Assessment of image quality in maxillofacial cone-beam computed tomography imaging

The aim was to evaluate image quality produced by a cone-beam CT (CBCT) scanner under various imaging modes. 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). Overall, 67 CBCT scans were obtained by modifying the entire range of kilovolt (kV) and milliampere (mA) settings, using the CS 9300 CBCT scanner (Carestream Health, Inc., Rochester, NY). A total of 24 individual raters rated the images to evaluate line pairs visible. Upon completion of the evaluation process, 4 kV and mA combinations (85 kV × 12 mA, 90 kV × 4.0 mA, 60 kV × 6.3 mA, and 65 kV × 2.5 mA) were selected for further investigation. In all 10 dry skulls were scanned to measure the defect size of simulated root resorption in 4 different modes. Intraclass correlation (ICC) analysis was used to compare the agreement between the defect sizes measured from the scans compared to the actual physical volume. Low kV settings (60 kV) used in combination with moderate-to-high mA settings (4.0–15 mA) produced the best-perceived image quality, resulting in up to 56% reduction in the total radiation amount (mGy cm2) generated. High kV settings (85–90 kV) used in combination with high mA settings (8.0–15 mA) produced the lowest image quality. All 4 selected imaging modalities presented a high level of accuracy in detection of root resorption volume compared to actual physical volume (ICCs between 0.93 and 0.98). 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.