Urs Moser

A device for in vivo measurements of quantitative ultrasound variables at the human proximal femur

Quantitative ultrasound (QUS) at the calcaneus has similar power as a bone mineral density (BMD)- measurement using DXA for the prediction of osteoporotic fracture risk. Ultrasound equipment is less expensive than DXA and free of ionizing radiation. As a mechanical wave, QUS has the potential of measuring different bone properties than dual X-ray absorptiometry (DXA,) which depends on X-ray attenuation and might be developed into a tool of comprehensive assessment of bone strength. However, site- specific DXA at the proximal femur shows best performance in the prediction of hip fractures. To combine the potential of QUS with measurements directly at the femur, we developed a device for in vivo QUS measurements at this site. Methods comprise ultrasound transmission through the bone, reflection from the bone surface, and backscat- ter from the inner trabecular structure. The complete area of the proximal femur can be scanned except at the femoral head, which interferes with the ilium. To avoid edge artifacts, a subregion of the proximal femur in the trochanteric region was selected as measurement region. First, in vivo measurements demonstrate a good signal to noise ratio and proper depiction of the proximal femur on an attenuation image. Our results demonstrate the feasibility of in vivo measurements. Further improvements can be expected by refinement of the scanning technique and data evaluation method to enhance the potential of the new method for the estimation of bone strength.

In Vivo Measurements of Ultrasound Transmission Through the Human Proximal Femur

Quantitative ultrasound (QUS) measurements can be used to estimate osteoporotic fracture risk. The commonly used variables are the speed of sound (SOS) and the frequency dependent sound attenuation (broadband ultrasound attenuation, [BUA]) of a wave propagating through the bone, preferably the calcaneus. The technology, so far, is less suitable for direct measurement in vivo at the spine or the femur for prediction of bone mineral density (BMD) or fracture risk at the main osteoporotic fracture sites. To improve the clinical performance of QUS, we built a device for direct QUS measurements at the human femur in vivo. In vivo images of ultrasound transmission at one of the main fracture sites, the proximal femur, could be acquired. The estimated precision of SOS measurements of 0.5% achieved at the femur is comparable with the precision of peripheral QUS devices.