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A Method of Superimposition of CBCT Volumes in the Posterior Cranial Base

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A Method of Superimposition of CBCT Volumes in the Posterior Cranial Base A Method of Superimposition of CBCT Volumes in the Posterior Cranial Base A Thesis Submitted to The Temple University Graduate Board In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE In ORAL BIOLOGY By Jared R. Gianquinto, D.M.D. Orhan C. Tuncay, D.M.D. Advisor, Department of Orthodontics James J. Sciote, D.D.S., Ph.D., M.S., Committee, Department of Orthodontics Jie Yang, D.D.S., M.Med.Sc., M.S., D.M.D. Committee, Department of Radiology August, 2011 i ABSTRACT Three dimensional imaging in the form of Cone Beam Computed Tomography has become prevalent in the field of orthodontics. Analytical methods of resulting volumetric data sets have not kept pace with the technology capable of producing them. Current 3D analysis techniques are largely adaptations of existing 2D methods, offering no clear diagnostic advantage over traditional imaging techniques in light of increased radiation exposure, and cannot be compared with norms generated from 2D image capture sources. In order to study morphology in 3D, data sets must be generated for longitudinal studies and native 3D analytical methods must also be developed. Existing methods of CBCT volume superimposition are cumbersome, involving complex software pipelines and multiple systems to complete the process. The goal of the current study was to develop a reproducible method of CBCT volume superimposition in the posterior cranial base in a single software package, and construct an easy to follow, step-by-step manual to facilitate future studies in craniofacial morphology. Existing anonymized sequential CBCT volumes of three subjects meeting inclusion criteria were obtained from the Kornberg School of Dentistry Department of Radiology. Volumes for each subject were imported into AMIRA software, resampled to a standardized 0.5mm voxel size and superimposed with a mutual information algorithm. Posterior cranial base surface data was extracted using a semi-automatic technique. Resulting surface distance data was compiled and visualized through application of color maps. A streamlined image processing protocol was produced and documented in a detailed step-by-step manual. ii Surface distance analysis of serial segmentations was performed to verify reliability of the process. Surface distance deviations greater than 0.5mm consistently fell below 0.2 percent of the total surface area. Sequential scan superimpositions of all three subjects exhibited mean surface distances of less than 0.15mm. Two out of three subjects exhibited deviations of greater than 0.5mm in less than 1 percent of the total surface area, suggesting consistent sub- voxel accuracy of the protocol. iii ACKNOWLEDGEMENTS First and foremost, I would like to thank Dr. Orhan Tuncay for his wisdom, guidance and dedication to the specialty. Your tireless and selfless devotion to the department and relentless pursuit of the future are truly inspiring. Thank you for believing in me. I would like to thank Dr. James Mah for graciously providing access to data collected by the University of Nevada at Las Vegas, and for numerous discussions regarding Mutual Information theory. Your work continues to inspire. Dr. Jie Yang, Dr. Htin Gyaw and the Department of Radiology staff were essential to the success of this project. Without your guidance and help in collecting data from the archives, this project could not have been possible. To Dr. Bryon Viechnicki, thank you for discovering Amira software, leading the way and sharing your successes. Finally, to my family. Thank you for your unwavering support in all of my pursuits. iv TABLE OF CONTENTS ABSTRACT ....................................................................................................................ii ACKNOWLEDGEMENTS ........................................................................................... iv LIST OF TABLES ..........................................................................................................x LIST OF FIGURES ........................................................................................................xi CHAPTER ONE: INTRODUCTION ......................................................................... 1 CHAPTER TWO: REVIEW OF LITERATURE .........................................................3 2.1 Cephalometric Radiography ...................................................................................3 2.1.1 Cephalometric Superimposition .......................................................................4 2.1.2 Controversy in Cephalometrics ........................................................................4 2.1.3 Cranial Base Morphology and Stability ............................................................5 2.2 Cone Beam Computed Tomography .......................................................................7 2.2.1 CBCT Limitations ...........................................................................................8 2.2.2 Artifacts ...........................................................................................................9 2.2.3 Partial Volume Averaging ................................................................................9 2.2.4 Undersampling ................................................................................................9 2.2.5 Cone Beam Effect .......................................................................................... 10 2.2.6 Image Noise ................................................................................................... 12 v 2.2.7 Patient Related Artifacts ................................................................................ 12 2.3. 3D Biomedical Imaging and Analysis Software ................................................... 13 2.3.1 Multiplanar Reformation ................................................................................ 14 2.3.2 Surface Rendering ......................................................................................... 14 2.3.3 Volume Rendering ......................................................................................... 15 2.3.4 Image Segmentation ...................................................................................... 15 2.3.5 Image Registration ......................................................................................... 16 2.4 Previous Research from Temple University Department of Orthodontics ............. 18 2.4.1 Thesis Project of Dr. Michael Nuveen ............................................................ 18 2.4.2 Thesis Project of Dr. Can Nguyen .................................................................. 18 2.4.3 Thesis Project of Dr. John Slattery ................................................................. 19 2.4.4 Thesis Project of Dr. David Lee ..................................................................... 20 2.4.5 Thesis Project of Dr. Robert J. Murray ........................................................... 20 2.4.6 Thesis Project of Dr. Wilbert Saavedra .......................................................... 21 2.4.7 Thesis Project of Dr. Ched Smaha .................................................................. 21 2.4.8 Thesis Project of Dr. Bryan Hiller .................................................................. 22 2.4.9 Thesis Project of Dr. Jacob Orozco ................................................................ 22 2.5 Recent Works in 3D Morphometrics .................................................................... 23 CHAPTER THREE: AIM ........................................................................................ 27 CHAPTER FOUR: MATERIALS AND METHODS............................................... 28 vi 4.1 Subject Selection .................................................................................................. 28 4.2 Image Acquisition ................................................................................................ 29 4.3 Superimposition of Cranial Base Models ............................................................. 29 4.4 3D Surface Model Construction ........................................................................... 30 4.4.1 Segmentation ................................................................................................. 30 4.4.2 Segmentation Reliability ................................................................................ 32 4.5 Analysis of Registration Accuracy........................................................................ 32 CHAPTER FIVE: RESULTS .................................................................................... 34 5.1 Segmentation Reliability ...................................................................................... 34 5.2 Superimposition Analysis ..................................................................................... 37 CHAPTER SIX: DISCUSSION ................................................................................. 41 6.1 Data Collection .................................................................................................... 41 6.2 Data Processing .................................................................................................... 42 6.3 Image Segmentation ............................................................................................. 43 6.4 System Accuracy .................................................................................................. 43 6.5 System Deficiencies ............................................................................................
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