The Black Rock volcanic cluster consists of 30 small volume monogenetic volcanoes. The volcanoes of this cluster have exhibited bimodal volcanism for > 9 Ma. The most recent eruption of Ice Springs volcano ~600 yrs. ago along with ongoing geothermal activity attests to the usefulness of a hazard assessment for this area. The likelihood of a future eruption in this area is estimated to be between a 0.16 and 24% chance over the next 1 Ka (95% confidence). The explosivity and nature of many of these eruptions is not well known. In particular, the physical volcanology of Tabernacle Hill suggests a complicated episodic eruption. Initial phreatomagmatic eruptions at Tabernacle Hill are reported to have begun no later than ~14 Ka. The initial eruptive phase produced a tuff cone approximately 150 m high and 1.5 km in diameter with distinct bedding layers. Recent mapping and sampling of Tabernacle Hill's lava and tuff cone deposits was aimed at better constraining the sequence of events, physical volcanology, and energy associated with this eruption. Blocks located on the rim of the tuff cone of were mapped and analyzed to yield preliminary minimum muzzle velocities of 60-70 m s-1. After the initial phreatomagmatic explosions, the eruption style transitioned to a more effusive phase that partially filled the tuff cone with a semi-steady state lava lake 200 m wide and 15 m deep. Eventually, the tuff cone was breached by the impinging lava resulting in large portions of the cone rafting on top of the lava flows away from the vent. Eruption onto the Lake Bonneville lake bed allowed the Tabernacle Hill lava flows to flow radially from the tuff cone and cover an area of 19.35 km², producing a very uniform high aspect ratio (100:1) flow field. Subsequent eruptive phases cycled several times between effusive and explosive, producing scoria cones and more lava flows, culminating in an almost complete drainage of the lava lake through large lava tubes and drain back.

Purpose: The purpose of this study was to assess the radiographic changes in periapical status and analysis of healing determined using periapical radiographs (PA) versus cone beam computed tomography (CBCT) pre-operatively and at 3-64 months following endodontic treatment. Methods: Pre/post treatment radiograph and CBCT scans of patients who had NSRCT, NSReTx, or SRCT from July 2011-December 2018 at VCU Graduate Endodontic clinic were included in this study. Volumetric and linear measurements of periapical lesions on initial and recall PA and CBCT images were performed using three calibrated examiners. Changes and differences in the estimated area from PA to CBCT were compared using the Wilcoxon signed-rank test. McNemar’s chi-squared test was used to determine agreement in the proportion of lesions that were absent (0x0) between the PA and corresponding view of CBCT. This data was used to calculate the sensitivity, specificity, positive predictive value (PPV), and negative predicative value (NPV). Results: A total of 51 patients with a median healing time of 13 months were included in the analysis. Significant healing was observed on both PA and CBCT images (p-value Conclusion: Assessment using CBCT revealed a lower healing rate for all treatment categories compared with periapical radiographs. CBCT was more likely to detect the presence of a PARL, whereas a periapical radiograph would be less sensitive to detection of a PARL. Significant healing cannot be detected at an earlier point in time with PA radiographs or CBCT.

Objectives: The aim of the current study is to establish the reliability of linear cephalometric measurements made on mandibles and their respective 3D printed models created from different voxel resolutions from a cone beam CT machine. Materials and methods: Ten dry mandibles obtained from the Department of Oral Pathology, Radiology and Medicine at The University of Iowa College Of Dentistry were used for this study. All mandibles were scanned on the i-CAT FLX cone beam CT machine (Imaging Sciences International, LLC, Pennsylvania, USA) using voxel resolutions of .30mm, .25mm and .20 mm in a 16cm x 8cm field of view using 360° rotation. The 3D models were reconstructed and saved as .STL files using 3D Slicer software and send to a 3D printer for printing. Two observers measured the 10 mandibles and 30 3D printed models. The measurement were repeated on 50% of the samples after at least one week interval. Cronbach’s alpha and intraclass correlation coefficient were calculated to measure reliability. Results: Good to excellent interobserver and intraobserver reliability was achieved across most of the measurements. There was no difference in reliability across models made from different voxel sizes. Conclusion: The current study successfully showed that the reliability of measurements made on 3D printed models of dry skull mandibles created using fused deposition modeling technique using images of different voxel sizes from an i-CAT FLX CBCT machine are valid, reproducible, and reliable and can be used for diagnostic and clinical purposes.

Currently in our clinic, a mega-voltage cone beam computed tomography (MVCBCT) scan is performed before each treatment for patient localization. For non-small cell lung cancer (NSCLC) patients, a strain gauge is used as an external surrogate to indicate tumor motion in both the planning stage and the treatment stage. However, it is likely that the amplitude of tumor motion varies between treatment fractions without a corresponding change in the surrogate signal. Motion amplitude larger than what was planned may underdose the tumor and overexpose normal tissues. The overall objective of this project is to extend the capabilities of MVCBCT for respiratory motion management by taking advantage of 2D projection images. First, a new method was developed to detect ipsi-lateral hemi-diaphragm apex (IHDA) motion along superior-inferior (SI) direction in 3D. Then a respiratory correlated reconstruction method was implemented and verified. This method is able to create MVCBCT volume in the full exhale (FE) and the full inhale (FI) phases, respectively. The diaphragm to tumor motion ratio (DTMR) was derived by quantifying the absolute position of the tumor and IHDA in these two volumes. The DTMR and the extracted IHDA motion were further used to calibrate the strain gauge signal. Second, an organ motion detection approach was developed, in which the detection is converted into an optimal interrelated surface detection problem. The framework was first applied to tumor motion extraction, which enables accurate detection for large tumors (with a diameter not smaller than 1.9cm). The framework was then applied to lung motion extraction and the extracted lung motion model was used to create a series of displacement vector fields for a motion compensated (MC) reconstruction. The accuracy of both tumor extraction and the MC approach was validated, which shows their clinical feasibility. Last but not least, a novel enhancement framework was developed. The aim of this approach is to eliminate the overlapping tissues and organs in the CBCT projection images. Though scattering and noise is the major problem, the proposed method is able to achieve enhanced projection images with a higher contrast to noise ratio (CNR) without compromising detection accuracy on tumors and IHDA.

The purpose of this investigation is to analyze the flow pattern of cooling fluids in the 3D "twister-effect" mixing chamber and to approximate the free surface behaviors exiting the 2D spray nozzle. The cone angle and free surface height located at the end of the free surface are two significant factors to determine the spraying area on a heated plane. This process is a reasonable representation of many industrial cooling application. The whole system consists of 4 inlet tubes connected to the top of the mixing chamber, and the spray nozzle is located under the chamber. Four different refrigerants, like FC-72, FC-77, FC-87 and methanol were used for the turbulent flow simulations. According to different fluid properties, the cone angle, free surface, pressure drop and Reynolds number can be investigated at different flow rates. First, at a certain volumetric flow rates, the velocities in x, y, z directions were found on the positive x-axis (0 degree), y-axis (90 degrees), negative x-axis (180 degrees) and y-axis (270 degrees) at 8.0 x 10-4m below the top of chamber. After the transformations, the interpolated and averaged radial, circumferential and axial velocities were used in the 2D nozzle simulations. Finally, the cone angle, the radial locations of the free surface and the pressure drop were obtained in each scenario. As the results, higher volumetric flow rate produced higher free surface height and cone angle. Also, FC-87 created the highest free surface height and cone angle among all four working fluids in both volumetric flow rates. It means that FC-87 can produce the largest spraying area on the heated surface. Fluctuation, spinning and eddy circulation can be found in the velocity plot because of the turbulent flow syndromes. When comparing two different nozzle designs, it was found that the nozzle without mixing chamber gave a larger cone angle and free surface height. Alternatively, the design in this investigation produced a relatively narrow jet concentrated to the stagnation zone.

A conical nozzle with two separate inlets within its top plate is analyzed. One of the inlets is in the center of the top plate, which is free to rotate, whereas the other inlet is positioned away from the center. The fluid entering through the outer inlet slot causes the top plate of the nozzle to spin. Several fluids including FC-77, FC-72, FC-87, and Methanol running at different flow rates were investigated to observe the effect that their particular properties have on the geometry of the fluid's free surface exiting the nozzle. Another variation performed was the geometry of the nozzle. The outer inlet slot was positioned at various radial distances along the top plate. For this nozzle, the top plate remained stationary and swirling was introduced to the fluid at the inlets. It was observed that the faster flow rates caused an increase in the free surface height and cone angle. For the various radial locations of the outer inlet slot, it was noted that a position at approximately 75% of the nozzle radius produced the largest free surface height. The largest cone angle was produced when the outer inlet slot was positioned at the edge of the nozzle top plate. Another factor that increased the radial height and cone angle of the free surface was the working fluid used in the study. A larger Reynolds number produced a larger cone angle and larger free surface height (while a smaller Reynolds number produced a less significant cone angle and free surface height).

As alterações volumétricas da cavidade oral, nasal e espaço faríngeo após a cirurgia ortognática, têm sido objetivo de muitos estudos, uma vez que, essas alterações dependem da direção e magnitude da movimentação dos segmentos ósseos, porém, poucos são os trabalhos que combinam os diferentes métodos para a avaliação da nasofaringe. O objetivo deste estudo foi correlacionar o espaço aéreo faríngeo em pacientes com fissura labiopalatina, submetidos à cirurgia ortognática com avanço de maxila e/ou recuo de mandíbula, por meio da análise do volume e área seccional mínima utilizando imagens de tomografia computadorizada de feixe cônico e pela rinomanometria anterior modificada (técnica fluxo-pressão) no pré e pós-operatório de um ano da cirurgia ortognática. Desse modo, a amostra foi composta por 41 indivíduos, que foram avaliados no pré-operatório e no pós-operatório, na qual, avaliou-se a área seccional mínima pela rinomanometria anterior modificada expressos em mm2 e pelas imagens de tomografia de feixe cônico, que foram importadas em DICOM e avaliadas pelo software Dolphin Imaging 11.0, obtendo os valores numéricos de volume (V), expressos em cm3, bem como a área seccional mínima, expressa em mm2. Notou-se que, em todas as variáveis, houve aumento médio dos valores no pós-operatório em relação ao pré-operatório. Além disso, notouse uma diferença estatisticamente significante ao comparar os resultados dos volumes e da área seccional mínima da área nasofaríngea no pré e pós-operatório pelo software Dolphin Imaging 11.0 ao aplicar o Teste de Wilcoxon. Observou-se também, o aumento discreto da área nasofaríngea avaliada pela rinomanometria, no préoperatório de 105,9 mm2 para 107,1 mm2 no pós-operatório, mas sem diferença estatisticamente significante com p=0,493 pelo Teste de Wilcoxon. E ao comparar a ASM pela TCFC (ASMD) e pela rinomanometria (notou-se diferença estatística (p= 0,033) pelo Teste de Wilcoxon. Por conseguinte, concluiu-se que, existe diferença estatisticamente significante entre a área seccional mínima obtida da TCFC com a rinomanometria pela técnica de fluxo-pressão. / The volumetric changes of the oral cavity, nasal cavity and pharyngeal space after orthognathic surgery have been the objective of many studies, since these alterations depend on the direction and magnitude of the movement of the bone segments, however, there are few studies that combine the different methods for evaluating the nasopharynx. The objective of this study was to correlate the pharyngeal air space in patients with cleft lip and palate submitted to orthognathic surgery with maxillary advancement and / or mandible retreatment, by means of volume analysis and minimum sectional area using conical beam computed tomography by modified anterior rhinomanometry (flow-pressure technique) in the pre- and postoperative year of orthognathic surgery. Thus, the sample consisted in 41 individuals, which were evaluated preoperatively and postoperatively, in which the minimum sectional area was determined by modified anterior rhinomanometry expressed in mm2 and by conical beam tomography images, which were imported into DICOM and evaluated by Dolphin Imaging 11.0 software, obtaining the numerical values of volume (V), expressed in cm3, as well as the minimum sectional area, expressed in mm2. It was observed that, in all variables, there was an average increase in postoperative values in relation to the preoperative period. In addition, a statistically significant difference was observed when comparing the results of the volumes and the minimum sectional area of the nasopharyngeal area in the pre and postoperative period by the Dolphin Imaging 11.0 software when applying the Wilcoxon Test. It was also observed a discrete increase in the nasopharyngeal area evaluated by rhinomanometry, in the preoperative period from 105.9 mm2 to 107.1 mm2 postoperatively, but without a statistically significant difference with p = 0.493 by the Wilcoxon test. When comparing ASM by CBCT (ASMD) and rhinomanometry (a statistical difference (p = 0.033) was noted by the Wilcoxon test. Therefore, it was concluded that there is a statistically significant difference between the minimum sectional area obtained from the CBCT with rhinomanometry.

On s'intéresse à la localisation de l'axe du cône de Mach lié au déplacement supersonique d'un source acoustique en milieu réverbérant à l'aide d'un nombre limité de microphones. L'application faisant l'objet du financement doctoral est la localisation de tireurs embusqués, dans le cadre de la protection du combattant. Le principe du retournement temporel stipule que, lors de la réémission des mesures renversées dans le temps depuis leurs positions respectives, tout se passe comme si le champ de pression acoustique se propageait en remontant le temps et focalisait à l'endroit de la distribution de sources. Cette focalisation est d'autant plus efficace que les positions de capteurs ont tendance à former une surface fermée autour des sources. On considère une distribution discrète de microphones à hauteur constante dans une rue rectiligne. Dans une première approche, le déplacement supersonique est modélisé selon le principe de Huygens-Fresnel comme une sommation de sources monopolaires. Cela permet une formulation analytique du problème direct pouvant être résolue par des simulations numériques simples en accord avec un montage expérimental de synthèse de cône de Mach au moyen d'une ligne de haut-parleurs. La résolution du problème inverse se fait en calculant numériquement le champ rétropropagé depuis les positions des microphones jusque dans des tranches verticales disposées le long de la rue. L'utilisation d'un critère statistique d'ordre supérieur permet de réduire la contribution des termes de sources dans le champ rétropropagé, à l'origine d'une divergence du champ de pression autour des positions de microphones. L'axe du cône de Mach peut alors être localisé avec une bonne précision angulaire. Dans une deuxième approche, on considère un front d'onde conique réel en déplacement supersonique. Les temps d'arrivée obéissent à des lois de retard bien précises. Notre modèle de réverbération permet de prédire la plupart des pics correspondant à l'arrivée au point de mesure des signaux impulsionnels réfléchis. La réverbération n'a pas un effet aussi bénéfique dans le cadre d'une source supersonique réelle que dans le cas d'une source statique, ni même que dans celui de la ligne de haut-parleurs, car la source supersonique présente des contraintes géométriques particulières dont le retournement temporel ne tient pas compte, étant donnée la différence de géométrie des ondes directe (un cône) et retournée dans le temps (une superposition d'ondes sphériques). Cependant, la focalisation autour du passage de l'axe est observée dans les tranches horizontales, avec une qualité dépendant fortement de l'agencement de l'antenne de microphones. / We are interested into the localisation of the Mach cone --- created by the supersonic motion of an acoustic source into a reverberant medium --- by means of a limited amount of microphones. The application concerns sniper localisation, hence protection of the soldier. Theory of time-reversal states that when reemitting measures reversed in time from their respective positions, everything happens as if the pressure field were propagating travelling backwards in time and focused on the source distribution. This result is enhanced when the microphone distribution over space forms a closed surface surrounding the sources, according to Kirchhoff-Helmholtz formula. Aiming at a physically and technologically implementable method, we consider a discrete distribution of microphones, disposed at a constant height in a reverberating area reproducing the geometry of a straight narrow street.The problem shows specific constraints due to its specific geometry that we aim to use sparsely. In a first approach, we consider the supersonic displacement from the viewpoint of Huygens-Fresnel principle as a discrete sum of monopolar sources, which allows an analytical formulation of the direct problem solvable by simple numerical simulations. This model is in agreement with an experimental framework, were the Mach cone is synthesized by means of a loudspeaker array. The resolution of the inverse problem is made by computing the time-reversed pressure field into vertical slices disposed along the street. The use of a fourth-order spatiotemporal statistical criterion (kurtosis) allows to reduce unwanted contribution of source term causing a divergence around microphone positions. A maximum of kurtosis is observed around the intersection between the time-reversal slice and the Mach cone axis, allowing localisation of the latter with good angular precision. In a second approach, we investigate the previous method on a real Mach cone. It is necessary to adopt the point of view of dynamical space-time geometry to understand the behaviour of the times of arrival of the different image sources. It is also necessary to take into account the finiteness of the reberberating walls. Our geometrical theory of reverberation allows a modelisation of the direct problem in good agreement with experimental measurements. We show that the effect of reverberation does not enhance time-reversed focalisation as well as it does with a static source. This is mainly due to geometric constraints that are not reproduced in the time-reversed wavefront superposition. The resolution of the inverse problem strongly depends on the disposition of the microphone set: on the 9 configurations, only one allows detection of the axis.

<p>In this project several tests were performed to evaluate the performance of an On-Board Imager® (OBI) mounted on a clinical linear accelerator. The measurements were divided into three parts; geometric accuracy, image registration and couch shift accuracy, and image quality. A cube phantom containing a radiation opaque marker was used to study the agreement with treatment isocenter for both kV-images and cone-beam CT (CBCT) images. The long term stability was investigated by acquiring frontal and lateral kV images twice a week over a 3 month period. Stability in vertical and longitudinal robotic arm motion as well as the stability of the center-of-rotation was evaluated. Further, the agreement of kV image and CBCT center with MV image center was examined.</p><p>A marker seed phantom was used to evaluate and compare the three applications in image registration; 2D/2D, 2D/3D and 3D/3D. Image registration using kV-kV image sets were compared with MV MV and MV-kV image sets. Further, the accuracy in 2D/2D matches with images acquired at non-orthogonal gantry angles was evaluated. The image quality in CBCT images was evaluated using a Catphan® phantom. Hounsfield unit (HU) uniformity and linearity was compared with planning CT. HU accuracy is crucial for dose verification using CBCT data.</p><p>The geometric measurements showed good long term stability and accurate position reproducibility after robotic arm motions. A systematic error of about 1 mm in lateral direction of the kV-image center was detected. A small difference between kV and CBCT center was observed and related to a lateral kV detector offset. The vector disagreement between kV- and MV-image centers was  2 mm at some gantry angles. Image registration with the different match applications worked sufficiently. 2D/3D match was seen to correct more accurately than 2D/2D match for large translational and rotational shifts. CBCT images acquired with full-fan mode showed good HU uniformity but half fan images were less uniform. In the soft tissue region the HU agreement with planning CT was reasonable while a larger disagreement was observed at higher densities. This work shows that the OBI is robust and stable in its performance. With regular QC and calibrations the geometric precision of the OBI can be maintained within 1 mm of treatment isocenter.</p>

<p>Contemporary algorithms employed for reconstruction of 3D volumes from helical cone beam projections are so called non-exact algorithms. This means that the reconstructed volumes contain artifacts irrespective of the detector resolution and number of projection angles employed in the process. In this thesis, three iterative schemes for suppression of these so called cone artifacts are investigated.</p><p>The first scheme, iterative weighted filtered backprojection (IWFBP), is based on iterative application of a non-exact algorithm. For this method, artifact reduction, as well as spatial resolution and noise properties are measured. During the first five iterations, cone artifacts are clearly reduced. As a side effect, spatial resolution and noise are increased. To avoid this side effect and improve the convergence properties, a regularization procedure is proposed and evaluated.</p><p>In order to reduce the cost of the IWBP scheme, a second scheme is created by combining IWFBP with the so called ordered subsets technique, which we call OSIWFBP. This method divides the projection data set into subsets, and operates sequentially on each of these in a certain order, hence the name “ordered subsets”. We investigate two different ordering schemes and number of subsets, as well as the possibility to accelerate cone artifact suppression. The main conclusion is that the ordered subsets technique indeed reduces the number of iterations needed, but that it suffers from the drawback of noise amplification.</p><p>The third scheme starts by dividing input data into high- and low-frequency data, followed by non-iterative reconstruction of the high-frequency part and IWFBP reconstruction of the low-frequency part. This could open for acceleration by reduction of data in the iterative part. The results show that a suppression of artifacts similar to that of the IWFBP method can be obtained, even if a significant part of high-frequency data is non-iteratively reconstructed.</p>