Wednesday, April 18, 2012

New Approach for Brain Cancer

Gold Nanoparticles, Three Types of
Imaging Used to Remove Brain Tumors
By Tiffany Kaiser, April 16, 2012

Stanford University researchers can completely remove tumors without harming healthy tissue

Stanford University researchers have combined tiny, laboratory-made nanoparticles with three imaging methods to successfully remove brain tumors entirely.

Sam Gambhir, MD, Ph.D, study leader and professor and chair of radiology at Stanford University School of Medicine, has created tiny nanoparticles that are capable of highlighting tumor tissue both before and during removal with the help of three imaging techniques. This not only helps researchers remove brain tumors completely, but it also allows them to avoid messing with healthy brain tissue.

Brain tumors are not easy to remove. The major issue with removal is making sure to leave as much healthy brain tissue intact as possible. On the other hand, this means that some cancer cells could be left behind that aren't visible to the surgeon's eye, or are embedded in healthy tissue.

Glioblastomas, which are rough-edged tumors with finger-like projections that invade healthy tissues, and micrometastases, which are tiny tumor patches created by the replication of cells from the primary tumor, are two major issues with tumor removal as well.

But now, Gambhir has created a new technique that could help the 14,000 U.S. citizens diagnosed with brain cancer annually. The nanoparticles he developed are small, gold spheres that measure less than about five one-millionths of an inch in diameter. They are coated with an MRI contrast agent called gadolinium, and are injected intravenously to surround tumor tissue, but not healthy tissue.

The blood vessels that sustain a brain tumor are leaky, and the nanoparticles end up bleeding out of these vessels and embedding themselves in tumor tissue. Then, using their enhanced gold cores, they become visible using three different types of imaging.

The first type is the standard magnetic resonance imaging (MRI), which identifies a tumor's boundaries before surgery. However, MRI alone cannot determine the growing tumor's position during surgery.

That's where photoacoustic imaging comes in. This method uses pulses of light that are absorbed by the gold cores in the nanoparticles, and causes the particles to heat up. This creates a detectable ultrasound and produces a three-dimensional image of the tumor. This allows for removal of the tumor during surgery.

The third and final imaging method is called Raman imaging, which causes a layer of the gold nanoparticles to radiate nearly undetectable amounts of light in certain patterns. The gold cores enhance the signals from the Raman imaging so that a microscope can catch them. After the tumor is removed via MRI and photoacoustic imaging, Raman is used to show micrometastases that are left behind in healthy tissue. This allowed for the removal of these projections.

This isn't the first time gold nanoparticles were used to fight cancer. Back in 2008, MIT researchers used gold nanoparticles, which can melt when exposed to certain wavelengths of infrared light, to carry drugs into the body and release them in certain areas of the body.

Source: Science Daily

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