201 research outputs found

    Magnetic-plasmonic nanoparticles for multimodal bioimaging and hyperthermia.

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    257 p.El término "teranóstica" hace referencia a la integración inteligente de diagnósticos y terapias. Esta capacidad de obtener imágenes y tratar tumores simultáneamente con nanopartículas puede resultar ventajosa frente a las técnicas convencionales de diagnóstico y terapia. Así, una ventaja adicional tanto para la obtención de imágenes como para el tratamiento es poder estudiar las enfermedades in vitro utilizando diversos métodos de obtención de imágenes y combinándolos con tratamientos novedosos.La síntesis y optimización de nanopartículas híbridas que combinan propiedades magnéticas y plasmónicas se ha estudiado durante esta tesis. Además, estas nanoestructuras pueden funcionalizarse con moléculas adicionales para aplicaciones en imagen e hipertermia. La utilización de estas nanopartículas híbridas se ha estudiado para su uso específico como agentes de contraste para resonancia magnética, dispersión Raman mejorada en la superficie y microscopía de fluorescencia en modelos celulares 2D y 3D y en modelos ex vivo. Además, se ha evaluado la aplicación de los híbridos para calentamiento fototérmico en modelos celular 2D y 3D y etiquetado específico de células en modelos celulares 2D

    GPU-Accelerated Algorithms for Compressed Signals Recovery with Application to Astronomical Imagery Deblurring

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    Compressive sensing promises to enable bandwidth-efficient on-board compression of astronomical data by lifting the encoding complexity from the source to the receiver. The signal is recovered off-line, exploiting GPUs parallel computation capabilities to speedup the reconstruction process. However, inherent GPU hardware constraints limit the size of the recoverable signal and the speedup practically achievable. In this work, we design parallel algorithms that exploit the properties of circulant matrices for efficient GPU-accelerated sparse signals recovery. Our approach reduces the memory requirements, allowing us to recover very large signals with limited memory. In addition, it achieves a tenfold signal recovery speedup thanks to ad-hoc parallelization of matrix-vector multiplications and matrix inversions. Finally, we practically demonstrate our algorithms in a typical application of circulant matrices: deblurring a sparse astronomical image in the compressed domain

    Standardisation of magnetic nanoparticles in liquid suspension

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    Suspensions of magnetic nanoparticles offer diverse opportunities for technology innovation, spanning a large number of industry sectors from imaging and actuation based applications in biomedicine and biotechnology, through large-scale environmental remediation uses such as water purification, to engineering-based applications such as position-controlled lubricants and soaps. Continuous advances in their manufacture have produced an ever-growing range of products, each with their own unique properties. At the same time, the characterisation of magnetic nanoparticles is often complex, and expert knowledge is needed to correctly interpret the measurement data. In many cases, the stringent requirements of the end-user technologies dictate that magnetic nanoparticle products should be clearly defined, well characterised, consistent and safe; or to put it another way—standardised. The aims of this document are to outline the concepts and terminology necessary for discussion of magnetic nanoparticles, to examine the current state-of-the-art in characterisation methods necessary for the most prominent applications of magnetic nanoparticle suspensions, to suggest a possible structure for the future development of standardisation within the field, and to identify areas and topics which deserve to be the focus of future work items. We discuss potential roadmaps for the future standardisation of this developing industry, and the likely challenges to be encountered along the way

    Standardisation of magnetic nanoparticles in liquid suspension

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    Suspensions of magnetic nanoparticles offer diverse opportunities for technology innovation, spanning a large number of industry sectors from imaging and actuation based applications in biomedicine and biotechnology, through large-scale environmental remediation uses such as water purification, to engineering-based applications such as position-controlled lubricants and soaps. Continuous advances in their manufacture have produced an ever-growing range of products, each with their own unique properties. At the same time, the characterisation of magnetic nanoparticles is often complex, and expert knowledge is needed to correctly interpret the measurement data. In many cases, the stringent requirements of the end-user technologies dictate that magnetic nanoparticle products should be clearly defined, well characterised, consistent and safe; or to put it another way—standardised. The aims of this document are to outline the concepts and terminology necessary for discussion of magnetic nanoparticles, to examine the current state-of-the-art in characterisation methods necessary for the most prominent applications of magnetic nanoparticle suspensions, to suggest a possible structure for the future development of standardisation within the field, and to identify areas and topics which deserve to be the focus of future work items. We discuss potential roadmaps for the future standardisation of this developing industry, and the likely challenges to be encountered along the way

    초고자장 자기공명영상의 B1+ 불균일성 완화를 위한 전자기 퍼텐셜 기반의 하이브리드 모드 성형 연구

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    학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2021. 2. 박남규.Magnetic resonance imaging (MRI) is one of the most popular diagnostic imaging tools with its safety and applicability. By increasing the strength of operating B0, MRI has improved image quality, and recent research has enabled the imaging modality to increase the operating B0 fields over 7T, which is in the ultra-high-field (UHF) range. UHF MRI has various advantages, including the enhancement of the signal-to-noise ratio (SNR), spectral and spatial resolutions, and contrast. Especially, UHF MRI has an irreplaceable strength in precise scanning of the brain tissue to examine various neurological disorders. Nonetheless, the increase of the operating magnetic field causes the severe issue of RF B1+ field inhomogeneity, which is detrimental to homogeneous retrieval of the intensity, SNR, and contrast in MR image. To tackle the critical issue of inhomogeneity, a multitude of approaches for shimming the B1+ inhomogeneity have been proposed. Among them, RF passive shimming by pad structure filled with dielectric materials has proven its validity as a safe and well-compatible solution applicable to clinical applications. While successful in controlling the field distribution, most of the past efforts utilizing the local enhancement of B1+ in the vicinity of the pad structures, especially those in contact with the body, often resulted in deterioration of the global B1+ homogeneity over the ROI. Therefore, a study on a scheme for achieving the global homogeneity of B1+ is required. In this dissertation, we propose the notion of the mode shaping based on the evanescent coupling of the electromagnetic potentials to address the issue of B1+ field homogeneity. Treating the human head as a resonator, we apply an auxiliary potential well evanescent coupled to the head potential, to investigate the effects of the auxiliary potential configuration on the mode shaping and the resultant field homogenization. From the analysis and optimization, we obtain a robust mode shaping pad solution to achieve 2D global homogenization of axial B1+ field for the phantom of various geometry and the realistic voxel model of heterogeneous materials, which is applicable to the conventional 2D MRI scanning. Furthermore, extending the mode shaping approach with symmetry breaking, we propose the mode shaping solutions for 3D global homogenization of B1+ field. For the practical assessment of the feasibility of the mode shaping solutions, the SAR and robustness analysis of the solutions are also conducted. We believe that this study will expand the capability of the RF passive shimming in UHF MRI by providing an unconventional viewpoint and systematic guideline for the mitigation of B1+ inhomogeneity.자기 공명 영상법은 안정성과 확장성을 바탕으로 가장 광범위하게 이용되고 있는 영상 기법 중 하나이다. 자기 공명 영상법은 동작 정 자기장을 높임으로써 영상의 질을 향상시킬 수 있는데, 최근에는 7T 이상의 초고자장 자기 공명 영상법이 활용되고 있다. 초고자장 자기 공명 영상법은 신호 대비 잡음도, 공간 시간 해상도, 대조도 등을 향상시키는데, 이를 통해 특히 뇌 정밀 영상 촬영에 대체 불가한 강점을 가진다. 이러한 장점에도 불구하고 정 자기장의 증가는 고주파 신호 B1+ 필드의 불균일성을 야기하며, 이는 다시 이미지 퀄리티를 떨어뜨리는 등 원치 않는 영향으로 이어진다. B1+ 필드 불균일성 문제를 해결하기 위해 다양한 방법이 시도되었으며, 이 중에서도 유전체 물질로 채운 구조물인 패드를 이용한 수동 보정 접근은 기존 시스템에 호환이 되고 안정성을 인정받아 임상에서의 적용 가능성이 알려져 있는 대표적인 전략이다. 필드 패턴을 바꾸어주는 효과를 기반으로 하여 관심 영역에 붙여 주변부의 불균일성을 성공적으로 완화하는 이 방법은 최근 고 유전체 물질의 활용과 더불어 관심을 받고 있지만, 관심 부분 영역 전체에 대해서는 악영향을 수반하므로 광역 균일화를 위한 방법에 대한 연구가 필요하다. 본 학위 논문에서는, B1+ 필드의 광역 균일화를 위한 방법으로 퍼텐셜의 에바네센트 커플링을 기반으로 한 모드 성형 방식을 제안한다. 인체를 공진기로 보고 그것과 에바네센트 결합을 하는 보조 퍼텐셜을 적용함으로써 모드 성형 능력을 확인하였으며, 그것을 조절함으로써 스캐닝하려는 대상의 형태나 물질 분포에 강건한 축성 B1+ 필드의 광역 균일화를 구현할 수 있다. 또한, 해당 개념을 확장하여 삼차원 광역 균일화를 수행하는 모드 성형법을 제안한다. 이와 더불어, 이러한 모드 성형법의 실제적 적용가능성을 평가하기 위해 SAR와 강건성 분석을 수행하였다. 본 연구는 초고자장 자기 공명 영상법의 B1+ 불균일성 완화에 대한 색다른 시각과 체계적인 방법을 제공함으로써 고주파 신호 균일화에의 수동 보정 방법의 역할을 확장하는 지침이 될 것으로 기대된다.Abstract i Table of Contents iv List of Tables viii List of Figures ix Chapter 1. Introduction 1 1.1 Ultra-high-field magnetic resonance imaging: promising scheme for clinical imaging 2 1.2 Inhomogeneity problem in UHF MRI: Motivation 5 1.3 Dissertation overview 7 Chapter 2. Theory and method for the B1+ shimming 9 2.1 Electromagnetics in the UHF MRI 10 2.1.1 Principal physics of MRI system in view of electromagnetics 10 2.1.2 Issue of RF B1+ field inhomogeneity in UHF MRI 14 2.2 B1 shimming in UHF MRI 17 2.2.1 Current approaches and achievements for B1+ shimming 17 2.2.2 Background and motivation of our strategy for B1 shimming: mode shaping pad 21 2.3 Optical mode shaping based on evanescent coupling for mitigation of B1+ inhomogeneity 23 2.3.1 UHF MRI systems as an optical waveguide 23 2.3.2 Mode shaping via evanescent coupling in optics 24 2.3.3 Evanescent coupling of electromagnetic potentials in UHF MRI 26 2.4 Conclusion 29 Chapter 3. Hybrid mode shaping with auxiliary EM potential for global 2D homogenization 30 3.1 Mode shaping for 2D MRI scanning 31 3.2 Concept of hybrid mode shaping with auxiliary EM potential 34 3.3 Optimization process 38 3.4 Effect of the phantom and pad geometry and other material parameters of the pad 47 3.5 Effect of the inhomogeneous distribution of materials: human voxel model 52 3.6 Effect of the mode shaping potential pad on the SAR distributions 56 3.7 Robustness and stability of the mode shaping solution 59 3.8 Conclusion 61 Chapter 4. Hybrid mode shaping with auxiliary EM potential for global 3D homogenization 63 4.1 Mode shaping for 3D MRI scanning 64 4.2 Hat pad potential for lower-order mode excitation 66 4.3 Asymmetric shifted pad potential 72 4.4 Effect of the shifted potential pad on the SAR distribution 79 4.5 Robustness of the mode shaping with asymmetric potential pad 81 4.6 Conclusion 83 Chapter 5. Conclusion 84 Appendix A. Supplements for Chapter 3 86 A.1 Material and geometry for the MIDA voxel model 86 A.2 Excitation with realistic TEM coils 91 Appendix B. Supplements for Chapter 4 93 B.1 Cylinder can solution for the global homogenization 93 Appendix C 97 Bibliography 98 Abstract in Korean 109Docto

    Magnetic Nanomaterials

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    The constant search for innovative magnetic materials increasingly leads to the creation of highly engineered systems built in different forms (films, wires, particles), structured on the nanoscale in at least one spatial direction, and often characterized by the coexistence of two or more phases that are magnetically and/or structurally different. In magnetic systems, the nanometric structural characteristics of the constituent elements, together with the type and strength of the magnetic interactions between them, determine the overall magnetic behavior and can lead to the appearance of unexpected and amazing magnetic phenomena. Indeed, the study of the magnetic properties of nanomaterials continues to arouse great interest for their intriguing fundamental properties and prospective technological applications. This Special Issue contributes to broadening the knowledge on magnetic nanomaterials, demonstrating the breadth and richness of this research field as well as the growing need to address it through an interdisciplinary approach. The papers collected in this book (two reviews and eight regular articles) report cutting-edge studies on the production and characterization of a variety of novel magnetic nanomaterials (nanoparticles, nanocomposites, thin films and multilayers), which have the potential to play a key role in different technologically advanced sectors, such as biotechnology, nanomedicine, energy, spintronics, data storage, and sensors

    High-performance time-series quantitative retrieval from satellite images on a GPU cluster

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    The quality and accuracy of remote sensing instruments continue to increase, allowing geoscientists to perform various quantitative retrieval applications to observe the geophysical variables of land, atmosphere, ocean, etc. The explosive growth of time-series remote sensing (RS) data over large-scales poses great challenges on managing, processing, and interpreting RS ‘‘Big Data.’’ To explore these time-series RS data efficiently, in this paper, we design and implement a high-performance framework to address the time-consuming time-series quantitative retrieval issue on a graphics processing unit cluster, taking the aerosol optical depth (AOD) retrieval from satellite images as a study case. The presented framework exploits the multilevel parallelism for time-series quantitative RS retrieval to promote efficiency. At the coarse-grained level of parallelism, the AOD time-series retrieval is represented as multidirected acyclic graph workflows and scheduled based on a list-based heuristic algorithm, heterogeneous earliest finish time, taking the idle slot and priorities of retrieval jobs into account. At the fine-grained level, the parallel strategies for the major remote sensing image processing algorithms divided into three categories, i.e., the point or pixel-based operations, the local operations, and the global or irregular operations have been summarized. The parallel framework was implemented with message passing interface and compute unified device architecture, and experimental results with the AOD retrieval case verify the effectiveness of the presented framework.N/

    Magnetic Hybrid-Materials

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    Externally tunable properties allow for new applications of suspensions of micro- and nanoparticles in sensors and actuators in technical and medical applications. By means of easy to generate and control magnetic fields, fluids inside of matrices are studied. This monnograph delivers the latest insigths into multi-scale modelling, manufacturing and application of those magnetic hybrid materials
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