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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

ACCURACY OF CONE-BEAM COMPUTERIZED TOMOGRAPHY IN DETERMINING THE THICKNESS OF THE PALATAL MASTICATORY MUCOSA

Hardison, Justin 23 April 2012 (has links)
BACKGROUND: The aim was to compare the thickness of the palatal masticatory mucosa as determined on a cone-beam computerized (CBCT) scan versus thickness determined via bone-sounding. METHODS: A total of twenty patients requiring palatal surgery participated. Thickness of the palatal tissue was measured at various points radiographically and clinically. The two techniques were compared to determine the agreement of the two measurement modalities. RESULTS: Analysis of variance determined that there was no significant difference between the two methods. A small bias of the radiographic measurement being larger was found to be statistically significant (0.09 ± 0.69mm; p <0.0001). Moreover, the tissue thickness was shown to increase as the distance from the gingival margin increased and the tissue over the molars was thinner than the tissue over the premolars. CONCLUSIONS: CBCT can be used to accurately determine the soft tissue thickness of the palatal masticatory mucosa with minimal bias.
2

Renal Arterial Blood Flow Quantification by Breath-held Phase-velocity Encoded MRI

Wallin, Ashley Kay 14 May 2004 (has links)
Autosomal dominant polycystic disease (ADPKD) is the most common hereditary renal disease and is characterized by renal cyst growth and enlargement. Hypertension occurs early when renal function is normal and is characterized by decreased renal blood flow. Accordingly, the measurement of blood flow in the renal arteries can be a valuable tool in evaluating disease progression. In studies performed in conjunction with this work, blood flow was measured through the renal arteries using magnetic resonance imaging (MRI). In order to validate these in vivo measurements, a vascular phantom was created using polyvinyl alcohol (PVA) and also scanned using MRI under controlled steady flow conditions. Ranges of vessel diameters and flow velocities were used to simulate actual flow in a normal and diseased population of adults and children. With the vessel diameters studied in this experiment, minimization of field of view and an increase in spatial resolution is important in obtaining accurate data. However, a significant difference does not exist between the results when using the 160 or 200 mm FOV. An increase in the number of phase encodings provides improved results, although an increase in image acquisition time is observed. Velocity-encoding in all three orthogonal directions does not improve image data. This method of using MRI to measure flow through a vessel is shown to be both accurate and reproducible, and the protocol providing the most correct results is prescribed. Breath-hold phase-velocity encoded MRI proves to be an accurate and reproducible technique in capturing flow and has the potential to be used for the purpose of observing hemodynamic changes in the renal arteries with the progression of ADPKD.

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