Around a third of all people worldwide suffer from movement disorders of the digestive tract – in their case the food pulp is moved too quickly or too slowly through the stomach and intestines. In order to be able to diagnose such disorders more easily in the future, researchers have now developed a special sensor capsule. It is swallowed and can measure its exact position using an external magnetic field. The data sent to a smartphone then reveals where things are getting stuck in the digestive tract or where the peristalsis has changed abnormally. The system has already worked well in pigs. If confirmed in humans, it could help diagnose irritable bowel syndrome, gastric paralysis, chronic constipation and other movement disorders.
In the case of movement disorders of the digestive tract, the normal peristalsis of the stomach or intestines is disturbed. This can lead to chronic constipation, colic and constant vomiting. Sometimes inflammation and blockages also inhibit the transport of the chyme or lead to uncontrollable bowel activity, such as in Crohn’s disease or fecal incontinence. However, diagnosing the origin of these ailments is sometimes lengthy and time-consuming. Patients usually have to swallow contrast media and undergo X-ray or magnetic resonance imaging. In some cases, catheters with pressure sensors are also used to check peristalsis. “It would be better if the monitoring of digestive activity could take place under everyday conditions, using non-invasive, mobile methods that are less burdensome for the patient,” explain Saransh Sharma of the California Institute of Technology and his colleagues.
Magnetic field as a location aid
One possibility for such examinations are sensor and video capsules that can be swallowed. They transmit images and measurement data directly from the stomach and intestines and can thus provide clues about the condition of the digestive tract. So far, however, such capsules do not reveal exactly where they are in the stomach or intestines. In addition, they broadcast for a maximum of twelve hours – too short for a complete passage. Movement disorders can therefore hardly be detected with them. To change this, Sharma and his team have now developed a sensor pill that can pinpoint its position in the stomach and intestines with an accuracy of five to ten millimeters. This is made possible by a magnetic field sensor in the capsule in conjunction with an external magnetic field. This is generated by a magnetic coil that can be placed in a backpack, hung from a chair or placed under the bed sheet.
When the sensor capsule, known as iMAG, moves through the digestive tract after swallowing, it measures the magnetic field strength around it. By comparing it with a second sensor attached to the outside of the skin, the system can determine the position of the capsule. “The external reference sensor is important because humans are not always exactly the same distance from the wearable magnetic coil,” explains co-author Khalil Ramadi of New York University. “So without the reference, it’s hard to pinpoint the exact location of the capsule.” The magnetic data measured by the small sensor is sent to a smartphone or other receiver via a radio module that is also integrated in the capsule and processed there together with the data from the reference sensor.
Test in pig successful
Sharma and his team have already tested how well this system works in live pigs, whose digestive system is very similar to ours. As the swallowed sensor capsule migrated through the animal’s stomach and intestines over several days, the research team was able to track its position with an accuracy of five to ten millimeters. The tests have already made it possible to diagnose anomalies such as fecal incontinence based on capsule movements. The sensor capsule was also suitable for mapping the tortuous loops of the intestine: “The successful reconstruction of the intestinal anatomy shows that the capsule can also trace complex and winding paths through the digestive tract,” report Sharma and his team. “These are often difficult to visualize using other imaging methods such as X-rays or computed tomography.”
According to the scientists, the sensor capsule opens up new possibilities for diagnosing movement and transit disorders in the digestive tract. “Quantitative measurement of the transit times in the stomach and intestines is essential to diagnose and treat diseases such as gastric paralysis, irritable stomach, Crohn’s disease, reflux, chronic constipation or fecal incontinence,” explain Sharma and his colleagues. “The real-time readings of the iMAG capsule, which are accurate to the millimeter, could therefore be of considerable clinical importance.” Further tests on pigs and other large mammals are planned as the next steps before a first clinical study can take place in humans.
Source: Saransh Sharma (California Institute of Technology, Pasadena) et al., Nature Electronics, doi: 10.1038/s41928-023-00916-0