UltraScan™ 650 relies on CyberLogic’s patented NTD technology. The NTD is based on measuring transit times of ultrasound signals propagating through the forearm, which allows direct measurement of the amount of bone. The NTD has been validated with computer simulations, in vitro studies, and clinical data, and represents a completely distinct approach to processing of ultrasound data. Conventional bone sonometers evaluate the speed of sound (SOS) and broadband ultrasound attenuation (BUA); these parameters are only weakly correlated with bone mineral density (BMD). In contrast, the high degree of correlation (r = 0.93) of the UltraScan 650 output with BMD is due to the use of the NTD technology. A number of papers and patents related to the NTD technology can be found in the References. Specifically, a summary of the key clinical data can be found in: (A comprehensive paper summarizing the performance of the UltraScan 650 in a clinical trial can be found in our publication by Stein et al. in Ultrasound in Medicine & Biology.) The simulation and in vitro data can be found, respectfully, at: “Ultrasound Simulation in Bone” and “Ultrasonic Assessment of the Radius in vitro”.