Digital Diagnostics (Sep 2023)
Bone mineral density radiopaque templates for cone beam computed tomography and multidetector computed tomography
Abstract
BACKGROUND: Cone beam computed tomography is widely applied for diagnostics and planning various manipulations in the maxillofacial region, for example, dental implantation. Its advantages include high spatial resolution, low radiation exposure, and cost-effectiveness. However, it has a significant drawback: the inability to determine the density of the jaw bone in Hounsfield Units (HU). AIMS: This study aimed to develop radiopaque templates with sets of X-ray density based on potassium hydrophosphate and beta-tricalcium phosphate, to study templates on various cone beam computed tomography and multidetector computed tomography devices, and to determine a cross-calibration algorithm for assessing the bone mineral density of the jaw in HU. MATERIALS AND METHODS: The bone mineral density template comprised microtubes (0.25 ml) with potassium hydrophosphate concentrations of 49.96, 99.98, 174.99, 349.99, and 549.98 mg/ml, and a suspension of beta-tricalcium phosphate with an equivalent concentration of potassium hydrophosphate 1,506 mg/ml, designed to simulate the types of bone density according to C. Mish. The study was carried out on two multidetector computed tomography and four cone beam computed tomography machines. Cross-calibration was referred on the “standard” multidetector computed tomography 1 mode 120 kV, 200 mA. RESULTS: There was a significant scatter of the X-ray values (HU for multidetector computed tomography and GV for cone beam computed tomography) vs. bone mineral density, with varying slopes, bias, and curve shapes. After cross-calibration, good comparability corresponding to the multidetector computed tomography 1 mode was shown. The median of the differences before cross-calibration was 160 relative units (HU, GV), after decreased by 10 times and amounted to 16 rel. units (p=0.000). The mean difference for cone beam computed tomography was significantly higher (30 rel. units) than for multidetector computed tomography (8 rel. units) (p=0.024, Mann–Whitney U test). CONCLUSION: The developed radiopaque template enables the standardization of densitometric indicators for cone beam computed tomography and various multidetector computed tomography modes. On average, the spread after cross-calibration is reduced by 10 times, which makes it possible to classify bone tissue in HU according to C. Mish.
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