Spatially resolved detection of the scattering coefficient and the capillary network of tissue by using a random laser

• Applicant: Professor Dr.-Ing. Michael Schmidt
• Subject Area: Biomedical Systems Technology ; Measurement Systems ; Production Automation and Assembly Technology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 414732368

For medical diagnostics, imaging is an essential technique to guide and assist the clinical staff. Often, recent developments in physics allow the investigation of new methodologies and the investigation of new disease related parameters to detect diseases. In this study, the random laser (RL) will be studied for the usage as a new tool for tissue imaging with the aim to provide the spatial resolved feedback about the micro structure of the tissue under investigation by turning the tissue itself into a RL.A RL can be set-up by combining a scattering medium with a laser dye. With external optical pumping, the random laser is generated. For example, tissue or intralipid can be soaked or mixed with Rhodamin 6G. If this mixture is pumped with a frequency doubled Nd:YAG Laser, a RL will be built. The spectrum of the emitted light will allow conclusions on the scattering properties of the medium under investigation. This easy set-up of the RL enables to collect information about the tissue under investigation with a robust set-up. It is expected that the collected spectra can be used to derive two types of information. First, information about the capillary network should be reconstructable and, second, the spatially resolved scattering coefficient of the tissue under investigation can be reconstructed. To do so, the planned research focuses on getting a fundamental understanding of the behaviour of random lasers in biological tissue. Due to the behaviour of the random laser, it is expected that especially the smaller vessel structures can be analysed. Therefore, tissue classification especially for cancerous lesions might be easily done with a random laser. After injection of the dye, its perfusion changes for different time spans between injection and measurement. Within the scope of this project, the effects of different amount of perfusion of the fluorescence dye are investigated and evaluated with the help of tissue mimicking phantoms to study the RL in a controlled environment. These different amounts of perfusion are used to reconstruct the scattering coefficient of the tissue and to derive information about the capillary network.Compared to established optical technologies, the RL should allow a fast and precise way for measuring capillary networks and scattering coefficients. The new approach with a RL has the advantage of using a very simple, potentially very robust and fast set-up. Moreover, small changes of both parameters are expected to be measurable. Therefore, the changes of tissue in early stage diseases like carcinomas should be able to be studied for understanding the development of the disease as well as the RL should allow its detection.

• DFG Programme: Research Grants