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Raman recalled in medical call
C.V. Raman, (top) a Raman image of a mouse liver after the injection of nanoparticles

Eighty years after C.V. Raman made history from a two-storied building in Bowbazaar in Calcutta, his discovery — called the Raman effect — has been honed to produce a medical tool that will give a better insight into diseases such as cancer.

The Raman effect, which India’s first science Nobel Laureate discovered while at the Indian Association for Cultivation of Science in Calcutta, has been harnessed to create a diagnostic tool which is about 1,000 times more powerful than what’s in use at present. With this tool, you can get the minutest details of a tissue.

Heading the project is a non-resident Indian, Sanjiv Sam Gambhir. The Ambala-born scientist heads the Molecular Imaging Program at Stanford University in the US. Their work was reported online in the Proceedings of the National Academy of Sciences, US, last week.

“Our work is directly dependent on the Raman effect and we are grateful to the original discoveries of Dr Raman,” Gambhir says.

The new tool, called Raman spectroscopy, has been used to get images of normal tissues and tumours in live mice. This is an entirely new way of imaging living subjects, which is not based on anything previously used, says Gambhir. For instance, you can examine a cluster of cells that are cancer hit, and look at the effect of a particular medicine on the diseased cells.

Raman spectroscopy works by detecting photons, or light particles, scattered when a laser beam is focused on molecules. Typically, one in a million of these photons scatters in a different frequency and can be “captured” to give a better understanding of a molecule’s structure and location.

Most techniques in use give a picture of the larger anatomy. This method looks at it from the tissue level and thereby makes it possible to have a closer examination of the body. All you need is a few hundred cells to get a picture.

“The advantage is tremendous. If it works, it could certainly make an early detection of cancer possible,” says Jyotsna Rao, a nuclear medicine specialist at Apollo Gleneagles, Hyderabad.

In their experiments, the Stanford researchers injected tiny nanoparticles into the animal body. These nanoparticles, serving as beacons, emitted signals that could be measured and converted into a visible indicator of their location in the body when a laser light beamed on them from outside.

More importantly, it is for the first time that scientists have found that one image can give multiple dimensions of a particular problem. This they describe as multiplexity. “Usually, we can measure one or two things at a time. With the new technology, we are likely see 10, 20 or 30 things at once,” Gambhir says.

Gambhir compares the Raman spectroscopy to the development of the positron emission tomography (PET), which is a lot more powerful than the common MRI (magnetic resonance imaging). PET was discovered more than two decades ago. Though it is yet to be commonplace in India, it has already become a routine imaging technique in hospitals in the West. “But nobody understood the impact of PET then,” he says.

Moreover, the scientists think that the Raman spectroscopy, once it becomes available, will be a lot cheaper. This is because the imaging agents used, unlike the X-ray, do not depend on radioactivity, explains Gambhir.

But although the technique is highly sensitive, it has one drawback — it has limited depth and can measure up to a few centimetres. “So it is more suited for imaging of the breast, skin or during endoscopy,” he says. The Raman spectroscopy will also take a few years to reach the market.

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