Sensor capsule reveals digestive disorders

Signals from the intestines and the like: A novel sensor capsule could help to diagnose irritable stomachs, intestinal blockages, constipation and other movement disorders in the digestive tract. The pill, which is equipped with a magnetic sensor, transmits measurement data to a smartphone or another computer and thus reveals where the food is moving through the body too quickly or too slowly. The pill could be used at home and thus replaces expensive stationary X-ray tests.

Around a third of all people worldwide suffer from temporary or permanent movement disorders of the digestive tract. In them, the normal peristalsis of the stomach or intestines is disturbed or the passage is narrowed and blocked. As a result, they suffer from reflux, irritable stomach, colic, chronic constipation or faecal incontinence. However, diagnosing these conditions is sometimes tedious and time-consuming. Patients usually have to swallow contrast media and have X-rays or magnetic resonance imaging performed. In some cases, catheters with pressure sensors are used to check peristalsis.

measurement from inside

“It would be better if the monitoring of digestive activity could take place under real-life 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. Although there are already sensor and video capsules that can be swallowed, these 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.

A sensor pill that can locate its exact position in the stomach and intestines with an accuracy of five to ten millimeters could now provide a remedy. This is made possible by measuring an external magnetic field. This is generated by a magnetic coil which the patient can carry around in a backpack, but which can also be hung on a chair or placed under the bed sheet. This field is measured by a tiny sensor built into the swallowable capsule.

Magnetic data for position determination

As this sensor capsule moves through the digestive tract, it continuously 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 from New York University. “Without the reference, it’s therefore difficult to determine the exact position 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. The swallowed capsule measures its position either at previously defined time intervals or whenever it receives an external command.

Real-time data from the pig intestine

Sharma and his team first 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.” Sensors based on radio frequency transmitters, on the other hand, have the problem that the radio waves are partially absorbed by the body tissue and their resolution is low.

Help with diagnosis and therapy

According to the scientists, the sensor capsule, which they have dubbed iMAG, 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.”

Also positive: The technology built into the capsule and the accessories is commercially available and inexpensive. According to the team, the sensor capsules are well suited for mass production. Further tests on pigs and other large mammals are planned as the next steps before a first clinical study can take place in humans. (Nature Electronics, 2023; doi: 10.1038/s41928-023-00916-0 )

Source: Massachusetts Institute of Technology