Proceedings of the British Institute of Radiology Ultrasonic assessment of bone, 29 May 1991

Tissue characterisation of bone. Conventional industrial nondestructive testing (NDT) and medical applications of ultrasound tend to use frequencies in the range 2.5–10 MHz. Owing to the highly attenuating nature of cancellous bone, frequencies less than 1 MHz have to be used, adopting a transmission technique where one transducer acts as transmitter and a second acts as receiver. Osteoporosis may be defined as a change in density and structure predominantly of cancellous bone leading to a reduction in skeletal integrity and hence an increased risk of fracture. We may use ultrasound to characterize the physical properties of a material such as cancellous bone, measuring either the velocity or attenuation. Velocity is calculated by dividing the thickness of a sample by the transit time for an ultrasonic pulse through it. A measurement of bone velocity as opposed to limb velocity may be obtained by correcting for overlying soft-tissue. Broadband ultrasonic attenuation (BUA) describes the increase in ultrasound attenuation over a particular frequency range, typically 0.2–0.6 MHz. Bone measurement systems.