Feasibility of bone assessment with leaky lamb waves in a bone phantom

The quantitative ultrasound (QUS) technique is now widely used for non-invasive assessment of osteoporosis. The use of leaky Lamb waves is very attractive since they propagate throughout the cortical thickness of long bones, which means that the entire thickness of the bone is interrogated. The feasibility of bone assessment with leaky Lamb waves is investigated in a bone phantom by using the axial transmission method used to characterize long human bones. A pair of transducers with a center frequency of 500 kHz is used to generate leaky Lamb waves in bone phantoms consisting of Lucite plates with thicknesses of 1, 3, and 5 mm. The thickness values represent typical values of the cortical thicknesses of skeletal sites, such as the radius, tibia, and femur. Both antisymmetric and symmetric leaky Lamb waves are excited along the plates in water. The results show that the peak frequencies and the amplitudes of excited Lame modes strongly depend on the frequency-thickness product. This study suggests that the use of leaky Lamb waves for ultrasonic bone assessment is feasible.