SIZE OF CORTICAL BONE AND RELATIONSHIP TO BONE-MINERAL DENSITY ASSESSED BY QUANTITATIVE COMPUTED-TOMOGRAPHY IMAGE SEGMENTATION

RATIONALE AND OBJECTIVES. The accuracy of the measurement of the size of cortical bone on computed tomography (CT) images of human vertebrae was evaluated using an automated contour detection and segmentation p rocedure. METHODS. Forty human lumbar vertebrae were scanned using 8-m m slices and an automated detection for definition of trabecular and c ortical region of interest. The vertebrae were embedded in a polyester resin and 8-mm-thick midvertebral specimens were excised using a diam ond circular saw. Contact radiographs of these specimens were performe d and, after photograph magnification, the cortical area was measured using computerized planimetry. RESULTS. Cortical area measured on CT i mages was highly correlated with the area measured by planimetry on th e specimens (r = .91; P < .001) with, however, a systematic overestima tion. A significant relationship was found between density and width o f the cortex (r = .56; P < .001). CONCLUSIONS. Computed tomography is able to assess the size of cortical bone in human vertebrae, but a thr eshold detection algorithm, as used in the current study, is not adequ ate to obtain the precise anatomic dimensions.