Ultrasonic Bone Assessment Using a Backscatter Difference Technique

Abstract

Osteoporosis is a bone disease which disrupts the balance of cell destruction and new cell construction within bone. This decay leads to increased porosity within the bone tissue and heightened fracture risk. The focus of our research is the diagnosis of the bone disease osteoporosis with ultrasound. An ultrasonic wave centered around 3.5 MHz is sent into 55 cubic bone specimens taken from the porous interior of 14 donated femurs. The sound waves echo off of the bone, one device both sends and listens to the signal. The signal which is analyzed, the echo, is referred to as backscatter. The characteristics of the decay of the signal reveal the mechanical properties, mainly density, of the bone. The difference spectrum was averaged first over entire cubical specimen then again over the whole set of bone samples while varying the choices of where the signal was analyzed. This meta-analysis showed how the difference spectrum responds on average to analysis parameters. The difference spectrum changes when the time segments placed on the backscatter sound wave, the gates, change. Delaying the gates too late causes signal to noise ratio problems, and widening the gates gives finer resolution and shifts metrics such as the mean and slope of the difference spectrum. Conclusion: The difference spectrum does change on average when gate parameters vary, which informs the lab which choices might not be worth running through the analysis.