Its an evolution 3D microscope that lets researchers watch cells moving
in the body, revealing everything from the spread of cancer to an embryo
developing.

Called lattice
light-sheet microscopy, technique generates 3-D images as videos. This can
capture live organisms at scales ranging from single molecules to early-stage
embryos. Developed by Eric Betzig,
who just weeks ago won a Nobel chemistry prize. It gives an unprecedented glimpse into the body, and could
revolutionise medicine. A new 3D
microscope can image cells in the body, watching as cancer spreads or an embryo
develops, for instance. The
technique, called lattice light-sheet microscopy, generates extraordinarily
sharp, 3-D images and videos of live organisms at scales ranging from single
molecules to early-stage embryos.
k = 2 / π λ and the y axis is defined as the
axis of the cone,
which has a half-angle of θ This animation reveals a model for
what happens in metastasis, showing cancer cells (green) crawling through a
primary tumor (orange spider web). Light
sheet microscopy involves illuminating the specimen from the side, sweeping a
thin pencil of light, termed a Bessel beam, across the imaging field
geometric-optics
The images from
that section are recorded, the specimen is moved a tiny fraction and the
process repeated. As the 2D sections can then be integrated into a 3D
image. The process is fast enough to record dynamic events within the
sample. To reduce the time taken to scan a section, Betzig had the idea of
dividing the beam into seven parallel parts. Over the last decade, powerful new
microscopes have dramatically sharpened biologists' focus on the molecules that
animate and propel life. The imaging platform developed by Eric Betzig,
who just weeks ago won a Nobel prize, and colleagues at the Howard Hughes
Medical Institute's Janelia Research Campus offers another leap forward for
light microscopy.
Light sheet microscopy involves illuminating the
specimen from the side, sweeping a thin pencil of light, termed a Bessel beam,
across the imaging field. The images from that section are recorded, the specimen
is moved a tiny fraction and the process repeated. The 2D sections can
then be integrated into a 3D image. The process is fast enough to record
dynamic events within the sample. To reduce the time taken to scan a section,
Betzig had the idea of dividing the beam into seven parallel parts. The
techniques have improved biologists' ability to visually track the movements of
cells' tiniest structures – but there were always trade-offs. Imaging
cells at high resolution in three dimensions usually meant sacrificing imaging
speed, as well as subjecting cells to significant light-induced toxicity. 'What
happens is you end up designing the questions you ask around the tools that are
available,' Legant says.

Infections in the
body as the T cell expressing a plasmid (orange) approaching a target cell
expressing a plasma membrane marker fused to tagRFP (blue), as seen from the
side (top) and from the viewpoint of the APC (bottom).
'With the lattice light sheet, the Betzig team can now optimize their
imaging technology for the questions that biologists want to answer.
The new microscope evolved from one Betzig unveiled
in 2011. To apply a super-resolution structured illumination technique
developed at Janelia by the late Mats Gustafsson, Betzig's team moved the
Bessel beam to produce a lattice-like pattern of light. 'With that we not
only get rid of the side lobe stuff, we actually push the resolution a bit
beyond the diffraction limit,' he says.
To reduce the time required to move the Bessel beam
each time a sample was imaged, the developers split the beam into seven
parallel parts, so each travelled just one-seventh of the original
distance. Suddenly, the cells they were imaging seemed healthier.

'What
was shocking to us was that by spreading the energy out across seven beams
instead of one, the phototoxicity went way down,' Betzig says.
'What I learned from that experience is that
while the total dose of light you put on the cell is important, what's far more
important is the instantaneous power that you put on the cell.'Volume
renderings at eight consecutive time points of a single specimen of the
protozoan T. thermophila taken from a 4D data set spanning 1250 time points.
The new microscope operates in two modes. One
uses the principles of structured illumination to create very high-resolution
images. In this case, the final image is created by collecting and processing
multiple images of every plane of the sample.

Imaging can be sped up to capture
faster processes, albeit at lower resolution, with an alternative 'dithered'
mode. Light exposure, and thus damage to cells, is lower in the dithered
mode; in many cases, tagged proteins are naturally replaced by cells before
their signal fades appreciably. 'So there are many cells you could look at
forever in 3D,' Betzig says.
Thirty teams of
biologists have come to Janelia over the past year to find out what the lattice
light sheet microscope can reveal about the systems they study. Chen,
Legant, and Wang have worked with the researchers to optimize the technology
for a variety of experiments. Cells in prophase (left) and anaphase
(right), The graph shows the distribution of growth rates at different
stages of mitosis, averaged across nine to twelve cells.


The microscope is
also fast enough to track the rapid growth and retraction of cytoskeletal
Betzig wants the lattice light sheet to be widely
used, even as technology development continues in his own lab. His team
has built a second microscope for Janelia's Advanced Imaging Center, where it
will be available to visiting scientists free of charge, and deployed two more
of the microscopes to labs at Harvard and the University of California, San
Francisco. In fact, Betzig's team freely shares its designs, providing
detailed instructions to scientists with the expertise to build their own
version of the instrument. Zeiss has licensed the Bessel beam and lattice light
sheet microscopy. 'It takes a huge amount of effort to move from a
successful high-tech prototype to broader adoption of an imaging technology,'
Betzig says. 'Ultimately, commercialization is the crucial last step to
ensuring that these technologies can have broad impact in the research
community.'
components in dividing cells, and gentle enough to monitor the molecular
dynamics of developmental processes that unfold over many hours. 'We know
what the microscope can offer in terms of the imaging, but I think there are a
lot of applications we haven't even thought of yet,' Legant says.
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