Raman goes deep into the body
doi:10.1038/nindia.2008.175 Published online 4 April 2008
Sanjiv Sam Gambhir is hoping that diseases won't remain silent killers for long. He is confident that earlier detection of ailments will make a major difference to the way we handle diagnostics now.
He has reasons to feel strongly about this. Gambhir, born in India and brought up in the U.S., has just co-developed a new tool that can make medical imaging 1000 times sharper at costs far lesser than the conventional Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET).
"Someday earlier detection of diseases through both blood testing and imaging will fundamentally change most of our lives," Gambhir says sitting in his lab at the Stanford University School of Medicine.
His team has developed a new type of imaging system, called Raman spectroscopy, which can illuminate details of tumours and tissues with remarkable precision. They have used it to image both normal tissues and tumours in mice. This is the first time Raman spectroscopy has been used to image deep within the body, by injecting tiny nanoparticles (in this case gold nanoparticles and single-wall carbon nanotubes) as markers.
When laser light is beamed from a source outside the body, these particles emit signals and their location in the body can be pin-pointed from outside. Their effect also lasts indefinitely, so the particles keep emitting signals as long as they are in the body.
"I am very proud to be able to use strategies that have their roots in discoveries from the great Indian scientist Chandrasekhara Venkata Raman. His fundamental discoveries of inelastic light scattering will continue to find many new applications," Gambhir, who moved to the U.S. when he was six, says.
Raman spectroscopy emits signals that are stronger and longer-lived than other available methods, and the type of particles used in this method can transmit information about multiple types of molecular targets simultaneously.
"Our applications of the Raman effect into living subjects for the purpose of imaging are just one of the many potential applications that I think will continue to grow," he adds. The method is usually used to measure one or two things at a time. However, with the new application, it will be possible to see scores of things at one go.
Gambhir says he and his colleagues at Stanford will now try to build better imaging instruments to utilize the Raman effect to study biochemical processes deep within the living body. "We are trying to move into some applications in cancer patients in the next 18 to 24 months."
The immediate applications of the technique would be for small animal imaging of cancer models to help understand basic cancer biology and develop better drugs against cancer.
- Keren, S. et al. Noninvasive molecular imaging of small living subjects using Raman spectroscopy. P. Natl. Acad. Sci. USA doi: 10.1073/pnas.0710575105