Judges’ Queries and Presenter’s Replies

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Presentation Discussion

  • Icon for: Terri La Count

    Terri La Count

    May 22, 2012 | 02:14 p.m.

    This technique will have many uses in biological applications, such as skin analyses, due to the factors noted in the presentation. I really enjoyed the graphics employed in the video presentation to explain the concepts of this technique.

  • Icon for: Donald Conkey

    Donald Conkey

    May 23, 2012 | 01:51 p.m.

    The application of this research to real problems is exciting and an area that I look forward to being a part of in the next few years.
    Two-photon or multi-photon microscopy is currently limited to imaging about 1 mm deep into tissue. After 1 mm the intensity of the ballistic beam is too low for nonlinear affects. However, with this technique we can potentially increase the intensity of the light 10-1000X at depths greater than 1 mm, thus enabling an extension of the imaging depth.
    One area that currently uses two-photon microscopy for imaging is in neuroscience. However, to image the brain the skull must either be thinned or removed before imaging to reduce the effects of scattering. This technique opens the door to imaging the brain without removing or thinning the skull, which would would be a great help to neuroscientists and rats.
    An interesting area that could benefit from this technique is in photodynamic therapy for cancer. In photodynamic therapy small particles are inserted into the body. After insertion they find and attach themselves to cancer cells. After attachment high intensity light illuminates the body and the particles attached to the cancer. The wavelength of light is selected to be highly absorbed by the particles. Thus when illuminated the particles heat up and destroy the cancer cells. Unfortunately, this technique is limited in the depth it can be used due to diffusion of light. However, by focusing the light through the tissue at the particles we could attack cancer cells deeper in the body.
    Another area being explored with this technique is optical trapping. Potentially optical traps could be created in the body or blood stream through the tissue by the creation of a high intensity focus with this method. Thus, allowing manipulation of particles in the blood stream – or other parts of the body.
    One exciting aspect of this research is how new it is. I expect to see an explosion of ideas for implementation of this focusing technique in the next several years as these techniques are explored and implemented.

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Icon for: Donald Conkey


University of Colorado at Boulder
Years in Grad School: 4

High speed light focusing through dynamic turbid media

Controlling light propagation through scattering media at high speeds is critical for applications in biomedical imaging. As light propagates through biological tissue it becomes increasingly scattered, thus limiting the optical imaging depth to less than 1 mm. Recently introduced wavefront control techniques should allow for deeper imaging in biological materials. These techniques rely on the deterministic nature of multiple scattering to shape the incident wavefront and pre-compensate for the scattering effects of light propagation. However, living biological materials have structural changes which occur on the millisecond timescale, altering the path of light. This fast rate of change makes current methods of focusing through turbid media too slow. Most current methods use liquid crystal spatial light modulators, whose switching speed is typically in the 10s of Hz: much slower than the kHz rate required for the millisecond timescale of biological tissues. Thus, new high-speed techniques for optimizing wavefronts are required to implement focusing through biological samples. We have developed a new high-speed wavefront optimization technique, which utilizes off-axis binary-amplitude computer-generated holography. The computer-generated holograms are implemented via a deformable mirror device (DMD) based on micro-electro-mechanical technology, which can be updated at high data rates. We demonstrate this technique measuring a transmission matrix with 256 input modes and a single output mode in 33.8 ms and creating a focus with a signal to background ratio of 160. We also demonstrate focusing through a highly temporally dynamic, strongly scattering sample.