Calibration-free Laser-Induced Breakdown Spectroscopy (LIBS) for the elemental analysis of tissue

• Applicant: Professor Dr.-Ing. Michael Schmidt
• Subject Area: Joining and Separation Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502911968

Medical imaging has its application in diagnostics as well as in therapeutics. For medical diagnostics, in addition to computer-aided imaging and image processing, investigations of disease related parameters like the elemental composition are becoming increasingly important. Additionally, it is highly desired to avoid the use of contrast agents.As Laser-Induced Breakdown Spectroscopy (LIBS) can fulfil these requirements, it will be investigated in this project to be applied as a potentially new tool for tissue imaging – for the clinical routine as well as for the scope of research. In both sectors mentioned, biochemical alterations are currently the main focus of attention; alterations of elements, however, are mostly overlooked due to a lack of reliable methods. It is thus the long-time goal to apply LIBS as a method allowing a precise investigation of tissue ex-vivo and in-vivo. By this, certain elements and, therefore, their concentrations can be used to gain a basic understanding of the function of the human body and as a disease related parameter with a high sensitivity and specificity.To enable this vision, the goal of this grant focusses on the investigation of a reliable and robust LIBS system, allowing absolute quantification of elements of tissue with a fine spatial resolution. To make this possible, a system which uses a plasma physical model to generate the right experimental parameters must be examined. With this, the first goal is to fully understand the plasma. This point is essential as the entire reliability of the LIBS method depends on this. Therefore, the first work packages of the project will investigate the plasma properties in the case of tissue. While the plasma in general has to be in local thermodynamic equilibrium and optically thin to minimize reabsorption, at the same time its properties depend on laser parameters such as pulse energy and spot size. Moreover, they depend on tissue specifics such as the absorptivity and the stiffness of the substrate under investigation. These dependencies have to be studied.With realizing the robust LIBS system for tissue investigations, in this proposal finally samples from patients with iron overload and Wilson’s disease are investigated to show that the LIBS set-up is capable of easily finding the excess of iron or copper in both diseases. In this respect, the overall guiding hypothesis behind these working packages is that by understanding the plasma process of laser ablation it is possible to enable calibration-free LIBS.From these technological advances, new insights may be generated by for example studying cell migration as a function of local elemental concentrations as this may pinpoint to the mechanism of cancer metastasis. A rather practice-oriented use case is the application of LIBS as a tool for disease identification. In summary, it is expected that a LIBS system as proposed in this manuscript is capable of pushing medical research in many fields.

• DFG Programme: Research Grants