Thesis (M.S.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains viii, 88 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 62-66).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 209-211). Available also in a digital version from Dissertation Abstracts.

Dissertation (Ph.D.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 101-107).

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. Vita. "December 2005" Includes bibliographical references.

Recent developments in CT technology has resulted in a continuing expansion of CT practice. CT has become a major source of exposure in diagnostic radiology. Therefore, the European Union, in an ionizing radiation protection directive, has classified computed tomography as a high dose diagnostic procedure and has pointed to the need to reduce the dose to the patient. Efforts towards dose reduction in CT have been recommended by international organizations. The European Commission (EC) have recommended the setup and the implementation of CT dose guidance levels for the most frequent examinations to promote strategies for the optimization of CT doses. These dose guidance levels should be derived using data from a wide scale survey. Therefore, it is of great interest whether there are dose quantities whose values are easy to obtain, which can correctly reflect the patient dose and allow assessment of the risk associated with the CT examination. The most widely used CT Dose Quantity is the computed tomography dose index (CTDI). Another important dose quantity is the Dose Length Product (DLP), which includes the patient, or the phantom volume irradiated during a complex examination. The main purpose of this study is the measurement of CTDI and DLP during the most frequent CT examinations at the University Hospital of Patras. Also scan lengths used for the same type of examinations will be monitored. For the same types of examinations effective doses will be calculated. Four CT examination was selected because of their frequency, Routine Head, Routine Chest, Routine Abdomen and Cervical Spine. The protocols of these exams were compared with the European Commission’s recommendations. Data were collected from 120 patients, 30 for each examination. Data on the scanning parameters and the patient dose were selected from the CT scanner, a GE LightSpeed 16. Moreover, data were collected about the sex, the age and the weight of the patient undergone the examination. The mean values of CTDIw, DLP and Effective Dose were calculated for each protocol and were compared with the recommendations of European Commission. Moreover, an evaluation of the dose indication of the CT scanner was made. Using a head and a body CT Dose phantom made by PMMA, an ionization chamber and an electrometer, the CTDI was measured for each examination protocol. These values were compared with the indications of CT and the correspondent values published by ImPACT. / Τα τελευταία χρόνια έχει παρατηρηθεί επέκταση της χρήσης του Υπολογιστικού Τομογράφου(ΥΤ). Ο ΥΤ είναι η κυριότερη πηγή ακτινοβολίας ανάμεσα σε όλες τις ακτινοδιαγνωστικές εξετάσεις. Για αυτό το λόγο η Ευρωπαϊκή Ένωση, σε μια κατευθυντήρια οδηγία για την προστασία από ιοντίζουσες ακτινοβολίες σημείωσε την ανάγκη μείωσης της δόσης στον ασθενή. Προσπάθειες για τη μείωση της δόσης από ΥΤ έχουν γίνει από διεθνείς οργανισμούς, οι οποίοι έχουν προτείνει τον καθορισμό επιπέδων αναφοράς για τις πιο συχνές εξετάσεις ΥΤ με σκοπό την ανάπτυξη στρατηγικών για τη μείωση της δόσης από ΥΤ. Τα επίπεδα αναφοράς πρέπει να προκύπτουν από έρευνες μεγάλης κλίμακας. Για αυτό το λόγο οι ποσότητες της δόσης που χρησιμοποιούνται πρέπει να είναι εύκολο να υπολογιστούν, αλλά να αντανακλούν σωστά τη δόση στον ασθενή και να επιτρέπουν τον υπολογισμό του κινδύνου που προέρχεται από τη χρήση της ακτινοβολίας. Η ποσότητα που χρησιμοποιείται ευρέως στη Δοσιμετρία από ΥΤ είναι ο Computed Tomography Dose Index, CTDI, το Γινόμενο Δόσης Μήκους (Dose Length Product, DLP) το οποίο συνυπολογίζει τον όγκο του ασθενή ή του ομοιώματος που έχει ακτινοβοληθεί κατά τη διάρκεια μιας πλήρους εξέτασης. Ο κύριος σκοπός αυτής της εργασίας είναι η μέτρηση του CTDI και του DLP για τις πιο συχνές εξετάσεις ΥΤ στο Πανεπιστημιακό Γενικό Νοσοκομείο Πατρών. Ακόμα υπολογίζεται το μέσο μήκος εξέτασης και η μέση ενεργός δόση για κάθε εξέταση. Επίσης ελέγχεται η αξιοπιστία των ενδείξεων της δόσης στην κονσόλα του ΥΤ. Επιλέχτηκαν τέσσερις εξετάσεις ΥΤ λόγω της συχνότητας τους, αυτές είναι: η εξέταση κεφαλής, θώρακα, κοιλίας και αυχένα. Τα πρωτόκολλα αυτών των εξετάσεων συγκρίνονται με τις συστάσεις της European Commission. Συνολικά συλλέχτηκαν δεδομένα από 120 ασθενείς, 30 για κάθε εξέταση. Δεδομένα που αφορούσαν τις παραμέτρους της σάρωσης κάθε ασθενή συλλέχτηκαν από την κονσόλα του ΥΤ, ο οποίος είναι ένας GE LightSpeed 16. Επιπλέον συλλέχτηκαν δεδομένα σχετικά με το φύλλο, την ηλικία και το βάρος του ασθενή που υποβλήθηκε σε εξέταση. Υπολογίστηκε η μέση τιμή του CTDIw, του DLP και της ενεργού δόσης για κάθε πρωτόκολλο και συγκρίθηκαν με τα όρια που προτείνει η European Commission σαν DRL. Επιπλέον, έγινε αξιολόγηση της τιμής της δόσης όπως αυτή εμφανίζεται στην κονσόλα του ΥΤ. Για αυτό το λόγο έγιναν μετρήσεις σε ένα ομοίωμα κεφαλής και σε ένα ομοίωμα σώματος κατάλληλο για την δοσιμετρία ΥΤ. Επιπλέον, χρησιμοποιήθηκε ένας θάλαμος ιονισμού και ένα ηλεκτρόμετρο. Έτσι μετρήθηκε η τιμή του CTDI για κάθε πρωτόκολλο χρησιμοποιώντας τις ίδιες παραμέτρους σάρωσης. Οι τιμές που μετρήθηκαν συγκρίθηκαν με τις ενδείξεις του ΥΤ αλλά και με τις τιμές που έχει δημοσιεύσει το Imaging Performance Assessment of CT scanners (ImPACT).

Thesis (MSc (Radiography))--Cape Peninsula University of Technology, 2017. / Background: Metabolic syndrome (MetS) is a clustering of cardiovascular disease (CVD) risk factors which include abdominal obesity, hyperglycaemia, hyper-triglyceridaemia, low HDL-cholesterol and hypertension. This cluster of metabolic deviations is believed to be the primary driver of the double global epidemic of diabetes (DM) and CVD, conditions which account for much of the social and economic global burden of disease. Similar to the global trend, a high prevalence of MetS (62%) and type 2 Diabetes Mellitus (T2DM) (28.2%) has been reported for the South African mixed ancestry population, with CVD risk significantly higher in subjects with DM. The increase in MetS prevalence is driven by the obesity epidemic and anthropometric cut-off values to define MetS for this particular component of the disease has been reported to differ widely between different populations and ethnicities. Currently the waist circumference (WC) cut-off value for MetS diagnosis needs to be determined and validated per ethnic group as opposed to the previously used European derived cut-off values (Alberti et al., 2006; 2009). Validation of the WC cut-off value needs to be against one of the so called gold standards of central obesity measurement, such as Computer Tomography (CT). This technique can measure subcutaneous fat (SAT) and visceral fat (VAT) individually, which is important because VAT has been reported to be associated with MetS and CVD. The current study forms part of a large research group, investigating the prevalence and risk factors for MetS and T2DM in the South African mixed ancestry population.

The purpose of this study is to evaluate the past and recent literature in order to determine the role of pre-operative CT scans in chronic otitis media. We aim to find consensus on the diagnostic ability of CT imaging in various anatomical parts of the middle ear and mastoid, and how this knowledge can affect clinical and surgical management. In context of all literature, there has been mixed results when looking at the sensitivity and specificity of middle ear structures. There was favorable consensus for CT's diagnosis of erosion of the malleus-incus complex, lateral semicircular canal, the facial nerve canal, and presence of soft tissue in the middle ear cavity. There were mixed results with respect to the erosion of tegmen tympani, and sigmoid sinus. Lastly, there was an unfavorable consensus when looking at the erosion of the stapes, oval window, and round window. Various studies conclude that the information gained from CT regarding the condition of the mastoid and middle ear can influence both the type of surgical method used and the success rate by reducing the risk of complications and recurrence of disease. In many studies, the methodology and interpretation of the CT scans are not very well presented. This unfortunately disallows meta-analysis between studies as the number of uncontrolled variables is too large. In the future, we hope that more information is provided as to the method of interpretation as well as the type of CT scanner and dosage. This will allow for a more meaningful result when comparing sensitivities and specificities towards middle ear pathologies, and it will allow for better examination of image quality and usefulness in context of the risk of radiation. Many otologists make routine use pre-operative CT scans in cases of chronic otitis media while others are more selective. In order to reach a consensus, however, more research focused on specific the decision-making process of physicians.

A possibilidade de exploração das imagens oferecida pela tomografia computadorizada cone beam (TCCB) permite investigações mais detalhadas do paciente. Este estudo, empregando alguns destes recursos, se propôs a comparar medidas cefalométricas realizadas sobre telerradiografias convencionais e reconstruções de perfil total e unilaterais obtidas da TCCB. Análises cefalométricas de 30 pacientes foram realizadas por um examinador calibrado sobre as reconstruções da TCCB e as telerradiografias convencionais. A reprodutibilidade dos fatores cefalométricos foi investigada por meio do coeficiente de correlação intraclasse em cada imagem. O método de Bland-Altman foi utilizado para averiguar a performance diagnóstica de cada imagem em relação às medidas de cada fator cefalométrico. O coeficiente de correlação intraclasse evidenciou semelhança de reprodutibilidade entre os exames. Quando os valores dos fatores cefalométricos foram comparados, observou-se forte concordância diagnóstica entre as mensurações realizadas sobre telerradiografias convencionais e imagens reconstruídas por TCCB. Conclui-se que, em pacientes sem assimetrias faciais importantes, a telerradiografia convencional e as reconstruções total e unilaterais a partir da TCCB oferecem desempenho de reprodutibilidade e resultado de análise cefalométrica semelhantes. / The possibility to explore images afforded by the cone beam computer tomography (CBCT) technique allows investigating patients in more detail. The present study uses some of these resources to compare cephalometric measurements obtained from conventional cephalograms and total and half-skull synthesized cone beam computed tomography (CBCT) cephalograms. Cephalometric analyses of 30 clinically symmetric patients; were conducted by a calibrated examiner on conventional and CBCTsynthesized cephalograms. Reproducibility was investigated using the intraclass correlation coefficient. The Bland-Altman analysis was used to assess the agreement of the measurements from each factor obtained by conventional, total, right and left CBCT-synthesized cephalograms. The intraclass correlation coefficient revealed similar levels of reproducibility. When the measurements obtained from conventional and CBCT-synthesized cephalograms were compared, the Bland-Altman analysis showed a strong agreement between them. Half-skull CBCT-synthesized cephalograms offer the same diagnostic performance and equivalent reproducibility in terms of cephalometric analysis as observed in conventional and total CBCT-synthesized cephalograms.