University of Houston Cullen College of Engineering


Professor Creating Color-Coded MRIs


Toby Weber

Medical diagnoses from the state of an injured knee to the possible existence of a tumor can hinge on a readout from a magnetic resonance imaging machine (MRI). But these images don’t always provide answers. In black and white and with sometimes-poor focus, they can often be too difficult for even an experienced physician to interpret.

In a project recently funded by the National Science Foundation, Li Sun, associate professor in the Cullen College of Engineering’s Department of Mechanical Engineering, is developing a new class of contrasting agent that will make MRI images easier to read. At the heart of this research are iron nanostructures that will provide something entirely new to MRIs: color.

“Currently, MRIs are in black and white. If you use one of the existing contrasting agents, you only adjust the grayscale, which makes the bright parts of the image brighter and the dark parts darker. These nanostructures will allow you to use different colors to identify each type of tissue,” said Sun.

This new feature will be made possible by the unusual shapes of the iron nanostrucutures Sun is working to mass produce. While most currently available nanostructures are shaped like spheres or rods, these come in less common shapes, like dumbbells or tubes . These shapes make each type of nanostructure respond only to a specific magnetic frequency.

Currently, unusual shapes can be created using lithography, which is essentially a stencil-based fabrication technique. Lithography, however, is expensive and can only create these shapes at the micron level (millionths of a meter) instead of the necessary nanolevel (billionths of a meter). To economically produce structures on the nanoscale, Sun is developing a fabrication method that combines nanotemplates, which are essentially molds for the nanoparticles, and electrochemical synthesis, which introduces a small electrical current into a chemical solution to generate a reaction.

After these nanostructures are produced, they are then coated in proteins that bond only with certain types of cells, such as those that make up a ligament or a specific internal organ.

In a clinical setting, these new contrasting agents will be introduced into a patient, most likely in a liquid to be ingested to through an injection. The patient will then undergo an MRI, with the machine programmed to scan at the magnetic frequencies assigned to the different nanostructures in the patient.

The MRI machine will then assign each type of nanostructure it senses a particular color (nanostructures that bond with a ligament as red, or with bone as blue, for example). All the scans will then be combined into a single, color-coded image that leaves no doubt as to what is being shown.

“Inside your body you can use frequency information to separate these particles,” said Sun. “That’s what gives you a colored picture.”

Producing easier-to-read MRIs is not the only use for these nanostructures, though. The ability to both bond with specific cell types and respond to magnetic fields opens up other uses for them, as well. Individual cells, such as stem cells, could be tagged with the nanostrucutures and then tracked in the human body. And nanostructures that bond with cancer cells could be heated with a high-frequency magnetic field, killing the cancer cells but leaving nearby healthy cells intact, Sun said.

“This is high-risk, high-reward research,” said Sun. “If we’re successful, we’ll not only change how much we can learn from an MRI, but impact a lot of other areas of healthcare and research,” he said.

Sun’s research is supported by a three-year, $300,000 grant from the National Science Foundation. It was originally funded with a seed grant from the Alliance for Nanohealth. Collaborators on this project include assistant professor of mechanical engineering Dong Liu and researchers with the University of Texas Health Science Center.



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