Light is a great tool for imaging the outside of the body and for looking at the interior using endoscopes, but looking through more than a few millimeters of tissue typically requires other modalities such as X-rays and ultrasound. Using light to peer through skin, muscle, and other soft tissues has remained an elusive goal for many scientists. Now, a team from Carnegie Mellon University has come up with a remarkable new way of using light to look deep into tissues like never before.
Since tissues are highly irregular, they scatter light in all directions. This results in fuzzy images that don’t provide the necessary resolution to identify important anatomical features or pathologies. The new technique from Carnegie Mellon uses finely tuned ultrasound to compress and relax soft tissue so it creates a virtual lens that focuses the light coming through. The researchers liken their approach to making tissue more transparent, and their method can be used to focus through different tissues and to different depths.
The approach has major significance for looking into the brain, diagnosing diseases of the skin, and for spotting deeply seated tumors.
Some details about the technology from the study abstract in journal Light: Science & Applications:
A virtual optical graded-index (GRIN) lens can be sculpted in the medium using in situ reconfigurable ultrasonic interference patterns to relay images through the medium. Ultrasonic wave patterns change the local density of the medium to sculpt a graded refractive index pattern normal to the direction of light propagation, which modulates the phase front of light, causing it to focus within the medium and effectively creating a virtual relay lens. We demonstrate the in situ relay imaging and resolving of small features (22 µm) through a turbid medium (optical thickness = 5.7 times the scattering mean free path), which is normally opaque. The focal distance and the numerical aperture of the sculpted optical GRIN lens can be tuned by changing the ultrasonic wave parameters. As an example, we experimentally demonstrate that the axial focal distance can be continuously scanned over a depth of 5.4 mm in the modulated medium and that the numerical aperture can be tuned up to 21.5%.
Here’s Maysam Chamanzar, the leader of the research, explaining the new science and its applications:
Study in Light: Science & Applications: Ultrasonically sculpted virtual relay lens for in situ microimaging
Via: Carnegie Mellon