Medical imaging using photoacoustics

Illumination with light generates ultrasonic waves

With its combination of optical and acoustic methods, photoacoustic imaging (PAI) has the potential to markedly improve medical diagnostics of soft tissue.

Unlike traditional sonography, PAI involves illuminating the tissue with light thus thermally stimulating it. This leads to a thermoelastic expansion in the tissue molecules, resulting in a pressure wave. The ultrasound waves generated in this way can be detected and provide precise information about anatomical structures and physiological processes in the tissue. The process is based on the fact that certain tissue components, such as blood vessels, absorb the emitted light to varying degrees. In photoacoustic imaging, this leads to different contrasts.

Real-time visualization of soft biological tissues

Photoacoustic imaging thus offers general advantages over conventional methods, such as better soft tissue contrast and the possibility of obtaining anatomical and functional information simultaneously. An important field of application for photoacoustic imaging is non-invasive diagnostics in medicine. The method enables real-time visualization of tumours, vascular structures and tissue changes, thus helping with early detection and treatment.

Highly sensitive probe for photoacoustic imaging in medical technology

The very first commercially available PAI systems use expensive tunable highpower lasers as a light source, as well as converters originally developed for ultrasound imaging, and they connect the probe to a stationary signal processor via long coaxial cables that are susceptible to noise. Sensor systems designed and optimized for photoacoustic imaging are still lacking.

Using a novel fusion of different technologies and methods, researchers at Fraunhofer IPM working on the PASMIE project now are aiming to develop a highly sensitive probe for photoacoustic imaging in medical technology. Central to this is the integration of ultrasound converters and light sources within one housing. This will enable higher integration density and minimized costs thanks to the use of laser diodes.