Photoacoustic temperature measurements for hyperthermia

In this research project in collaboration with Dr. Miuras group, the hyperthermic stimulation of cells and tissue is investigated in vitro. To study hyperthermia, it is essential to determine the exact temperature increase over the period of heat exposure in order to investigate the response of cells to targeted thermal stimulation. A continuously emitting thulium laser is used to heat the cells. Its radiation is very strongly absorbed by water and ensures a very rapid temperature increase at high power. For temperature measurement, a photoacoustic non-contact method is developed, which uses the temperature dependence of the thermal expansion coefficient of water. To query the temperature curve, repeating Q-switched pulses of a holmium laser are used, which can address any place in the curve via scanner.

A concrete therapeutic application of photoacoustic temperature measurement and control is applied in the project RegiLas, where the retina of patients in the early stages of age-related macular degeneration is to be stimulated. Here it is to be investigated whether a progress of the disease can be prevented by targeted hyperthermia.

Schematic sketch of the heating and measurement setup. The radiation of a continuously emitting thulium laser is guided via an optical fiber and used to heat the medium. A Q-switched holmium laser is used to excite the photoacoustics. The beam can be directed with a scanner to any position on the culture dish. A hydrophone outside the bowl wall detects the ultrasonic pressure waves, from which the temperature can be measured at any point at any time.

Own publications, peer reviewed:               

1. Miura Y, Seifert E, Rehra J, Kern K, Theisen-Kunde D, Denton M, Brinkmann R. Real-time optoacoustic temperature determination on cell cultures during heat exposure: a feasibility study. Int J Hyperthermia 2019; 36(1):466-472.
2. Miura Y, Pruessner J, Mertineit CL, Kern K, Münter M, Moltmann M, Danicke V, Brinkmann R. Continuous-wave Thulium Laser for Heating Cultured Cells to Investigate Cellular Thermal Effects. Journal of visualized experiments : JoVE 2017(124).