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A young woman checked into University Hospital Freiburg in
southwestern Germany, complaining of numbness in her arms and signs of
a mild stroke. Relying on conventional diagnostic techniques, local
physicians soon found that the young woman was suffering from a fairly
uncommon condition consisting of a blood clot in the aortic arch, a
part of the body’s main artery, the aorta.
by Douglas Clark
The condition was effectively treated with a standard treatment: a
simple prescription of a blood-thinning agent, such as aspirin or
warfarin. But with the stroke reversed and other symptoms relieved, the
young woman no doubt still had questions and concerns about her health.
Was this a one-time occurrence, and would there be any further medical
consequences? And what had caused this to happen in the first place?
These were just some of the questions that 30-year-old physician and
training radiologist Dr. Alex Frydrychowicz also asked himself about
the woman’s case. Unfortunately, standard diagnostic techniques
currently provide no satisfying explanations for these questions.
That’s why this young doctor has taken it upon himself to find his own
answers that may one day help patients exactly like this young woman.
Hopes of redefining standard diagnostics
Today, circulatory conditions like the one this young woman suffered
from are diagnosed using three-dimensional contrast-enhanced magnetic
resonance (MR) angiography, a process by which dye is added to the
bloodstream to provide contrast between blood and internal structures
of the body. Images are then recorded using magnetic resonance imaging
equipment. This technique very effectively reveals any arterial
blockage, such as the clot in the young woman’s case. Unfortunately, it
doesn’t allow doctors to fully understand the blood-flow conditions
that may have contributed to the blockage, or to look for resulting
flow disturbances that could potentially cause subsequent health
problems.
Dr. Frydrychowicz’s current research is aimed at redefining these
diagnostic standards and, eventually, widening the range of treatment
options. His inspiration to do so, however, didn’t strike him at the
bedside of this female patient; rather, it came to him in a lecture
hall many months earlier.
A year and a half ago, Frydrychowicz attended a talk given by his
now-collaborator, physicist Michael Markl, PhD, who was discussing his
work in cardiac-wall imaging. During his doctoral work at Freiburg
University and post-doctoral work at Stanford University, Markl had
developed cardiac and blood-flow imaging techniques that relied on MR
scans and EnSight visualizations. Frydrychowicz was immediately struck
by the diagnostic potential of Markl’s work.
“I was just sitting there listening to him and had four or five ideas
about what to do with this technique—and at that time he had no
clinical collaborator,” recalls Frydrychowicz.
The two were a perfect match and soon paired up to begin applying the
technique to various arteries. Their work together began with imaging
of the aortic, iliac, and femoral arteries. Their team now boasts 12
members in Freiburg, and they’ve since been joined by two groups of
research partners in Switzerland. The Swiss partners are currently
studying blood-flow in the cerebral arteries, as well as designing
replicas of arteries to simulate blood-flow in the lab.
Images show how researchers at University Hospital Freiburg in southwestern Germany are
using magnetic resonance scans in combination with EnSight
visualizations to analyze blood-flow characteristics, in the hopes of
improving the diagnosis and treatment of life-threatening conditions
such as aneurysms.
Of the growing collaboration, Frydrychowicz says, “It’s rather
fascinating to meet people who have different ideas for this technique
and to be able to work with them—there are a million and a half vessels
to look at.”
Flow visualizations tell a more complete story
Markl’s technique differs from conventional diagnostics methods because
it relies on three-dimensional time-resolved MR scans that integrate
three-directional flow information. This allows the team to study the
size and shape of internal structures, as well as record more-complex
information about blood-flow throughout the artery. The flow data are
then fed into a software program called EnSight, from Computational
Engineering International (CEI), where blood-flow can be visualized and
analyzed in detail.
EnSight has been critical to the team’s work, because without it, the
same level of flow analysis would be impossible. Commenting on
EnSight’s usefulness in his work, Frydrychowicz explains that “Michael
started using EnSight in his work at Stanford, and we continued using
it here, because there is no other program that is comparable.”
The team has also developed its own software to study findings and to
better understand flow conditions’ effects on specific arterial wall
parameters.
“By combining the visualization with our [in-house] software tool and
the ability to extract certain flow features, we can really say that
pressure is changing on the [arterial] walls. And if we can really
understand what is going on in, say, aneurysms, then we can use that
for medical purposes,” says Frydrychowicz.
Getting to the heart of the matter
By linking specific flow conditions with specific medical conditions,
the team is headed towards its goal—and aneurysms are one important
area of focus in their work. Aneurysms form when a weak spot in the
wall of the artery begins to stretch under the pressure of blood
flowing through the artery. As the blood pressure stretches the weak
spot in the artery, the area essentially begins to blow up like a
balloon, forming an aneurysm. The condition is potentially fatal,
because the arterial wall can eventually stretch to the point of
rupturing.
Aneurysms are a specific target for the team because current diagnosis
and care don’t take into consideration the effects of blood-flow
characteristics. Today, for example, specific flow conditions are not
considered when deciding whether surgery is needed to treat the
ailment. Rather, the decision to operate is mainly based on the size of
the aneurysm, and on how quickly it grows. Not all cases, however, fit
neatly into these two parameters. Some patients who are at risk
according to size and growth-rate assessments may not necessarily
benefit from surgery, for example. And avoiding unneeded surgery would
be a lifesaving measure in itself, since the procedures has a risky 5%
mortality rate.
Frydrychowicz is quick to point out specific instances he has seen in
his own research. “I just had a patient who was doing underwater
rugby—a very stressful activity—and he had a 7 to 8cm aneurysm, but
nothing happened. So why is his aneurysm not rupturing or growing,
while others are? In the end, it may have nothing to do with size,”
Frydrychowicz points out. “I think if we follow up on 100 patients
[with aneurysms] we can really say something about it, and that’s where
we’re headed.”
While Dr. Frydrychowicz’s work is still in the research phase, with
approximately 60 adult patients studied so far, he estimates that in
two to three years, the team will have collected and analyzed the data
they need. If successful, the benefits to patients are clear: more
specific diagnoses, and for some patients, the avoidance of not only
costly but very risky surgery.
So, while the young woman mentioned earlier may not be able to benefit
from Dr. Frydrychowicz’s research today, she and other patients may
soon. Until then, she can rest assured that by taking part in the
research study herself, she may well have contributed to the
advancement of medical care, as well as to her own future well-being.
More information
The magic of magnets
As the name implies, radiology once focused on X-rays, but today
magnetic resonance imaging (MRI) is also a diagnostic mainstay. Unlike
X-rays, MRI relies on radiofrequency waves and a powerful magnetic
field to produce images of tissue and internal organs. Learn more about
MRI basics, and read about MRI's development and the technology behind
it.
Understanding aneurysms
Aneurysms most often occur in the arteries, but they can actually occur
in any blood vessel. Read more about aneurysms and the various forms
they take.
Blocking the way
Clotting is critical to health, but the formation of a clot, also known
as a thrombus, in the bloodstream can lead to serious medical
conditions, and even death, because it can block the proper flow of
blood throughout the body. Understand more about how clots form and
the conditions they can lead to.
EnSight and medical research
Read more about how other medical researchers are using EnSight to
better understand the body and develop more-effective medical
treatments.
3D Visualization Used in Engineering Finds a Home in Human Heart Research, linkoping.pdf
N.C. State Researchers Recreate Aerosol Inhalation in Virtual Reality, ncsu-particles.pdf
Research at the University Hospital Freiburg
To read more about the work being done in Dr. Frydrychowicz’s and Dr.
Markl’s department at the University Hospital Freiburg, click here.
For further reading about the medical case of the young woman discussed
in this article, see the article Dr. Frydrychowicz and his colleagues
published in the American Heart Association’s Circulation magazine:
Alex Frydrychowicz, Ernst Weigang, Andreas Harloff, Friedhelm
Beyersdorf, Jürgen Hennig, Mathias Langer, and Michael Markl.
“Time-Resolved 3-Dimensional Magnetic Resonance Velocity Mapping at 3 T
Reveals Drastic Changes in Flow Patterns in a Partially Thrombosed
Aortic Arch.” Circulation 2006 113: e460 - e461.
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