Estimation of Cortical Bone Microstructure From Ultrasound Backscatter

Area of Science:

• Biomedical Engineering
• Materials Science
• Orthopedics

Background:

• Cortical bone microstructural properties are crucial for bone strength and fracture risk.
• Current methods for assessing bone porosity are often invasive or limited in scope.
• Multichannel ultrasound offers a potential noninvasive approach to evaluate bone microstructure.

Purpose of the Study:

• To develop and validate a numerical model for estimating ultrasound backscatter from cortical bone pores.
• To investigate the use of spectral backscatter analysis for quantitative assessment of cortical bone microstructural properties.
• To establish a noninvasive ultrasound method for characterizing pore size distribution in cortical bone.

Main Methods:

• Finite-difference time-domain (FDTD) method for numerical simulation of ultrasound backscatter.
• Ex vivo ultrasound backscatter measurements on human tibia samples using a linear array transducer.
• Spectral analysis of ultrasound data to derive backscatter and attenuation coefficients.
• Comparison with microstructural parameters (pore size, density, thickness) obtained from scanning acoustic microscopy.

Main Results:

• A model predicting backscatter coefficient based on pore diameter distribution was derived.
• Ultrasound backscatter parameters accurately predicted cortical bone pore structure and material properties (adjusted R²: 0.28–0.59).
• Combined assessment of cortical thickness and backscatter parameters showed high prediction accuracy, comparable or superior to areal bone mineral density (aBMD).

Conclusions:

• Ultrasound spectral backscatter analysis is a promising noninvasive technique for characterizing cortical bone porosity and pore size distribution.
• This method has the potential to improve fracture risk assessment, particularly for osteoporosis.
• A mobile, nonionizing ultrasound system for assessing bone thickness, velocity, and pore size could significantly impact osteoporotic fracture prevention.