Mammogram results may signal the presence of breast cancer tumors, but doctors still have to sample and test actual tissue to be sure. The trick is to remove and check as little as possible of the right tissue.
Likewise, in performing surgery to remove tumors, doctors want to make certain they get all of the problem tissue and that can mean removing areas around the tumor, some of it good tissue, just to be sure.
University of Illinois researchers are developing a new imaging method using tiny magnetic nanoparticles and laser light that may make such procedures more precise in the future.
Eventually, the technique could eliminate the need to take tissue samples at all to perform biopsies, although proving that is still many years away, UI Professor Stephen Boppart said recently.
"It allows the physician to get a better idea of where should I take out that tissue instead of randomly get a little here and a little there," said Boppart, a UI professor of electrical and computer engineering and bioengineering who's also a medical doctor.
The technique developed by Boppart, post-doctoral researcher Amy Oldenburg and colleagues uses special nanoparticles – a nanometer is a billionth of a meter – of iron oxide as "contrast agents" designed to yield pictures of tissue at a cellular and even subcellular level.
The particles, which can be introduced by injection or intravenously, travel through the bloodstream and may be treated to make them drop out and attach when they encounter tumor tissue.
"We can modify them so they go to specific tumor cells," said Boppart, who is developing the technique with UI chemistry Professor Kenneth Suslick, speech and hearing science Professor Kenneth Watkin and Andrew Webb, a former UI scientist now at Penn State.
He said the UI researchers are working on chemically attaching small molecules to the particles that naturally bind to certain proteins, called receptors, found in tumors but not in healthy tissue.
Once the particles are introduced, a magnet is run over the area to make the particles modulate, or move back and forth.
The researchers then shine a laser light on the area, which penetrates the tissue – think of a flashlight shining through the palm of your hand – and scatters off the moving particles, creating signals that can be collected and turned into a highly detailed image.
Modulating the particles allows researchers to separate the area where they're located cleanly from the background. Boppart likened the effect to someone waving their hand in the air to get attention as opposed to simply raising it.
"We have a dynamic agent, something that's moving," he said. "We can get a much higher sensitivity of detection for that reason. We have very high resolution."
Boppart said the particles already are approved for use as contrast agents in magnetic resonance imaging, or MRI, and should present no danger to patients. The body will expel them naturally.
"Iron is very common in the body," he said. "They're certainly biocompatible and the concentrations that are used are very low."
The National Institutes of Health recently funded the work with $1.7 million over the next four years as part of a program designed to accelerate medical discoveries. Boppart said that grant will pay for further developing the nanoparticles on the way to using the imaging technique in conjunction with biopsies and as a guide in surgical procedures.
Boppart also is working with surgeons at Carle Foundation Hospital, imaging tissue removed for biopsy at this point to show the quality of results the technique can yield. In the future, the plan is to have Carle doctors actually use the technique themselves in surgery.