New absorbers for photoacoustic imaging

Project title: Synthesis, photophysics and preclinical application of targeted absorbers for photoacoustic imaging
Principal investigators: Cristian Strassert, Andreas Faust
Project time: 07/2016 - 06/2018
Project code: FF-2016-16

The photoacoustic effect has been known about for over 100 years now. Even Graham Bell, the inventor of the telephone, already recognized that light pulses can be absorbed and converted into sound waves. This effect has now been rediscovered for use in medical diagnostics. When long-wave lasers emit light in pulses, they give rise to ultrasonic signals which make structures inside the body visible. In contrast to fluorescence imaging, in which dyes emit light, the ultrasound which occurs is not subjected to any dispersion in the tissue, which means it can deliver defined imaging signals. What are still not available, however, are so-called absorbers for making good medical images with photoacoustics.

The body’s own dyes, such as haemoglobin, can act as these necessary absorbing structures. But the function can also be fulfilled by absorbers brought in from outside which, in association with an active substance, recognize individual structures. As applications in research and in hospitals are still in their infancy, there are hardly any effective absorbers so far which absorb within the appropriate wavelength range and which convert light pulses into soundwaves as efficiently as possible. Also, such absorbers need to be without any luminescence and must not form any reactive oxygen species – i.e. forms of oxygen which, in higher concentrations, can be harmful. The important thing in developing such absorbers is that biocompatibility, biodistribution and in vivo stability are assured. In this project Dr. Andreas Faust, a chemist, and Dr. Cristian Strassert, a photophysicist, are aiming to develop such absorbers, which can be used to produce better photoacoustic images in future – of mice as well as of patients – than has been the case so far.