Development of Pinhole X-ray Fluorescence Imaging System to Measure in vivo Biodistribution of Gold Nanoparticles

학위논문(박사)--서울대학교 대학원 :융합과학기술대학원 융합과학부,2019. 8. 예성준.목적: 본 연구의 목표는 금나노입자의 체내 농도 분포 측정을 위한 핀홀 엑스선 형광 영상시스템을 개발하고, 시간에 따른 쥐의 체내 금나노입자 분포 영상을 획득하여 개발 영상시스템이 전임상시험에 활용 가능함을 실험적으로 증명하는 것이다. 2차원 cadmium zinc telluride (CZT) 감마 카메라를 사용하여 K-shell 엑스선 형광 신호를 측정함으로써, 영상 획득 시간과 피폭 방사선량을 줄일 수 있다. 또한, 본 연구는 샘플의 복잡한 전처리 과정 없이 금나노입자의 체외 농도를 측정할 수 있는 silicon drift detector (SDD)를 사용한 L-shell 엑스선 형광 측정 시스템을 개발하고자 한다. 방법: 금나노입자의 농도와 K-shell 엑스선 형광 신호 사이의 교정 곡선을 획득하기 위해 0.0 wt%, 0.125 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%의 금나노입자 샘플을 반지름 2.5 cm인 아크릴 팬톰에 삽입하여 140 kVp 엑스선을 1분씩 조사하였다. K-shell 엑스선 형광 신호는 금나노입자가 삽입되어 있는 아크릴 팬톰으로부터 측정한 엑스선 스펙트럼에서 금나노입자가 삽입되어 있지 않은 아크릴 팬톰으로부터 측정한 엑스선 스펙트럼의 차이를 통해 추출하였다. 금나노입자 주입 후 측정 데이터만으로 금나노입자의 엑스선 형광 영상을 획득하기 위해 인공지능 convolutional neural network (CNN) 모델을 개발하고 적용하였다. 실험용 쥐로부터 추출한 장기의 금나노입자 농도 측정을 위해 L-shell 엑스선 형광 시스템측정을 개발하였으며, 이 시스템은 SDD 측정기와 40 kVp의 선원을 이용하여 2.34 μg – 300 μg (금나노입자)/30 mg (물) (0.0078 wt%-1.0 wt%)의 금나노입자와 L-shell 엑스선 형광 신호 사이의 교정 곡선을 얻어 장기 내 축적된 금나노입자의 질량을 측정하였다. 핀홀 엑스선 형광 영상시스템을 이용하여 실험용 쥐에 금나노입자를 주입 후 시간에 따른 신장 내 금나노입자 농도 영상을 획득하였다. 안락사 후 적출한 양쪽 신장, 간, 비장, 혈액의 금나노입자 농도를 L-shell 엑스선 형광 체외 측정 시스템과 ICP-AES를 사용하여 측정하였고 영상시스템을 통해 획득한 농도와 비교·검증하였다. 영상 획득 시 실험용 쥐에 조사되는 방사선량은 TLD를 실험용 쥐의 피부에 붙여 측정하였다. 결과: 엑스선 형광 영상 분석을 통해 측정한 실험용 쥐의 오른쪽 신장 내 금나노입자의 농도는 주입 직후 1.58±0.15 wt%였으며, 60분 후 그 농도는 0.77±0.29 wt%로 감소하였다. 개발한 인공지능 CNN 모델을 적용해 금나노입자 주입 전 영상의 획득 없이 금나노입자의 엑스선 형광 영상을 생성할 수 있었다. 적출한 장기에서 측정된 금나노입자의 신장 내 농도는 L-shell 엑스선 형광 측정법으로 0.96±0.22 wt%, ICP-AES로는 1.00±0.50 wt% 였다. 영상 획득 시 실험용 쥐의 피부에 전달된 방사선량은 금나노입자 주입 전과 후 영상을 모두 획득 시(총 2분) 107±4 mGy, CNN 모델 적용 시(1분) 53±2 mGy로 측정되었다. 결론: 2차원 CZT 감마 카메라와 핀홀 콜리메이터를 사용한 엑스선 형광 영상시스템은 영상 획득 시간과 피폭 방사선량을 크게 감소시켰으며, 살아있는 쥐의 시간에 따른 체내 금나노입자 분포 변화를 영상화 할 수 있음을 증명하였다. 또한 L-shell 엑스선 형광 측정 시스템은 복잡한 전처리 과정 없이 체외 금나노입자의 농도를 정확하게 측정할 수 있었다. 본 개발 시스템을 금속나노입자의 체내 분포 연구를 위한 전임상시험용 분자영상장비로서 활용할 수 있을 것으로 기대한다.Purpose: This work aims to show the experimental feasibility for a dynamic in vivo X-ray fluorescence (XRF) imaging of gold in living mice exposed to gold nanoparticles (GNPs) using polychromatic X-rays. By collecting K-shell XRF photons using a 2D cadmium zinc telluride (CZT) gamma camera, the imaging system was expected to have a short image acquisition time and deliver a low radiation dose. This study also investigated the feasibility of using an L-shell XRF detection system with a single-pixel silicon drift detector (SDD) to measure ex vivo GNP concentrations from biological samples. Methods: Six GNP columns of 0 % by weight (wt%), 0.125 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt% and 2.0 wt% inserted in a 2.5 cm diameter polymethyl methacrylate (PMMA) phantom were used for acquiring a linear regression curve between the concentrations of GNPs and the K-shell XRF photons emitted from GNPs. A fan-beam of 140 kVp X-rays irradiated the phantom for 1 min in each GNP sample. The photon spectra were measured by the CZT gamma camera. The K-shell XRF counts were derived by subtracting the photon counts of the 0 wt% PMMA phantom (i.e., pre-scanning) from the photon counts of the GNP-loaded phantom (i.e., post-scanning). Furthermore, a 2D convolutional neural network (CNN) was applied to generate the K-shell XRF counts from the post-scanned data without the pre-scanning. For a more sensitive detection of the ex vivo concentrations of GNPs in the biological samples, the L-shell XRF detection system using the single-pixel SDD was developed. Six GNP samples of 2.34 μg–300 μg Au/30 mg water (i.e., 0.0078 wt%–1.0 wt% GNPs) were used for acquiring a calibration curve to correlate the GNP mass to the L-shell XRF counts. The kidney slices of three Balb/C mice were scanned at various periods after the injection of GNPs in order to acquire the quantitative information of GNPs. The concentrations of GNPs measured by the CZT gamma camera and the SDD were cross-compared and then validated by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The radiation dose was assessed by the measurement of TLDs attached to the skin of the mice. Results: The K-shell XRF images showed that the concentration of GNPs in the right kidneys from the mice was 1.58±0.15 wt% at T = 0 min after the injection. At T = 60 min after the injection, the concentration of GNPs in the right kidneys was reduced to 0.77±0.29 wt%. The K-shell XRF images generated by the 2D CNN were similar to those derived by the direct subtraction method. The measured ex vivo concentration of GNPs was 0.96±0.22 wt% by the L-shell XRF detection system while it was 1.00±0.50 wt% by ICP-AES. The radiation dose delivered to the skin of the mice was 107±4 mGy for acquiring one slice image by using the direct subtraction method while it was 53±2 mGy by using the 2D CNN. Conclusions: A pinhole K-shell XRF imaging system with a 2D CZT gamma camera showed a dramatically reduced scan time and delivered a low radiation dose. Hence, a dynamic in vivo XRF imaging of gold in living mice exposed to GNPs was technically feasible in a benchtop configuration. In addition, an L-shell XRF detection system can be used to measure ex vivo concentrations of GNPs in biological samples. This imaging system could provide a potential in vivo molecular imaging for metal nanoparticles to emerge as a radiosensitizer and a drug-delivery agent in preclinical studies.CHAPTER I. INTRODUCTION 1 I.1 Applications of Metal Nanoparticles in Medicine 1 I.2 Molecular Imaging of Metal Nanoparticles 3 I.3 X-ray Fluorescence Imaging 5 I.3.1 Principle of X-ray Fluorescence Imaging 5 I.3.2 History of X-ray Fluorescence Imaging 8 I.3.3 Specific Aims 12 CHAPTER II. MATERIAL AND METHODS 15 II.1 Monte Carlo Model 15 II.1.1 Geometry of Monte Carlo Simulations 15 II.1.2 Image Processing 21 II.1.3 Radiation Dose 27 II.2 Development of Pinhole K-shell XRF Imaging System 28 II.2.1 System Configuration and Operation Scheme 28 II.2.2 Pinhole K-shell XRF Imaging System 31 II.2.2.1 Experimental Setup 31 II.2.2.2 Measurement of K-shell XRF Signal 36 II.2.2.3 Signal Processing: Correction Factors 39 II.2.2.4 Application of Convolutional Neural Network 42 II.2.3 K-shell XRF Detection System 45 II.2.3.1 Experimental Setup 45 II.2.3.2 Signal Processing 47 II.2.4 L-shell XRF Detection System 49 II.2.4.1 Experimental Setup 49 II.2.4.2 Signal Processing 51 II.3 In vivo Study in Mice 53 II.3.1 Experimental Setup 53 II.3.2 Dose Measurement 56 CHAPTER III. RESULTS 57 III.1 Monte Carlo Model 57 III.1.1 Geometric Efficiency, System and Energy Resolution 57 III.1.2 K-shell XRF Image by Monte Carlo Simulations 59 III.1.3 Radiation Dose 69 III.2. Development of Pinhole XRF Imaging System 70 III.2.1 Pinhole K-shell XRF Imaging System 70 III.2.1.1 Energy Calibration and Measurement of Field Size 70 III.2.1.2 Raw K-shell XRF Signal 73 III.2.1.3 Correction Factors 78 III.2.1.4 K-shell XRF Image 81 III.2.2 K-shell XRF Detection System 85 III.2.3 L-shell XRF Detection System 89 III.3 In vivo Study in Mice 92 III.3.1 In vivo K-shell XRF Image 92 III.3.2 Quantification of GNPs in Living Mice 96 III.3.3 Dose Measurement 101 CHAPTER IV. DISCUSSION 102 IV.1 Monte Carlo Model 102 IV.2 Development of Pinhole K-shell XRF Imaging System 104 IV.2.1 Quantification of GNPs 105 IV.2.2 Comparison between MC and Experimental Results 107 IV.2.3 Limitations 108 IV.2.3.1 Concentration 108 IV.2.3.2 System Resolution 110 IV.2.3.3 Radiation Dose 111 IV.2.4 Application of CNN 112 IV.2.5 Future Work 114 CHAPTER V. CONCLUSIONS 115 REFERENCES 116 ABSTRACT (in Korean) 123Docto

혁신이 고용구조와 경제성장에 미치는 영향에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 기술경영·경제·정책전공, 2015. 8. 이정동.In the 1990s and the early part of the 2000s, many countries in the world have gone through the jobless growth in which employment stalled while economy grew. In many countries since the global financial crisis, there has also been occasions where the unemployment rate has increased instead of falling although the economy has bounced back. Likewise, South Korea has been going through this jobless growth since the middle of the 2000s. There are various claims in the circles of economics as to the cause of such phenomenon, one of which is that its due to technological innovation. That is, as technologies progress, productivity and output increases, but the demand for jobs decreases and has a bad influence on employment. Particularly, in the case of South Korea, which has reached the highest degree of intensity in its investment in R&D as continuous investment therein has increased, points are being raised that this is the cause of the jobless growth. Not only the quantitative aspect of employment but also the qualitative aspect is an issue, and, while technological innovation increases the demand for skilled laborers, it stunts the demand for unskilled laborers. That is, it brings about skill-biased technology change. Especially, Brynjolfsson and McAfee (2014) claimed in their book The Second Machine Age that, as information communication technology advances, new technologies and machines replace jobs faster, technological innovation causes skill-biased technology change and capital-biased technology change, and leads to income polarization. However, the recently raised arguments are only considering the direct influences that innovation has on employment. The innovation affects employment through various routes. Especially, when diversity of products increases through innovation, it leads to indirect influences in which new demand is created and the employment increases. Therefore, the influence of innovation on employment and growth should be examined with its indirect effects as well as direct. Hence, in this study, using the computable general equilibrium model, which is capable of concurrently considering various aspects of economy, it was intended to examine what influence innovation has on employment structure and economic growth. For this, knowledge-based Social Accounting Matrix and knowledge-based computable general equilibrium model have been constructed. The result of the study utilizing the knowledge-based computable general equilibrium model is summed up as follows. Viewed from the employment aspect first, additional innovative activities turned out to increase the total demand of labor, increasing the demand for unskilled, skilled, and high-skilled labor all together. The demand for the high-skilled labor especially showed the highest increase rate. When examined by the industry, the high-tech manufacturing which invests heavily in R&D also showed the greatest rate of employment increase. In sequence, when viewed from the aspect of economic growth, additional innovative activities turned out to have a positive influence on economic growth, which led to the increase in all production elements added values. In the case of capital, high-skilled labor, and knowledge, however, while their weights in added values have increased, unskilled and skilled labors weights in added value turned out to have decreased by the capital-biased technology change and the skill-biased technology change. Accordingly, the foregoing turned out to have a bad influence on income distribution and deepened income polarization. Meanwhile, when viewed by the industry, due to the additional innovative activities, the output of the manufacturing industry turned out to show a higher increase rate than that of the service industry.Abstract Contents List of Tables List of Figures Chapter 1. Introduction 1.1 Research background 1.2 Research motivation and purpose 1.3 Outline of the study Chapter 2. Theoretical Background 2.1 Innovation and employment 2.1.1 Compensation mechanism 2.1.2 Innovation and employment: The empirical evidence 2.1.3 Product innovation and Process innovation 2.1.4 Skill-Biased Technological Change 2.1.5 Capital-Biased Technological Change 2.2 Innovation and Employment in Digital Age 2.2.1 Ability of New Machines 2.2.2 Technological Advance and Inequality 2.3 Knowledge-Based Computable General Equilibrium 2.4 Contribution of the Study Chapter 3. Methodology 3.1 Construction of knowledge-based Social Accounting Matrix 3.1.1 Social Accounting Matrix 3.1.2 Input?Output Table 3.1.3 Household Income and Expenditure Survey 3.1.4 Knowledge-Based Social Accounting Matrix 3.1.5 Household Classification 3.1.6 Classification of Labor 3.1.7 Integrated SAM 3.2 Fixed Capital Stock and Knowledge Capital Stock 3.2.1 Fixed Capital Stock 3.2.2 Knowledge Stock 3.3 Construction of Knowledge-Based CGE Model 3.3.1 Structure of Knowledge-Based CGE 3.3.2 Equation of Knowledge-Based CGE Model Chapter 4. The effect of innovation on employment structure and economic growth 4.1 Background and Purpose of Study 4.2 Analytical framework 4.3 Simulation analysis 4.3.1 Scenario 4.3.2 Change of Employment 4.3.3 Economic Growth 4.3.4 Income Distribution 4.4 Effect According to Changes in Elasticities of Substitution between Factor Inputs 4.4.1 Influence of Changes in Elasticities of Substitution between Factor Inputs on Employment 4.4.2 Influence of Changes in Elasticities of Substitution between Factor Inputs on Economic Growth 4.5 Sub-Conclusion Chapter 5. Conclusion 5.1 Summary of findings and policy implications 5.2 Significance and limitation of study, and future research Bibliography Abstract (Korean)Docto

Dab2 expressed in tumor positively regulates the migration of endothelial cells

1

Conceptual approach to workspace planning indicators for the habitability of high-rise office building

학위논문(박사)--서울대학교 대학원 :건축학과,2005.Docto

Xenopus 배아 발생 과정에서 TGF-beta 신호전달경로를 조절하는 분자들의 기능에 관한 연구

DoctorTGF-beta signaling plays major roles in various developmental processes including germ-layer specification, patterning, left-right asymmetry, and organogenesis. TGF-beta signals are propagated into the nucleus by Smad complex activated by TGF-beta receptors, and many regulators have been implicated in the regulation of Smad activation by the receptors. In this study, I analyzed the developmental functions of regulators of TGF-beta signaling including XDab2 and Xdpcp in Xenopus development in order to gain a better understanding of the molecular mechanisms underlying the germ-layer specification and angiogenesis in Xenopus embryos.1. Role of XDab2 in Xenopus embryonic angiogenesisThe molecular mechanisms governing the formation of the embryonic vascular system remain poorly understood. Here, I show that Disabled-2 (Dab2), a cytosolic adaptor protein, has a pivotal role in the blood vessel formation in Xenopus early embryogenesis. Xenopus Disabled-2 (XDab2) is spatially localized to the blood vessels including the intersomitic veins (ISV) in early embryos. Both antisense morpholino oligonucleotide (MO)-mediated knockdown and overexpression of XDab2 inhibit the formation of ISV, which arise from angiogenesis. In addition, I found that activin-like signaling is essential for this angiogenic event. Functional assays in Xenopus animal caps reveal that activin-like signals induce VEGF expression and this induction can be inhibited by XDab2 depletion. However, XDab2 MO has no effects on the induction of other target genes by activin-like signals. Furthermore, I show that the disruption of the sprouting ISV in XDab2-depleted embryos can be rescued by coexpression of VEGF. Taking together, I suggest that XDab2 regulates the embryonic angiogenesis by mediating the VEGF induction by activin-like signaling in Xenopus early development. 2. Role of Xdpcp in Xenopus germ-layer specificationPhosphotyrosine binding (PTB) domains, which are found in a large number of proteins, have been implicated in signal transduction mediated by growth factor receptors. However, the in vivo roles of these PTB-containing proteins remain to be investigated. Here, I show that Xdpcp (Xenopus dok-PTB containing protein) has a pivotal role in regulating mesendoderm formation in Xenopus, and negatively regulates the activin/nodal signaling pathway. I isolated cDNA for xdpcp and examined its potential role in Xenopus embryogenesis. I found that Xdpcp is strongly expressed in the animal hemisphere at the cleavage and blastula stages. The overexpression of xdpcp RNA affects activin/nodal signaling, which causes defects in mesendoderm formation. In addition, loss of Xdpcp function by injection of morpholino oligonucleotides (MO) leads to the expansion of the mesodermal territory. Moreover, I found that the axis duplication by ventrally forced expression of activin is recovered by coexpression with Xdpcp. In addition, Xdpcp inhibits the phosphorylation and nuclear translocation of Smad2. Furthermore, I also found that Xdpcp interacts with Alk4, a type I activin receptor, and inhibits activin/nodal signaling by disturbing the interaction between Smad2 and Alk4. Taken together, these results indicate that Xdpcp regulates activin/nodal signaling that is essential for mesendoderm specification

메디톨로지: 의료 온톨로지 데이터의 가시화를 위한 툴

2

대용량 온톨로지 데이터의 가시화 연구

2

Regulation of Wnt signaling pathway by targeting Dishevelled for ubiquitin-mediated degradation

1

Negative Regulation of Activin/Nodal Signaling by a Novel PTB Protein in Xenopus Embryogenesis

2

Identification of a novel ubiquitin ligase regulating Dishevelled in Wnt signaling pathways

1