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Nanoparticles Promise Sharp New Imaging

July 29, 2010
Written by: , Filed in: Diagnostic Imaging
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A new nanoparticle technique could lead to imaging so precise it could show a single cell, according to the authors of a study published this week in the journal Nature Communications.

The technique uses magnetic nanoparticles as contrast agents. A pulsing magnetic field shakes the nanoparticles. A photoacoustic image is taken, and then image-processing techniques remove everything from the image except what’s vibrating.

Psychoacoustic imaging involves a pulse of laser light that slightly heats a cell, causing it to vibrate. That produces ultrasonic waves that can be detected through tissue. The researchers said the nanoparticle technique should also apply to other types of imaging.

The procedure potentially solves a problem common to all imaging techniques that do not use radioactive tracers: background noise from surrounding tissues.

“Although the tissues are not nearly as effective at generating a signal as the contrast agent, the quantity of the tissue is much greater than the quantity of the contrast agent, and so the background signal is very high,” said lead researcher Xiaohu Gao, PhD. Dr. Gao, assistant professor of bioengineering at the University of Washington in Seattle, was quoted in a university news release.

He compared the new technique to Tourist Remover photo-editing software, which can delete unwanted people by combining several photos of the same scene and keeping only the parts of the image that aren’t moving.

“We are using a very similar strategy,” Dr. Gao said. “Instead of keeping the stationary parts, we only keep the moving part.

“We use an external magnetic field to shake the particles. Then there’s only one type of particle that will shake at the frequency of our magnetic field, which is our own particle.”

The researchers demonstrated the technique in synthetic tissue. Next will come work with lab animals.

The 30-nanometer particle consists of an iron-oxide magnetic core with a thin gold shell that does not touch the core. The shell absorbs infrared light and could also be used for conducting optical imaging, delivering heat therapy, or attaching a biomolecule that would bond to specific cells.

Coauthor Matthew O’Donnell, PhD, professor of bioengineering and dean of engineering at the University of Washington, said the nanoparticle technique could usher in a new generation of imaging at the molecular level. That, he said, would allow medical assays and cell counts to be done inside the body, without the necessity of a biopsy.

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