New details about Alzheimer's detection, secret transmissions over public networks, more
OSA meeting to showcase state-of-the-art discoveriesWASHINGTON, Sept. 27 -- Frontiers in Optics 2006--the 90th Annual Meeting of the Optical Society of America (OSA)--will showcase a wide range of the latest research breakthroughs in optical science and engineering. The meeting will be held from Oct. 8-12 at the Rochester Convention Center in Rochester, N.Y., the city known as the birthplace of modern-day optics. Co-located with Laser Science XXII, the annual conference of the American Physical Society Division of Laser Science, the meeting will also celebrate 90 years of innovations in optics, feature Nobel Laureates speaking on timely global issues such as energy, and will honor holography pioneer Emmett Leith. Reporters interested in obtaining a badge for the meeting should contact Keira Shein at 410.363.9494, [email protected].
PLENARY PRESENTATIONS HIGHLIGHT GLOBAL ENERGY ISSUES WITH OPTICS SOLUTIONS, AND EARLY DETECTION OF ALZHEIMER'S DISEASE
In a plenary and awards presentation, Steven Chu of Lawrence Berkeley National Laboratory will provide a scientist's perspective on the global energy problem, with emphasis on climate change, then will outline our current options and some areas of energy research that may lead to society-transforming technologies. At the core of the United States' greatest problems--national security, economic competitiveness, the environment--is the need, Chu says, to secure clean, affordable and sustainable sources of energy. Chu will explain how optics research can help to decrease the demand of energy per person and the creation of new sources of clean energy that do not increase carbon dioxide levels in the atmosphere. Lee Goldstein of Harvard Medical School will describe evidence that optical tests can detect the signs of Alzheimer's disease in the eye even before symptoms appear in the brain. The same beta-amyloid proteins that are the hallmark of the disease have been found in rare cataracts in the eye. Non-invasive bio-optical laser technology developed by Goldstein and his colleagues is being clinically tested to detect the cataracts and confirm the presence of the proteins. This research offers the prospect of detecting and treating Alzheimer's early. Such optical tools also offer the promise of improved drugs for Alzheimer's, as researchers could better test the effectiveness of Alzheimer's drugs by monitoring changes in the eye. (Monday, Oct. 9, 8 a.m.-12 p.m.)
The following papers represent some of the many research highlights to be presented at the meeting:
- A Single-Pixel Digital Camera
- Encouraging New Details on How Brain Recovers from Strokes
- Stealthy Transmissions over a Fiber Optic Network
- Changing Blood-Cell Shapes Provide Clues for Fighting Malaria, Sickle-Cell Diseases
- Monitoring Cerebral Blood Flow with Ordinary Infrared Light
- New Eye Instrumentation Promises Earlier Detection and Treatment of Diseases
- Astronomy Techniques Pave Way For Better Eye Exams
A Single-Pixel Digital Camera
A single-pixel camera, scientists at Rice University believe, could eventually lead to a consumer product that requires less power consumption and storage space without sacrificing image detail. The new approach aims to confront one of the basic dilemmas of digital imaging, namely the huge waste of data in going from a million numbers (the light levels from a picture taken with a megapixel camera) to something like 10,000 numbers, corresponding to the result of a data-reduction transformation that takes place right on the chip inside the camera.
The Rice camera saves space and energy by eliminating the first step. It gets rid of the million pixels and goes right to a transformed version (about 10,000 numbers rather than a million) by viewing the scene with a single pixel. Instead of looking once at the object using a million pixels, it looks 10,000 times using one pixel. In each of those viewings, however, the light from the object reflects off the myriad surfaces of a digital micromirror device, the same technology used in projection TVs and digital movie projectors. Each time the pixel views the object, the array of micromirrors assumes a different set of randomly chosen orientations. Using the total light reflected for each viewing, along with the known mirror-orientation pattern, offline computation can then be used to reconstruct a clear image. To summarize, the acquisition of imaging data is reduced many-fold (saving on data storage), only a single pixel is needed (freeing up valuable space in the primary image detector), and the bulk of the processing can be offloaded to a remote computer rather than a chip inside the camera, thus greatly reducing power needs and extending the usefulness of batteries.
Rice researchers Richard Baraniuk and Kevin Kelly say that an additional virtue of the camera is that with only a single pixel, the detector (a photodiode) can be as fancy as one wants, for applications beyond consumer snapshots. It can even accommodate wavelengths currently unavailable to digital photography, such as x-ray, terahertz waves, even radar. One of their main tasks is to reduce the time it currently takes for their prototype device to record an image. The tradeoff for reducing storage space, pixels, and power consumption is to increase the time it takes to obtain a picture since the cyclops-like pixel must blink 10,000 or more times to capture the image. (Paper FWN3, "A Single Pixel Camera Based on White-Noise Compressed Sensing," Oct. 11, 2:15-2:30 p.m.)
Encouraging New Details on How Brain Recovers from Strokes
New study results provide more-encouraging-than-expected new information on how the brain can recover after severe strokes if treated early. Presenting the first published experiment monitoring blood flow and individual brain cells at the same time, researchers will show how nerve cells in living mice can restore their original structure even after a severe disruption of blood flow (similar to what would occur after a major stroke resulting from a blood clot). Tim Murphy of the University of British Columbia will present minute-by-minute details on this surprising recovery process, which suggests that rapid treatment could offer new hope to human stroke patients.
Using laser light and fluorescent compounds, Murphy and his colleagues watched how the disruption of blood flow affects the structure of microscopic nerve cells (neurons) in the brains of live mice. To see individual nerve cells, the researchers studied special mice with brain neurons that contain the YFP protein, which lights up in response to laser light. In addition, the researchers introduced a fluorescent polymer that fails to enter blood cells but gets absorbed by plasma, the liquid portion of blood. When irradiated by the same laser light that irradiates the neurons, the plasma glows and blood cells show up as dark structures on a bright background. This enables the team to look simultaneously at blood flow as well as important nerve-cell structures that can be damaged during a stroke, namely spines and dendrites, which together form the part of a neuron that receives nerve signals.
Showing the importance of diagnosing and treating a stroke quickly, Murphy's team found that if blood flow is restored within 10-60 minutes following even severe stroke conditions, the dendrite and spine structure is mostly restored, demonstrating that the brain's ability to recover from a stroke may be even more remarkable than previously thought. Preliminary measurements suggest that the nerve cells with recovered structure restore their function as well, according to the researchers. (Paper FWJ4, "Stroking the Synapse: Insight into Ischemic Damage and Recovery from in vivo 2-Photon Imaging of Individual Synapses," Oct. 11, 11:15-11:45 a.m.)
Stealthy Transmissions over a Fiber Optic Network
A new technique sends secret messages under other people's noses so cleverly that it would impress James Bond--yet the procedure is so firmly rooted in the real world that it can be instantly used with existing equipment and infrastructure. Bernard Wu and Evgenii Narimanov of Princeton University will present a method for transmitting secret messages over existing public fiber-optic networks, such as those operated by Internet service providers. This technique could immediately allow inexpensive, widespread, and secure transmission of confidential and sensitive data by governments and businesses.
Wu and Narimanov's technique is not the usual form of encryption, in which computer software scrambles a message. Instead, this is a more hardware-oriented form of encryption--it uses the real-world properties of an optical-fiber network to cloak a message. The sender transmits an optical signal that is so faint that it is very hard to detect, let alone decode.
The method takes advantage of the fact that real-world fiber optics systems inevitably have low levels of "noise," random jitters in the light waves that transmit information through the network. The new technique hides the secret message in this optical noise.
In the technique, the sender first translates the secret message into an ultrashort pulse of light. Then, a commercially available optical device (called an OCDMA encoder) spreads the intense, short pulse into a long, faint stream of optical data, so that the optical message is fainter than the noisy jitters in the fiber-optic network. The intended recipient decodes the message by employing information on how the secret message was originally spread out and using an optical device to compress the message back to its original state. The method is very secure: even if eavesdroppers knew a secret transmission was taking place, any slight imperfection in their knowledge of how the secret signal was spread out would make it too hard to pick out amidst the more intense public signal. (Paper FMJ5, "Achieving Secure Stealth Transmission via a Public Fiber-Optical Network," Oct. 9, 5-5:15 p.m.; for more information, see http://www.opticsexpress.org/abstract.cfm?id=89578)
Changing Blood-Cell Shapes Provide Clues for Fighting Malaria, Sickle-Cell Diseases
Living cells are not constant little balls. Responding to various chemical and temperature changes, cells change their shape and their volume. The outer layers (membranes) of red blood cells, for example, can change by tens of nanometers on time scales of tens of milliseconds. Now an MIT group has figured out a way of studying such tiny, quick fluctuations, and how they are related to the cell's osmotic behavior--that is, to the cell's ongoing effort to maintain a balance in the concentration of ions between itself and its surroundings. It can do this, for instance, by admitting or expelling water. If the osmotic imbalance becomes too great, however, the cells can burst, an action called lysis. Often diseased cells are more prone to lysis, which in turn is signaled by changes in the way the membrane flickers (a swelling cell flickers less), hence the interest in numerically monitoring activity at the cell's boundary.
Gabriel Popescu, a researcher in the MIT laser spectroscopy lab of Michael Feld, says that their optical microscopy measurements of the role of osmotic pressure in red blood cell flickering are likely to help in understanding clinical problems such as the effects of the malaria virus on the red blood cell membrane and changes in the mechanical properties of the cells during sickle cell disease. Such basic knowledge, largely unknown until now, paves the way toward better understanding and strategies for treating those and many other diseases involving red blood cells. (Paper FTuE1, "Red Blood Cell Fluctuations During Osmolarity Changes," Oct. 10, 8-8:15 a.m.)
Monitoring Cerebral Blood Flow with Ordinary Infrared Light
In work that promises a whole set of new tools for cancer therapy, stroke rehabilitation, and neonatal care, researchers will present the first technique that measures blood flow in the tiniest blood vessels (microvasculature) of the main part of the brain, known as the cerebrum. What's more, the technique does not use x-rays or any other form of ionizing radiation, but simply light in the near-infrared range.
Turgut Durduran and his colleagues at the University of Pennsylvania take advantage of the fact that near-infrared light (wavelength range 600-950 nm) can penetrate a few centimeters into tissue. Shining near-infrared laser light onto the surface of the scalp creates a pattern of dark and light spots known as speckles. These speckles appear because individual photons of light travel slightly different paths through tissue, and then combine (interfere) with one another to form patterns of light and dark spots. Moreover, when the photons bounce off (scatter) from individual blood cells, they cause the spots to flicker. The researchers observe fluctuations in the intensity of a single tiny speckle (only six microns, or millionths of a meter, in size). The fluctuations provide noninvasive information about underlying blood flow in the brain while an individual is monitored for illness, undergoes a medical procedure, or performs an action. Such information about cerebral blood flow was previously off limits to all techniques except MRI and those involving radiation.
By putting optical probes on various points on the scalp, the researchers have performed three-dimensional imaging of cerebral blood flow (CBF) in animals. By developing this technique further over the next few years, the researchers envision that the technique may enable real-time monitoring of CBF in intensive care units for adults and babies. Another promising possibility is to monitor the effectiveness of tumor therapy. According to Durduran, preliminary indications show that tumors that respond poorly to cancer treatment have a very distinct blood flow pattern from those that respond well. (Paper JThA2, "Functional Imaging of Blood Flow in Brain and in Tumors during Therapy," Oct. 12, 8:30-9 a.m.)
New Eye Instrumentation Promises Earlier Detection and Treatment of Diseases
Employing methods from astronomy and physics, researchers will present advances in eye instrumentation that promise to detect eye diseases much earlier--and thereby increase chances of saving vision in patients. Drs. Ann Elsner and Benno Petrig of Indiana University will present a new tool for detecting eye diseases resulting from diabetic retinopathy, a class of retina-related eye diseases that affects 45 percent of those with diabetes and includes diabetes-related cataracts and glaucoma. Even the most clinically advanced instruments available today often have difficulty obtaining high quality images of the retina. They often miss subtle changes such as nerve-tissue damage that, untreated, lead to permanent vision loss.
To get better retinal images, the Indiana researchers make use of near-infrared light that is "linearly polarized," a sort of filtering of light that also occurs when light enters polarizing sunglasses. If light is imagined as an ocean wave traveling to shore, its electric field is like a bunch of surfers bouncing up and down on top of it. Usually the surfers are all bobbing at slightly different angles. Linear polarization means that the electric fields (surfers) are all lined up in the same direction--straight up in the case of "vertical polarization." With light waves, the surfers can be tilted at an angle, even sideways (horizontal polarization) or upside down.
In the Indiana technique, the researchers send light at 20 different polarization angles into the retina. By detecting how the retina interacts with each polarized beam, and comparing images, they obtain improved, high-contrast images of arteries and veins in the retina. The researchers used this technique in 11 patients with diabetic retinopathy, and strive to design a smaller and less expensive version of their device over the next year. (Paper FTuY2, "Polarimetric Imaging of Retinal Arteries and Veins in Diabetic Retinopathy," Tuesday, Oct. 10, 4:30-4:45 p.m.)
Astronomy Techniques Pave Way For Better Eye Exams
Other research groups are using a technique borrowed from astronomy, called adaptive optics (AO), which uses a special mirror whose surface can be deformed to help a telescope remove the effect of atmospheric distortion to obtain clearer images of far-away stars. In ophthalmology, adaptive optics can correct for the imperfections in the optics of the human eye. These imperfections distort light entering and exiting the eye, and prevent ophthalmologists from obtaining the best possible image of the retina.
Over the last five years, researchers have introduced laser-based ophthalmoscopes that use adaptive optics technology. By correcting for the imperfections and sharpening images of the eye, these instruments scan the eye to produce real time, cellular-level views of the living retina. The images are of unprecedented quality, enabling video images of microscopic blood flow and photoreceptors for diagnosis of eye diseases. However, the prototypes have been expensive: the deformable mirror that compensates for the imperfections costs $60,000 alone. It was large and difficult to deploy in clinics.
Making a more compact, robust and affordable AO system that could readily be used in clinical settings is the goal of a research team at the University of California. Yuhua Zhang of the University of California, Berkeley will present a new-generation AO scanning laser ophthalmoscope (AOSLO) that uses a micro-electro-mechanical deformable mirror. This miniature, flexible mirror could potentially be mass-produced, thus offering the prospect of a smaller, more cost-effective AO system.
The researchers used AOSLO to detect abnormal distribution of the density of color-sensing cones in patients with retinal degenerative diseases such as retinitis pigmentosa. These diseases cause deterioration of the cones in the retina and frequently lead to blindness. The instrument could be a major tool for improving the understanding and diagnosis of these diseases. According to Zhang, the AOSLO now is available for research labs and hospitals for studying and treating eye diseases, and it is reasonable to predict that within a couple of years it has the potential to become an instrument in an eye doctor's office. (Paper FMG1, "MEMS-Based Adaptive-Optics Scanning Laser Ophthalmoscope," Monday, Oct. 9, 1-1:30 p.m.)
Celebrating its 90th anniversary in 2006, the Optical Society of America brings together an international network of the industry's preeminent optics and photonics scientists, engineers, educators, technicians and business leaders. Representing over 14,000 members from more than 80 different countries, OSA promotes the worldwide generation, application and dissemination of optics and photonics knowledge through its meetings, events and journals. Since its founding in 1916, OSA member benefits, programming, publications, products and services have set the industry's standard of excellence. Additional information on OSA is available on the Society's Web site at www.osa.org.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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