2013 Volume 133 Issue 11 Pages 2075-2081
Nutrition feeding tubes are widely used in hospitals for patients who have difficulty in swallowing. The tube is expected to stay within the stomach, but is sometimes drawn up to the esophagus, which might cause diseases such as pneumonia. Therefore, it is necessary to confirm that the tip of tube exists in the stomach. For safely and easy monitoring of the tip position of the feeding tube within the body, we have developed a method using ac magneto-susceptometry to detect a magnetic marker that was inserted at the tube tip. We analyzed the magnetic field generated by the line current of a rectangular excitation coil and determined the geometry to detect the signal field in a direction perpendicular to the excitation field. The generated ac dipole-field in synchronization with the excitation field was measured as the voltage with a detection coil fixed near the excitation coil. As a result, we could detect the signal down to the order of 1 nT at a depth of 15 cm from the detection coil.