BLANC - Blanc

Assessment of Bone Biomechanical Health using Nonlinear Acoustic Techniques – BONUS

Submission summary

1-Scientific background and objectives :The Laboratoire d'Imagerie Paramétrique (LIP), the Laboratoire UltraSons Signaux et Instrumentation (LUSSI) and the Laboratoire de BioMécanique (LBM) are collaborated to propose a NonLinear (NL) UltraSound (US) study coupled with biomechanical experiments for bone investigation. For the past fifteen years, these laboratories have brought significant findings in trabecular or cortical bone tissue characterization domain. Several linear US techniques have been developed and fully validated (osteoporosis diagnostic, microgravity bone changes). These devices provide two parametric images of BUA (attenuation) and UBV (velocity). They are partially correlated to Bone Mineral Content (BMC, estimated by Xrays techniques), without separating properly their part of elasticity and density contribution. It is now well-known that bone fragility and fracture risk is not only related to low bone mass but to bone micro and macro-damage characteristics. NL US approaches, extensively developed in NDT domain, have demonstrated that damaged materials exhibit high level of nonlinearity, and particularly non classical hysteretic behavior. Very few papers are related to NL bone tissue characterization. However these techniques have a high potential for biomechanical bone tissue assessment, from the measurement of NL US parameters (non-classical NL parameter related to hysteretic behavior) and (classical NL parameter related to the 2nd order term of the stress/strain relation). Direct comparison of these NL US measurements with biomechanical parameters during calibrated fatigue experiments will allow to correlate progressive induced-damaging in bone with NL parameters.First objective is to develop and define the best approach to quantify the NL parameters for in vitro bone samples. Second objective, thanks to appropriate biomechanical experiments, is to correlate the NL coefficients with mechanical characteristics of bone. In order to complete this US / biomechanical approach, we propose, from existing waves propagation numerical models, to develop a model of wave propagation in a complex biphasic heterogeneous medium such as bone including both classical and hysteretic nonlinearities.2-Description of the project, methodology :Preliminary NL US results have been obtained using different modalities (harmonic generation, resonance frequency shift, waves interaction) in bones samples. Based on these first observations of non-classical NL behavior, LUSSI and LIP propose to develop LF/HF (Low Frequency/High Frequency) waves interaction techniques dedicated to bone NL parameters assessment. A LF excitation, which induces pressure variation in the medium, interacts with a HF wave. The resulting phase wave celerity variation is measured either from a HF wave phase demodulation technique, or from sidelobes levels measurements (Nonlinear Waves Modulation Spectroscopy, NWMS technique). Both phase modulation and NWMS methods allow the calculation of and NL parameters. LBM propose three different biomechanical tests to evaluate quasi-static parameters (such as Young's modulus, hysteresis and post-yield damage), fatigue damage and fracture toughness for calibrated bone samples, in order to extract mechanical parameters in parallel with NL US measurements. Additional quantification measurements such as microscopy or high resolution X-rays tomography are planned in order to provide microcracks density and BMC. To complete experimental measurements, a numerical approach of wave propagation in NL media will be developed. From these models including classical and hysteretic nonlinearity, the influence of micro-damage characteristics (crack density, size and orientation) will be studied.3-Expected results :We expect to demonstrate that NL US techniques are an appropriate and sensitive tool to assess different levels of damage in bone. Parallel measurements using linear US, microscopy and X-rays will also confirm that NL U...

Project coordination

Pascal LAUGIER (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 390,000 euros
Beginning and duration of the scientific project: - 36 Months

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