Correlation signal processing for determination of the spatial distributions of temperature and acoustic characteristics of the medium

Abstract

It is required in some applications to determine spatial temperature distribution inside investigated object, when direct measurement is impossible, and IR and microwave methods do not provide acceptable spatial resolution. For example, such problems arise in diagnostics of soft biological tissues lying at a depth of about 10 cm or more, and in hyperthermia. To do this, thermal acoustic radiation of the object can be used, which is similar to thermal electromagnetic radiation. It is required to solve the complicated inverse radiation-scattering problem. The intensiometric approach allows determining temperature by signal power measuring at each receiver and by subsequent processing. The correlation processing approach involves calculating the cross correlation functions for each pair of receivers. This approach improves the resolution. The acoustic field focusing is used to further improve the sensitivity and resolution. Moreover, the receiver system can be supplemented with transmitters creating a controlled noise field that is similar to the thermal acoustic field of the object. In this case, the algorithm is proposed that uses three data sets obtained under different experimental conditions. This algorithm allows to separately reconstruct the spatial distributions of temperature, absorption coefficient, and sound speed. [This study was supported by RFBR under Grant No. 21-32-70003]