Ultrasound and bone: from material evaluation to clinical applications

The ultrasonic bone‐screening market is rapidly advancing, driven by an aging population and the increasing prevalence of osteoporosis. In Japan alone, more than 6000 ultrasonic bone densitometry systems are currently in operation. Leveraging the inherent advantages of quantitative ultrasound (QUS) methods—its safety, ease of use, absence of ionizing radiation, portability, and low cost—various techniques have been developed for in vivo bone screening. Yet, despite this widespread clinical use, the complex material properties and structural heterogeneity of bone tissue hinder precise ultrasonic evaluation of bone. This paper reviews applications of ultrasonic methods for assessing reduced bone mass (skeletal status) and deterioration in bone properties. Attention is given to a Japanese in vivo ultrasonic evaluation method that utilizes the characteristic propagation of two longitudinal wave propagation in cancellous bone. Finally, the paper briefly mentions the piezoelectric properties of bone, which may contribute to ultrasonic fracture healing.