Reducing CBCT radiation dose and maintaining image quality for reliable cephalometric measurements – proof of concept

Abstract

Introduction: CBCT is increasingly used as tool for orthodontic diagnosis, either as an adjunct or replacement to traditional imaging techniques. Methods to reduce the increased CBCT radiation doses by optimizing exposure settings are essential for the orthodontic patient population. Methods: A human cadaver was scanned in the Morita Accuitomo 170® CBCT machine under the manufacturer recommended settings (5mA, 90kV, 360⁰) and multiple combinations of decreased exposure settings: 1, 2.5, 5 mA - 60, 70, 80, 90 kV - 180⁰ and 360⁰ rotation arc. Radiation dose was recorded for each exposure setting. Ten examiners (3 faculty, 7 residents) identified anatomic landmarks on 24 reconstructed cephalometric images and 7 cephalometric values were recorded. Measurement errors were compared and matched by exposure settings. Results: No significant differences in measurement errors were observed between 360⁰ -180⁰ rotation, 5mA - 2.5mA, 90kV - 80kV images. The radiation dose was reduced by 50% when mA was lowered to 2.5mA instead of 5mA and by 45% when the rotation arc was 180° instead of 360°. The lowest settings (1mA or 60kV) had increased error and were considered non-diagnostic. Conclusions: Orthodontists can lower the CBCT exposure settings in order to greatly reduce radiation dose and still maintain sufficient image quality for cephalometric diagnosis.