Dose optimization of cone beam computed tomography: measurement of parotid absorbed dose and image quality assessment

Cone-beam computed tomography (CBCT) is a three-dimensional (3D) imaging technology used in dentistry. This study aimed to reduce radiation exposure by adjusting CBCT parameters while ensuring that image quality remained suitable for diagnostic purposes. This controlled experimental study was conducted between February and July 2022 at the private Alpha Center for Dental Radiology in Erbil, Kurdistan Region of Iraq. The PaX-i3D SMART CBCT system, thermoluminescent dosimeters, and a specialized head and neck dosimetry phantom were used to measure the parotid gland. Tube voltage varied from 75 to 99 kVp, and tube current varied from 4 to 10 mA. For the image quality assessment, a dry human mandible immersed in water was exposed to CBCT X-rays with the same dosimetry exposure settings. Subjective image assessment was performed randomly by four dental and maxillofacial radiologists. The highest absorbed dose recorded was 654.47 µGy at 94 kVp and 8.1 mA, while the lowest was 198.5 µGy at 80 kVp and 4 mA. Out of the 32 scans, 19 images were considered acceptable based on clinical evaluation, and their absorbed dose ranges were lower than the default exposure setting of the device. Statistically, there was a strong positive correlation between absorbed dose, kVp, and mA, and a non-significant correlation between image quality and kVp in five (4, 4.5, 6, 8, and 10) of the seven mA groups. Optimizing CBCT settings to 80 kVp and 4 mA significantly reduced the radiation dose to the parotid gland while maintaining diagnostic image quality. This finding supports the adoption of lower mA and kVp settings in clinical practice to enhance patient safety without compromising diagnostic effectiveness.