Neuron Microscope, Treating Bone Cancer, Futuristic Lighting At FiO
How we understand the brain today is akin to how Lewis and Clark knew the United States in 1803—its broad outlines were understood but much of its territory was still undiscovered. Part of the problem is that while we know the major functions associated with many regions of the brain and generally understand how individual neurons work, we do not have a good way of observing the brain in action on the level of individual neurons. Functional MRI is a powerful way to image the activity in entire areas of the brain, but it lacks the temporal or spatial resolution to image individual neurons firing.
A new way of observing the brain in action involves light. At Frontiers in Optics, Henry Liu will discuss how he uses a new technique called self-phase modulation imaging to measure neuronal transmission. Developed by Martin Fischer, Warren Warren and their Duke University colleagues, self-phase modulation imaging basically separates a signal from the background noise (largely scattered light). The signals, in this case, are tiny changes in the optical properties of neurons that occur when they fire. Normally, these optical changes are hard to measure because they are obscured by scattering, but sculpting the laser pulse (femtosecond pulse shaping) at very high update rates makes separation possible.
Liu and his colleagues have studied living neurons cultured on Petri dishes that come from a region of the rat brain implicated in Alzheimer's disease. They can activate the neurons chemically and observe them firing. So far, they have not developed the resolution to be able to see individual neurons firing, but they are working on pushing the technique to that limit. The technique has a lot of promise because it should be able to observe the firing of neurons non-invasively, with low enough laser power to be safely used in living animals. It may one day help as a diagnostic tool to predict the onset of Alzheimer's disease and monitor its progress. The technique would have to prove safe and effective in clinical trials before it is widely available, however.
Presentation FWD2, "Intrinsic Nonlinear Optical Signatures of Neuronal Activity," Wednesday, Oct. 22, 8:45 a.m., Highland E, Rochester Riverside Convention Center
UNDERSTANDING BONE AND LIGHT INTERACTIONS FOR TREATING BONE CANCER
Understanding how different kinds of bone tissue scatter and absorb light may be a key to devising a new multi-modal treatment for human bone cancer based on activating anti-cancer drugs with light.
To do this, researchers must do more than think outside the box—they must think outside the "slab." Here's why: tissues are generally researched as uniform or layered slabs. Bone tissues have different optical properties and occur in a cylindrical shape. Refining a light-based treatment that is sensitive to these differences has traditionally been a challenge. Now researchers at Oregon State University and Oregon Health & Science University are changing that.
Explains Ph.D. candidate Vincent Rossi, the project's lead researcher, "Not much is known about the optical properties of different bone tissues. We measure the absorption and scattering properties of bone by creating a two-layer system within the cylinder to give us a finer level of detail on light propagation within bone." Using a fiber optic system to send and collect light waves through bone, the team analyzes the scattering and absorbing properties of bone tissue using reflectance spectroscopy of wavelengths. Data from the two-layer system is modeled by computer programs that simulate the light distribution.
The treatment being investigated is called photodynamic therapy (PDT). It is used extensively to treat soft-tissue cancers; bone is the next frontier. At this stage of research bones from dogs are used. If validated in humans, here's how PDT might function as part of a multi-modal treatment approach to bone cancer: after surgically removing tumors, a surgeon would place light-sensitive, anti-cancer drugs—which are easily taken up by cancer cells—in specific locations to retard recurrence. To activate the drugs with light, physicians would then use information from the Oregon team's two-layer system to guide light delivery to the bone tissue. Says Rossi, "Getting enough light in the right place has been one of the limiting factors."
Presentation FTuK1, "Understanding Light Propagation in Bone for Photodynamic Therapy of Osteosarcoma," Tuesday, Oct. 21, 10:30 a.m., Highland D, Rochester Riverside Convention Center
THE FUTURE OF SOLID-STATE LIGHTING
Solid-state lighting refers to the effort to produce energy-efficient lighting in a semiconducting light emitting diode (LED). Rensselaer Polytechnic Institute scientist E. Fred Schubert, a pioneer in LED research, will report on the first-time achievement of units operating at both high currents and power levels.
How efficient can LEDs be? Modern incandescent bulbs, which heat up when currents flow through their filaments, produce approximately 15 lumens of light per watt of input electricity. Compact fluorescent lights can do much better: typically 50 lumens/watt. LEDs can do still better: with the potential to produce an estimated 300 lumens/watt. In the lab 150 lumens/watt has already been achieved. LEDs work in this way: electrons are dislodged by an applied voltage leaving a movable vacancy behind. When the electron and the vacancy again combine, they can produce a piece of light, a photon. These photons now come in a wide variety of wavelengths, making LEDs more and more popular for lighting applications. They are already being used for automobile brake lights and traffic lights. Increasingly auto running lights are LEDs.
Schubert's own lab has produced a number of lights using various semiconductor materials, which in turn exhibit a spectrum of different colors.