The application of three-dimensional quantitative computed tomography to the maxillofacial skeleton

Objectives: To develop a method for three-dimensional quantitative computed tomography (QCT) of the maxillofacial skeleton. Methods: The linearity of reference phantom consisting of five hydroxyapatite (HA) rods was tested under various conditions, including the size of field of view, the position of object, and reconstruction algorithm, on three different scanners. The calibrated HA concentration value and the absolute Ca content of the mandible removed from fresh cadaver was compared in order to evaluate the calibration error. Results: There was a high correlation between average CT number and HA concentration in the phantom rods. There was a 4-5% difference in results from the three scanners, High density areas, corresponding to more than 75% HA, were extracted from the original image. Data were reconstructed three-dimensionally and combined using a 32-bit computer system. A three-dimensional distribution of bone density superimposed on the maxillofacial skeleton was produced. Conclusion: Three-dimensional QCT of the maxillofacial skeleton has potential as a means of analysing bone density. Difference in performance of different CT scanners should be considered when comparing results.