Optical Temperature Change Estimate of 60 GHz MMW Radiation Mediated Heating in Nervous Tissue with Rhodamine B and Rhodamine 6G Fluorescent Indicators

Effects of millimetre wave (MMW) radiation in biological objects have been studied for the last several decades. The volume of research on the topic is proportional to the number of new methods and techniques in biological sciences capable of picking up and characterising the MMW-triggered changes in the functionality of the biological object. Yet, regardless of the characterising technique employed, there is always a question of comparison of MMW-related heating and equivalent conductive heating effect in the sample. Moreover, for a number of reasons related to the complexity of fresh tissue's natural organisation and technical imperfections of available today's temperature sensors, the measurement of MMW-associated heating of fresh tissue could be challenging or unreliable. Here, we test the reliability and applicability of two commercially available fluorescent dyes – Rhodamine B and Rhodamine 6G – as a temperature reporter in fresh nervous tissue exposed to intense MMW radiation (100 mW). Results demonstrate the advantages and disadvantages of either dye, their performance, and some practical aspects of usage.