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Triple-Imaging Nanoparticles Aid Brain Surgery

April 16, 2012
Written by: , Filed in: Neuroradiology
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Nanoparticles optimized for three different kinds of imaging can sharply increase the accuracy of surgical brain tumor removal.

So indicates a study published online Sunday in Nature Medicine. The study used gold nanoparticles coated with gadolinium MRI contrast agent and with materials that emit Raman signals. Senior author Sanjiv “Sam” Gambhir, MD, PhD, led the study team, and his Stanford University School of Medicine lab created the particles.

Dr. Gambhir is professor and chair of radiology, the Virginia and D. K. Ludwig professor for clinical investigation in cancer research, and director of the Molecular Imaging Program at Stanford.

He said the new nanoparticles should increase surgical precision especially in the removal of glioblastomas, the most aggressive form of brain tumor. About 3,000 cases are diagnosed annually in the United States. The median survival time without treatment is three months, but surgical removal typically prolongs a patient’s life by less than a year. Dr. Gambhir explained:

With brain tumors, surgeons don’t have the luxury of removing large amounts of surrounding normal brain tissue to be sure no cancer cells are left. You clearly have to leave as much of the healthy brain intact as you possibly can.

Glioblastomas send tiny, fingerlike projections into healthy tissues, following blood vessels and nerve tracts. They also can generate micrometastases, invisible to the naked eye, in nearby healthy tissue. So surgeons need some way to exactly delineate the boundaries between tumors and healthy tissue.

That’s where the triple-threat imaging nanoparticles come in. They’re injected into the bloodstream. “The tiny blood vessels that feed a brain tumor are leaky, so we hoped that the spheres would bleed out of these vessels and lodge in nearby tumor material,” Dr. Gambhir said.

In mice, they did exactly that. So surgeons used MRI to map the tumor preoperatively. Then photoacoustic imaging—in which pulses of light are absorbed by the nanoparticles’ gold cores, heat up slightly, and produce detectable ultrasound signals—guided in real time the removal of the bulk of the tumor.

Finally, Raman imaging (minuscule amounts of light given off in a signature pattern by part of the nanoparticle coating, amplified by the particles’ gold cores, and detected by a special microscope) showed residual bits of the tumor that might otherwise have been missed. Dr. Gambhir summed up:

Now we can learn the tumor’s extent before we go into the operating room, be guided with molecular precision during the excision procedure itself, and then immediately afterward be able to ‘see’ once-invisible residual tumor material and take that out too.

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One Response to “Triple-Imaging Nanoparticles Aid Brain Surgery”

  1. Radiology Daily»AlertArchive » Triple-Imaging Nanoparticles Aid … - All about nano technology - NanoTechno.org on April 16th, 2012 at 12:04 pm

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