PROJECT SUMMARY/ABSTRACT This research will advance our understanding of osteoporosis. Osteoporosis is a disease in which bones become fragile and more likely to break. If not prevented or if left untreated, osteoporosis can progress painlessly until a bone fractures. It is a major public health threat for an estimated 44 million Americans. In particular, osteoporotic fractures of the proximal femur are the most common and often result in high rates of morbidity and mortality. An average of 24 percent of hip fracture patients aged 50 and over die in the year following their fracture. This represents a serious socioeconomic health problem that is expected to worsen as the size of the elderly population increases. Numerous publications have demonstrated that bone mineral density alone cannot entirely differentiate between osteoporotic and healthy subjects and that the structural make-up of trabecular bone provides additional information to assess the risk of fracture. Imaging of the proximal femur has not yet been performed in vivo with high resolution. In MRI, this is mainly due to signal to noise issues and a lack of dedicated imaging coils. With the proposed technique, in vivo 3D-images of the entire proximal femur with sufficient high spatial resolution to visualize the trabecular microstructure will be acquired. Structural parameters of the trabecular bone will be derived from these images. These parameters have been shown to be well suited for predicting hip fracture. Through early detection, the progression and response to therapy can be monitored more sensitively, and the risk of hip fracture effectively ascertained. The proposed study will provide the first assessment of trabecular bone microstructure in the proximal femur. The results of the proposed research may also influence treatment strategies.