TRANSLATIONAL RESEARCH:
Engineer-clinician collaborations yield innovative,
applied solutions
Funded via the W.H. Coulter
Translational Research Partnership in Biomedical Engineering,
these research projects recently concluded in year one of the
partnership. This partnership fosters early-stage collaborations
between University of Wisconsin biomedical engineering researchers
and practicing physicians that will enable researchers to deliver
their advances more quickly to patients.
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Fast, efficient MR imaging
imaging is kind of like a quarter-mile drag race,”
says Associate Professor Walter
Block. “You load it up with fuel, you use all of the MR signal
right away, and then you have to wait for the MR to refuel.”
In essence, that stop-and-start cycle is why a magnetic
resonance imaging (MRI) session lasts an hour, rather than just minutes.
And after it’s all said and done, it’s why images of such
body parts as the knee or breast still aren’t as useful as they
could be.
A technique called steady-state imaging enables MRI
technicians to maintain higher signal levels over longer intervals,
says Block. But images obtained with this method lack sufficient contrast
between crucial body components such as fat and tissue or bone and cartilage.
The problem is in how—and how quickly—the
MRI machine can encode the image data. “To use these steady-state
mechanisms, you have to be able to complete experiments very quickly—on
the order of 2.5 milliseconds,” he says. “And conventional
raster imaging wastes a lot of time preparing the magnetization and
then returning it to the equilibrium.”
To capture an image, an MR scanner commonly conducts
hundreds to thousands of little “experiments,” or encodings,
that help to make up the big picture. The conventional Cartesian rasterization
method sweeps horizontally to gather MR data. This method can yield
as few as five echoes of the body’s data per second.
In contrast, Block developed a 3-D radial steady-state
imaging technique that enables him to acquire the body’s signals
radially, in a manner that looks like a toy Koosh ball. “With
this, we can get on the order of 250 to 400 echoes per second and reduce
the resolution from 1 millimeter down to one-third to one-half a millimeter,
depending on our magnetic field strength,” he says.
The result, he says, is a great improvement in the
sharpness of MR images and in the contrast between body components like
bone and cartilage.
While MR radial data-acquisition techniques aren’t
totally new, clinicians are hesitant to adopt them because of variations
across MR scanners. So, in addition to his imaging technique, Block
developed per-patient MR scanner calibration schemes, as well as per-patient
methods to measure and correct variable system delays that occur when
the part of the body being imaged isn’t in the center of the MR
scanner magnet.
Now Block is concentrating on implementing his technique
on new, higher-field MR scanner magnets. He and colleagues, including
Radiology Assistant Professor Rick Kijowski
and Associate Professor Frederick Kelcz, are
setting up clinical trials at several hospitals around the country to
learn whether they can replace a half-hour MR exam with one that takes
just five minutes.
Students Jessica Klaers, Ethan Brodsky, Youngkyoo
Jung, Josh Jacobson and Catherine Moran also worked on the project.
