R&D Highlights

Ruikang K. Wang of University of Washington suggests an article in the July issue of the "SPIE Journal of Biomedical Optics" on a noninvasive, label-free imaging modality that can simultaneously measure the anatomical, chemical, and fluid-dynamic parameters required for quantification of the metabolic rate of oxygen (MRO₂).

In "Label-free oxygen-metabolic photoacoustic microscopy in vivo," Junjie Yao and colleagues at Washington University in St. Louis (USA) demonstrate label-free metabolic photoacoustic microscopy (mPAM) with small-vessel resolution to noninvasively quantify MRO₂ in vivo in absolute units.

mPAM has strong potential for the study of metabolism in cancer and other metabolic diseases, the researchers say. The modality can accurately measure tissue volume, vessel cross-section, concentration of hemoglobin, oxygen saturation of hemoglobin, and blood-flow speed. These measurements can be helpful for fundamental pathophysiological studies and early diagnosis and treatment of disease, as most diseases, especially cancer and diabetes, manifest abnormal oxygen metabolism.

 mPAM image on top is of the total concentration (CHb) of hemoglobin. The area indicated by the dashed box is enlarged at bottom and shows the oxygen saturation (sO₂) of hemoglobin.

Current techniques either lack high resolution or rely on exogenous contrast, the researchers say. Compared with other oxygenation indexes of tissue, such as oxygen saturation (sO₂) of hemoglobin and partial oxygen pressure (pO₂), the researchers say MRO₂ is superior "because it directly reflects the rate of oxygen consumption instead of the static oxygen concentration."

Other benefits and possible applications for mPAM cited in the article:

• High spatial resolution is essential for micro-hemodynamic studies, such as monitoring of local hemorrhage caused by mini-strokes.
• High sensitivity is critical for studies concerning small metabolic changes, such as monitoring neuro-vascular coupling in response to physiological challenges.
• The potential for real-time imaging through fast optical scanning or ultrasonic-array detection is important for studies for monitoring epileptic seizures.
• High spatial scalability enables correlation of microscopic and macroscopic studies (e.g., monitoring of local neuron firing and overall brain activity) based on the same contrast.

Source: Journal of Biomedical Optics 16, 076003 (2011); doi:10.1117/1.3594786.

With our seemingly insatiable appetite for energy and the rampant growth of nanotechnologies, the convergence of alternative energy technologies and nanotechnologies was inevitable. That convergence is now occurring.

SPIE Fellow Akhlesh Lakhtakia, editor-in-chief of the "Journal of Nanophotonics," recommends reading a survey article published in the journal in May by SPIE member Louay Eldada: "Nanotechnologies for efficient solar and wind energy harvesting and storage in smart-grid and transportation applications."

Eldada states that nanostructured thin films of copper indium gallium selenide (CIGS) are being used for high-efficiency photovoltaic modules. Nanocomposites are being used as blade materials, lubricants, and de-icing coatings in wind turbines.

 Water beads on hydrophobic butterfly wings.

Advanced nanocoatings are often inspired by nature. For instance, Eldada points to research on ice-releasing properties of rough hydrophobic coatings, which mimic lotus leaves and the thin outer membranes of butterfly wings. These biomaterials naturally repel water because they resemble a bed of nails.

Nanostructured electrodes and electrolytes also find use in storage batteries for use in alternative-energy generating systems, smart grids, and electric vehicles.

Eldada identifies both current developments as well as opportunities for further research.

Source: Journal of Nanophotonics 5, 051704 (2011); doi:10.1117/1.3574149.

The development of target-detection algorithms specific to hyperspectral image data is an active area of research; standard algorithms and their proposed variations are continuously being investigated.

Among these standard algorithms are the matched-filter and the adaptive-coherence/cosine estimator; which, according to the authors of an article in the May 2011 issue of "Optical Engineering," are limited by their use of second-order statistics.

In "Hyperspectral target detection using regularized high-order matched filter," Zhenwei Shi, Shuo Yang, and Zhiguo Jiang of Beijing University of Aeronautics and Astronautics suggest that target detection in real hyperspectral data benefits from higher-order statistics because targets do not follow normal distributions in real data.

Additionally, the authors believe that target spectral variation can be addressed by the addition of a regularized term to the algorithm. Thus, they develop the RHF (Regularized high-order matched filter) and test the algorithm against standard second-order and kernel-based algorithms.

They tested the algorithms on various synthetic and one real image, and the curves of the receiver operating characteristics (ROC) are used as a metric for comparison.

From the target-detection results on a real image, in which the RHF outperforms all other algorithms, the authors conclude that "the RHF could behave better in the case [where] targets of interest only occupy a few pixels, and spectra of targets have some variations."

This new algorithm shows promise for target detection in hyperspectral image data in the case the authors describe.

(Recommended by SPIE member Sarah Lane of Georgia Tech Research Institute Electro-Optical Systems Lab.)

Source: Optical Engineering 50, 057201 (May 2011); doi: 10.1117/1.3572118.

In an advance that could open new avenues for solar cells, lasers, metamaterials, and more, researchers at the University of Illinois (USA) have demonstrated the first optoelectronically active 3D photonic crystal.

"We've discovered a way to change the three-dimensional structure of a well-established semiconductor material to enable new optical properties while maintaining its very attractive electrical properties," said Paul Braun, a professor of materials science and engineering and of chemistry who led the research effort.

The researchers used an epitaxial approach with gallium arsenide to create a 3D photonic crystal LED from the bottom up. This approach eliminates many of the defects introduced by top-down fabrication methods.

The team published its advance in "Nature Materials" and also presented a paper on electrically active 3D photonic and plasmonic crystals at SPIE Optics + Photonics in August.

See a video of Braun describing his research with 3D crystals in the SPIE Newsroom.

Source: Nature Materials 10, 676-681 (2011); doi: 10.1038/nmat3071 

To help libraries contain costs, SPIE implemented a 10% rollback in pricing for institutional subscriptions to the SPIE Digital Library (SDL) in 2010 and kept prices frozen through 2011.

In an effort to continue providing optics and photonics educational resources to as many people as possible, SPIE is reducing prices by another 5% for 2012.

Along with this price cut, SPIE is expanding SDL services, features, and content, and is planning a new platform change and upgrade next year.

The world's largest resource for optics and photonics research, the SDL features nearly 320,000 journal and proceedings articles published from 1990 to the present and adds approximately 18,000 new articles annually.

Read more short technical articles on optics and photonics and view recent video interviews with the top researchers in the field in the SPIE Newsroom.

You can also sign up for monthly e-alerts in any of the 13 technical areas that the SPIE Newsroom covers.

Have a question or comment about this article? Write to us at spieprofessional@spie.org.