Electronic Thesis and Dissertation Repository

Degree

Master of Clinical Science

Program

Orthodontics

Supervisor

Dr. Richard Bohay

2nd Supervisor

Dr. Jerry Battista

Joint Supervisor

Abstract

Introduction: Cone Beam CT imaging is prevalent in dentistry yet much is unknown with regard to how radiation dose to the patient varies between different CBCT scanners and imaging protocols. Scanner and protocol specific effective dose calculations will aid in optimizing individualized protocols for clinical applications.

Purpose: To determine the effective dose for a range of imaging protocols using the Sirona GALILEOS Comfort CBCT scanner.

Materials and Methods: Calibrated InLight nanoDot OSL dosimeters (Landauer, Glenwood, Ill) were placed at 26 select sites in the head and neck of a modified, human tissue-equivalent RANDO phantom. Effective dose was calculated using the measured local absorbed doses, accounting for the fractional volume and type of tissue exposed, and applying the 2007 ICRP1 tissue weighting factors. In total, 12 different scanning protocols were investigated varying the field of view, mAs, contrast and resolution parameters.

Results: The effective doses for a repeated protocol (full maxillomandibular scan, maximum (42) mAs, high contrast and resolution) were 140, 141 and 142 µSv. This compares to 100 µSv for a maxillary scan and 107 µSv for a mandibular scan with identical mAs, contrast and resolution settings. Effective dose remained between 140-142 µSv for maxillomandibular scans at 42 mAs with varying contrast and resolution settings.

Conclusions: Changes to mAs and beam collimation have a significant influence on effective dose. Effective dose varies linearly with mAs. Collimating to obtain a narrower maxillary or mandibular scan decreases effective dose by approximately 28% and 23% respectively as compared to a full maxillomandibular scan. Changes to contrast and resolution settings have little influence on effective dose. This study provides data for setting individualized patient exposure protocols in order to minimize patient dose from ionizing radiation used for diagnostic or treatment planning tasks in dentistry.



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