Magnetic field probe for determining a disposition of an implantable magnetic marker

Abstract

During both invasive and non-invasive treatments and therapies, inaccuracies in locating the areas of interest mean that not all the area is treated, or the treatment is incomplete. A magnetic field probeis provided that improves determination of a disposition of an implantable magnetic marker, the probe comprising a firstand secondmagnetic sensor, substantially disposed along a transverse axis intersecting the longitudinal axis of the probe. The firstand secondmagnetic sensors are close to the distal endof the probe, and are separated by a minor sensor separation. A thirdmagnetic sensor is provided close to the proximal end, separated by a major sensor separation from the second magnetic sensorclose to the distal end, the major sensor separation being larger than the minor sensor separation; and the ratio of the major sensor separation to the minor sensor separation is in the range 1.25 to 40, preferably in the range 1.6 to 7.6. In this example, the second magnetic sensor is functionally configured and arranged to co-operate with both the first magnetic sensor and the third magnetic sensor. This may be implemented using three or more magnetic sensors. This provides a probe capable of accurately determining one or more dispositions of the implantable magnetic marker when the distal end of the probe is close to the marker and also when it is further away. In particular, including the pair of sensors close to the distal end may increase the sensitivity and accuracy of the probe.