Quantitative Ultrasound Scanner for Bone Loss Detection - Evaluated at the Distal Radius

Quantitative ultrasound (QUS) has emerged as an engineering technology for monitoring bone quantity and quality. It has been shown to correlate well to both fracture risk and mechanical properties. Bone loss in space in zero-gravity is known to be rapid (e.g., approximately 2% per month in average) and leads to increased fracture risk and longer earth-bound recovery periods. The current research aims to enhance current QUS technology to allow for diagnostic readings at multiple anatomical sites, possibly allowing whole body estimates, while alternative (to water-bath) acoustic coupling methods are investigated. The anatomic site currently of interest here is the Distal Radius, a high fracture-risk site in bone loss diseases such as Osteoporosis. Five fixed cadaver distal forearms were scanned using both original QUS technology and the first generation of new acoustic coupling (G1). The QUS parameters were compared to internal trabecular bone parameters obtained with a vivaCT (SCANCO Medical), and Trabecular-Number correlated to QUS Attenuation of the original and G1 methods with R 2 of 0.61 and 0.59, respectively. However, the Broadband Ultrasound Attenuation (BUA) proved to be an unreliable measure with highly nonlinear slopes in both the original and G1 system. Complex bone geometries can play a large roll in ultrasound propagation and measurement variability at the distal radius. Currently, 23 bones are being evaluated for the correlation of QUS parameters to vivaCT measured properties through computer simulations and experimental methods. In simulation, the BUA regions are highly linear (average fit R 2 = 0.997), however it remains poorly correlated to structural parameters (R 2 =0.26 compared to BV/TV). The speed of sound in simulation has very high correlation to structural parameters (R 2 =0.80 compared to BV\TV). With expansion of coupling methods and understanding of QUS performance at the distal radius, it may be possible to provide better bone quality diagnostics non-invasively.