Quantitative computed tomography of bone mineral density in the mandible -imaging the topographical distribution of bone mineral density by automatic segmentation of jaw structures

Purpose. Confirmation of a new technique for evaluating bone mineral densit y (BMD). Colored coded imaging of topographical distribution of bone minera l density in the spongy substance. Method. For 20 patients, dental CT examinations of the mandible were made i n axial slices. Spongy substance and cortical bone pixels were automaticall y segmented at foramina mentalia level by means of threshold fixation. The segments were separated in areas relevant to implantology. For each region, BMD was measured by means of quantitative computed tomography (QCT). Spong iose substance of 20 mandibles was segmented by using three treshold interv als to image topographical BMD distribution. Results. Cortical bone and spongy substance could be automatically segmente d for 20 mandibles. BMD could be measured in each region. The results were comparable with those of other techniques. Three threshold intervals were s egmented for 20 mandibles in the spongy substance to depict topographical B MD distribution. Conclusions. Areas of low BMD can be detected by imaging topographical BMD distribution. This way, subjective rating by the examiner is eliminated.