Topography of acoustical properties of long bones: from biomechanical studies to bone health assessment

The article presents a retrospective view on the assessment of long bones condition using topographical patterns of the acoustic properties. The application of ultrasonic point-contact transducers with exponential waveguides on a short acoustic base for detailed measurements in human long bones by the surface transmission was initiated during the 1980s in Latvia. The guided wave velocity was mapped on the surface of the long bones and the topographical patterns reflected the biomechanical peculiarities. Axial velocity profiles obtained in vivo by measurements along the medial surface of tibia varied due to aging, hypokinesia, and physical training. The method has been advanced at Artann Laboratories (West Trenton, NJ) by the introduction of multifrequency data acquisition and axial scanning. The model studies carried out on synthetic phantoms and in bone specimens confirmed the potential to evaluate separately changes of the bone material properties and of the cortical thickness by multifrequency acoustic measurements at the 0.1 to 1 MHz band. The bone ultrasonic scanner (BUSS) is an axial mode ultrasonometer developed to depict the acoustic profile of bone that will detect the onset of bone atrophy as a spatial process. Clinical trials demonstrated a high sensitivity of BUSS to osteoporosis and the capability to assess early stage of osteopenia.