Desenvolvimento de uma metodologia para controle da qualidade de imagens em equipamentos de tomografia computadorizada de feixe cônico odontológico

Abstract

Cone-beam CT (CBCT) systems have been used for diagnostic radiology of head and neck, and dentomaxillofacial surgery applications. Different dental CBCT devices are being developed and released, with a wide variability of exposure parameters and fields of view. Although they have sufficient diagnostic quality, some of the drawbacks of the dental CBCT devices are their inability of discriminating soft tissue because of its low contrast resolution, and the inaccuracy to give information about soft tissue quality. Standard quality control procedures and phantoms for conventional CT are not fully applicable for CBCT devices. Furthermore, there is a lack of quantitative methods for image quality analysis suitable for dental CBCT. The aim of this study was to develop and implement a feasible methodology for image quality analysis for different dental CBCT devices. The methodology was based on conventional CT quality control procedures, and adapted to overcome the limitations of dental CBCT. A prototype phantom was specially designed to allow the acquisition of image quality parameters relevant for dental imaging. CBCT devices were divided into categories for the analysis, related to their Field of View (FOV): Small Field of View (SFOV) and Full Field of View (FFOV). The following image quality parameters were evaluated: filed uniformity, image noise, contrast-to-noise ratio, CT number accuracy, artifacts, spatial resolution and geometric distortion. Applicability of the methodology was assessed using one SFOV and four different FFOV CBCT devices. Large differences in image quality performance were seen between the CBCT devices. Furthermore, a CT number calibration method was developed and tested, which enables CBCT devices for bone density evaluation. Concluding, a new methodology was implemented and proved to be viable for use on different CBCT devices with a variability of fields of view. Based on the evaluations, the prototype phantom will be optimized and validated for quality assurance on CBCT devices.