Researchers at Caltech’s Department of Medical Engineering have made significant progress in medical imaging by using wavefront shaping inspired by astronomy. Wavefront shaping is a method used to correct optical distortion caused by the Earth’s atmosphere in astronomical imaging. Similar to the Earth’s atmosphere, biological tissue also scatters light, making microscopic images of blood vessels, nerves, and cancer cells appear distorted.
In astronomy, the light that reaches telescopes is distorted by the earth’s atmosphere, resulting in blurry images of planets, satellites, and other cosmic objects. The earth’s atmosphere is what’s known as a scattering medium; it scatters light, making images appear unfocused and cloudy. Wavefront shaping is a method of generating focused light by reversing the optical distortion caused by the atmosphere.
Wang’s lab employs a photo-refractive crystal to act as a “magic mirror” that cancels out the distortion of light caused by tissue. The first key metric is speed. Since biological tissue is alive and moving, the entire wavefront shaping process must be done within a millisecond. “Only when you have the same object in the same state at the same location during the time reversal process can we cancel the wavefront distortion,” says Wang, who is also the Andrew and Peggy Cherng Medical Engineering Leadership Chair.
When light waves are passed through a material with properties that allow it to amplify light—also called a gain medium—the electrons in the gain medium release energy in the form of additional light. This process amplifies the light waves, forming light that travels in a straight line—known as a laser. Similarly, a laser gain medium is used to amplify the scattered light waves getting to and reflecting off the magic mirror.