Combining MRI with ultrasound gives a quicker technique for breast
18 November 2013
The Fraunhofer Institute for Biomedical Engineering has
developed a technique that combines MRI with ultrasound scans to make
biopsy taking quicker and less traumatic for breast cancer patients.
Researchers from the Fraunhofer Institute for Biomedical
Engineering IBMT in St Ingbert and the Fraunhofer Institute for
Medical Image Computing MEVIS in Bremen are working together on the
project, called MARIUS (magnetic resonance imaging using ultrasound
— systems and processes for multimodal MR imaging).
To test whether a breast tumour is malignant a tissue sample must
be taken with a fine needle guided by ultrasound imaging. However,
around 30% of tumours are invisible to ultrasound, which requires
MRI imaging to ensure correct needle insertion. This can require
several steps of MRI imaging, removal from the scanner, and needle
insertion before the needle is inserted accurately in the tumour
tissue. This exhausts patients and is also costly, because the
procedure occupies the MRI scanner for a significant period.
The new technique would require just one scan of the patient’s
entire chest at the beginning of the procedure, meaning that the
patient only has to enter the scanner once. The subsequent biopsy is
guided by ultrasound; the system would transform the initial MRI
scan and accurately render it on screen. Doctors would have both the
live ultrasound scan and a corresponding MR image available to guide
the biopsy needle and display exactly where the tumour is located.
The biggest challenge is that the MRI is performed with the patient
lying prone, while during the biopsy she lies on her back. This
change of position alters the shape of the patient’s breast and
shifts the position of the tumour significantly. To track these
changes accurately, ultrasound probes, which resemble ECG
electrodes, are attached to the patient’s skin to provide a
succession of ultrasound images during the MRI scan. This produces
two comparable sets of data from the two imaging techniques.
When the patient undergoes a biopsy in another examination room, the
ultrasound probes remain attached and continually record volume data
and track the changes to the shape of the breast. Special algorithms
analyze these changes and update the MRI scan accordingly. The MR
image changes analogously to the ultrasound scan. When the the
biopsy needle is inserted into the breast tissue, the doctor can see
the reconciled MRI scan along with the ultrasound image on the
screen, greatly improving the accuracy of needle guidance towards
“We’re currently working on an ultrasound device that can be used
within an MRI scanner,” says IBMT project manager Steffen Tretbar.
“These scanners generate strong magnetic fields, and the ultrasound
device must work reliably without affecting the MRI scan.”
Ultrasound probes that can be attached to the body to provide 3D
ultrasound imaging are also being developed by the team as part of
The software developed for the technique is also
completely new. “We’re developing a way to track movements in real
time by means of ultrasound tracking,” explains MEVIS project
manager Matthias Günther. “This recognizes distended structures in
the ultrasound images and tracks their movement. We also need to
collate a wide range of sensor data in real time.” Some of the
sensors gather data about the position and orientation of the
attached ultrasound probes while others track the position of the
The primary objective of MARIUS is to develop ultrasound tracking to
aid breast biopsies. Nevertheless, the developed components could
also be used in other applications. For instance, the MARIUS system
and its movement-tracking software could allow slow imaging
techniques such as MRI or positron emission tomography (PET) to
accurately track the movements of organs that shift even when a
patient is lying still.
Aside from the liver and the kidneys, which change shape and
position during breathing, this includes the heart, whose
contractions also cause motion. Thanks to a technique applied to
reconstruct the image, the heart would appear well defined on MRI
scans instead of blurred.
The technology could also be applied to treatments that use particle
or X-ray beams. For tumours located in or on a moving organ, the new
technology could target the rays so that they follow the movement.
These beams could hit the tumour with more precision than currently
possible and reduce damage to healthy surrounding tissue.