DETERMINING THE POSITION OF A DEVICE INSIDE BIOLOGICAL TISSUE

摘要

The position of a device such as an endotracheal tube 100 inside biological tissue is detected by a probe 20 which generates a small magnetic field which is disturbed by a magnetically permeable metal band 104 in the device when a narrow end of the probe is positioned immediately adjacent to tissue containing the metal band. The probe 20 comprises a central coil producing an AC magnetic field positioned between two co-axial coils for sensing disturbances in the field. Signals from the sensing coils are amplified, integrated, and sent to respective inputs of a comparator which controls the frequency of an oscillator. Thus the frequency emitted by a speaker 34 and the selection of one of a series of LED's 36 indicate the proximity of the metal band 104.