ASPECTS OF DENTAL AND MAXILLOFACIAL CONE BEAM COMPUTED TOMOGRAPHY (CBCT)

Abstract

Cone-beam computed tomography (CBCT) has emerged as a potentially low dose method for imaging of various body regions including the dental and maxillofacial region. The radiation doses of CBCT are greater than those seen with dental radiography but lower than those seen with conventional CT. When dealing with medical use of ionising radiations, the radiation protection principles of justification and optimisation should be addressed. The use of CBCT within primary dental care in the UK has not been investigated. Existing information regarding its use is based on secondary health care surveys. A questionnaire survey was used to investigate the uses of CBCT in primary dental care with respect to aspects of justification, optimisation, clinical uses, training and reporting. There have been numerous studies on the diagnostic accuracy efficacy using CBCT for root fractures, most of which were ex vivo. Anthropomorphic phantom designs with appropriate amounts of hard and soft tissue equivalents have often not been used, which might increase risks of bias and concerns about applicability. Therefore, there is a need to review this systematically to consider these concerns, along with a laboratory study to examine the impact of different anthropomorphic phantom designs upon diagnostic accuracy efficacy for horizontal root fracture (HRF). The principle of optimisation embodies the need to obtain a diagnostically acceptable image with minimum radiation exposure. HRF occur mostly in children and young adults, for whom optimisation is particularly important. Objective and subjective image quality in a laboratory study is important to determine a low-dose CBCT protocol for this sensitive age group. Ex vivo studies are static and the image quality will not reproduce clinical situation when there are artefacts from patient movement, therefore there is a need to develop a simple method to detect movement in CBCT that is easily applied in vivo. The survey provides new information about the use of CBCT in UK dental practices with no evidence to suggest excessive use of CBCT. Small or medium fields of view (FOVs) are the most frequent examination, carried out in adult patients for implant dentistry purposes. While there were some concerns regarding knowledge of exposure factors used for CBCT, there is no suggestion of frequent use in children and young people. The systematic review showed that a substantial proportion of ex vivo studies of diagnostic accuracy efficacy using CBCT for root fractures have risks of bias and concerns about the applicability of ex vivo studies related to the anthropomorphic phantom design. The laboratory study, which was the first study to consider anthropomorphic phantom design and its impact on the diagnostic accuracy efficacy of observers for the diagnosis of HRF, found that it had no significant impact. An ex vivo study on diagnostic accuracy efficacy for HRF demonstrated that a reduction in radiation dose compared with the manufacturer’s guidance was possible without experiencing a significant loss of diagnostic accuracy efficacy. An initial exploratory trial for develop a method for recording patient movement was performed, but further improvements are needed before embarking on a clinical trial.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Keith Horner (Supervisor) & Chrysoula Theodorakou (Supervisor)