Computerized Analysis of Gray-Value Profiles in Spongy and Cortical Bone

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Abstract
Osteoporosis is characterized by a loss of bone mineral density and deterioration of structure. The authors present a structural parameter for the quantitative assessment of osteoporotic changes in vertebral bone. In 40 patients without or with known osteoporotic fractures, spongiosa and cortical bone mineral density was measured in lumbar vertebrae 1 to 3 by quantitative CT. Additional axial high-resolution CT slices were obtained for the structural analysis. In the spongiosa, the gray-value profile along a horizontal line in the CT slice was used, whereas in the cortical shell a profile was obtained from the cortical ridge. Both profiles were intersected with a horizontal line of variable position, and the maximum number of intersections was determined. The maximum number of intersections is significantly higher in cases with fractures (spongiosa 48.6, cortical shell 77.3) than in cases without fractures (spongiosa 42.1, cortical shell 62.4). It also correlates with bone mineral density and age. The presented method shows significantly different numeric results for patients with and without osteoporotic fractures. The analysis is easy to perform and provides additional information on the bone structure that may be used in combination with bone mineral density measurements.