EuroSafe Imaging 2020
Performed at one institution, Not applicable, Dosimetric comparison, Artifacts, Technical aspects, Radiation safety, Physics, Cone beam CT, Radioprotection / Radiation dose, Radiation physics, Head and neck, Physics in Medical Imaging
Cone-beam computed tomography (CBCT) is a widely used imaging modality in dentistry, with applications found in several subspecialties such as implant planning and endodontics. The ever-increasing use of CBCT has raised concerns regarding its impact on the collective dose; whereas it has been shown that a highly optimized CBCT scan is able to reach patient doses similar to panoramic radiography, high-dose protocols with exposure levels similar to (or higher than) multi-detector CT have been reported in literature. 
A commonly used optimization technique in CT is tube current modulation (TCM), which is a type of automatic exposure control (AEC) in which the tube current is adapted throughout the scan to ensure appropriate exposure of large and/or dense regions and to avoid exposure of regions with low tissue quantity and/or density. TCM can be based on a scout (topogram) image acquired prior to scan, on real-time detector feedback during scan acquisition, or both. TCM in CT has been shown to reduce radiation dose considerably, including for scans of the head. 
Out of approximately 50 companies that (have) manufacture(d) dental CBCT scanners, and out of nearly 300 CBCT models that have been commercialized since the late 1990s, only very few have incorporated a form of angular tube current modulation.  Nonetheless, the asymmetrical distribution of hard and soft tissues in the head, in combination with the off-center posiion of the rotation isocenter in dental CBCT scans, suggest that the tube current can be adapted throughout the scan to compensate for differences in attenuation (Fig. 1). Evidence is lacking regarding the performance of angular TCM vs. fixed-current scanning in dental CBCT, taking into consideration the variety of field of view (FOV) sizes and positions used in clinical practice.
The aim of this study was to derive TCM curves for dental CBCT that compensate for differences in attenuation between projection angles, and to perform an initial evaluation of radiation dose and image quality of TCM-based vs. fixed-current CBCT scans.