The number of osteoporosis patients is increasing every year in Japan. Bone mineral density (BMD), which is the helpful feature quantity in diagnosing osteoporosis, is generally measured in the central part of the vertebral body. It's possible to measure BMD at each location in X-ray CT images having a high spatial resolution. If bone mineral density of the vertebral body is not homogeneous, grasp of the lower BMD location inside the vertebral body may be helpful to clinical diagnosis. In this paper, using X-ray CT images of 80 subjects (40 male and 40 female subjects), BMDs of trabecular bones from the 12th thoracic vertebra to the 1th sacral vertebra (S1) were measured at each location. The present study showed that anterior and central locations of thoracolumbar and lumbar vertebra, and posterior, inferior, and central locations of S1 had lower BMD values. Therefore, at the thoracolumbar and lumbar vertebra, if the BMDs of anterior or central locations are selectively measured, prediction of fracture risk at vertebral bodies could be improved.
