| Popis: |
Cone-beam computed tomography (CBCT) has become increasingly popular in dentistry. It is usually associated with radiation doses that are lower than those seen with conventional computed tomography (CT) but greater than those seen with dental radiography. Because exposure to ionising radiation is associated with risks, the radiation protection principles of justification and optimisation should be applied. These are especially important in children and young people due to their greater risk of developing stochastic effects. Justification requires a balancing of the radiation risk with the potential benefits and the latter is dependent on diagnostic efficacy. There has been a proliferation of articles published on dental CBCT and there is a need to review this systematically so that diagnostic efficacy can be judged. In terms of optimisation, radiation dose reduction can be achieved in various ways, but the use of barrier materials to protect younger patients in CBCT has not been adequately tested. Reduction in exposure parameters in CBCT will lower doses but at the expense of a loss of image quality. While some efforts have been made to relate radiation exposure and image quality in CBCT, there is a need to develop low-dose CBCT protocols specifically for children and young people. The first aim of this thesis was to survey current uses of CBCT in children and young people in three United Kingdom dental hospitals. The second aim was to determine the efficacy of thyroid shielding in a child phantom testing several different designs, materials and thickness of thyroid shields. The third aim was to evaluate the evidence on diagnostic efficacy of dental CBCT for root fractures in permanent, non-endodontically treated, anterior teeth by conducting a systematic review. The fourth aim was to evaluate objective and subjective image quality in a laboratory study to determine a low-dose CBCT protocol which maintains adequate diagnostic image quality for a clinical indication in children. Finally, the aim was to evaluate this low-dose protocol in terms of image quality in real clinical situations. A high adherence to the European guidelines No 172 on radiation protection in dental CBCT was found amongst the surveyed hospitals. Thyroid shielding was found to be effective in dose reduction when performing a large field of view CBCT scan in a child phantom, but design influenced efficacy. The systematic review showed that research articles investigating CBCT diagnostic accuracy for vertical and horizontal root fractures had deficiencies in methodology, while only one study was identified addressing higher levels of diagnostic efficacy. A low-dose imaging protocol was identified in a laboratory study, which has been shown to be an effective tool in dose reduction providing an adequate diagnostic image quality and reducing radiation doses considerably for clinical indications in the anterior maxilla in children and young people. |
