The extra energy information provided by spectral x-ray imaging using novel photon counting x-ray detectors may allow for improved decomposition of materials compared to conventional and dual-energy imaging. The information content of spectral x-ray images, however, depends on how the photons are grouped together. This thesis deals with the theoretical aspect of optimising material discrimination in spectral x-ray imaging. A novel theoretical model was developed to map the confidence region of material thicknesses to determine the uncertainties in thickness quantification. Given the thickness uncertainties, photon counts per pixel can be optimised for material quantification in the most dose efficient manner. Minimisation of the uncertainties enables the optimisation of energy bins for material discrimination. Using Monte Carlo simulations based on the BEAMnrc package, material decomposition of up to 3 materials was performed on projection images, which led to the validation of the theoretical model. With the inclusion of scattered radiation, the theoretical optima of bin border energies were accurate to within 2 keV. For the simulated photon counts, excellent agreement was achieved between the theoretical and the BEAMnrc models regarding the signal-to-noise ratio in a decomposed image, particularly for the decomposition of two materials. Finally, this thesis examined the implementation of the Medipix detector. The equalisation of pixel sensitivity variations and the processing of photon counting projection images were studied. Measurements using the Medipix detector demonstrated promising results in the charge summing and the spectroscopic modes of acquisition, even though the spectroscopic performance of the detector was relatively limited due to electronic issues known to degrade the equalisation process. To conclude, the theoretical model is sufficient in providing guidelines for scanning parameters in spectral x-ray imaging and may be applied on spectral projection measurements using e.g. the redesigned MedipixRX detector with improved spectroscopic performance, when it becomes available.

Despite popular and scientific interest in mummies, very few studies of ancient Egyptian mummy collections, especially from the same area, have been conducted. As such, this research is the first comprehensive analysis of mummies from Akhmim, Egypt and is one of only a few studies that investigate a large mummy collection from both a biological and cultural point of view. A group of 25 mummies from the Akhmim Mummy Studies Consortium database was evaluated using computed tomography. Using computed tomography and the associated imaging software, two dimensional (2D) x-ray scan images were analyzed, then processed and edited to generate three dimensional (3D) models of each mummy. Both the 2D and 3D images of each mummy were used to collect both biological information and cultural data in a nondestructive manner. Results from this study indicated that the population of Akhmim was very diverse. Furthermore, this research both supports and challenges conventional wisdom on how ancient Egyptians were mummifying their dead.

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Thesis (Ph.D.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 15, 2006) Vita. Includes bibliographical references.

Resumo: O propósito deste trabalho foi verificar a posição das cabeças da mandíbula nas suas respectivas fossas mandibulares em individuos com diferentes má-oclusões Classe I, II e III. Foram utilizadas tomografias computadorizadas volumétricas de 60 indivíduos em avaliação préortodôntica do sexo masculino e feminino. Com o gabarito preconizado por Pereira (1997), obtivemos medidas lineares dos espaços articulares anterior, posterior e superior de cada ATM. Após análise estatística, concluiu-se que as cabeças da mandíbula nos casos de Classe III do lado esquerdo apresentaram, com significancia estatística, maior deslocamento anterior em relação a fossa mandibular. Os casos de Classe II do lado esquerdo, embora sem significância estatística, apresentaram tendência de maior deslocamento porterior da cabeça da mandíbula enquanto os grupos de Classe I do mesmo lado apresentaram tendência a posição centralizada. Os grupos de Classe I e III do lado direito apresentaram maior tendência de deslocamento centralizado, enquanto os grupos de.Classe II do mesmo lado apresentaram maior tendência de deslocamento posterior porém sem significância estatística / Abstract: The purpose of this study was to determine the condyle position in their respective mandibular fossa in different individuals with Class I, II and III malocclusions. Cone Beam Computer Tomographies (CBCT) from 60 male and female individuals were taken in the pre-orthodontic treatment. The answer key developed by Pereira (1997) provides us the linear measurements of the anterior, posterior and superior spaces of TMJ. After statistic analysis, we can conclude that the condyle position in Class III individuals on the left side, showed, with statistical significance, more tendency to anterior condyle dislocation in the mandibular fossa. In Class II cases on the left side, although not statistically significant, tended to posterior condyle deviation position. Class I group on the same side showed a tendency towards central position. Class I and III groups on the right side showed a higher tendency to central position, while Class II groups in the same side showed a higher tendency to posterior position, but without statistical significance / Orientador: Edmundo Médici Filho / Coorientador: Jefferson Luis Oshiro Tanaka / Banca: Sibele Pereira de Oliveira / Banca: Julio Cezar de Melo Castilho / Mestre

Throughout the development of computed tomographic (CT) imaging the challenges of capturing the heart, with its perpetual, vigorous motion, and in particular the tiny detail within the coronary arteries, has driven technological progress. Today, CT is a widely used and rapidly growing modality for the investigation of coronary artery disease, as well as other cardiac pathology. However, limitations remain and particular patient groups present a significant challenge to the CT operator. This thesis adds new knowledge to the assessment of these difficult-to-image patients. It considers patients with artefact from coronary artery calcification or stents, examining the remarkable diagnostic performance of high definition scanning, as well as material subtraction techniques using dual energy CT, alongside ways in which current technology might be revisited and refined with the use of alternative image reconstruction methods. Patients with challenging heart rate or rhythm abnormalities are considered in three studies; how to achieve diagnostic image quality in atrial fibrillation, the safety of an aggressive approach to intravenous beta-blocker use prior to coronary imaging, and the development of patient information to address anxiety as a source of tachycardia and motion artefact. Finally, the novel application of a single source, dual energy CT scanner to additional cardiac information is considered, with studies of myocardial perfusion CT and delayed iodine enhancement imaging, to identify ways in which non-coronary imaging might be exploited to more thoroughly evaluate a patient’s coronary artery status. These findings are presented in the context of developing technology and together offer a range of potential options for operators of cardiac CT when faced with a difficult-to-image patient.

X-ray Computer Tomography (CT) is well suited to the inspection of Fibre-Reinforced-Plastic (FRP) composite materials. However, a range of limitations currently restrict its uptake. The aim of the present research was to develop advanced inspection procedures that overcome these limitations and increase the scope of composite structures that can be inspected by industrial cone beam CT. Region of Interest (ROI) CT inspection of FRP laminated panels was investigated and two data completion methods developed to overcome reconstruction errors caused by truncated projection data. These allow accurate, highly magnified regions to be reconstructed on objects that extend beyond the Field-of-View (FOV) of the detector. The first method extended the truncated projection data using a cosine signal tailing off to zero attenuation. This method removed the strong 'glowing' artefacts but an inherent error existed across the reconstructed ROI. This did not affect the defect detectability of the inspection but was viewed as problematic for applications requiring accurate density measurements. The second method used prior knowledge of the test object so that a model could be created to estimate the missing data. This technique removed errors associated with ROI reconstruction thus significantly improving the accuracy. Techniques for extending the FOV were developed and applied to the inspection of FRP wind turbine blades; over 1.5X larger than the conventional scanning FOV. Two data completion methods were developed requiring an asymmetrically positioned detector. The first was based on the cosine tailing technique and the second used fan beam ray redundancy properties to estimate the missing data. Both produced accurate reconstructions for the 'offset' projection data, demonstrating that it was possible to approximately double the FOV. The cosine tailing method was found to be the more reliable. A dual energy image CT technique was developed to extend the optimum dynamic range and improve defect detectability for multi-density objects. This was applied to FRP composite/Titanium lap joints showing improved detectability of both volumetric and planar defects within the low density FRP. The dual energy procedure was validated using statistical performance measures on a specially fabricated multi-density phantom. The results showed a significant improvement in the detail SNR when compared to conventional CT scans.

Thesis (MSD) --Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Orthodontics and Dentofacial Orthopedics). / Includes bibliographic references: leaves 37-42. / Background: Craniofacial skeletal asymmetry is a common finding in the general population that often goes undetected. Interest in this topic has led to many studies aimed at describing this type of asymmetry, its distribution and etioIogy. The cranial base, being cIosely related to the face and brain, is a key component in craniofacial growth and may also display varying amounts of asymmetry contributing to this anomaly. Though many studies have explored underlying skeletal asymmetry, most of them were limited by their two-dimensional method of investigation. With the advent of three-dimensional technology, more recent studies have had the advantage of studying the cranial base in its true anatomic form, resulting in greater accuracy of analysis. Despite access to this technoIogy, there is still a lack of literature regarding the cranial base in a normal population. Determining average skull base dimensions will provide a set of normative data that can be used as a reference for future studies. Material and Methods: Pre-treatment Cone Beam Computed Tomography (CBCT) films of 160 esthetic human subjects previously used by another investigator were screened for use in our current research. These DICOM files were imported into InVivoDental5.3 software (Anatomage[TM]; San Jose, Calif.) for screening and 70 CBCT scans were selected for analysis. All patients were classified as cervical vertebral stage 4 and above. The images were oriented in all three planes of space for uniformity and 14 bilateral anatomic landmarks were identified on each scan. A mid-sagittal reference plane was created using crista galli as the origin, and extending a perpendicular passing through the middle of the right and left clinoid points connected by a line, and through posterior points basion and opisthion. Each landmark was given an x-, y- and z- coordinate representing its three dimensional position and bilateral linear measurements to the reference plane were recorded using the software system. Statistical Analysis: InVivoDental5.3 software was used to calculate linear distances between each landmark and the mid-sagittal plane. This data was exported into Microsoft excel for analysis. Descriptive statistics of our sample and paired t-tests with a 5% significance level, or p value of 0.05, were performed. Results: The means of the right and left measurements of each bilateral landmark were calculated along with their standard deviations. A comparison between right and left means was accomplished with the use of paired t-tests. 12 1andmarks did not show a statistical difference in their locations on either side of the mid-sagittal plane. However, the means of 2 landmarks were found to be statistically significant. These were euryon (p = 0.01) and the jugular foramen (p = 0.00) Conclusion: The overall trend of our data indicated that the cranial base in a normal population, without craniofacial anomaly, displays symmetry, with the exception of the location of euryon and the jugular foramen. These findings are in accordance with those of similar three-dimensional studies. It is likely that the significant findings were due to tracing error, given the indiscrete location of euryon and the large, relatively asymmetric shape of the jugular foramen. However, if these structures are truly asymmetric, we can infer from our sample of symmetric patients, that there is no clinical relevance. Further studies with an increased sample size, additional landmarks or a more discrete sample can be performed to continue describing the skull base. The results of this study offer valuable reference data that can be used as a baseline for future studies.

Ectopic thyroid gland is a developmental anomaly that results from the arrest of thyroid tissue along its path of descent from the floor of mouth to the pre tracheal position in the lower neck. It is typically found along the thyroglossal duct with the base of the tongue being the most common site. Apart from mediastinal extension of goiter, the incidence of true intrathoracic ectopic thyroid tissue is rare. Presence of ectopic thyroid has been reported not only in the chest but also in the abdomen and pelvis. Pericardial and intracardiac locations are extremely uncommon and right ventricle location is predominant among the described cases. We describe a case of incidentally detected ectopic thyroid tissue in a rarer location—adjacent to the left atrium. The patient, who had undergone a nephrectomy for renal oncocytoma 5 years ago, presented with unintentional weight loss and left sided flank pain, prompting a workup to rule out abdominal malignancy. Findings on the computed tomography (CT) scan of the abdomen and pelvis prompted further investigation including a chest CT which showed a heterogeneously enhancing mass near the left atrium. Given its location, further radiological investigations played an important role in eliminating the differential diagnosis of paraganglioma. The mass was surgically resected and discovered to be a hyperplastic thyroid nodule on histologic examination.

The emergence of new technologies and improved computing power helped to introduce a renewed vitality in morphological research in recent decades. This is especially apparent in the new advances made in understanding the evolutionary morphology of the skeletal system in extinct and extant squamate reptiles. The new data generated as a result of the recent increase in attention are relevant not only for systematic analyses but also are valuable in their own right for contributing to holistic perspectives on organismal evolution, mosaic evolution in the rates of change in different anatomical systems, and broader patterns of macroevolution. A global community of morphological researchers now can share data through online digital collections, but opportunities for continued advance are hindered because we lack even basic data on patterns of variation of the skeletal system for virtually all squamate lineages. Most work on skeletal morphology of squamates is based on a sample size of n=1; this is an especially noticeable phenomenon for studies relying on X-ray computed tomography technology. We need new collections of skeletal specimens, both material and digital, and new approaches to the study of skeletal morphology. Promising areas for continued research include the recent focus on skeletal elements not traditionally included in morphological studies (especially systematic analyses based upon morphological data) and efforts to elucidate patterns of variation and phylogenetically informative features of disarticulated skeletal elements. Anat Rec, 297:344-348, 2014.