Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New technique takes cues from astronomy and ophthalmology to sharpen microscope images

14.04.2014

The complexity of biology can befuddle even the most sophisticated light microscopes.

Biological samples bend light in unpredictable ways, returning difficult-to-interpret information to the microscope and distorting the resulting image. New imaging technology developed at the Howard Hughes Medical Institute's Janelia Farm Research Campus rapidly corrects for these distortions and sharpens high-resolution images over large volumes of tissue.


This image is a frame grab from a video showing imaging from an adaptive optics (AO) microscope operating in two-photon excitation (TPE) mode. Imaging shows a membrane-labeled subset of neurons in the brain of a living zebrafish embryo. This image shows what one would see with adaptive optics (AO) and deconvolution turned on.

Credit: Courtesy of Eric Betzig Lab, HHMI Janelia Farm Research Campus

The approach, a form of adaptive optics, works in tissues that do not scatter light, making it well suited to imaging the transparent bodies of zebrafish and the roundworm Caenorhabditis elegans, important model organisms in biological research. Janelia group leader Eric Betzig says his team developed the new technology by combining adaptive optics strategies that astronomers and ophthalmologists use to cancel out similar distortions in their images.

In a report published online on April 13, 2014, in the journal Nature Methods, Betzig, postdoctoral fellow Kai Wang, and their colleagues show how the technique brings into focus the fine, branching structures and subcellular organelles of nerve cells deep in the living brain of a zebrafish. These structures remain blurry and indistinct under the same microscope without adaptive optics. "The results are pretty eye-popping," Betzig says. "This really takes the application of adaptive optics to microscopy to a completely different level."

... more about:
»astronomy »images »structures »zebrafish

"Our technique is really robust, and you don't need anything special to apply our technology. [In the future] it could be a very convenient add-on component to commercially available microscopes," says Wang, a postdoctoral researcher in Betzig's lab.

Over the last decade, Betzig and others have taken a cue from astronomers in using adaptive optics to correct for the light-bending heterogeneity of biological tissues. Astronomers apply adaptive optics by shining a laser high in the atmosphere in the same direction as an object they want to observe, Betzig explains. The light returning from this so-called guide star gets distorted as it travels through the turbulent atmosphere back to the telescope. Using a tool called a wavefront sensor, astronomers measure this distortion directly, then use the measurements to deform a telescope mirror to cancel out the atmospheric aberrations. The correction gives a much clearer view of the target object they want to observe.

A microscopy technique that Betzig developed in 2010 with Na Ji, who is now also a group leader at Janelia, achieves similar results by using an isolated fluorescent object such as a cell body or an embedded bead in the tissue as the "guide star." This target is imaged many times from many different angles to determine the correction that should be applied. While this approach works even in scattering tissues such as the mouse brain -- where the new technique does not -- the process is slow and exposes a sample to a lot of potentially damaging light. To improve images of large samples where the aberration changes quickly with position, researchers needed to speed up the correction process.

Betzig and Wang focused on devising an adaptive optics strategy for new microscopy methods that image dynamic processes non-invasively and at high resolution. Such technologies – such as the Bessel beam plane illumination microscope that Betzig's team developed in 2011 and the simultaneous multiview light sheet microscope developed by Janelia lab head Philipp Keller in 2012 – perform well on cells or small embryos, but image quality degrades in larger samples.

Those microscopes are used exclusively to image transparent samples, narrowing the scope of the problem. Betzig and Wang needed a rapid, non-invasive way to correct for heterogeneities in the composition of cells and tissues, but because it would only be used on transparent tissue, they did not need to compensate for light-scattering.

"If you're in a regime where there is no scattering, then you can do exactly what the astronomers do," Betzig says, explaining that because transparent tissue would not scramble the light waves returned from a guide star, they could detect and measure its wavefront directly.

The team created a guide star by focusing light from the microscope into a glowing point within the sample. Using a technique called two-photon excitation, they could penetrate infrared light deep within the tissue and illuminate a specific point. The wavefront sensor would then determine how the light that returned from this guide star had warped as it passed through the tissue, so that the appropriate correction could be applied.

However, because biological tissue is so heterogeneous, the situation was more complicated. "In biology, unlike astronomy, the wavefront errors are really complex," Betzig says. "As light from the guide star returns to the sensor, the wavefront gets much bumpier in microscopy than in astronomy. If you fix the guide star at a single point, that bumpiness confuses the sensor, so you don't get a good correction." Furthermore, a correction that works at one point won't be effective at a spot elsewhere in the sample that bends light waves in a different way.

The solution to this problem, Betzig and Wang determined, is to scan the guide star over a small region of the sample, instead of parking it in one spot. For the sensor to interpret the information returned from this moving guide star, the light must be made stationary, or "descanned." This is achieved by bouncing the light off the same mirrors that tilt to project the guide star to different points in the specimen. The resulting wavefront is used to generate an average correction over the scanned region.

Betzig explains that a similar strategy is incorporated into adaptive optics that corrects images of patients' retinas, which are distorted when light passes through the eye's cornea and lens. Measuring and correcting those aberrations is complicated by movements of patients' eyes, so ophthalmic imaging uses descan to average out motion-induced errors.

"We combined the descan concept from the ophthalmologists with the laser guide stars of the astronomers, and came up with what amounts to a really good solution for aberrating but non-scattering transparent samples, like the zebrafish," Betzig says.

"We kept on pushing this technology, and it turns out it works," says Wang. "When we compare the image quality before and after correction, it's very different. The corrected image tells a lot of information that biologists want to know."

To image of a large section of tissue, a microscope might generate and compile tens of thousands of images of smaller volumes, each requiring its own adaptive optics correction. So it is essential that those corrections are determined and applied quickly, Betzig says. The new technique handles the task well, updating its corrections in just 14 milliseconds. And when the microscope is used in its two-photon mode, the adaptive optics work automatically. "You don't have to slow down or do anything different," Betzig says. "It's just happening in the background as you're running the microscope."

Jim Keeley | Eurek Alert!
Further information:
http://www.hhmi.org

Further reports about: astronomy images structures zebrafish

More articles from Physics and Astronomy:

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

nachricht New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>