Basic study of the measurement of bone mineral content of cortical and cancellous bone of the mandible by computed tomography.
OBJECTIVE
To develop an algorithm for automatic separation of cortical from cancellous bone in the mandible and for measuring mandibular bone mineral content (BMC).


METHODS
A dried mandible was scanned together with a reference phantom by spiral CT. A new algorithm was developed specifically for the mandible and cross-sectional images reconstructed in the buccolingual plane. The cortical bone was extracted with a threshold of 80% of the peak height in the line-scan profile and the cancellous bone extracted separately. The volume and BMC were estimated. Images of cortical and cancellous bone were displayed in a plane approximating the orientation used for dental radiography and BMC expressed as aluminium-equivalents (Al-eqs).


RESULTS
The ratio of cortical to cancellous bone by volume was 22:78, and the ratio of the BMC 60:40. Comparison of BMC from reconstructed CT with Al-eqs showed good correlation but was 1.5 times higher with CT.


CONCLUSIONS
It is possible to separate cancellous from cortical bone automatically from CT images and to measure the BMC.
Department of Dental Radiology, Kagoshima University Dental School, Kagoshima City, Kagoshima, Japan.
Y
Y
Iwashita
D015502:Absorptiometry, Photon; D000465:Algorithms; D019412:Anatomy, Cross-Sectional; D015519:Bone Density; D002119:Calcium Carbonate / Q000032:analysis; D003626:Data Display; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed
D002119:Calcium Carbonate