Calcium sulfate setting monitoring with ultrasonic backscattering analysis

Abstract

[Otros] Ultrasonic backscattering techniques are used to monitor the setting process of calcium sulfate. A 3.5 MHz frequency A-scan pulse-echo system is used to obtain the acoustic properties of a cylindrical sample of calcium sulfate (diameter= 36 mm; thickness= 18 mm). The temperature of the sample and the rf backscattering signal are measured every two seconds during the whole setting process (53 min; 1590 rf-signals). Apparent backscattering integral (AIB) [1], Nakagami parameter [2] and sound speed are calculated from each measured rf signal. A positive correlation is observed between the sound velocity, the AIB and the Nakagami parameter during the setting process, identifying three states of the sample: liquid, transient and solid. Sound velocity changes from 1480 m/s (liquid) to 2700 m/s (solid), meanwhile AIB changes between -15 dB and 0 dB. In the transient phase, the three parameters are sensible to the fast change in the mechanical properties of the medium. The presented results show that, by performing backscattering analysis, the state of a sample in a setting process can be determined, which could have application in monitoring changes in guided bone regeneration processes for dental implant procedures.