Project B13 - Magnetoelectric 3D Mapping in Gastrointestinal Diagnostics

Gastrointestinal motility refers to the coordinated movement of the digestive tract, allowing for the proper digestion and absorption of nutrients. Several gastrointestinal and neurological diseases are closely associated with abnormal motility especially of the small bowel. Gastrointestinal diseases such as irritable bowel syndrome (IBS), gastroparesis, chronic intestinal pseudo-obstruction, and inflammatory bowel disease (IBD) as well as neurodegenerative disorders such as Parkinson`s disease often exhibit disruptions in gastrointestinal motility which result in symptoms like abdominal pain, bloating, constipation, diarrhea, and malabsorption of nutrients significantly impacting the patient`s quality of life and increasing morbidity and mortality.

Diagnosing and evaluating these gastrointestinal motility disorders pose challenges in clinical practice. Currently, only a limited number of modalities are available to quantify or visualize gastrointestinal functionality. However, the existing diagnostic options have notable limitations in clinical settings: low sensitivity, time-consuming procedures, and high costs. Moreover, most existing methods lack the ability to assess gastrointestinal motility during physical activity, which is important for understanding real-life functioning and to individually adapt treatment strategies.

Current wireless motility capsules (WMC), i.e., ingestible microdevices applied for intestinal diagnoses and treatment of gastrointestinal disorders, allow monitoring of the gastrointestinal tract under real-life conditions without interrupting daily activities by tracking pH, endoluminal pressure and temperature along the gastrointestinal tract. However, these capsules lack a direct assessment of the pill`s location within the human anatomy, so their use for motility diagnostics is very limited. Real-time tracking of WMC in the gastrointestinal tract with high spatial resolution and local accuracy, but without the use of harmful X-rays, is crucial for the diagnosis and treatment of gastrointestinal diseases. Furthermore, current WMC are active and thus require a substantial number of electronic components and a battery resulting in a considerable large size of about 3 cm in length. Thus, swallowing is at least uncomfortable, in many cases even impossible. Especially for patients with pathological situations in the intestine such as strictures, these large diameters of the pills pose a contraindication. As a result, the use of today's WMCs is often not possible in clinically relevant situations.

In the new funding period, the use of ME sensors for the evaluation of gastrointestinal motility is to be investigated in this new project. It will investigate whether the use of a significant smaller (< 5 mm) and battery-free magnetic probes (endoluminal) for the diagnosis of motility in the intestine is feasible, and how its 3D movement in the human body can be detected with magnetoelectric (ME) sensors (superficial/cutaneous). Finally, the question will be answered whether this approach is even suitable for use in diagnostics under everyday conditions with normal physical activity

The magnetic probe to be applied is a MEMS cantilever with an integrated hard magnet at its tip that acts as a narrow-band transmitter when resonantly excited. In vivo excitation can be provided either by excitation electronics integrated into a probe pill or by external excitation coils. Last would result in a completely passive probe, where external coils fixed on the patient’s body could be used as spatial references for the localization. The cantilever-based ME sensors of the CRC are characterized by a high-quality factor, which leads to a particularly high magnetic sensitivity in the sensors’ resonance combined with a detection limit in the pT regime. Once the sensor frequency is matched to the frequency of the magnetic probe, the ME sensor will listen very sensitive to the probe and simultaneously effectively suppresses interference from other sources. By using several such tuned ME sensors at the same time at various selected positions, a precise 3D localization and tracking of the probe should be possible.

In the project, first application studies will be carried out using a torso/intestinal phantom including flow and 3D movement of the probe and will then be transferred into body donors (postmortem) where bowel movement is simulated by continuous flushing of the small intestine with water. The resolution with which a 3D localization and tracking of the magnetic probe with ME sensors can be realized is studied, and whether localization is even possible when the patient is moving. Battery-free operation of the probe is also explored, and a miniaturization < 1 cm³ of the probe is pursued.

In a second study, the applicability of the above-described magnetoelectric 3D mapping in the context of endoscopy is to be investigated. The field of flexible endoscopy has revolutionized the way we diagnose and treat various medical conditions within the human body. Flexible endoscopes, equipped with a light source and a camera, are commonly used in clinical practice to visualize the inner surface of the gastrointestinal tract. However, one significant challenge that clinicians face during endoscopic procedures, especially colonoscopy, is accurately tracking the distal tip of the endoscope within the complex anatomy of the human body to correlate the pathological structures to the correct anatomic location.

So far, only one approach is available on the market for the use in colonoscopy involving an electromagnetic tracking system. These systems utilize sensors embedded in the endoscope and an external electromagnetic field generator to track the position and orientation of the distal tip. This system only visualizes the geometric position of the scope without any relation to anatomical landmarks within the human body. To improve the localisation problem, novel actuators are being fabricated and researched in this project. These actuators will be attached to the distal tip of an endoscope, respective signals will be picked up by ME sensors at the body surface of the patient thereby calculating the precise position and orientation of the scope within the body in a 3D image in relation to anatomical landmarks defined by CT (computed tomography) or MRI (magnetic resonance imaging) scan.

Methods for localization and tracking of the WMC developed in this project are being developed in cooperation with project B2, the integration of the micromagnets is being carried out in cooperation with project Z1. The designated ME sensor concepts applied in this project comprise resonant ME cantilevers, converse-effect sensors and surface acoustic wave sensors.

Involved Researchers

Person		Role
	Prof. Dr. Mark Ellrichmann Medicine Interdisciplinary Endoscopy, Medical Department 1	Project lead
	Prof. Dr. Fabian Lofink Materials Science MEMS-Applications	Project lead

Role within the Collaborative Research Centre

Close cooperation is planned with the following partners:

Project-related Publications