RESEARCHERS at the Helmholtz Zentrum München and the Technische Universität München are using a combination of light and ultrasound to visualise fluorescent proteins in living tissue.
The new method, multi-spectral opto-acoustic tomography (MSOT) allows the visualisation of protein seated at least 6mm deep into living tissue. Prior to this, modern technologies could not produce high-resolution fluorescence images from this depth because of the strong scattering of light.
In the Nature Photonics journal, the Munich researchers describe how they can reveal genetic expression within live fly larvae and fish by ‘listening to light’. MSOT could have future implications for the examination of tumours or coronary vessels in humans.
MSOT combines light and ultrasound to investigate subcellular processes in live organisms. The technology allows the rendering of three-dimension images through thicker layers of tissues than light microscopy.
MSOT involves illuminated the living sample from multiple angles using flashes of laser light that are absorbed by fluorescent pigments in the tissue of the genetically modified fish. The fluorescent pigments absorb the light, a process that causes slight local increases temperature, which in turn result in tiny local volume expansions.
In effect, the short laser pulse gives rise to an ultrasound wave that the researchers pick up with an ultrasound microphone.
The researchers then used mathematical formulas on a computer to evaluate and interpret the specific distortions caused by scales, muscles, bones and internal organs to generate a three-dimensional image.
The result of this multi-spectral opto-acoustic tomography is an image with a spatial resolution better than 40 micrometers. Examination can be conducted while the sample is sedated, and no harm is done to the sample.
The process allows the use of a range of fluorochrome pigments, including fluorescence protein technology pigment, and clinically approved fluorescent agents, in order to observe metabolic and molecular processes in all kinds of living organisms, from fish to mice and humans.
