Smart Needles to Make Injections Safer

A needle embedded with an optical sensor could make medical procedures like epidurals much safer. (Image courtesy of Medisight.)

We’ve all been on the receiving end of a medical needle. Some of us shut our eyes and pretend it isn’t happening, some of us turn our heads off to the side, and others stoically insist on watching the procedure. All of us, however, assume the needle will hit the right target.

While this assumption is correct the majority of the time, certain procedures like epidurals require doctors to precisely guide needles through multiple layers of tissue. This leaves room for error, and missing the desired target can have consequences ranging from reduced effectiveness all the way to stroke or paralysis.

To mitigate these risks, a team of researchers from MIT and Massachusetts General Hospital (MGH) has now developed an optical sensor that can be embedded into an epidural needle. This sensor will help doctors guide the needle into the correct location, eliminating any need for guesswork and making operations safer.

Raman Spectroscopy

The sensor employs a technique called Raman spectroscopy to determine chemical properties of tissue. This technique uses laser light to measure energy shifts caused by molecular vibrations. The returned laser light can identify different molecules by their chemical fingerprint—the unique pattern of energy shifts they produce.

The measured properties, including the concentrations of albumin, actin, collagen, triolein and phosphatidylcholine, are used to identify different layers of tissue in the body. In the case of an epidural, the needle must pass through five distinct layers of tissue before reaching the epidural space: skin, fat, supraspinous ligament, interspinous ligament and ligamentum flavum. With exact knowledge of which tissue the needle tip is in, doctors can know exactly when it’s in the correct spot.

Other sensors tested by the team could only distinguish some of the eight layers surrounding the epidural space. The Raman spectroscopy sensor, however, distinguishes all eight layers with 100 percent accuracy.

The eight types of tissue doctors must navigate when injecting a needle into the epidural space. The Raman spectroscopy sensor can accurately distinguish them all.(Image courtesy of Medisight.)

“The era of blind procedures is one we need to move away from, because we’re very interested in improving safety and quality,” said Jeanine Wiener-Kronish, chief of Anesthesia at MGH. “This sensor could allow us to take a fairly blind procedure and be able to get more information about where the needle is.”

While the advantages of the sensor are clear, don’t expect to see one at your next doctor appointment. The sensor has only been tested on pig tissue and has yet to be tested in human patients. Furthermore, the sensor is still too large to fit in most epidural needles, so the team is planning to reduce the diameter from 2 mm down to just 0.5.

The team from MIT and MGH has started a company called Medisight Corp. to take its technology further. To learn more about the team and its sensor, visit Medisight's website.

For more news at the intersection of engineering and medicine, check out the five 3D printing technologies on every bioengineer’s wish list.