Ingestible sensors may help doctors identify gastrointestinal disorders. MIT News

Engineers at the Massachusetts Institute of Technology (MIT) and the California Institute of Technology (Caltech) have demonstrated an ingestible sensor that can monitor its position as it moves through the digestive tract. This may help doctors more easily diagnose gastrointestinal motility disorders such as constipation, gastroesophageal reflux disease, and gastroparesis.

This tiny sensor works by detecting a magnetic field produced by an electromagnetic coil located outside the body. Since the strength of the magnetic field varies with distance from the coil, the sensor position can be calculated based on the magnetic field measurements.

In a new study, researchers have shown that the technology can be used to track sensors as they move through the digestive tract of large animals. Such devices may replace more invasive procedures such as endoscopy currently used to diagnose movement disorders.

“Many people around the world suffer from gastrointestinal dysmotility or hypomotility, and having the ability to monitor gastrointestinal motility without going to the hospital can really help patients understand what is happening. It’s important to understand,” says Associate Professor Giovanni Traverso, who has a PhD in mechanical engineering from the Massachusetts Institute of Technology and was a gastroenterologist at Brigham and Women’s Hospital.

Traverso is one of the senior authors of the new study, along with Azita Emami, Caltech professor of electrical and medical engineering, and Mikhail Shapiro, Caltech professor of chemical engineering and Howard Hughes Medical Institute investigator. Saransh Sharma, a graduate student at Caltech, and Khalil Ramadi SM ’16, PhD ’19, now an assistant professor of bioengineering at New York University, are the lead authors. paperappeared today nature electronics.

magnetic sensor

Affecting approximately 35 million Americans, GI motility disorders can occur in any part of the digestive tract, resulting in the inability of food to pass through it. They are usually diagnosed using nuclear imaging or X-rays, or by inserting a catheter containing a pressure transducer that senses contractions in the digestive tract.

Researchers at the Massachusetts Institute of Technology and Caltech wanted to come up with an alternative that is less invasive and could be performed in patients’ homes. Their idea was to develop a capsule that could be swallowed and send out a signal that would reveal where it was in the digestive tract. This will allow doctors to determine which part of the digestive tract is causing the slowdown and make better decisions about how to treat the patient’s condition.

To achieve that, the researchers took advantage of the fact that the magnetic field produced by an electromagnetic coil weakens in a predictable way as the distance from the coil increases. Their magnetic sensor is small enough to fit in an ingestible capsule, measures the magnetic field around them, and uses that information to calculate their distance from a coil outside the body.

“Because magnetic field gradients uniquely encode spatial locations, these small devices can be designed to sense magnetic fields at their respective locations,” says Sharma. “After the device measures the field, we can back calculate what the device’s position is.”

To precisely locate the device inside the body, the system also includes a second sensor outside the body that acts as a reference point. This sensor can be taped to the skin, and by comparing the location of this sensor to the location of the sensor in the body, researchers can calculate exactly where the ingestible sensor is in the digestive tract.

The ingestible sensor also contains a wireless transmitter that transmits magnetic field readings to a nearby computer or smartphone. The current version of the system is designed to take measurements each time it receives a wireless trigger from your smartphone, but it can also be programmed to take measurements at specific intervals.

“Our system can support localization of multiple devices simultaneously without compromising accuracy. It also has a large field of view, which is essential for human and large animal research,” says Emami.

The current version of the sensor can detect the magnetic field from the electromagnetic coil at a distance of 60 cm or less. The researchers envision the coil being placed in the back of a patient’s backpack or jacket, or even the toilet, so that the ingestible sensor can measure whenever it is within range of the coil.

location tracking

Researchers tested the new system in a large animal model, placing an ingestible capsule in the stomach and monitoring its position for several days as it traveled through the digestive tract.

In the first experiment, the researchers provided two magnetic sensors attached to each other with a small stick so they could know the exact distance between them. They then compared their magnetic field measurements to this known distance and found that the measurements were accurate to a resolution of about 2 mm. This is much higher than the resolution of previously developed magnetic field-based sensors.

The researchers then performed tests using a single ingestible sensor and an external sensor attached to the skin. By measuring the distance from each sensor to the coil, the researchers showed that they could track ingested sensors as they traveled from the stomach to the colon until they were excreted. Researchers compared the accuracy of the strategy to her X-ray measurements and found it to be within 5 to 10 mm.

“Using an external reference sensor helps account for the problem that each time an animal or human is near the coil, it may not be in exactly the same position as the last time. , it’s hard to pinpoint where this pill is, unless you have a consistent reference that’s always in the same place,” Ramadi says.

This kind of monitoring could make it much easier for doctors to pinpoint which part of the digestive tract is causing slow digestion, researchers say. “I think the ability to characterize motility without requiring radiation or the placement of more invasive devices lowers the barriers to which people are evaluated,” Traverso says.

The researchers are now working with collaborators to develop the manufacturing process for the system, further characterize its performance in animals, and hope to eventually test it in human clinical trials.

This study was funded by the National Science Foundation, the Lautenberg Innovation Initiative, and the Heritage Medical Research Institute.