Introduction: Osteoporosis is the systematic loss of bone mass and structural integrity. It creates a public health burden affecting over 200 million people worldwide; fracture and re-fracture healthcare costs are estimated to be $2.75 billion in Australia alone, and will rise with an ageing population. Early diagnosis of osteoporosis and osteopenia (low bone density) is crucial to prevent fractures. Quantitative Ultrasound (QUS), provides a non-ionizing, portable, and cost-effective method that has been shown to reliably predict osteoporotic fracture risk [1,2]. There is however, a limited understanding of ultrasound wave propagation through cancellous bone, and hence its clinical acceptance is severely restricted . We have recently demonstrated a novel ultrasound signal processing technique that describes a sample specific transit time spectrum (TTS) [4, 5]. This current study shows that an ultrasound transit time spectrum may be used to determine bone volume fraction.
Methods: 21 cancellous bone samples were extracted from 5 human femoral heads. All samples were measured with microCT to derive the true bone volume fraction (BVF) value. Transmission ultrasound signals of 1 MHz were recorded for each sample and a TTS derived via digital deconvolution of the measured ultrasound input and output signals. The ultrasound BVF was then calculated from the TTS.
Results: A coefficient of determination (R2) of 82% was achieved between ultrasound estimated BVF and microCT derived BVF values. Furthermore, we have shown that it is possible to derive BVF without prior knowledge of ultrasound velocity through a particular bone sample.
Conclusions: This study demonstrates a novel technique for ultrasonic characterisation of cancellous bone. For the first time, BVF estimations have been performed independent of the sound velocity through bone. The novel UTTS method may provide us with a more precise and effective technique for osteoporotic fracture risk prediction using non-ionising ultrasound.