The precision of gastric motility and volume sensing by implanted magnetic sensors

Information about size and movement of stomach has to be acquired for medical research and for reliable control of the implantable active gastric electrical stimulation device. Standard methods were not applicable, thus a simple two-coil AC measuring system has been designed and also successfully tested in vivo with coils stitched to stomach wall of laboratory animals. The achieved measurement range was 10–120 mm with 5% accuracy and 1 mm resolution. In order to suppress significantly the directional dependence of the system, we have built three-axial sensor. The resulting error in distance estimation caused by angular misalignment is below 10% for transmitter coil rotation up to 45°.