Quality assessment of ultra low dose-low dose orthopantomograms reconstructed from CBCT for orthodontic purposes

Abstract

Introduction: This study aimed to analyze the image quality of standard dose orthopantomograms (sd-PAN), extracted PAN from standard dose cone-beam computed tomography (CBCT [extr-PAN]), and from reduced-dose ultra low dose-low dose CBCT (rd-PAN). Methods: Image pairs, sd-CBCT and sd-PAN, of patients were selected if taken within 6 months of each other. From the sd-CBCT, an extr-PAN was extracted, and a simulated rd-PAN (sim rd-PAN) was constructed using a filtering technique. Three experienced orthodontists assessed image quality by means of 9 yes-and-no statements. For subjective statements (1-5), observers’ opinions of technical acceptability and visibility of anatomic structures, observers indicated their disagreement or agreement. For objective statements (6-9), regarding comparability to a gold standard, observers indicated the presence of dental structures. Positive response rates were calculated for the subjective statements. Agreement rates with the gold standard were calculated for the objective statements. Thresholds for acceptable image quality were if ≥2 observers agreeing with the subjective statements or agreeing with the gold standard (objective statements) for 90% for sd-PANs and 85% for both extr-PANs and sim rd-PANs. Results: In total, images of 43 patients were included. For the subjective statements, only the sd-PAN met the threshold for technical adequacy (95.3%) and suitability for orthodontic treatment planning (95.3%). For objective statements 6, 7, and 9, extr-PAN and sim rd-PAN images met the threshold for acceptable quality, whereas the sd-PAN met the threshold for statements 6 and 9. Differences in agreement with the gold standard among images were small (85.7%-87.8%). Conclusions: Sd-PAN images demonstrated superior image quality. Although extr-PAN and sim rd-PAN showed reduced diagnostic image quality for orthodontic diagnosis, differences among the 3 types of PAN regarding the gold standard were small.