Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Ansari, Armin, Committee Member ; Hertel, Nolan, Committee Chair ; Wang, Chris, Committee Member. Includes bibliographical references.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Ansari, Armin, Committee Member ; Wang, C.-K. Chris, Committee Member ; Hertel, Nolan, Committee Chair.

After a Radiological Dispersal Device (RDD) event, there will not be time to transport people to a whole-body-counter (WBC), since it is a specialized instrument. This work will assess the feasibility of using handheld spectrometers for measuring the radioactivity that may have been inhaled by a victim as a consequence of an RDD event. Measurements were made with a handheld isotope identifier using a slab phantom and several radioactive point sources. A Lawrence Livermore National Laboratory (LLNL) Realistic Torso Phantom and a set of phantoms based on Medical Internal Radiation Dose (MIRD) reports were also used in this work. These phantoms include the human skeleton and have tissue-equivalent organs. Computational models were developed of all of the phantoms using the Monte Carlo Transport code MCNP. After validation of the computer model, MCNP runs were conducted using other sources that are likely to be used in a RDD. Calculations were then done to find the Minimum Detectable Activity (MDA) of all sources used. The Minimum Detectable Dose (MDD) was then calculated for the MIRD phantoms at various times after inhalation.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Nolan Hertel; Committee Member: Armin Ansari; Committee Member: Chris Wang; Committee Member: Rebecca Howell.

M. S.

Assaying internal contamination due to inhalation is a primary concern in developing emergency procedures related to Radioactive Dispersal Devices (RDD). One method of determining internal contamination makes use of a common medical instrument, a Thyroid Uptake System (TUS). The TUS used in this research has two collimators a thyroid uptake collimator and a bioassay collimator. Both collimators were considered and modeled in MCNP to be used in conjunction with six MIRD-type (Medical Internal Radiation Dose) phantoms. The collimators were placed in four positions on the phantoms the front right lung, the back right lung, the neck, and the thigh. Unit sources of Cs-137, Co-60, I-131, Ir-192, Am-241, and Sr/Y-90 were placed in the organs of the phantoms. MCNP particle tallies were performed over the detector crystal volume to determine the count-rate contributions from the unit source in each organ. Biokinetic modeling was performed using DCAL (Dose and Risk Calculation System) to generate coefficients to describe activity as a function of time in various organs. By folding the count-rate results with the organ concentrations, the detector response as a function of time after intake has been determined. This work was performed under funding provided by the Radiation Studies Branch of the Centers for Disease Control and Prevention.

CNPq / Neste trabalho foram desenvolvidos phantoms para dois protótipos de tomografia com feixe de prótons (pCT). Um phantom foi desenvolvido para um protótipo de um mini tomógrafo utilizando um feixe de prótons de baixa energia, que está sendo desenvolvido na Universidade Tecnológica Federal do Paraná (UTFPR). O protótipo encontra-se em fase de teste no cíclotron CV-28 do Instituto de Engenharia Nuclear (IEN). Dois outros phantoms foram desenvolvidos para um protótipo de pCT no Centro Médico da Universidade de Loma Linda – CA, EUA (LLUMC). Os código GEANT4 e SRIM foram utilizados para simular todos os elementos que compõe os protótipos. Também foram feitos aprimoramentos no protótipo da UTFPR/IEN, entre eles um sistema de controle eletrônico do mecanismo, operado por um programa através de um computador, alteração no sistema de colimação para melhorar a resolução e a reconstrução de imagens obtidas por simulações. Foram realizados testes experimentais de perda de energia de prótons em polietileno de alta densidade (PEAD) no CV-28. Também foi feito experimentos de perda de energia de prótons em camadas de Poliestireno no LLUMC e comparação com dados simulados. Esses dois phantoms em PEAD foram construídos e testados no protótipo do LLUMC e um programa foi desenvolvido para a análise dos dados. / In this work phantoms were developed for two tomographic systems with proton beam (pCT). A phantom was developed for a mini scanner using a low energy proton beam, which is being developed at the Federal University of Technology - Parana (UTFPR) and tested at the CV-28 cyclotron at the Institute of Nuclear Engineering (IEN). Two additional phantoms were developed for the pCT prototype at Loma Linda University Medical Center – CA, USA (LLUMC). SRIM and Geant4 codes were used to simulate all the elements of the prototypes. Improvements were made in the UTFPR/IEN prototype such as electronic control system of mechanism, controlled by a computer program, upgrade in the collimation system to improve the resolution of reconstructed images obtained by simulations. Experimental energy loss tests were done with polyethylene protons of high density (PEAD) in CV-28. Experiments of energy loss in layers of polystyrene at the LLUMC were also done and compared with simulated data. Both phantoms were constructed and tested in the prototype of LLUMC and a program was developed for data analysis.

Este trabalho apresenta o desenvolvimento de um estimulador galvânico vestibular para ser usado em experimentos de imageamento por ressonância magnética funcional (fMRI). Em experiências de fMRI é necessário a produção de estímulos somatossensoriais no paciente. Os estímulos devem ser sincronizados com a sequência de pulsos da fMRI. O estimulador foi dividido em circuitos analógicos (colocados dentro da sala do magneto) e circuitos digitais (sala de comando do sistema de MRI). A comunicação entre os circuitos é feita através de fibra óptica. Experimentos de fMRI realizados com voluntários demonstraram que o estimulador proposto é capaz de manter a sincronização com sistema de fMRI e pode ser usado para localizar as áreas do cérebro que são ativados pelo sistema vestibular. / This work presents the development of a galvanic vestibular stimulator to be used in functional magnetic resonance imaging experiments (fMRI). In fMRI experiments it is required the production of somatosensory stimuli in the patient must be sincronized with the fMRI pulse sequence. The stimulator circuits were divided in analog circuits (placed within the magnet room) and digital circuits (placed in the MRI command room). The communication between the circuits is made through optical fiber. fMRI experiments performed with volunteers demonstrated that the proposed stimulator is able to keep the sincronization with the MRI system and can be used to locate the brain areas that are activated by the vestibular system.

CAPES / Este trabalho apresenta a adaptação do código Geant4 para conversão de imagens DICOM (Digital Imaging and Communications in Medicine) de crânio, obtidas em tomografia convencional (CT), em um phantom antropomórfico virtual. O trabalho foi baseado no exemplo médico denominado “Código Dicom”, disponibilizado pelos desenvolvedores do código Geant4. Durante a execução do trabalho foram feitas reestruturações no exemplo “Código Dicom” para a conversão direta de imagens tomográficas em um phantom virtual. Foram retirados do código todos os passos referentes aos eventos físicos nucleares. Foi reformulado o arquivo DicomHandler.cc para não realizar a compressão dos pixels da imagem de CT. Em seguida foi realizada a conversão direta de imagens tomográficas, de um phantom físico de polietileno (PEAD) com núcleo central de acrílico e de um crânio real humano, em phantoms virtuais para o código Geant4. Os resultados demonstraram que com este código é possível a reconstrução de áreas anatômicas com geometrias complexas, partindo do uso de imagens tomográficas reais. / This work presents the adaptation of the Geant4 code for converting DICOM (Digital Imaging and Communications in Medicine) images of a skull, obtained in conventional tomography (CT), into a virtual anthropomorphic phantom. The work was based on the medical example named "Dicom Code" provided by the developers of the code Geant4. During the execution, restructurings using the "Dicom Code" example were made to achieve the direct conversion of tomographic images into a virtual phantom. All the steps referring to nuclear physical events were removed. The file DicomHandler.cc was reformulated in order to avoid the pixels compression of the CT image. The CT images of a physical polyethylene (PEAD) phantom with acrylic core and a real human skull were then converted into virtual phantoms for the code Geant4. The results showed that with this code, it may be possible the reconstruction of anatomical areas with complex geometries, based on the use of real tomographic images.

Este trabalho apresenta o desenvolvimento de um estimulador galvânico vestibular para ser usado em experimentos de imageamento por ressonância magnética funcional (fMRI). Em experiências de fMRI é necessário a produção de estímulos somatossensoriais no paciente. Os estímulos devem ser sincronizados com a sequência de pulsos da fMRI. O estimulador foi dividido em circuitos analógicos (colocados dentro da sala do magneto) e circuitos digitais (sala de comando do sistema de MRI). A comunicação entre os circuitos é feita através de fibra óptica. Experimentos de fMRI realizados com voluntários demonstraram que o estimulador proposto é capaz de manter a sincronização com sistema de fMRI e pode ser usado para localizar as áreas do cérebro que são ativados pelo sistema vestibular. / This work presents the development of a galvanic vestibular stimulator to be used in functional magnetic resonance imaging experiments (fMRI). In fMRI experiments it is required the production of somatosensory stimuli in the patient must be sincronized with the fMRI pulse sequence. The stimulator circuits were divided in analog circuits (placed within the magnet room) and digital circuits (placed in the MRI command room). The communication between the circuits is made through optical fiber. fMRI experiments performed with volunteers demonstrated that the proposed stimulator is able to keep the sincronization with the MRI system and can be used to locate the brain areas that are activated by the vestibular system.