A Prototype of Ultrasound Forearm Bone Densitometer in Validation with pDXA Bone Densitometer

Abstract

'Osteoporosis' is highly prevalent in India and in other parts of the world. The aged population of both sexes is at higher risk for the disorder. In India, the dual energy X-ray absorptiometry (DXA) bone densitometer, which is considered as the 'gold' standard to measure bone mineral density (BMD) at the hip, spine, and forearm is costly and not widely available. On the other hand, ultrasound (US) based bone densitometer is low cost, and is widely available. The accuracy of the device varies widely between the manufactures. The aim of this study was to design and construct a prototype of US forearm bone densitometer to measure BMD with good sensitivity compared to peripheral (p) DXA as standard. The prototype of the device was constructed using a pair of wideband, flat, composite US transducers (diameter=10mm) operating at a central frequency equal to 0.5MHz. The following US parameters were measured accurately at one third length of ulna bone using the digital storage oscilloscope (DSO): i). Ultrasonic transmit time (ΔT, μsec), and ii). Ultrasonic attenuation (ΔV in volt). The device was validated with a bone phantom with the known BMD value supplied by the pDXA manufacturer. A total number of 40 women, and men, aged 30 years and below, as well as aged 45 years and above were studied. In each subject, both forearm BMD (g/cm2) by pDXA and US parameters of the ulna bone by the prototype bone densitometer was measured at standard conditions. All the obtained data were analyzed statistically. It was found that, in total women studied (n=20), the forearm BMD by DXA was correlated statistically significantly with both the measured ΔT and ΔV values by the prototype bone densitometer. On the other hand, in total men studied (n=20), the forearm BMD by pDXA was correlated statistically significantly only with measured ΔT value by the prototype bone densitometer. Also, it was found that, in old age women group (n=10), the calculated percentage difference in the mean values of US parameters was greater statistically significant than the corresponding BMD value when compared to young women's group (n=10). On the other hand, in old age men group (n=10), the calculated percentage difference in the mean values of both US parameters and BMD value were not statistically significant, when compared to the corresponding values of young women's group (n=10). The prototype device can be useful in the evaluation of the disease with good accuracy.