The measurements of ultrasound parameters on calcaneus by two-sided interrogation techniques

Recently, ultrasound techniques have become an important alternative in the assessment of osteoporosis. The speed of sound (SOS) and broadband ultrasound attenuation (BUA) on calcaneus are commonly used in an ultrasound densitometer for osteoporosis evaluation. However, the quantitative ultrasound (QUS) parameters provided by a densitometer using most commercial ultrasound instruments are based on the assumption of a fixed bone thickness. Information on bone thickness is a critical factor for accurate estimation of SOS through conventional approaches; yet, the thickness of bone tissue is not available through in vivo measurements and it is almost impossible to obtain the thickness of bone tissue via conventional approaches. Therefore, the SOS measurements will be incorrect. The purpose of this work is to develop a two-sided interrogation technique for the SOS measurements that is less susceptible to bone thickness. The results show that this proposed technique can obtain a better SOS estimation on bone tissue. Using bone phantoms that mimic actual tissue, the validity of the approach is confirmed with measurements showing high accuracy (>99%) and low standard deviation (<0.5%). Finally, the measurements of 14 healthy subjects are also reported. The results show that this technique can provide the bone thickness information to reduce the SOS estimation errors compared with the fixed bone thickness assumption.