Measurement of bone mineral density is the principal diagnostic method used in clinical practice and in research studies, both to identify patients who have the disease and to follow their response to therapeutic agents. The technique used most widely is dual-energy X-ray absorptiometry (DXA), which has advantages of low cost and radiation exposure, and high precision and accuracy of 1-2% and 4-8%, respectively [1, 2]. Based on the association between the low BMD and increased risk of fracture [3], BMD-based treatment guidelines have been developed [4]. There is, however, a considerable overlap between BMD of patients who sustain fragility fractures and those who do not [5-9]. The problem arises because the fragility is determined not only by the quantity of the bone (measured as bone density), but also by its "quality" which is believed to be related to the preservation of the normal trabecular pattern [10]. Bone quality is not specifically assessed using current diagnostic methods. Information about bone quality, however, would be of substantial clinical and scientific value, as it would complement the BMD measurement when selecting patients for therapy and when studying bone loss or assessing effects of therapeutic agents.