Ultrasonic Assessment of Cancellous Bone Based on the Two-Wave Phenomenon

The investigation of cancellous bone using ultrasound measurements is not an easy task due to the solid complex trabecular structure filled with fluid-like bone marrow. It is expected that the ultrasound propagated in cancellous bone contains valuable information about the complex structure. In this chapter, the methods to derive useful information by the two-wave phenomenon-based ultrasonic assessment of cancellous bone is introduced. First, the measurements and mathematical descriptions of the two-wave phenomenon are presented in Sect. 6.1. Here, a conventional mathematical method to understand the phenomenon and fundamental results of the experimental measurements are introduced. Next, in Sect. 6.2, the computational simulation methods using models representing real bone structures, the numerical or statistical separation techniques of the two waves, and machine learning techniques for deriving material information are discussed. Finally, in Sect. 6.3, the results and the current limitations of the clinical assessment with a device using the two-wave phenomenon are introduced.