WEDNESDAY, April 2 (HealthDay News) -- Stanford University
researchers have developed a new imaging system that illuminates
tumors deep inside the body and lets doctors view details 1,000
times smaller than previously possible.
Raman spectroscopy uses tiny nanoparticles injected into the
body to serve as beacons for lasers, according to a description the
method published in this week's online issue of the
Proceedings of the National Academy of Sciences.
When a laser beam outside the body hits them, the specialized
particles emit signals that can be converted into a visible
indicator of their location in the body. These strong, long-lived
signals can simultaneously transmit information about multiple
molecular targets.
"Usually we can measure one or two things at a time," senior
author Dr. Sanjiv Sam Gambhir, a professor of radiology at
Stanford's School of Medicine, said in a prepared statement. "With
this, we can now likely see 10, 20, 30 things at once."
The new system utilizes the Raman effect, which occurs when
light is shined on an object. The light causes roughly one in 10
million photons to bounce off the object's molecules with an
increase or decrease in energy, called Raman scattering. This forms
a unique measurable pattern, called a spectral fingerprint, for
each type of molecule.
The Stanford research team tested the system on mice, injecting
them with various engineered Raman nanoparticles and then viewing
the anesthetized mice under a special microscope where they were
exposed to laser light. The nanoparticles, for example, would be
"tagged" with different pieces of proteins that sought out
different tumor molecules.
In these experiments, the team spotted targets 1,000 times
smaller than what is viewable with the most precise fluorescence
imaging available. Since the Raman effect lasts indefinitely, as
long as the particles stay in the body they can work as
signals.
Because of these findings, the technique could be useful during
tumor surgery on humans by aiding in the removal of even the most
microscopic bits of cancerous tissue, the researchers said.
Gambhir's lab is further studying these Raman nanoparticles,
including optimizing their size and dosage and evaluating possible
toxicity. A clinical trial using gold nanoparticles in humans in
conjunction with a colonoscopy to indicate early-stage colorectal
cancer is being planned.
More information
The U.S. National Library of Medicine and the National
Institutes of Health has more about
diagnostic imaging techniques.
