Influence of soft tissues on ultrasonic lamb waves in synthesised soft tissue-bone phantoms

6th World Congress of Biomechanics, WCB 2010 - In Conjunction with 14th International Conference on Biomedical Engineering, ICBME and 5th Asia Pacific Conference on Biomechanics, APBiomech, Singapore, 1-6 August 2010Majority of existing quantitative ultrasound (QUS) techniques in today's clinic examine the first-arriving-signal (FAS) to assess bone properties for the ease in identifying FAS in captured time domain signals. However, FAS can fail to access fine details of bone including those relevant to osteoporotic properties, as a result of its large wavelength. Awareness of this weakness has led to increasing preferences to use other wave modes subsequent to FAS in ultrasound signals by taking advantage of their shorter wavelengths. Of particular interests are transverse waves. Transverse wave modes have been demonstrated capable of offering precision-enhanced assessment of bone properties. Nevertheless soft tissues coupled with bone can exert remarkable influence on these wave modes propagating in bone, lowering assessment accuracy without appropriate rectification. Such a coupling effect is largely ignored in clinical QUS. Characteristics of various ultrasonic wave modes in synthesised soft tissue-bone phantoms (fabricated using bone- and soft tissue-mimic materials) were interrogated using a three-dimensional finite element simulation technique and an in vitro testing approach. Effect of thickness and elastic property of overlying soft tissues on ultrasonic waves was examined and calibrated quantitatively. Results have shown that appropriate compensation for the medium coupling effect on ultrasonic waves is of vital necessity when developing high-precision QUS techniques for clinical bone assessment.Department of Mechanical EngineeringRefereed conference pape