Assessment of Image Quality in Maxillofacial CBCT Imaging

INTRODUCTION: This study evaluated image quality produced by a cone-beam CT (CBCT) scanner under various imaging modes.;METHODS: A modulation transfer function (07-538, Nuclear Associates, Carle Place, NY) was placed in an anthropomorphic head phantom (RS-250, Radiology Support Devices, Long Beach, CA). Sixty-seven CBCT scans were obtained by modifying the entire range of kilovolt (kV) and milliampere (mA) settings using the Kodak 9300 CBCT scanner (Carestream, Rochester, NY). Twenty-four individual raters (12 orthodontic residents and 12 faculty) rated the images to evaluate line pairs visible. Upon completion of the evaluation process, four kV and mA combinations (85 kV x 12 mA, 90 kV x 4.0 mA, 60 kV x 6.3 mA, and 65 kV x 2.5 mA) were selected for further investigation. Ten dry skulls were used to test the diagnostic accuracy of the selected imaging modalities. The skulls were scanned to measure the defect size of simulated root resorption in four different modes. Intra-class correlation (ICC) analysis was used to compare the accuracy of the root defect measured from the scans compared to the actual physical volume.;RESULTS: Low kV settings (60kV) used in combination with moderate-to-high mA settings (4.0-15mA) produced the best image quality, resulting in up to 56% reduction in the total radiation amount (mGy·cm 2) generated. High kV settings (85-90kV) used in combination with high mA settings (8.0-15mA) produced the lowest image quality. All four selected imaging modalities presented a high level of accuracy in detection of root resorption volume compared to actual physical volume (ICCs between 0.93-0.98), confirming that subjectively high rated images can be used interchangeably with the images generated by standard settings of the scanner.;CONCLUSIONS: Radiation exposure from CBCT scans can be reduced while maintaining adequate image quality and diagnostic accuracy by performing scans using low kV and moderate-to-high mA settings.