Lighting The Way: Developments in Optical Physics Open the Door for Medical Imaging Breakthrough

The idea of using penetrating light to look inside the human body is over a hundred years old. In 1895, German physicist Wilhelm Röntgen discovered a radiant leak in his electron tube. More importantly, he noticed the this radiation had the power to pass through living tissue. Röntgen had unwittingly invented the X-ray machine. Less than a year later, John Hall-Edwards took Röntgen’s discovery from the lab to the examination room, pioneering the use of X-rays in a clinical setting. In the coming decades light would prove a valuable ally to medical science, as the field of Radiology would explode helping to diagnose an incredible spectrum of disease. Again, the work of physicists has paved the way for a revolution in biomedical imaging. 

 

                              

Meet Allard Mosk. In 2007, Mosk and Ivo Vellekoop were able to shine visible light through an opaque surface and focus it on the other side. At first, they viewed their accomplishment as nothing more than a “bar trick” in the world of optical physics, an impressive, seemingly-impossible feat but one with ultimately little significance or application.  Mosk and Vellekoop’s “trick” bore two papers that would caught the eye of bioengineer Lihong Wang. Wang refined Mosk’s method and was the first to use it on an in vivo target, imaging an ink stained gel that had been inserted into the ear of a mouse. Light shone upon this mouse’s ear, or any other opaque material, is scattered randomly within. Wang’s technique involves shinning light through an ultrasound beam within the specimen and using a “time-reversing” mirror to selectively undo its scattering. Wang’s mirror uses a computer that is able to decipher the pattern by which a material scatters light. This is done sampling how minute changes in the angle of the light entering the material effects the path of the scattered light. Once a pattern has been determined, the mirror conforms to reflect the light along the exact same path it traveled through the material. The reflected light returns to the point it crossed the ultrasound beam, adding its energy to the light passing through. This high-energy ultrasound beam can then be moved around the specimen activating injected fluorescent dyes. 

Wang believes that one-day visible light will be used to as a powerful diagnostic tool and help to circumvent intrusive exploratory surgeries. He imagines a world in which we are able to pinpoint the location of tumors and perform tissue biopsies without the patient having to go under the knife. Wang’s technique not only makes it easier for physicians to look inside the body but will also allow them to do so more frequently. As someone who sufferers from ankle arthritis, this technology could allow my doctor to closely monitor the progress of the condition without having to perform an invasive arthroscopy. Wang’s technology is still a ways from being able to perform such a feat, but the future certainly looks bright. 

Posted by John Slepchuk (Group A)