Monitoring the setting of injectable calcium-based bone cements using pulse-echo ultrasound

The existing standards for determining the setting time of injectable bone substitutes suffers from poor reproducibility and subjectivity. We previously presented an ultrasonic pulse-echo technique that can follow the entire setting reaction on-line, without any mechanical manipulation of the sample. For calcium sulfate hemihydrate (CSH), the new method shows good agreement with the standards, but with much better reproducibility. One problem with the new technique was its sensitivity to temperature fluctuations. In this paper we present a temperature compensation scheme that automatically corrects the measurements for losses caused by temperature changes. The modified method is verified with experiments on α-tricalcium phosphate (α-TCP). Because α-TCP has longer setting time than CSH, the initial method, which is sensitive to temperature, did not work.