Pulse-Echo Measurements of Bone Tissues. Techniques and Clinical Results at the Spine and Femur

The aim of this chapter is to review the available pulse-echo approaches for the quantitative evaluation of bone health status, with a specific application to the assessment of possible osteoporosis presence and to the fracture risk prediction. Along with a review of the main in-vivo imaging approaches for skeletal robustness evaluation and fracture risk assessment, further understanding into Radiofrequency Echographic Multi Spectrometry (REMS), an ultrasound-based method measuring clinically relevant bone districts (i.e. lumbar vertebrae and proximal femur), is provided, and the further potentialities of this technology are discussed. Currently, the bone mineral density (BMD) provided by dual X-ray absorptiometry (DXA) is considered an established indicator for osteoporosis status assessment and fracture risk prediction, however, in order to obtain more accurate results, an additional step beyond BMD would be necessary, which means including data on bone quality for an improved evaluation of the disease and its consequences. REMS is a technology which allows both osteoporosis diagnosis, through the BMD estimation, and the prediction of fracture risk, through the computation of the Fragility Score; both measures are obtained by the automatic processing of unfiltered ultrasound signals acquired in correspondence of anatomical reference sites.