August 14, 2015
Max Planck Institute of Quantum Optics
Physicists have developed a method using laser-generated X-rays
and phase-contrast X-ray tomography to produce three-dimensional images of soft
tissue structures in organisms.
FULL STORY
Physicists from
Ludwig-Maximilians-Universität, the Max Planck Institute of Quantum Optics and
the TU München have developed a method using laser-generated X-rays and
phase-contrast X-ray tomography to produce three-dimensional images of soft
tissue structures in organisms.
With laser light,
physicists in Munich have built a miniature X-ray source. In so doing, the
researchers from the Laboratory of Attosecond Physics of the Max Planck
Institute of Quantum Optics and the Technische Universität München (TUM)
captured three-dimensional images of ultrafine structures in the body of a
living organism for the first time with the help of laser-generated X-rays.
Using light-generated radiation combined with phase-contrast X-ray tomography,
the scientists visualized ultrafine details of a fly measuring just a few
millimeters. Until now, such radiation could only be produced in expensive ring
accelerators measuring several kilometers in diameter. By contrast, the
laser-driven system in combination with phase-contrast X-ray tomography only
requires a university laboratory to view soft tissues. The new imaging method
could make future medical applications more cost-effective and space-efficient
than is possible with today's technologies.
When the physicists
Prof. Stefan Karsch and Prof. Franz Pfeiffer illuminate a tiny fly with X-rays,
the resulting image captures even the finest hairs on the wings of the insect.
The experiment is a pioneering achievement. For the first time, scientists
coupled their technique for generating X-rays from laser pulses with
phase-contrast X-ray tomography to visualize tissues in organisms. The result
is a three-dimensional view of the insect in unprecedented detail.
The X-rays required
were generated by electrons that were accelerated to nearly the speed of light
over a distance of approximately one centimeter by laser pulses lasting around
25 femtoseconds. A femtosecond is one millionth of a billionth of a second. The
laser pulses have a power of approximately 80 terawatts (80 x 1012 watts). By way of comparison: an atomic power plant generates
1,500 megawatts (1.5 x 109 Watt).
First, the laser pulse
ploughs through a plasma consisting of positively charged atomic cores and
their electrons like a ship through water, producing a wake of oscillating
electrons. This electron wave creates a trailing wave-shaped electric field
structure on which the electrons surf and by which they are accelerated in the
process. The particles then start to vibrate, emitting X-rays. Each light pulse
generates an X-ray pulse. The X-rays generated have special properties: They
have a wavelength of approximately 0.1 nanometers, which corresponds to a duration
of only about five femtoseconds, and are spatially coherent, i.e. they appear
to come from a point source.
For the first time,
the researchers combined their laser-driven X-rays with a phase-contrast
imaging method developed by a team headed by Prof. Franz Pfeiffer of the TUM.
Instead of the usual absorption of radiation, they used X-ray refraction to
accurately image the shapes of objects, including soft tissues. For this to
work, the spatial coherence mentioned above is essential.
This laser-based
imaging technique enables the researchers to view structures around one tenth
to one hundredth the diameter of a human hair. Another advantage is the ability
to create three-dimensional images of objects. After each X-ray pulse, meaning
after each frame, the specimen is rotated slightly. For example, about 1,500
individual images were taken of the fly, which were then assembled to form a 3D
data set.
Due to the shortness
of the X-ray pulses, this technique may be used in future to freeze ultrafast
processes on the femtosecond time scale e.g. in molecules -- as if they were
illuminated by a femtosecond flashbulb.
The technology is
particularly interesting for medical applications, as it is able to distinguish
between differences in tissue density. Cancer tissue, for example, is less
dense than healthy tissue. The method therefore opens up the prospect of
detecting tumors that are less than one millimeter in diameter in an early
stage of growth before they spread through the body and exert their lethal effect.
For this purpose, however, researchers must shorten the wavelength of the
X-rays even further in order to penetrate thicker tissue layers.
Story
Source:
The above post is
reprinted from materials provided by Max Planck Institute of Quantum
Optics. The original item was written by Thorsten Naeser.Note: Materials may be
edited for content and length.
Journal
Reference:
1. J. Wenz, S. Schleede, K. Khrennikov, M. Bech,
P. Thibault, M. Heigoldt, F. Pfeiffer, S. Karsch. Quantitative
X-ray phase-contrast microtomography from a compact laser-driven betatron
source.Nature Communications, 2015; 6: 7568 DOI: 10.1038/ncomms8568
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