617 research outputs found
Novel geometrical concept of a high-performance brain PET scanner. Principle, design and performance estimates
We present the principle, a possible implementation and performance estimates of a novel geometrical concept for a high-resolution positron emission tomograph. The concept, which can be for example implemented in a brain PET device, promises to lead to an essentially parallax-free 3D image reconstruction with excellent spatial resolution and constrast, uniform over the complete field of view. The key components are matrices of long axially oriented scintillator crystals which are read out at both extremities by segmented Hybrid Photon Detectors. We discuss
the relevant design considerations for a 3D axial PET camera module, motivate parameter and material choices, and estimate its performance in terms of spatial and energy resolution. We support these estimates by Monte Carlo simulations and in some cases by first experimental results. From the performance of a camera module, we extrapolate to the reconstruction resolution of a 3D axial PET scanner in a semi-analytical way and compare it to an existing state-of-the art brain PET device. We finally describe a dedicated data acquisition system, capable to fully exploit the advantages of the proposed concept. We conclude that the proposed 3D axial concept and the discussed implementation is a competitive approach for
high-resolution brain PET. Excellent energy resolution and Compton enhanced sensitivity are expected to lead to high-quality reconstruction and reduced scanning times
Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors
A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm × 1.4 mm pads arranged in a 32 × 16 array. The silicon detectors were located edgewise on opposite sides and flanked by two non-position sensitive BGO detectors. The scanner performance was measured for its sensitivity, energy, timing, spatial resolution and resolution uniformity. Using the experimental scanner, energy resolution for the silicon detectors is 1%. However, system energy resolution is dominated by the 23% FWHM BGO resolution. Timing resolution for silicon is 82.1 ns FWHM due to time-walk in trigger devices. Using the scattered photons, time resolution between the BGO detectors is 19.4 ns FWHM. Image resolution of 980 µm FWHM at the center of the field-of-view (FOV) is obtained from a 1D profile of a 0.254 mm diameter 18F line source image reconstructed using the conventional 2D filtered back-projection (FBP). The 0.4 mm gap between two line sources is resolved in the image reconstructed with both FBP and the maximum likelihood expectation maximization (ML-EM) algorithm. The experimental instrument demonstrates sub-millimeter resolution. A prototype having sensitivity high enough for initial small animal images can be used for in vivo studies of small animal models of metabolism, molecular mechanism and the development of new radiotracers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58094/2/pmb7_10_012.pd
Filters for X-ray detectors on Space missions
Thin filters and gas tight windows are used in Space to protect sensitive
X-ray detectors from out-of-band electromagnetic radiation, low-energy
particles, and molecular contamination. Though very thin and made of light
materials, filters are not fully transparent to X-rays. For this reason, they
ultimately define the detector quantum efficiency at low energies. In this
chapter, we initially provide a brief overview of filter materials and specific
designs adopted on space experiments with main focus on detectors operating at
the focal plane of grazing incidence X-ray telescopes. We then provide a series
of inputs driving the design and development of filters for high-energy
astrophysics space missions. We begin with the identification of the main
functional goals and requirements driving the preliminary design, and identify
modeling tools and experimental characterization techniques needed to prove the
technology and consolidate the design. Finally, we describe the calibration
activities required to derive the filter response with high accuracy.We
conclude with some hints on materials and technologies presently under
investigation for future X-ray missions.Comment: 45 pages, 11 figures Contribution to the Handbook of X-ray and
Gamma-ray Astrophysics in the chapter "Detectors for X-ray Astrophysics",
edited by Jan-Willem den Herder, Norbert Meidinger, Marco Feroc
Development Of A Scintillation Detector And The Influence On Clinical Imaging
The detector is the functional unit within a Positron Emission Tomography (PET) scanner, serving to convert the energy of radiation emitted from a patient into positional information, and as such contributes significantly to the performance of the scanner. While modern whole-body scanners use detectors composed of very many (i.e., 20000-30000) small pixels, typically ~4x4x20mm3 in size, several groups are actively investigating the performance of continuous crystals coupled to position sensitive photodetectors as an alternative detector design with a number of potential advantages, including improved spatial resolution and position sampling. This work in particular focuses on thick (≥14mm) continuous crystals in order to maintain the sensitivity of modern scanners. Excellent spatial resolution in continuous detectors that are thick, however, has proven difficult to achieve using simple positioning algorithms, leading to research in the field to improve performance. This thesis aims to investigate the effect of modifications to the scintillation light spread within the bulk of the scintillator to improve performance, focusing on the use of laser induced optical barriers (LIOBs) etched within thick continuous crystals, and furthermore aims to translate the effect on detector performance to scanner quantitation in patient studies.
The conventional continuous detector is first investigated by analyzing the various components of the detector as well as its limitations. It is seen that the performance of the detector is affected by a number of variables that either cannot be improved or may be improved only at the expense of greater complexity or computing time; these include the photodetector, the positioning algorithm, and Compton scatter in the detector. The performance of the detectors, however, is fundamentally determined by the light spread within the detector, and limited by the depth-dependence of the light spread and poor performance in the entrance region, motivating efforts to modify this aspect of the detector.
The feasibility and potential of LIOBs to fine-tune this light spread and improve these limitations is then studied using both experiments and simulations. The behavior of the LIOBs in response to optical light is investigated, and the opacity of the etchings is shown to be dependent on the parameters of the etching procedure. Thick crystals were also etched with LIOBs in their entrance region in a grid pattern in order to improve the resolution in the entrance region. Measurements show an overall improvement in spatial resolution: the resolution in the etched region of the crystals is slightly improved (e.g., ~0.8mm for a 25mm thick crystal), though in the unetched region, it is slightly degraded (e.g., ~0.4mm for a 25mm thick crystal). While the depth-dependence of the response of the crystal is decreased, the depth-of-interaction (DOI) performance is degraded as well. Simulation studies informed by these measurements show that the properties of the LIOBs strongly affect the performance of the crystal, and ultimately further illustrate that trade-offs in spatial resolution, position sampling, and DOI resolution are inherent in varying the light spread using LIOBs in this manner; these may be used as a guide for future experiments.
System Monte Carlo simulations were used to investigate the added benefit of improved detector spatial resolution and position sampling to the imaging performance of a whole-body scanner. These simulations compared the performance of scanners composed of conventional pixelated detectors to that of scanners using continuous crystals. Results showed that the improved performance (relative to that of 4-mm pixelated detectors) of continuous crystals with a 2-mm resolution, pertinent to both the etched 14mm thick crystal studied as well as potential designs with the etched 25mm thick crystal, increased the mean contrast recovery coefficient (CRC) of images by ~22% for 5.5mm spheres.
Last, a set of experiments aimed to test the correspondence between quantification in phantom and patient images using a lesion embedding methodology, so that any improvements determined using phantom studies may be understood clinically. The results show that the average CRC values for lesions embedded in the lung and liver agree well with those for lesions embedded in the phantom for all lesion sizes. In addition, the relative changes in CRC resulting from application of post-filters on the subject and phantom images are consistent within measurement uncertainty. This study shows that the improvements in CRC resulting from improved spatial resolution, measured using phantom studies in the simulations, are representative of improvements in quantitative accuracy in patient studies.
While unmodified thick continuous detectors hold promise for both improved image quality and quantitation in whole-body imaging, excellent performance requires intensive hardware and computational solutions. Laser induced optical barriers offer the ability to modify the light spread within the scintillator to improve the intrinsic performance of the detector: while measurements with crystals etched with relatively transmissive etchings show a slight improvement in resolution, simulations show that the LIOBs may be fine-tuned to result in improved performance using relatively simple positioning algorithms. For systems in which DOI information is less important, and transverse resolution and sensitivity are paramount, etching thick detectors with this design, fine-tuned to the particular thickness of the crystal and application, is an interesting alternative to the standard detector design
Dosimetric properties and radiation hardness of the storage phosphor europium doped potassium chloride for radiation therapy dosimetry
DissertationMultidimensional reusable dosimeters are extremely important for characterizing the complex dose distributions associated with modern radiation therapy techniques, such as intensity modulated radiation therapy (IMRT). In particular, reusability provides medical physicists a degree of confidence in dosimetric measurements through the acquisition of benchmarking datasets and through long-term, repeated use and performance monitoring. Yet a dosimeter that has all of the properties desired for radiation therapy use, such as reusability, high spatial resolution, and water-equivalence, is not currently available. The results of this dissertation demonstrate that the reusable storage phosphor europium doped potassium chloride, KCl:Eu2+, has the potential to significantly advance the state-of-the-art in radiation therapy dosimetry. Prototype chip and panel dosimeters were fabricated according to well-developed materials science processes. Dosimetric properties were studied by reading photostimulated luminescence (PSL) after irradiation with a laboratory optical system. Sensitivity was independent of dose rate and beam energy for commonly used therapy beams. Over-response to low-energy scattered photons was comparable to conventional radiographic film and reduced with lead foils. No significant changes in the PSL process were detected up to 5000 Gy dose history, indicating that the material could be reused up to 2500 times at 2 Gy per use, as in, for example, patient-specific IMRT quality assurance. Investigations of KCl:Eu2+ panel dosimeters show that sub-millimeter spatial resolution is achievable and that micron-scale dosimeters have a water-equivalent dose response with sufficient sensitivity over clinically relevant dose ranges. In conclusion, KCl:Eu2+ is demonstrated to have many desirable properties for radiation therapy dosimetry. This study provides a practical and theoretical knowledge base that advances and supports future KCl:Eu2+ dosimetry research
Mass-Market Receiver for Static Positioning: Tests and Statistical Analyses
Nowadays, there are several low cost GPS receivers able to provide both pseudorange and carrier phase measurements in the L1band, that allow to have good realtime performances in outdoor condition. The present paper describes a set of dedicated tests in order to evaluate the positioning accuracy in static conditions. The quality of the pseudorange and the carrier phase measurements let hope for interesting results. The use of such kind of receiver could be extended to a large number of professional applications, like engineering fields: survey, georeferencing, monitoring, cadastral mapping and cadastral road. In this work, the receivers performance is verified considering a single frequency solution trying to fix the phase ambiguity, when possible. Different solutions are defined: code, float and fix solutions. In order to solve the phase ambiguities different methods are considered. Each test performed is statistically analyzed, highlighting the effects of different factors on precision and accurac
Demosaicing multi-energy patterned composite pixels for spectral CT
Tese de mestrado integrado em Engenharia BiomĂ©dica e BiofĂsica, apresentada Ă Universidade de Lisboa, atravĂ©s da Faculdade de CiĂŞncias, 2016O desenvolvimento da Tomografia Computadorizada foi realizada na combinação de duas áreas cientĂficas, computação e imagiologia com base em raios-x. Em 1895, o cientista Wilhelm
Roentgen descobriu os raios-X: fotões de altas energias provenientes de transições eletrónicas
nos átomos. Estes são radiações eletromagnéticas que se propagam à velocidade da luz e são
ionizantes. Devido Ă s suas propriedades, os raios-x foram imediatamente rentabilizados como
uma ferramenta para explorar a composição da matéria. Os fotões interagem com a matéria
por dois mecanismos dominantes, dependendo da energia da radiação eletromagnética: efeito
fotoelĂ©trico e efeito de Compton. O efeito fotoelĂ©trico corresponde Ă interação dos fotões com os eletrões que se encontram nas Ăłrbitas de maior energia do átomo. O fotĂŁo transfere toda a sua energia para o eletrĂŁo, sendo parte dessa usada para superar a energia de ligação do eletrĂŁo e a energia restante Ă© transferida para o mesmo eletrĂŁo sob a forma de energia cinĂ©tica. O efeito de Compton corresponde Ă interação do fotĂŁo com o eletrĂŁo que se encontra numa das Ăłrbitas de menor energia. Depois da interação, o fotĂŁo Ă© desviado e o eletrĂŁo Ă© ejetado do átomo. O fotĂŁo desviado pode voltar a interagir com a matĂ©ria sob o efeito de Compton ou o efeito fotoelĂ©trico, ou simplesmente nĂŁo a interagir com a matĂ©ria. Os raios-X tĂŞm a sua intensidade diminuĂda em função das interações que ocorrem com o material que as absorve. A atenuação da energia destes acontece de maneira exponencial em função da espessura do material absorvente. Devido Ă s propriedades fĂsicas provocadas pelos raios-X, esta radiação foi estabelecida como uma ferramenta mĂ©dica. A tomografia convencional consistiu numa tĂ©cnica de diagnĂłstico na qual a aquisição de imagem Ă© realizada a partir de um filme radiográfico, que resulta da projeção das estruturas anatĂłmicas tridimensionais em imagens bidimensionais, com sobreposições de informação anatĂłmica. Em 1970, os cientistas Hounsfield e Cormack desenvolveram uma tĂ©cnica, a Tomografia Computadorizada, que possuĂa logo de inĂcio a vantagem de corrigir o problema da sobreposição de informação. A Tomografia Computadorizada reconstrĂłi as estruturas internas de um objeto a partir de mĂşltiplas projeções utilizando algoritmos de reconstrução. A diferenciação e classificação de diferentes tipos de tecidos tornou-se extremamente desafiante nesta tĂ©cnica, devido ao facto de que mesmo que dois materiais difiram em nĂşmero atĂłmico, dependendo da densidade de massa ou concentração, eles podem aparecer idĂŞnticos na imagem. Desta forma uma das soluções foi o estudo da Tomografia Computorizada Espectral, sendo esta uma tĂ©cnica promissora no desenvolvimento da imagiologia pois potencia a deteção e caracterização dos tecidos anatĂłmicos alĂ©m dos nĂveis atualmente atingĂveis com tĂ©cnicas de TC convencionais. A TC espectral leva em consideração que a radiação transmitida transporta mais informações para alĂ©m de mudanças de intensidade e que o coeficiente de atenuação depende nĂŁo sĂł do material, mas tambĂ©m da energia do fotĂŁo. A TC espectral difere das outras tĂ©cnicas no sentido em que utiliza as caracterĂsticas fĂsicas dos materiais em estudo em mais de dois espectros de energia. AtravĂ©s da aquisição de imagens em diferentes nĂveis de energia, a tĂ©cnica Ă© capaz de diferenciar os vários elementos do corpo com base na densidade dos materiais ou nos nĂşmeros atĂłmicos destes. As diferenças entre os vários tecidos sĂŁo exibidas atravĂ©s de distintas cores na imagem final. Uma tecnologia importante utilizada na CT Espectral Ă© a dos detetores de contagem de fotões, conhecidos por detetores hĂbridos. Estes detetores tĂŞm a particularidade de separar o espetro incidente em mĂşltiplos espetros, cuja forma depende dos limiares de energia impostos. Estes detetores operam num modo de contagem, ou seja, em vez de operarem em modo de integração tal como os detetores convencionais, estes efetuam a contagem individual dos fotões da radiação incidente a partir de limiares de energia estipulados. A influĂŞncia do ruĂdo electrĂłnico afeta a energia medida de cada fotĂŁo, contudo tendo em conta que estes detetores efetuam a contagem de fotões, o ruĂdo eletrĂłnico deixa de ter uma influĂŞncia tĂŁo significativa na qualidade da imagem adquirida. “K-edge Imaging” Ă© uma das abordagens utilizadas em sistemas de TC espectral; explora as propriedades fĂsicas de agentes de contrastes utilizados em tomografia computorizada e as suas respetivas propriedades fĂsicas. Os elementos utilizados para os agentes contrastes sĂŁo elementos pesados e altamente atenuantes, e cujo efeito fotoelĂ©trico ocorre ao mesmo alcance das energias utilizadas em TC. Deste modo, cada um desses elementos pesados tem um salto caracterĂstico na sua atenuação de raios-X, o qual corresponde Ă energia que ocorre o efeito fotoelĂ©trico. Como os eletrões envolvidos no efeito fotoelĂ©trico pertencem Ă orbital K, o salto caracterĂstico Ă© designado por "K-edge". “K-edge Imaging” explora a escolha do espetro de energia aplicado de forma a abranger o salto caracterĂstico destes elementos para identificar e localizar componentes especĂficos. No CPPM, o grupo imXgam desenvolveu uma micro-TC e uma PET / TC simultânea que incorpora a nova tecnologia de detetores hĂbridos desenvolvida pelo centro: o detetor XPAD3. Esta tecnologia nĂŁo sĂł permite trabalhar em modo de contagem de fotões, mas tambĂ©m Ă© capaz de selecionar informação energĂ©tica sobre os fotões detetados; consequentemente as capacidades do detector XPAD3 foram exploradas para desenvolver “K-edge Imaging”. Os artefactos que resultam de várias aquisições estĂŁo relacionados com o movimento. Para resolver esse problema, o CPPM desenvolveu um conceito de pixĂ©is compostos, que consiste numa matriz de pixĂ©is (3 Ă— 3) com 3 diferentes limiares de energia. Embora, os pixĂ©is compostos resolvam os artefactos de movimento, as imagens adquiridas perderam a resolução espacial. Assim, o projeto deste trabalho tem como objetivo a realização de "K-edge Imaging" em objectos em movimento em plena resolução espacial. Este projeto aborda o problema como um problema
“Inpainting”, onde as medidas desconhecidas para cada limiar de energia serão estimadas a partir de medidas parciais. Há uma vasta literatura sobre o problema “Inpainting”, assim como
noutra área de processamento de imagem, o “Demosaicing”. Estes sĂŁo mĂ©todos de restauração que removem regiões danificadas ou reconstroem porções perdidas da imagem. O problema “Demosaicing” tem um interesse particular para este trabalho em virtude do mĂ©todo recuperar informação de imagens coloridas (imagens RGB). A utilização do mĂ©todo “Demosaicing” em imagens adquiridas por sistemas TC Ă© praticamente inexistente, pelo que o objetivo deste projeto foi avaliar nĂŁo sĂł os mĂ©todos de restauração convencionais, mas tambĂ©m adaptar e avaliar o mĂ©todo “Demosaicing” Ă s imagens adquiridas por sistemas TC. Desta forma, as imagens espectrais foram tratadas como imagens coloridas: cada imagem adquirida por um limiar de energia foi configurada como uma cor. A imagem resultante foi submetida ao processo de recuperação que consistiu em acoplar as trĂŞs imagens obtidas por cada limiar de energia em uma imagem de cor( imagem RGB). Este trabalho exigiu, em primeiro lugar, o estudo do esquema de amostragem de imagens espectrais e a avaliação de desempenho dos mĂ©todos mais simples em relação ao ruĂdo, ao fator de subamostragem e Ă resolução espacial. As tĂ©cnicas mais sofisticadas como a “Inpainting” e ”Demosaicing” foram desenvolvidas e avaliadas especificamente para imagens espectrais tomográficas. ApĂłs a avaliação destas, foi realizado um “estado de arte” que comparou os mĂ©todos e, consequentemente, fez uma análise de qual o mĂ©todo mais adequado para imagens de TC espectral. A segunda parte deste projeto consistiu no estudo do padrĂŁo que os pĂxeis compostos devem seguir, de forma a definir um protocolo de aquisição. Para tal, foram testados dois tipos de padrões: regular e aleatĂłrio. A ideia de pĂxeis compostos foi obtida criando uma matriz com vários componentes que dependem do nĂşmero de limiar de energias que se quer utilizar. Conforme mencionado, no CPPM Ă© utilizado uma matriz de pixels com trĂŞs limiares de energia, desta forma, neste projeto, a possibilidade de aumentar o nĂşmero de limiares de energia foi tambĂ©m testado. Os objetivos do projeto foram alcançados uma vez que a avaliação dos mĂ©todos foi realizada e conclui-se que a nova abordagem apresentou melhores resultados que os mĂ©todos padrĂŁo. Conclui-se que as imagens adquiridas pelo mĂ©todo “Demosaicing” apresentam melhor resolução espacial. Relativamente ao padrĂŁo dos pixĂ©is compostos verificou-se que em ambos a reconstrução apresentou bom desempenho. A análise do aumento de nĂşmero de limiares de energia apontou para bons resultados, observados no uso de 4 nĂveis de energia, porĂ©m a nova abordagem “Demosaicing” teria de ser reformulada. De forma a alcançar os objetivos, este tema foi dividido em vários capĂtulos. No segundo capĂtulo foram introduzidos os conceitos fĂsicos envolvidos na tomografia espectral, desde a produção dos raios-X atĂ© ao desenvolvimento da tĂ©cnica propriamente dita. O terceiro capĂtulo abordou como o “estado de arte” foi efetuado, documentando o que foi realizado atualmente no campo em estudo. Nos capĂtulos 4 e 5 apresentou-se os materiais e mĂ©todos utilizados, assim como exposto as suas aplicações,e de forma mais particular a matemática e a programação envolvidas. No capĂtulo 6 apresentou-se os resultados alcançados e as respectivas observações. No Ăşltimo capĂtulo sumariou-se os resultados obtidos e as conclusões retiradas a partir destes.Computed Tomography is a diagnosis technique that uses X-ray radiation to create images of structures. This technique consists in reconstructing a quantitative map of the attenuation coefficients of the object sections from multiple projections using reconstruction algorithms. Since the attenuation coefficient is not unique for any material, the differentiation and classification of different tissue types by Computed Tomography has revealed to be extremely challenging. The solution has been provided through the development of an energy sensitive CT scanner, known as Spectral CT. This technique takes in consideration that the transmitted radiation carries more information than intensity changes, that the x-ray tube produces a wide range of energy spectrum and that the attenuation of radiation depends not only on the material but also on the photon energy. Spectral CT uses the attenuation characteristics at more than two energies which makes it possible to differentiate various elements in the body, based on their material density or atomic numbers. Therefore, this technique uses the new detector technology, the hybrid pixel detector. This detector allows the energy threshold setting. Combining the physical properties of different materials and the possibility of setting the energy threshold in the detectors, a new spectral imaging technique is used, K-edge imaging. This technique explores the discontinuity in the photoelectric effect, which is generated when photons interact with matter, and those interact with the shell electrons. Therefore, the Centre de Physique des Particules de Marseille developed a micro-CT and a simultaneous PET/CT scan based on hybrid pixel detector. The ability of tuning the energy threshold of each pixel independently was exploited to develop K-edge imaging and the proof of concept has been established on phantom and on living mice. In the context of pre-clinical imaging, objects are moving and the several acquisitions must be performed simultaneously to allow the registration set. For this purpose, CPPM had been working with composite pixels made of 9 (3Ă— 3) pixels with 3 different thresholds. This solves the motion artefact problem at the price of loss in spatial resolution. Therefore, the research project of this work aims at performing K-edge imaging on moving object at full spatial resolution. The problem is seen as an Inpainting problem where unknown measure must be estimated from partial measurements. A huge literature exists in the Inpainting, and especially in the field of Demosaicing, which is particularity of interest in this research project. The project consists in a study of the sampling scheme of spectral CT images and to evaluate the performance of simplest methods with respect to noise and spatial resolution. More sophisticated techniques of Inpainting and Demosaicing were tested, which were developed specifically for spectral CT images by incorporating prior on image. Therefore, an evaluation performance of all the reconstruction methods was successfully made, and a state-of-art was established. In this research project, in order to create the composite pixels concept, a set of dynamic strategies
of patterning composite pixels was achieved in order to define optimal protocols of acquisition
Kilovoltage Intensity Modulated Radiotherapy
Contrast enhanced kilovoltage radiotherapy could be a significant improvement over the standard of care in glioblastoma multiforme, but its potential benefit has been hindered by fears of insufficient dose falloff, high skin and skull dose, contrast delivery concerns, and high cost. This dissertation aims to address the validity of these fears.
Contrast delivery concerns are examined by assuming that sufficient dose can be safely delivered to the tumor. Iodine, gadolinium, and gold nanoparticle biological effect and delivery research is examined and the ideal contrast delivery methods are reported. Dose falloff and skull dose are then investigated through treatment planning and experimentation.
Our team has created, commissioned, and tested the first reported mechanism for delivering kilovoltage intensity modulated radiotherapy. This required the invention and production of a novel 6 x 6 cm2 multi-rod collimator (MRC) with an in-house control system. The MRC was mounted between a decommissioned portal imager and several phantoms loaded with radiochromic film. Plans were created and delivered, and the resulting films were analyzed.
Film results were examined for dose falloff and, for the Rando phantom, enhancement due to the presence of skull. Dose to the surface was found to be approximately 40% of maximum dose measured, with an increase to approximately 50% for anthropomorphic phantoms. While higher than the megavoltage dose, these results demonstrate that 40-50Gy could be delivered to a target even without contrast enhancement. Dose to the skull was found to be small enough to be clinically relevant, but well below the threshold for necrosis.
After factoring in an estimated twofold to threefold increase in dose at the tumor due to gold nanoparticle enhancement, it can be concluded that the kilovoltage beam is capable of producing a plan that is not considered clinically detrimental. Future work will involve actualizing the delivery of contrast to a glioblastoma multiforme tumor, applying arc therapies to minimize dose to the surface, and measuring for ourselves the dose enhancement produced by contrast enhancement
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