Three-dimensional Simulation of Quantitative Ultrasound in Cancellous Bone using the Echographic Response of a Metallic Pin

TL;DR

This study develops and validates a 3D simulation model for ultrasonic wave propagation in cancellous bone with a metallic pin, assessing how bone density and pin positioning affect ultrasound measurements for bone health estimation.

Contribution

The paper introduces a validated 3D simulation approach coupling finite difference time domain with micro-CT data for ultrasonic analysis in bone with metallic pins, highlighting the impact of pin orientation.

Findings

High correlation between simulated and experimental SOS (0.90)

SOS correlates strongly with bone volume fraction (R=0.82)

Pin orientation accuracy is crucial for reliable ultrasound measurements

Abstract

Degenerative discopathy is a common pathology which may require spine surgery. A metallic cylindrical pin is inserted into the vertebral body to maintain soft tissues and may be used as a reflector of ultrasonic wave to estimate bone density. The first aim of this paper is to validate a 3D model to simulate the ultrasonic propagation in a trabecular bone sample in which a metallic pin has been inserted. We also aim at determining the effect of changes of bone volume fraction (BV/TV) and of positioning errors on the quantitative ultrasound (QUS) parameters in this specific configuration. The approach consists in coupling finite difference time domain simulation with X-ray microcomputed tomography. The correlation coefficient between experimental and simulated speed of sound (SOS) (respectively broadband ultrasonic attenuation (BUA)) was equal to 0.90 (respectively 0.55). The results show a significant correlation of SOS with BV/TV (R = 0.82), while BUA values exhibit a non-linear behavior versus BV/TV. The orientation of the pin should be controlled with an accuracy of around 1{\textdegree} in order to obtain accurate results. The results indicate that using the ultrasonic wave reflected by a pin has a potential to estimate the bone density. SOS is more reliable than BUA due its lower sensitivity to the tilt angle.