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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.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis (M.Sc.). / Written for the Medical Physics Department. Title from title page of PDF (viewed 2008/12/09). Includes bibliographical references.

<p>Patients undergoing cardiac catheterization are potentially at risk of radiation-induced health effects from the interventional fluoroscopic X-ray imaging used throughout the clinical procedure. The amount of radiation exposure is highly dependent on the complexity of the procedure and the level of optimization in imaging parameters applied by the clinician. For cardiac catheterization, patient radiation dosimetry, for key organs as well as whole-body effective, is challenging due to the lack of fixed imaging protocols, unlike other common X-ray based imaging modalities. </p><p>Pediatric patients are at a greater risk compared to adults due to their greater cellular radio-sensitivities as well as longer remaining life-expectancy following the radiation exposure. In terms of radiation dosimetry, they are often more challenging due to greater variation in body size, which often triggers a wider range of imaging parameters in modern imaging systems with automatic dose rate modulation. </p><p>The overall objective of this dissertation was to develop a comprehensive method of radiation dose estimation for pediatric patients undergoing cardiac catheterization. In this dissertation, the research is divided into two main parts: the Physics Component and the Clinical Component. A proof-of-principle study focused on two patient age groups (Newborn and Five-year-old), one popular biplane imaging system, and the clinical practice of two pediatric cardiologists at one large academic medical center. </p><p>The Physics Component includes experiments relevant to the physical measurement of patient organ dose using high-sensitivity MOSFET dosimeters placed in anthropomorphic pediatric phantoms. </p><p>First, the three-dimensional angular dependence of MOSFET detectors in scatter medium under fluoroscopic irradiation was characterized. A custom-made spherical scatter phantom was used to measure response variations in three-dimensional angular orientations. The results were to be used as angular dependence correction factors for the MOSFET organ dose measurements in the following studies. Minor angular dependence (< ±20% at all angles tested, < ±10% at clinically relevant angles in cardiac catheterization) was observed.</p><p>Second, the cardiac dose for common fluoroscopic imaging techniques for pediatric patients in the two age groups was measured. Imaging technique settings with variations of individual key imaging parameters were tested to observe the quantitative effect of imaging optimization or lack thereof. Along with each measurement, the two standard system output indices, the Air Kerma (AK) and Dose-Area Product (DAP), were also recorded and compared to the measured cardiac and skin doses – the lack of correlation between the indices and the organ doses shed light to the substantial limitation of the indices in representing patient radiation dose, at least within the scope of this dissertation.</p><p>Third, the effective dose (ED) for Posterior-Anterior and Lateral fluoroscopic imaging techniques for pediatric patients in the two age groups was determined. In addition, the dosimetric effect of removing the anti-scatter grid was studied, for which a factor-of-two ED rate reduction was observed for the imaging techniques. </p><p>The Clinical Component involved analytical research to develop a validated retrospective cardiac dose reconstruction formulation and to propose the new Optimization Index which evaluates the level of optimization of the clinician’s imaging usage during a procedure; and small sample group of actual procedures were used to demonstrate applicability of these formulations.</p><p>In its entirety, the research represents a first-of-its-kind comprehensive approach in radiation dosimetry for pediatric cardiac catheterization; and separately, it is also modular enough that each individual section can serve as study templates for small-scale dosimetric studies of similar purposes. The data collected and algorithmic formulations developed can be of use in areas of personalized patient dosimetry, clinician training, image quality studies and radiation-associated health effect research.</p> / Dissertation

Cancer is one of the greatest causes of death in modern societies, affecting over 350,000 new cases every year in the UK. Although there are currently more than 100 different cancer types, breast and prostate cancer remain the most common types for women and men respectively. A number of different cancer types follow, with bladder cancer being the ninth most significant type, accounting for 3% of the total new cases. The currently employed techniques aim to diagnose the cancer at an early stage, where the symptoms are easier to be treated and the disease more likely to be cured. A further issue is that many cancers diagnosed will not affect a patient in their lifetime. The current gold standard for cancer diagnosis, biopsy followed by histopathology, is an invasive, restrictive technique and the screening tests suffer from low specificity, the need for a novel diagnostic concept is vital. Furthermore, the current clinical approach does not identify those patients most at risk of advancing disease. A promising approach consists of molecular vibrational spectroscopy techniques, which are based on the interactions of light with matter. One of these is Raman spectroscopy, a technique with wide applications in research and industry, which has the advantage of being non-invasive and chemically highly specific. In this thesis we explore the potential of a group of minimally invasive diagnostic techniques, based on Raman scattering, for prostate, breast and bladder cancer. In the case of the two most prevalent types of cancer, prostate and breast cancer, deep Raman spectroscopy has been employed to study the origin of Raman scattering (Chapters 5 and 6) in animal tissue and tissue phantoms, containing highly scattering materials resembling suspicious features found in tissues (calcifications). The spatial distribution of the Raman signal through the sample volume has been studied in relation to the optical properties and the composition of the sample, showing that a couple of transmission measurements would potentially cover the measuring volume of prostate of typical dimensions. Deep Raman measurements were also extended to animal and human tissue samples, in order to investigate the feasibility of collecting Raman scattering from human prostate tissue and its major tissue components (Chapter 6). Further improvements on these measurements were attempted by introducing the ‘’photon diode’’ element (Chapter 7) in order to achieve signal enhancement, which proved to be in the range of ×1-2.4, depending on the optical properties of the tissue and the depth of the probing element. The same ‘’photon diode’’ concept was utilised to attempt depth prediction of a calcification feature in sample volume (Chapter 8). Regarding bladder cancer, the minimally invasive approach adopted was Raman spectroscopy on urine samples, rather than deep Raman spectroscopy. Raman microscopy was employed in order to discriminate pathological features of bladder cancer between healthy and malignant urine samples. For that reason, the potential differences in urea’s distribution and interactions in urine from healthy and patients with bladder cancer were studied, resulting in promising diagnostic values (73% sensitivity, 80% specificity). The results presented in this thesis are expected to lead to a better understanding of the Raman scattering signals collection through biological tissues and help in this way the future design of Raman instruments aiming to target disease specific signals. This study shows promise for future application of Raman spectroscopy and paves the way towards the future integration of Raman spectroscopy in a non-invasive cancer diagnosis.

Made available in DSpace on 2014-10-09T12:46:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:44Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:99/06803-9

Made available in DSpace on 2014-10-09T12:52:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:44Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-08-07T14:35:13Z No. of bitstreams: 0 / Made available in DSpace on 2015-08-07T14:35:13Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Durante um procedimento cirúrgico cerebral existe o deslocamento das estruturas que é um problema tipicamente não-rígido e não-linear. A ultrassonografia intra-operatória é utilizada como guia cirúrgico e pode ser utilizada para correção das imagens pré- operatórias através do corregistro rígido entre estas e um sistema de rastreio. Isto torna possível a visualização do deslocamento das estruturas devida a remoção de parte delas durante o ato cirúrgico. O objetivo deste trabalho é um estudo do corregistro livre não-rígido a partir de um modelo in vitro experimental que simule uma situação cirúrgica de retirada de uma inclusão líquida, de forma controlada, para medir os deslocamentos das estruturas próximas, utilizando imagens de ultrassom. Alguns fantomas que simulam o tecido humano nas imagens de ultrassom, feitos de gelatina e parafina, foram escolhidos como modelo. Para realizar o corregistro foi escolhida a transformação geométrica por splines simples (B-Splines), o otimizador Limited- memory BroydenFletcherGoldfarbShanno (LBFGS) e a métrica de similaridade soma do quadrado das diferenças (SQD) e, utilizada a biblioteca Insight Segmentation and Registration Toolkit (ITK), assim como o estudo dos parâmetros adequados para a nossa tarefa. Foi demonstrado para as condições envolvidas que para as imagens em modo B as deformações até 5% e mapas de RF até 9%, sem nenhuma otimização dos parâmetros do corregistro, é factível sem uso excessivo de tempo computacional. Foi analisada a influência da grade em relação a dois tipos diferentes de deformação, ambas com valor de 2%. O tamanho da grade, levando em consideração o erro e o tempo, foram a 5x11 para as imagens em Modo B e 11x17 para os mapas de RF, independentemente do tipo de deformação. Os parâmetros do otimizador (Default Step Length, Gradient Convergence Tolerance e Line Search Accuraccy) também foram avaliados e os valores obtidos foram 1,6; 0,03 e 0,8 para as imagens modo B e 1,2; 0,05 e 1,0 para os mapas de RF. No entanto ao comparamos, utilizando os parâmetros propostos obtidos, os campos de deslocamentos esperados com os gerados pelo modo B e pelos mapas RF, foi demonstrado que os mapas de RF fornecem valores abaixo do esperado e que as imagens em modo B retratam mais fielmente os deslocamentos e isto se deve a escolha do conjunto de valores testados para o otimizador. Foram aplicados estes parâmetros em dois fantomas de parafina- gel e em dois de gelatina. Nos três primeiros fantomas foi retirada um inclusão líquida em várias etapas. Os deslocamentos das estruturas vizinhas foram avaliados durante as etapas de remoção para demonstrar os campos de sução e de torção. No último fantoma, que simula morfologicamente um cérebro humano, foram retiradas, em várias etapas, regiões sólidas, simulando a retirada de tecido e foram calculados os deslocamentos e demonstrados os campos provenientes deste tipo de intervenção. Os trabalhos futuros se concentrarão em utilizar os volumes para medir os movimentos das estruturas e em novos parâmetros do otimizador para os mapas de RF. / During a brain surgery there is the displacement of the structures that is a typical non- rigid and non-linear problem. Intraoperative ultrasound is used as a surgical guide and can be used for spatial correction of preoperative images through the rigid registration between these and a track system. This makes it possible to visualize the displacement of structures due to removal of some piece of them during surgery. This work is a study of the non-rigid free-from registration using an experimental in vitro model to simulate a surgical situation withdrawal of a fluid inclusion in a controlled manner, to measure the displacement of nearby structures, using ultrasound images. Some phantoms that simulate the human tissue in the ultrasound images made of gelatin and paraffin were chosen as a model. To perform the registration it was used the framework Insight Segmentation and Registration Toolkit (ITK) and were chosen a geometric transformation of simple splines (B-splines), the Limited-memory Broyden-Fletcher- Goldfarb-Shanno (LBFGS) optimizer and the similarity metric sum of the squared differences (SQD). The search for the suitable parameters for our task are done and it has been shown that for the conditions involved for B-mode images deformations up to 5% and RF maps up to 9% without any optimization of the parameters of registration, is feasible without excessive use of computational time. The influence of the grid was examined for two different types of deformation, both for 2%. The size of the grid, taking into account the error and time were the 5x11 for the images in B mode and 11x17 maps for RF, regardless of the type of deformation. The parameters of the optimizer (Default Step Length, Gradient Convergence Tolerance and Line Search Accuraccy) were also evaluated and the values obtained were 1.6, 0.03 and 0.8 for the B-mode images and 1.2, 0.05 and 1.0 for RF maps. However when comparing the expected displacement fields with the generated by B-mode images and the RF maps, using the obtained parameters, it have been shown that RF maps provide values are lower than expected and that the B-mode images portray more faithfully displacements. This is due to the choice set of values tested for the optimizer. Finally, image registration parameters for B-mode were applied in two paraffin-gel and two gelatin phantoms. In the first three phantoms the fluid inclusion was removed in several stages and the displacements of neighboring structures were evaluated during the removal steps to demonstrate the fields of suction and torsion. The last phantom, which morphologically mimics a human brain, a solid region was removed, also in several stages, simulating a surgery. The displacements were calculated and demonstrated the fields from this type of intervention. Future work will focus on using the volumes to measure the movements of the structures and new parameters test of the optimizer to RF maps.