Abstract

Introduction: Cone Beam Computed Tomography (CBCT) has an application in all dental specialties. CBCT is an aid in implant dentistry to evaluate anatomical landmarks in both quality and quantity. Hounsfield Unit (HU) values represent a grayscale that is standardized on CT machines relative to the density of water and air. It has been reported that the HU value represents an actual value of the bone density. However, recent studies at Loma Linda University have suggested that HU values retrieved using CBCT machines may be altered by various factors.

Purpose: The aim of this study is to evaluate the specific dosage factors (field of view, kVp, and mA) that influence the contrast resolution of images as measured by HU that are acquired from a phantom scanned with the CB MercuRay device.

Materials and Methods: A phantom was fabricated with 11 hydroxyapatite cylindrical disks with increasing mineral densities. Values ranged from a minimum of 0 mg/cm3 up to a maximum of 1000 mg/cm3. Scans with all available fields of View (FOV), kVp, and mA were stored and read with image viewing software. The variation of HU values with various adjustable settings was evaluated.

Results: HU values recorded varied significantly when changing adjustable settings. When changing among FOV and kVp, the HU were different statistically with ANOVA at p [less than or equal to] 0.001. With further analysis it was found that each FOV was statistically different from each other with Bonferroni-corrected Post Hoc test at p ^).05. The most variation in HU values was found with the 6 inch FOV. No statistically significant difference in HU values was found with changing the mA.

Conclusions: The HU values vary significantly by the FOV and kVp settings with CB MercuRay CBCT. Reducing amperage from 15 mA to 2 mA had very little effect on the HU values.

KEY WORDS: Cone Beam Computed Tomography, CB MercuRay, bone density, hydroxyapatite phantom, Hounsfield Unit, dental implant, scan field of view, dosage settings.

LLU Discipline

Periodontics

Department

Periodontics

School

Dentistry

First Advisor

Jeffrey Henkin

Second Advisor

Bernard Gantes

Third Advisor

Max Crigger

Fourth Advisor

Joseph M. Caruso

Fifth Advisor

Yoon Jeong Kim

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2009

Date (Title Page)

3-2009

Language

English

Library of Congress/MESH Subject Headings

Radiography, Dental, Digital -- methods -- dissertations; Cone-Beam Computed Tomography; Radiographic Image Interpretation, Computer Assisted; Image Enhancement -- methods; Tomography Scanners, X-Ray Computed; Bone Density.

Type

Thesis

Page Count

ix; 33

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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