In vitro assessment of a novel dual-energy cone beam computed tomography device

Abstract

<h3>Objective</h3> CT attenuation depends on atomic number and physical density of the object. Dual energy systems use two energy spectra and attenuation data from two different exposure conditions to estimate the effect of photoelectric absorption and Compton scatter in generating CT numbers. Based on this principle, a dual energy cone beam CT device (DE-CBCT, RCT-270, Ray Co. Ltd., Korea) was developed to assess jaw bone density and overcome limitations of gray level inhomogeneity in CBCT. <h3>Study Design</h3> We used a human skull phantom and varying concentrations of dipotassium phosphate (K₂HPO₄) to simulate trabecular and cortical bone. 0.2 ml polypropylene tubes with K₂HPO₄ (600mg/ml and 800mg/ml) were placed in empty sockets of the phantom at 3 discrete mandibular sites and scans were acquired. Next, to simulate temporal changes, we used varying concentrations of K₂HPO₄ (400 mg/ml-1200 mg/ml) in the extraction socket of a mandibular second premolar. All scans were made using the Rayscan DE-CBCT unit and repeated thrice. After each scan, the QRM-DE-CBCT phantom was also scanned with the same exposure factors for calibration. Scan calibration and bone density assessments were performed using the vendor's software. <h3>Results</h3> Calculated density of the same K₂HPO₄ placed at different locations (891± 144, 768 ± 29, 541 ± 126) was not statistically different. A similar result was obtained with K₂HPO₄ of higher density (1299 ± 58, 1203 ± 74, 998 ± 125). While simulating changing bone density, increasing concentrations of K₂HPO₄ yielded higher calculated densities, with a linear relationship between K₂HPO₄ concentrations and DE-CBCT calculated density (r² = 0.88). <h3>Conclusion</h3> This study provides an initial assessment of DE-CBCT as a method to better estimate object density which can impact monitoring osseous healing, evaluation of potential implant sites, and augmentation threshold for image segmentation. In ongoing studies, we are characterizing image quality parameters and further assessing the impact of anatomic location. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study