Tissue temperature monitoring using thermoacoustic and photoacoustic techniques

Abstract

Real-time temperature monitoring with high spatial resolution (~1 mm) and high temperature sensitivity (1 °C or better) is needed for the safe deposition of heat energy in surrounding healthy tissue and efficient destruction of tumor and abnormal cells during thermotherapy. A temperature sensing technique using thermoacoustic and photoacoustic measurements combined with a clinical Philips ultrasound imaging system (iU22) has been explored in this study. Using a tissue phantom, this noninvasive method has been demonstrated to have high temporal resolution and temperature sensitivity. Because both photoacoustic and thermoacoustic signal amplitudes depend on the temperature of the source object, the signal amplitudes can be used to monitor the temperature. The signal is proportional to the dimensionless Grueneisen parameter of the object, which in turn varies with the temperature of the object. A temperature sensitivity of 0.5 °C was obtained at a temporal resolution as short as 3.6 s with 50 signal averages.