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You searched for subject:(Tissue Section). Showing records 1 – 2 of 2 total matches.

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1. Geórgia Santos Joana. Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV.

Degree: Master, 2006, Centro de Desenvolvimento da Tecnologia Nuclear

Existe um grande número de estudos que examina a dependência entre energia e alcance para elétrons com energias desde alguns keVs até centenas de MeVs. Porém, a descrição quantitativa do transporte de elétrons de baixa energia é um problema complexo, especialmente devido à não disponibilidade de dados confiáveis para as seções de choque dos diferentes mecanismos por meio dos quais elétrons interagem com a matéria. Uma vez que os modelos analíticos de transporte de elétrons ou são incompletos ou apresentam dificuldades até o momento intransponíveis, os códigos de Monte Carlo têm sido a alternativa adotada nestas abordagens e são hoje extensivamente utilizados. É sabido que na interação de radiações ionizantes com o tecido vivo podem ocorrer danos severos em estruturas nos níveis celular e sub-celular. Uma vez que a transferência de energia de radiações ionizantes para o meio ocorre predominantemente através da interação dos elétrons secundários produzidos por esta com o material, existe um interesse especial na determinação da relação entre energia inicial e alcance para elétrons; especialmente os de baixa energia. Neste trabalho é estudada a relação entre energia inicial e alcance em meio biológico para elétrons com energias entre 110 eV e 50 keV. Para tal foi utilizado o código de Monte Carlo PENELOPE com o qual foram realizadas simulações do transporte de elétrons de baixa energia (110 eV a 50 keV) e dos fótons secundários gerados por estes provenientes de uma fonte monoenergética isotrópica localizada no interior de um meio tecido equivalente homogêneo. A partir daí, as grandezas de interesse foram calculadas e analisadas. Advisors/Committee Members: Teogenes Augusto da Silva, Carlos Henrique Costa Moreira, Suely Epsztein Grynberg.

Subjects/Keywords: FISICA NUCLEAR; Simulação computadorizada; Método Monte Carlo; Electrons; Seção de choque; Material equivalente a tecido; Elétrons; Computerized simulation; Monte carlo method; Transport; Cross section; Tissue equivalent materials

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Joana, G. S. (2006). Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV. (Masters Thesis). Centro de Desenvolvimento da Tecnologia Nuclear. Retrieved from http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=47 ;

Chicago Manual of Style (16th Edition):

Joana, Geórgia Santos. “Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV.” 2006. Masters Thesis, Centro de Desenvolvimento da Tecnologia Nuclear. Accessed December 14, 2019. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=47 ;.

MLA Handbook (7th Edition):

Joana, Geórgia Santos. “Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV.” 2006. Web. 14 Dec 2019.

Vancouver:

Joana GS. Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV. [Internet] [Masters thesis]. Centro de Desenvolvimento da Tecnologia Nuclear; 2006. [cited 2019 Dec 14]. Available from: http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=47 ;.

Council of Science Editors:

Joana GS. Estudo do alcance de elétrons com energias entre 110 eV e 50 KeV. [Masters Thesis]. Centro de Desenvolvimento da Tecnologia Nuclear; 2006. Available from: http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=47 ;

2. Han, Aiguo. Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models.

Degree: PhD, 1200, 2015, University of Illinois – Urbana-Champaign

This dissertation investigates the ultrasonic scattering from tumors. Tumors are complex acoustic scattering media and to date there has not been an adequate acoustic scattering model that fits them well. The tumor scattering mechanisms are studied herein by a step-wise approach: starting from simple (low-concentration cell pellet biophantoms) to moderately complex (high-concentration cell pellets) and to significantly complex media (actual tumors). The comparison between the backscattering coefficients (BSC) of lower- and higher-concentration cell pellet biophantoms suggest that high concentration of cells could lead to correlation in cell positions, causing additional scattering that may be modeled by the structure function. The structure function for the high-concentration cell pellet biophantom was isolated by comparing the BSC of the high-concentration biophantom to that of a very low-concentration biophantom where the cell spatial positions are assumed to be random. Polydisperse structure function models that take into account the polydispersity of scatterer radii are introduced and shown to be consistent with the structure function curves measured from BSC. The two-dimensional (2D) structure function is estimated from the histological sections, and shown to have a similar shape to the theoretical structure function and to that calculated from BSC. The comparison between cell pellets and tumors of the same cell type suggests that the anatomic details in tumors must be taken into account for modeling purposes, in addition to the scattering from cells. Also, histology studies suggest that the structure functions in tumors are slightly different from those in cell pellets: the tumor cell spatial arrangement is slightly more random compared to cell pellets. The effect of the structure function on parameter estimation is discussed. Further work is shown to be required for modeling the tumor structure function. Additionally, the comparison between different tumor types shows that ultrasound backscattering is sensitive to unique tumor structures. The EHS tumor has a distribution of clustered cells and shows a different BSC and structure function pattern than the tumors that have a homogenous distribution of cells. A scattering model is developed to detect the clustering feature. Overall, the dissertation improves our understanding of the acoustic scattering mechanisms in tumors, and improves the tumor scattering modeling. Advisors/Committee Members: O'Brien, William D. (advisor), O'Brien, William D. (Committee Chair), Oelze, Michael L. (committee member), Insana, Michael F. (committee member), Jin, Jianming (committee member), Franceschini, Emilie (committee member).

Subjects/Keywords: Quantitative Ultrasound; High-frequency Ultrasound; Tissue Characterization; Acoustic Scattering; Backscatter Coefficient; Structure Function; Pair Correlation Function; Attenuation; Cell Pellet Biophantom; Tumor; Tissue Section; Dense Media; Clustering

…x28;defined as the sound speed times the mass density) contrast between two tissue… …obtain operator- and system-independent quantitative information from the tissue under… …coefficient (BSC) which are intrinsic properties of the tissue and are not dependent on… …scattering models that mimic tissue anatomic structures can be fitted to the BSC versus frequency… …of model-based QUS techniques relies on the understanding of the tissue scattering… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Han, A. (2015). Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/72757

Chicago Manual of Style (16th Edition):

Han, Aiguo. “Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models.” 2015. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed December 14, 2019. http://hdl.handle.net/2142/72757.

MLA Handbook (7th Edition):

Han, Aiguo. “Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models.” 2015. Web. 14 Dec 2019.

Vancouver:

Han A. Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2015. [cited 2019 Dec 14]. Available from: http://hdl.handle.net/2142/72757.

Council of Science Editors:

Han A. Ultrasonic characterization of cell pellet biophantoms and tumors using quantitative ultrasound models. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2015. Available from: http://hdl.handle.net/2142/72757

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