Investigation of radiation level and assessment of dimensional accuracy of acquired CBCT images

Abstract

The aim of this study is to investigate whether the radiation dose level, during 3D cone beam computed tomography scanning of the patient, influences the dimensional accuracy of the reconstructed surface 3D models, and if it does, to analyse the accuracy improvement in relations to radiation dose levels. In this study is proposed a workflow where two datasets of images acquired with different radiation dose levels of the lower jaw were used for analysis, with the focus on region where the tooth was extracted on the patient’s mandible. Statistical evaluators used for analysis are Jaccard index, Dice coefficient and Tanimotto coefficient, while accuracy and precision were also used as a statistical measure. The results of evaluation of six sample images for two datasets by Jaccard index are ranging from 0.684 to 0.873 and 0.579 to 0.849, respectively, by Dice are 0.812 to 0.932, and 0.733 to 0.918, while by Tanimoto are ranging from 0.763 to 0.895, and 0.626 to 0.867, respectively. Regarding the accuracy and precision, the average difference for those six images is a little over 1% and 2%, respectively. Reconstructed tooth cavities were also obtained where volume analysis showed insignificant difference between two reconstructed surface 3D models of cavities. This was also confirmed with performed dimensional measurements obtained for the two tooth cavities, as well as bone density evaluation inside those cavities. Computer-aided inspection was also performed which shows similar results of two datasets. It can be concluded, on bases of the obtained results, that the reduced level of radiation dose during image acquisition doesn’t have significant impact on dimensional accuracy compared to the higher dosage.