QUANTIFICATION OF CANCELLOUS BONE-STRUCTURE USING SYMBOLIC DYNAMICS AND MEASURES OF COMPLEXITY

In this study we generalize symbolic dynamics to analyze two-dimension al objects and utilize measures of complexity to quantify the structur e of symbol-encoded images. This technique is applied to study quantit atively the structure of human cancellous bone by analyzing computed t omography images. First, the preprocessed images are transformed into symbols, applying a mixture of static and dynamic encoding. Next, the spatial distribution of cancellous bone is evaluated using measures of complexity. New parameters are introduced to quantify the cancellous bone architecture as a whole. The results exhibit that the complexity of the structure declines more rapidly than density during the loss of bone in osteoporosis, strongly suggesting an exponential relationship between bone mass and architecture. It is found that normal bone has complex ordered structure, while the structure during the initial stag e of bone loss is characterized by lower complexity and a significantl y higher level of disorder, which is maximal there. A strong grade of the bone loss leads again to ordered structure, however its complexity is minimal. In addition, this method is significantly sensitive to ch anges in structure of natural composite materials. [S1063-651X(98)0891 1-9].