College of Engineering University of Wisconsin-Madison
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BME MONITOR: The Biomedical Engineering Department Newsletter


2007 Newsletter
Featured articles

Experiential learning: BME undergrad design competition stresses real-world challenges

Research may yield improved treatment of diseased lungs

Translational research: Medicine, hand-delivered

Translational research:
Ultrasound waves reflect tissue mechanics

Translational research: 'Balloon' effect:
Blocking aneurysms

Translational research: For ACL repair,
closing the 'gap'

Translational research: Fast, efficient MR imaging

Translational research: Seven new projects launched

Graduate student service award honors Corrine Bahr

Regular Features

Message from the chair

Faculty news:
David Beebe cited as pioneer of miniaturization

In memoriam:
Prof. Paul Bach-y-Rita

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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.

Fast, efficient MR imaging

Walter Block

Walter Block
(View larger image)

Decorative initial cap Mimaging 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.

Comparison of MRI breast images.

Comparison of MRI breast images.
(View larger image)

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.

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Copyright 2007 The Board of Regents of the University of Wisconsin System

Date last modified: Monday,30-July-2007 15:43:00 CDT
Date created: 30-July-2007



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