Phase contrast improves
Phase contrast X-ray imaging has enabled
researchers at ETH Zurich, the Paul Scherrer
Institute (PSI) and the Kantonsspital
Baden to perform mammographic imaging
that allows greater precision in the assessment
of breast cancer and its precursors.
The technique could improve biopsy diagnostics
The researchers have succeeded in advancing
an emerging imaging technique
for breast investigations: the X-ray phasecontrast
mammography. The new developments
enable distinguishing between
the different types of microcalcifications
observed in breast tissue and help assigning
them to malignant lesions. The study
is published in “Nature Communications”.
One of the advantages of the phase contrast
technique is its ability to provide images
of high contrast. In the future, this
technique can aid physicians to determine
in a non-invasive way where premalignant
and malignant breast lesions are most likely
located. One goal of breast cancer screening
is to detect (groups of) microcalcifications
in the breast, because these may be associated
with early stages of breast cancer since
they often occur in connection with cancer
cell death. Mammographic screening does
not allow definite conclusions regarding the
underlining conditions that cause calcifications.
Only tissue biopsies that are examined
under the microscope by pathologists can
determine which lesions have caused the
Clinical equipment could be used
for phase contrast imaging
At the PSI, the use of phase contrast for
medical X-ray imaging has been investigated
for several years. X-ray radiation as
used in conventional mammography was
long considered not suitable for phase contrast
procedures because of its incoherence
and mixture of multiple wavelengths.
“The fact that we have now managed to
use these X-ray sources for the phase contrast
method in order to develop a new and
improved imaging method is a considerable step towards application in daily clinical
practice,” says Marco Stampanoni, Professor
at the Institute for Biomedical Engineering at
ETH Zurich and Head of the X-ray Tomography
Group at the PSI. He received an ERC
Consolidator Grant in 2012 to advance the
clinical use of X-ray phase contrast.
In X-ray phase contrast, the extent
in which tissue absorbs X-rays is not the
only quantity that is being measured but
also how tissue deflects radiation laterally
(refraction) and consequently how it influences
the sequence of oscillation peaks
and valleys of X-ray waves – the so-called
phase. Depending on the tissue type, the
overall scattering also varies. To be able
to measure the phase shift, researchers use three very fine grids. The first one is located
directly at the source. It ensures that
the object is illuminated with the required
coherence. Another grid is placed behind
the object and generates an interference
signal that is alysed by a third grid
downstream. Using suitable algorithms,
the researchers calculate the absorption,
phase and scattering properties of the object
from the interference signal. This information
can be used to generate sharp
and high-contrast images that show very
detailed soft tissue properties.
A discovery by Zhentian Wang, PostDoc
in Prof. Stampanoni’s team, initiated this
development: “During my trials with the
phase contrast method, I noticed that there are microcalcifications with different absorption
and scattering signals. That indicated
that the new method might identify different
types of calcifications,” he says. Wang
subsequently reviewed medical literature
and found studies that showed that a certain
type of calcification is more frequently associated
with breast cancer precursors.
“I was persuaded that my observation could
be very interesting for breast cancer diagnosis,
since it could distinguish between the different
types of microcalcifications,” says Wang.
The relevance of the new method was also
confirmed by the physicians who participated
in the study: “We are hopeful that the new
technique, in comparison to standard mammography,
will help to better indicate where a
biopsy must be carried out in the breast,” says
Rahel Kubik, Head of the Institute of Radiology
at the Kantonsspital Baden.
“Still, it is not ready for clinical use as it
needs to be validated in a larger number of cases,” says the radiologist.
Gad Singer, Head of the Institute of
Pathology at the Kantonsspital Baden,
added: “It is very encouraging that the new
method enables a distinction between the
different well-known microscopic types of
Whether the technology will make it to
clinical use also depends on the radiation dose.
“The aim will be to significantly improve
quality, resolution and diagnosis with the
same radiation dose as for a standard mammography
so that breasts can be better examined,”
says Nik Hauser, Head of Gynaecology
and of the Interdisciplinary Breast
Center at the Kantonsspital Baden.
“If we can significantly improve imaging,
this would enable better assessments of tumour
extent prior to surgery. Then the new
method will quickly become important.”
The foundation for a new imaging device
has been laid, says Hauser. “We are
optimistic that we soon will be able to
present further results.”
To date, the researchers have worked
with a prototype. They examined breast
tissue samples, but no patients have been
“One of our next aims will be to develop
a device for clinical use,” says Stampanoni.
Wang Z, Hauser N, Singer G, Trippel M,
Kubik-Huch RA, Schneider CW, Stampanoni
M. Non-invasive classification of
microcalcifications with phase-contrast
X-ray mammography. Nature Communications,
published online 15th May 2014.
New simple setup for
X-ray phase contrast
Imaging method improved by
scrambling X-rays from a new source
X-ray phase-contrast imaging can provide
high-quality images of objects with lower
radiation dose. But until now these images
have been hard to obtain and required
special X-ray sources whose properties are
typically only found at large particle accelerator
facilities. Using a laboratory source
with unprecedented brightness, scientists
from the Technische Universität München
(TUM), the Royal Institute of Technology
in Stockholm (KTH) and University College
London (UCL) have demonstrated a
new approach to get reliable phase contrast
with an extremely simple setup.
X-ray phase-contrast imaging is a method
that uses the refraction of X-rays through
a specimen instead of attenuation resulting
from absorption. The images produced with
this method are often of much higher quality
than those based on absorption. The
scientists in the team of Prof. Franz Pfeiffer, who is Head of Chair of Biomedical Physics
at TUM, are particularly interested in
developing new approaches for biomedical
X-ray imaging and therapy – including Xray
phase-contrast imaging. One main goal
is to make this method available for clinical
applications such as diagnosis of cancer or
osteoporosis in the future.
In their new study, the scientists have
now developed an extremely simple setup
to produce X-ray phase-contrast images.
The solution to many of their difficulties
may seem counter-intuitive: Scramble
the X-rays to give them a random structure.
These speckles, as they are called in
the field, encode a wealth of information
on the sample as they travel through it.
The scrambled X-rays are collected with
a high-resolution X-ray camera, and the
information is then extracted in a postmeasurement
analysis step. High accuracy and new X-ray source
Using their new technique, the researchers
have demonstrated the efficiency and versatility
of their approach.
“From a single measurement, we obtain
an attenuation image, the phase image, but
also a dark-field image,” explains Dr. Irene Zanette, lead author of the publication.
“The phase image can be used to measure
accurately the specimen’s projected thickness.
The dark-field image can be just as
important because it maps structures in the
specimen too small to be resolved, such as
cracks or fibres in materials,” she adds. The source’s high brightness is also key
to these results.
“In the source we used a liquid metal jet
as the X-ray-producing target instead of the
solid targets normally used in laboratory X-ray
sources,” says Tunhe Zhou from KTH Stockholm,
project partner of the TUM. “This
makes it possible to gain the high intensity
needed for phase-contrast imaging without
damaging the X-ray-producing target.”
To obtain all images at once, an algorithm
scans the speckles and analyses the
minute changes in their shape and position
caused by the specimen.
But not all components of the new instrument
are products of the latest cutting-edge
technology. To scramble the X-rays, “we have
found that a simple piece of sandpaper did the job perfectly well”, adds Dr. Zanette.
The researchers are already working
toward the next steps.
“As a single-shot technique, speckle imaging
is a perfect candidate for an efficient
extension to phase-contrast tomography,
which would give a three-dimensional insight
into the microstructure of the investigated
object,” Zanette explains.
I. Zanette, T. Zhou, A. Burvall, U.
Lundström, D. H. Larsson, M. Zdora, P.
Thibault, F. Pfeiffer, and H. M. Hertz.
Speckle-based X-ray Phase-contrast and
Dark-Field Imaging with a Laboratory
Source. Phys. Rev. Lett., 2014.
of upload: 16th Sep 2014