14 DAY TRIAL // Researchers at the Helmholtz Zentrum München – German Research Center for Environmental Health have taken another step in turning science-fiction into reality, when they have recently announced the creation of a new viewing technique, which is able to combine light with sound to look inside living creatures at unprecedented depths. In their proof-of-concept experiments, the team viewed fluorescent proteins inside living fly larvae and fish, and at the same time analyzed the genetic expressions that occurred within the organisms as they developed.
It's currently impossible for light to penetrate at great depths inside living organisms without damaging them, mostly due to a phenomenon known as strong light scattering. In a new study, published in the latest issue of the respected scientific journal Nature Photonics, the German researchers explain exactly how this new observation method works. They say that average microscopes, such as those used since the instruments first appeared, can only penetrate about 0.5 to one millimeter inside living tissue, before light scattering diffuses the light waves, and the most important details become obscured.
But the German team not only moved past this depth limitation, but exceeded it by at least 600 percent, when they used their new technique to render whole-body, 3-dimensional images of adult zebra fish, more than six millimeters deep. How this is achieved is a very complex process. The fish is first illuminated from all sides with laser light, fired at it in short, strong bursts. Because the models the researchers worked with were genetically modified for this experiment, they had in them a special pigment that absorbed this type of laser light.
When the fluorescent pigments absorb the light, this produces a local warming effect, and a small cellular expansion takes place, albeit very, very fast. When this happens, what you basically have are nothing else than ultrasounds moving through the body of the fish, which can be picked up using a classic ultrasound microphone. The only difference between these waves and the regular ones is that these are created by light, and not by a sound source.
“This 'multi-spectral opto-acoustic tomography,' or MSOT, opens the door to a whole new universe of research. For the first time, biologists will be able to optically follow the development of organs, cellular function and genetic expression through several millimeters to centimeters of tissue,” Dr. Daniel Razansky, one of the researchers who played a crucial role in the development process that led to the new technology, explains.
“MSOT can truly revolutionize biomedical research, drug discovery and healthcare. Since MSOT allows optical and fluorescence imaging of tissue to a depth of several centimeters, it could become the method of choice for imaging cellular and subcellular processes throughout entire living tissues,” the Director of the Helmholtz Zentrum München – German Research Center for Environmental Health Institute of Biological and Medical Imaging, Professor and Bioengineer Vasilis Ntziachristos, adds. He is also the chair for biological imaging at the Technische Universitat München.