The use of tonebursts as an alternative to broadband signals in the measurement of speed of sound in human cancellous bone

Speed of sound (SOS) measurements, typically made using 1 MHz broadband pul ses, we increasingly used in the clinical diagnosis of bone disorders. Prev ious in vitro studies indicate that broadband ultrasound pulses are suscept ible to distortion in cancellous bone, leading to imprecise arrival time an d SOS measurements. We investigated the effect of bandwidth and frequency o n SOS by comparing measurements made using 1 MHz broadband with 1 MHz and 3 00 kHz narrowband toneburst signals in 15 human proximal femur cancellous b one specimens. There was no significant difference in the value of SOS measured from the l eading edge of 1 MHz broadband, 1 MHz toneburst and 300 MHz toneburst signa ls. Values of SOS in later regions of 1 MHz and 300 kHz tonebursts fell sig nificantly(p < 0.001) when compared to earlier regions. This decrease in SO S levelled off by the third complete cycle of 300 kHz toneburst signals, re aching a plateau value of 1961 +/- 239 m s-1. No plateau SOS value was obta ined in 1 MHz tonebursts. The reproducibility of SOS, as measured by the co efficient of variation, was higher for later regions of 300 kHz tonebursts than for the leading edge of 300 kHz toneburst and 1 MHz broadband signals (p < 0.005). The correlation between ultrasound measured modulus and compre ssive Young's modulus improved when 300 kHz tonebursts(r(2) = 0.83) rather than 1 MHz broadband(r(2) = 0.77) signals were used to calculate SOS. The improved SOS reproducibility of later regions 300 kHz tonebursts sugges t that it may be beneficial to use such signals rather than 1 MHz broadband pulses in SOS measurement. Since no reliable SOS measurements could be obt ained from any region of 1 MHz tonebursts, the use of high frequency tonebu rst signals in cancellous bone has little value.