Abstract: An apparatus for producing magnetic field gradients includes (a) a first planar electromagnet coil set configured to produce a first magnetic field gradient with respect to a first axis, (b) a second planar electromagnet coil set configured to produce a second magnetic field gradient with respect to a second axis that is orthogonal to the first axis, (c) a third planar electromagnet coil set configured to produce a third magnetic field gradient with respect to a third axis that is orthogonal to the first and second axes, and (d) a controller configured to selectively provide power to the first, second, and/or third electromagnet coil sets to sequentially produce a localization magnetic field gradient with respect to each of the first, second, and third axes, at least a portion of each localization magnetic field gradient having a monotonically-varying magnetic field magnitude along a respective axis.

Abstract: A method for in-vivo monitoring of a target internal volume of a mammal that includes: (a) placing the target internal volume proximal to a three-dimensional magnetic field generator; (b) generating first, second, and third magnetic field gradients along respective first, second, and third axes that are mutually orthogonal; (c) measuring first, second, and third magnetic fields with a three-dimensional magnetic sensor disposed in an ingestible capsule, the ingestible capsule disposed in the target internal volume; (d) with a controller in electrical communication with the three-dimensional magnetic sensor, generating a magnetic sensor output signal that encodes a measurement of the first, second, and third magnetic fields; (e) broadcasting the magnetic sensor output signal from an antenna disposed in the ingestible capsule, and (f) receiving the magnetic sensor output signal with a receiver. The received magnetic field data can be used to determine the three-dimensional position of the ingestible capsule.