Feasibility of quantitative ultrasound measurement at the femur

Measurements of broadband ultrasonic attenuation (BUA) represent an established means of skeletal status assessment in osteoporosis. Today, the skeletal site the most widely used clinically is the calcaneus (heel bone). However, we hypothesized that fracture risk predictions could be improved if ultrasound measurements were performed directly at the main site of fracture, e.g. the upper femoral part. The goal of this paper is to demonstrate the feasibility of BUA measurements at the upper part of the femur, and to investigate the relationships of BUA to bone mineral density (BMD). Forty-eight excised human femurs were measured in transmission with a pair of focused 0.5-MHz central frequency transducers. Two dimensional scans were performed and the RF signals were recorded at each measurement point. A data acceptance criterion for ROI selection was established based on the goodness of the agreement between the signal transmitted through bone and a reference signal transmitted through water, and on the linearity of the frequency-dependent attenuation. Five measurements with repositioning were performed on each sample to determine the reproducibility. Our results are consistent with data previously shown at the calcaneus and demonstrate the feasibility of QUS measurements at the femur in vitro, with reasonable reproducibility.