. There are three types of virtual target, one is one spot target, another is C-shaped target, and the other is multiple targets. Each target was planned to be treated at 10 Gy by treatment planning system (TPS) of tomotherapy. The cylindrical phantom was placed on the tomotherapy table and irradiated as calculations of the TPS. Every frame which acquired by CCD camera was integrated and the doses were calculated in pixel by pixel. The dose distributions from the fluorescent images were compared with the calculated dose distribution from the TPS. The discrepancies were evaluated as gamma index for each treatment. The curve for dose rate versus pixel value was not saturated until 900 MU/min. The 2D dosimetry using the phosphor screen and the CCD camera is respected to be useful to verify the dose distribution of the tomotherapy if the linearity correction of the phosphor screen improved.

A Text-Based Data Mining and Toxicity Prediction Modeling System for a Clinical Decision Support in Radiation Oncology: A Preliminary Study

김광현,이석,심장보,장경환,양대식,윤원섭,박영지,김철영,Yuanjie Cao 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.4

The aim of this study is an integrated research for text-based data mining and toxicity prediction modeling system for clinical decision support system based on big data in radiation oncology as a preliminary research. The structured and unstructured data were prepared by treatment plans and the unstructured data were extracted by dose-volume data image pattern recognition of prostate cancer for research articles crawling through the internet. We modeled an artificial neural network to build a predictor model system for toxicity prediction of organs at risk. We used a text-based data mining approach to build the artificial neural network model for bladder and rectum complication predictions. The pattern recognition method was used to mine the unstructured toxicity data for dose-volume at the detection accuracy of 97.9%. The confusion matrix and training model of the neural network were achieved with 50 modeled plans (n = 50) for validation. The toxicity level was analyzed and the risk factors for 25% bladder, 50% bladder, 20% rectum, and 50% rectum were calculated by the artificial neural network algorithm. As a result, 32 plans could cause complication but 18 plans were designed as non-complication among 50 modeled plans. We integrated data mining and a toxicity modeling method for toxicity prediction using prostate cancer cases. It is shown that a preprocessing analysis using text-based data mining and prediction modeling can be expanded to personalized patient treatment decision support based on big data.

A New Plan-Scoring Method Using Normal Tissue Complication Probability for Personalized Treatment Plan Decisions in Prostate Cancer

김광현,이석,심장보,양대식,윤원섭,박영제,김철용,Yuanjie Cao,장경환 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.2

The aim of this study was to derive a new plan-scoring index using normal tissue complication probabilities to verify different plans in the selection of personalized treatment. Plans for 12 patients treated with tomotherapy were used to compare scoring for ranking. Dosimetric and biological indexes were analyzed for the plans for a clearly distinguishable group (n = 7) and a similar group (n = 12), using treatment plan verification software that we developed. The quality factor (QF) of our support software for treatment decisions was consistent with the final treatment plan for the clearly distinguishable group (average QF = 1.202, 100% match rate, n = 7) and the similar group (average QF = 1.058, 33% match rate, n = 12). Therefore, we propose a normal tissue complication probability (NTCP) based on the plan scoring index for verification of different plans for personalized treatment-plan selection. Scoring using the new QF showed a 100% match rate (average NTCP QF = 1.0420). The NTCP-based new QF scoring method was adequate for obtaining biological verification quality and organ risk saving using the treatment-planning decision-support software we developed for prostate cancer.

Czochralski법으로 성장된 RE : YAG(RE = Nd³⁺, Er³⁺) 단결정의 결함분석

박청호,주영준,김혜영,심장보,김철진,Park, Cheong Ho,Joo, Young Jun,Kim, Hye Young,Shim, Jang Bo,Kim, Cheol Jin 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.1

RE : YAG ($RE=Nd^{3+}$, $Er^{3+}$) single crystals are laser diodes and generally grown by Czochralski method with controlling the various growth parameter. Since the defects occurred by temperature gradient or the rotation speed of solid-liquid growth interface act as the decline of crystal optical property during the growth procedure, crystalline quality improvement via defects analysis is necessary. The etch pit density (EPD) analysis was used to confirm the surface defect of grown RE : YAG single crystal and to select the area of transmission electron microscopy (TEM) analysis. Defects in the specimen produced by tripod polishing method such as buckling, rod shaped, bend contours by internal stress, segregation and others were observed by using 200 kV TEM and 300 kV FE-TEM. RE : YAG 단결정은 레이저 발진 소재로 다양한 성장 변수를 제어하면서 Czochralski법으로 성장된다. 성장과정 동안 고액계면의 온도구배 및 회전속도에 의해 발생하는 결함들은 결정의 광학적 특성 저하로 작용하기 때문에 결함 분석을 통한 결정 품질의 향상을 필요로 한다. 격자결함 밀도 분석(EPD)을 통하여 성장된 RE : YAG 단결정의 표면 결함 존재를 확인하였고, 이를 통해 투과전자현미경(TEM) 분석영역을 선택하였다. 선택한 영역의 시편은 트라이포드 연마 방법으로 제작하였고, 200 kV 투과전자현미경과 300 kV 전계 방사형 투과전자현미경(FE-TEM)을 사용하여 buckling, rod shaped, 내부응력에 의한 bend contours, 편석 등의 결함들을 관찰하였다.