Abstract: A system for use with an implantable flow control device having an adjustable valve and a magnetic device coupled to the valve, the system including a locator tool and an electronic magnetic-based indicator tool. The locator tool includes a processing system and an electronic display. The indicator tool is configured to couple with the locator tool. The indicator tool includes an electronic compass module configured to detect and generate a first set of data based on an orientation of magnetic fields associated with the magnetic device as an indication of the setting of the valve and measure and generate a second set of data based on ambient background magnetic fields. The indicator tool electrically communicates the data to the locator tool. The processing system receives and uses the first and second sets of data generated from the electronic compass module to determine orientation of the magnetic device.

Abstract: A needle apparatus for aligning a needle with a port of an implantable infusion device includes a needle anchoring portion configured to axially fix the apparatus relative to a needle to be inserted into the port. The needle apparatus further includes a port locating portion fixable relative to the needle anchoring portion. The port locating portion includes a port location signal receiver module for receiving a signal from an implantable infusion device regarding the location of the port of the infusion device.

Abstract: A method (400) for scheduling transmissions of global beacons in a body area network (BAN). The BAN includes master nodes and slave nodes where master nodes are arranged in a tree topology. The method comprises propagating ascending global beacons (AGBs) from leaf nodes to a root node of the tree during an ascending period (S420), wherein an AGB includes at least reservations of time slots during a time round; processing AGBs by the root node to determine time slot occupancy information (S430); propagating descending global beacons (DGBs) from the root node to leaf nodes during a descending period (S440), wherein a DGB includes at least reservations of time slots during the time round; and processing DGBs by master nodes other than the root node to update at least the slot occupancy information included in the DGBs (S450).

Abstract: A medical implantable lead of the kind being adapted to be implanted into a human or animal body for monitoring and/or controlling of an organ inside the body has a penetrating fixation element in a distal end, which is adapted to penetrate into the tissue of the organ to fixate the lead such that a distal end of the lead will be in contact with the organ. The lead also has an electrode member to receive and/or transmit electrical signals from and/or to the organ. The lead has in a distal portion a movable member, which is displaceable in an axial direction of the lead and is actuated by a resilient member to be, in an initial state, maximally protruded in a distal direction in relation to the lead and which comprises a radiopaque material for forming of a first indication marker.

Abstract: A system for determining a position of a medical device within a body is provided that reduces positional error by establishing a reference origin closer to the device and/or simplifies the system by integrating components and functions. In one embodiment, a pair of drive electrodes are affixed to opposed surfaces of the body and create a pathway for transmission of current through a position sensor related to the medical device. A pair of reference electrodes proximate the drive electrodes are coupled to a common reference node outputting a reference signal establishing the reference origin. An electronic control unit determines the position of the medical device responsive to the position signal and the reference signal. In another embodiment, a patch affixed to an external surface of the body has a base layer and multiple devices supported on the base layer, electrically isolated from one another, and configured to perform different functions.

Abstract: A method of communicating with an ingestible capsule includes detecting the location of the ingestible capsule, focusing a multi-sensor acoustic array on the ingestible capsule, and communicating an acoustic information exchange with the ingestible capsule via the multi-sensor acoustic array. The ingestible capsule includes a sensor that receives a stimulus inside the gastrointestinal tract of an animal, a bidirectional acoustic information communications module that transmits an acoustic information signal containing information from the sensor, and an acoustically transmissive encapsulation that substantially encloses the sensor and communications module, wherein the acoustically transmissive encapsulation is of ingestible size. The multi-sensor array includes a plurality of acoustic transducers that receive an acoustic signal from a movable device, and a plurality of delays, wherein each delay is coupled to a corresponding acoustic transducer.

Abstract: A medical device incorporating magnetic material is introduced into the body of a patient. A time varying magnetic field is generated externally of the patient's body and which is of sufficient strength to magnetically induce motion in the device, thereby causing the medical device to vibrate within the patient's body. The frequency and the amplitude of the magnetic field oscillations can be continuously varied to control the vibrations induced in the medical device.

Abstract: A fixation device configured to anchor an implantable medical device within a patient includes a temporary biodegradable fixation mechanism configured to secure the device after implantation until the temporary fixation mechanism biodegrades and a chronic fixation mechanism configured to promote tissue growth that secures the device to tissue of the patient before the temporary fixation mechanism biodegrades.

Abstract: A data transmission system connected to a bone implant has an extra-corporeally arranged external transmitting unit an implantable internal first receiving unit adapted to be actuated by the external transmitting unit. An internal transmitting unit is adapted to be coupled and implanted to the implant. A second transmission section is located between the external transmitting unit and the internal first receiving unit, via which the internal transmitting unit is actuated. A second receiving unit and a first transmission section is located between the internal transmitting unit and the second receiving unit. The first transmission section operates with acoustic vibrations or waves.

Abstract: A system and method for metabolic MR imaging of a hyperpolarized agent includes exciting a single metabolic species of a hyperpolarized agent injected into a subject of interest. MR signals are acquired from the excited single metabolic species and an image is reconstructed from the acquired MR signals.

Abstract: A method for displaying a position of a medical device, such as a catheter, during insertion of the medical device into a patient is disclosed. In one example embodiment, the method includes obtaining a first set of detected position data relating to a location marker, then determining a possible first position of the location marker. A first confidence level relating to a match between the first set of detected position data and a first set of predicted position data is assigned. A determination is made whether the first confidence level meets or exceeds a first threshold. If the first confidence level meets or exceeds the first threshold, a determination is then made whether the first position of the location marker is within a first detection zone. If the first position of the location marker is within the first detection zone, the first position of the location marker is displayed.

Abstract: An applicator for delivering brachytherapy includes elongate members movable between collapsed and expanded configurations for delivering brachytherapy within a lumpectomy cavity, a vaginal cavity, or other target region. The elongate members may be expandable into a symmetrical or asymmetrical expanded configuration, e.g., into a generally spherical, pear-shaped, or planar configuration. A system for delivering brachytherapy includes the applicator and an access device for lining and/or dilating a body cavity and/or for receiving the applicator therein. The access device is advanced into a body cavity, an expandable member on the access device is inflated, the applicator is advanced into the access device, and the elongate members are expanded to deliver radiation to the target region.

Abstract: Devices, systems and methods for magnetically assisted agent delivery are included. These devices, systems, and methods make use of a plurality of magnets or magnetic configuration.

Abstract: Systems and methods for locating and defining a target location within a human body. The system can include at least one marker, a probe, and a detector for use in locating the markers by providing information to a surgeon that is representative of changes in proximity between the probe and the marker. The marker can have various detection characteristics, e.g., gamma radiation, that are detectable by an associated probe and detector. The tissue volume is removed by manipulating a cutting tool based on the proximity information provided by the detector, which can be used by the surgeon to define the boundary of the tissue volume. The systems and methods of the invention are particularly useful in locating and then removing a tissue volume or other target location from amorphous, pliable tissue (e.g., breast tissue) or other body parts.

Abstract: A volume of a patient can be mapped with a system operable to identify a plurality of locations and save a plurality of locations of a mapping instrument. The mapping instrument can include one or more electrodes that can sense a voltage that can be correlated to a three dimensional location of the electrode at the time of the sensing or measurement. Therefore, a map of a volume can be determined based upon the sensing of the plurality of points without the use of other imaging devices. An implantable medical device can then be navigated relative to the mapping data.

Abstract: A method for controlling movement of an imaging device in vivo, the method comprising the steps of providing an imaging device having a longitudinal axis and a magnetic component, said device to be inserted into a patient's body; providing a rotating magnetic field outside the patient's body; and advancing the rotating magnetic filed along the patient's body in a desired direction.

Abstract: A magnetically guiding system includes: a capsule medical device that has a magnet provided therein; an information acquiring unit that acquires physical information about magnetic guiding of the capsule medical device; a magnetic field generating unit that generates a magnetic field for magnetically guiding the capsule medical device; and a control unit that sets a magnetic field condition based on the physical information acquired by the information acquiring unit and controls the magnetic field generating unit to generate a magnetic field corresponding to the magnetic field condition.

Abstract: A living body observation system of the invention includes a living body information acquiring apparatus including: a living body information acquiring section; a wireless transmission section; a power source section for supplying driving power for driving the living body information acquiring section and the wireless transmission section; a magnetic field detecting section for outputting a detection result of a magnetic field from outside as an electric signal; and a power supply control section for controlling a supplying state of the driving power based on the electric signal, a magnetic field generating coil, a driving circuit for outputting a drive signal to the magnetic field generating coil, a switch for switching a generation state of a magnetic field, and a timer for outputting a signal for stopping output of the drive signal when a predetermined period has passed following switching from off to on of the switch.

Abstract: Apparatus for driving current in a power circuit of a medical device inserted into a body of a subject includes a power transmitter, which is adapted to generate, in a vicinity of the body, an electromagnetic field having a predetermined frequency capable of inductively driving the current in the power circuit. A passive energy transfer amplifier, having a resonant response at the frequency of the electromagnetic field is placed in proximity to the medical device so as to enhance the current driven in the power circuit by the electromagnetic field.

Abstract: Apparatus for driving current in a power circuit of a medical device inserted into a body of a subject includes a power transmitter, which is adapted to generate, in a vicinity of the body, an electromagnetic field having a predetermined frequency capable of inductively driving the current in the power circuit. A passive energy transfer amplifier, having a resonant response at the frequency of the electromagnetic field is placed in proximity to the medical device so as to enhance the current driven in the power circuit by the electromagnetic field.

Abstract: A wireless network having an architecture that resembles a peer-to-peer network has two types of nodes, a first sender type node and a second receiver/relay type node. The network may be used in a medical instrumentation environment whereby the first type node may be wireless devices that could monitor physical parameters of a patient such as for example wireless oximeters. The second type node are mobile wireless communicators that are adapted to receive the data from the wireless devices if they are within the transmission range of the wireless devices. After an aggregation process involving the received data, each of the node communicators broadcasts or disseminates its most up to date data onto the network. Any other relay communicator node in the network that is within the broadcast range of a broadcasting communicator node would receive the up to date data.

Abstract: A tag and a method of manufacturing a tag having an electronic device, which may be a transponder embedded in binding material, the method including applying a pre-coat of binding material to the transponder, at least partially curing the pre-coat of binding material, locating the resulting pre-coated transponder in further binding material and curing the further binding material. The method may further include applying a vacuum to the binding material and binding material, heating the binding materials and vibrating the binding materials. Apparatus for producing tags is also described and claimed. The tag has a construction which facilitates subcutaneous introduction into a target subject, such as an animal, and helps provide retention of the tag in the inserted position in the target subject.

Abstract: An apparatus and method is related to providing sensing functions that are similar to “human touch” when located in a prosthetic device such as a BION microstimulator that is implanted in a patient. The apparatus includes a power circuit, a communication circuit, and a sensor circuit. The power circuit provides power to the communication circuit and the sensor circuit. The sensor cooperates with the communication circuit, which communicates to the brain. The sensor uses various techniques to detect changes in the environment for the surrounding tissue using criteria such as reflectivity, impedance, conductivity, return signal spectrum, return signal rate, and return signal phase to name a few. For example, the impedance observed by the sensor changes when: the skin tissue is deformed around the sensor, or when the skin is surrounded by water. The sensory information is interpreted by the brain as an analog of touch or feel.

Abstract: An apparatus includes an implant delivery device configured to deliver an implant into a body. The implant delivery device includes a target member, an insertion member and an electronic circuit system. The target member has a distal end portion configured to be disposed within the body adjacent a target location. The insertion member is movably coupled to the target member. A distal end portion of the insertion member is configured to be disposed within the body and selectively coupled to the implant. The electronic circuit system is configured to produce an electronic signal in proportion to a distance between the distal end portion of the target member and the distal end portion of the insertion member when the target member and the insertion member are disposed within the body.

Abstract: A method for influencing and/or detecting magnetic particles in a region of action, magnetic particles and the use of magnetic particles is disclosed, which method comprises the steps of: —introducing magnetic particles into a region of action, —generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in the region of action —changing the position in space of the two sub-zones in the region of action by means of a magnetic drive field so that the magnetization of the magnetic particles change locally, —acquiring signals, which signals depend on the magnetization in the region of action, which magnetization is influenced by the change in the position in space of the first and second sub-zone, wherein the magnetic particles comprise a core region and a shell region, the core region comprising a magnetic material, wherein the magnetic mater

Abstract: A method and apparatus for tracking and illustrating the location of leads positioned within the volume is disclosed. For example, the lead electrodes can be positioned within a heart of a patient that can be tracked over time. The lead electrodes can be tracked with an electrode potential or bioimpedance tracking system to determine the position of the lead electrodes. A method and apparatus is disclosed to analyze the position information for analyzing the selected position of the lead electrodes.

Abstract: A medical-device magnetic guiding position detecting system that can prevent a decrease in the strength of a position detecting magnetic field in an operating area of a medical device is provided. The medical-device magnetic guiding position detecting system includes a medical device that is disposed in the body of a subject and that includes at least one magnet and a circuit including an internal coil, a first magnetic field generating unit for generating a first magnetic field in the operating area of the medical device, position detecting means for detecting an induction magnetic field induced in the internal coil due to the first magnetic field, and at least one pair of opposing coils for generating a second magnetic field that acts on the at least one magnet. The opposing coils forming each of the at least one pair are independently driven.

Abstract: Devices, systems and methods for magnetically assisted agent delivery are included. These devices, systems, and methods make use of a plurality of magnets or magnetic configuration. Two magnets are arranged such that the two magnetic fields overlap and can cancel at the location of the desired node point without canceling around that point.

Abstract: A magnetic force control system for guiding a medical instrument within a body includes: a controlled magnet coupled to the medical instrument; a controller magnet that exerts a magnetic force on the controlled magnet; a magnetically permeable shield, placed between the controlled magnet and the controller magnet, that selectively modulates the magnetic force by rerouting magnetic field lines; and a control system. A method for guiding a medical instrument within a body with magnetic force control includes: providing a controlled magnet coupled to the medical instrument, inserting the controlled magnet and medical instrument into the body, providing a controller magnet outside the body, placing a magnetically permeable shield between the controlled magnet and the controller magnet, applying magnetic force, and selectively modulating the magnetic force with the shield to vary at least one of amplitude and orientation of the magnetic force, thereby guiding the controlled magnet within the body.

Abstract: Some embodiments provide a system for external manipulation of magnetic nanoparticles in vasculature using a remotely placed magnetic field-generating stator. In one aspect, the systems and methods relate to the control of magnetic nanoparticles in a fluid medium using permanent magnet-based or electromagnetic field-generating stator sources. Such a system can be useful for increasing the diffusion of therapeutic agents in a fluid medium, such as a human circulatory system, which can result in substantial clearance of fluid obstructions, such as vascular occlusions, in a circulatory system resulting in increased blood flow.

Abstract: Some embodiments provide a system for external manipulation of magnetic nanoparticles in vasculature using a remotely placed magnetic field-generating stator. In one aspect, the systems and methods relate to the control of magnetic nanoparticles in a fluid medium using permanent magnet-based or electromagnetic field-generating stator sources. Such a system can be useful for increasing the diffusion of therapeutic agents in a fluid medium, such as a human circulatory system, which can result in substantial clearance of fluid obstructions, such as vascular occlusions, in a circulatory system resulting in increased blood flow.

Abstract: A system can be used to navigate or guide an instrument or device into an anatomy of a patient. The navigation can occur with the use of image data acquired of the patient. The image data can be registered to the patient space for navigation. Also, one or more coils can be used for tracking or localization.

Abstract: A system for and method of determining and compensating for the effect of a field influencing object on a field sensor, preferably a coil, that is within a navigational domain. The navigational domain contains navigational magnetic energy and disturbing magnetic energy, and the field influencing object produces the disturbing magnetic energy in response to the navigational magnetic energy. The correction system includes a first transmitter for projecting into the navigational domain field energy in a first waveform sufficient to induce a first signal value in the sensing coil. The system also includes a second transmitter for projecting into the navigational domain field energy in a second waveform sufficient to induce a second signal value in the sensing coil. The system further includes a signal processor for receiving the first signal value and for receiving the second signal value to determine the effect of the electrically conductive object on the field sensor.

Abstract: An electronic implant is designed to detect at least one technical or physiological patient parameter, and has an exhaustible power source. The electronic implant also has an integrated mobile wireless antenna, a low-current mobile wireless modem with a low maximum transmission power, a low-current mobile wireless field-strength-measuring unit, and a control unit connected to the field-strength-measuring unit and to the mobile wireless modem. The control unit triggers access to a mobile wireless network as a function of the transmission power needed for data transmission by the low-current mobile wireless modem, taking into account a mobile wireless field strength value determined by the field-strength-measuring unit, and also taking into account the urgency of the data content to be transmitted. Network access only occurs when the needed transmission power does not exceed a specific maximum value for the particular urgency.

Abstract: A surgical navigation system for navigating a region of a patient that may include a non-invasive dynamic reference frame and/or fiducial marker, sensor tipped instruments, and isolator circuits. The dynamic reference frame may be placed on the patient in a precise location for guiding the instruments. The dynamic reference frames may be fixedly placed on the patient. Also the dynamic reference frames may be placed to allow generally natural movements of soft tissue relative to the dynamic reference frames. Also methods are provided to determine positions of the dynamic reference frames. Anatomical landmarks may be determined intra-operatively and without access to the anatomical structure.

Abstract: A guiding system includes a capsule-type apparatus and a position controlling apparatus. The capsule-type apparatus includes a permanent magnet, which is fixed to a capsule-shaped casing, and is introduced into a subject. The position controlling apparatus includes a relative position controlling mechanism that changes a relative position between a predetermined axis and the subject, and a magnetic field generating mechanism that forms, in a space in which the subject is laid, a magnetic field that includes at least one of a component of a trapping magnetic field that attracts the permanent magnet to the predetermined axis and a component of a gradient magnetic field that attracts the permanent magnet in a direction same as or opposite to a direction in which the relative position is changed.

Abstract: A system including an implantable flow control device and an electronic valve indicator and locator device. The implantable device includes a valve and a magnetic device. The electronic device includes a locator tool, an indicator tool, and an adjustment tool. The indicator tool includes an electronic compass module for measuring an orientation of sensed magnetic fields and a locator tool interface module for electronically communicating sensed magnetic fields to the processing module. The locator tool has a processing module which receives and stores background magnetic field data, receives target magnetic field data when the indicator tool is coupled to the locator tool and positioned above the implanted device, and electronically determines the setting of the valve based on the background magnetic field data and the target magnetic field data. The adjustment tool aligns with the locator tool for modifying the valve setting when magnetically coupled to the implantable device.

Abstract: An implantable soft tissue prosthesis comprising a hollow shell formed of a flexible elastomeric envelope, the shell having an inner volume and an exterior surface, when the inner volume is filled with an elastomeric silicone tubing that is preshaped conforming to the inner volume of the shell, the prosthesis being adapted to be surgically implanted in a human breast.

Abstract: A method and apparatus for magnetically levitating and further steering of an intraluminal device, such as a swallowable microelectronic capsule, for monitoring bodily functions is provided. The method comprises diamagnetically-stabilized levitation, followed by dynamic modification of the external magnetic field producing the said levitation, so that the levitating intraluminal device can be steered in desired direction. The said intraluminal device contains appropriate sensors and reports in real time the forces and pressures exerted on it, as well as its position, so that the levitation and the steering can be dynamically adjusted using appropriate dynamic control of external magnetic devices such as solenoids.

Abstract: The present invention relates to an apparatus (100) for moving a target element (60, 70), which comprises a magnetic material (62, 72) and an active agent (61, 71), through an object, placing said target element (60, 70) at a predetermined position within the object and activating the active agent (61, 71), which apparatus (100) comprises:—selection means comprising a selection field signal generator unit (110) and selection field elements (116), in particular selection field magnets or coils, for generating a magnetic selection field (50) having a pattern in space of its magnetic field strength such that a first sub-zone (52) having a low magnetic field strength and a second sub-zone (54) having a higher magnetic field strength are formed in a field of view (28),—drive means comprising a drive field signal generator unit (130) and drive field coils (136a, 136b, 136c) for changing the position in space of the two sub-zones (52, 54) in the field of view (28) by means of a magnetic drive field so that the magne

Abstract: A method of navigating a medical device in an operating region in a subject. The method includes applying a magnetic field to the operating region and changing the magnetic moment of the medical device by selectively changing a physical condition of at least one magnet element in the medical device to change the orientation of the device with respect to the applied magnetic field.

Abstract: A wireless marker for localizing a target of a patient comprises a casing and a magnetic transponder at least partially received in the casing. The magnetic transponder produces a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation energy. The magnetic transponder also has a magnetic centroid. The marker also comprises an imaging element carried by the casing and/or the magnetic transponder. The imaging element has a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

Abstract: Methods and apparatus are provided for locating the position, preferably in three dimensions, of a sensor by generating magnetic fields which are detected at the sensor. The magnetic fields are generated from a plurality of locations and, in one embodiment of the invention, enable both the orientation and location of a single coil sensor to be determined. The present invention thus finds application in many areas where the use of prior art sensors comprising two or more mutually perpendicular coils is inappropriate.

Abstract: A system and method for locating an internal device separated by a boundary from and in wireless communication with an external device. External device includes an active emitter mechanism wherein a carrier signal is modulated by a location interrogation signal thereby generating an external RF power signal during transmission to the internal device. A secondary antenna of the internal device receives the external RF power signal and induces an RF power signal therein that is converted to a DC induced voltage signal. An indication signal proportional to the intensity of the DC induced voltage signal induced in the secondary antenna is produced by the external device. The process is repeated each time the user moves the external device to a new location proximate the patient's body until a maximum DC induced voltage signal measurement is ascertained representative of a specific area in which the internal device is located.

Abstract: Various methods and devices are provided for reorienting an implantable port. In one embodiment, an implantable port is provided and includes a base adapted to be anchored to tissue, and a housing pivotally mounted on the base and having a septum formed therein and adapted to receive fluid and to provide access to a fluid reservoir formed within the housing. In an exemplary embodiment, the housing can be pivotally mounted to the base using a ball and socket joint. For example, at least one of a distal surface of the housing and a proximal surface of the base is convex, and the other one of the distal surface of the housing and the proximal surface of the base is concave.

Abstract: An arrangement and a method for influencing and/or detecting and/or locating magnetic particles in a region of action include a driver generating a magnetic drive field so that magnetization of the magnetic particles changes. The magnetic particles include first and second magnetic particles. The arrangement further include a receiver having a first receiving probe providing a first signal and a second receiving probe providing a second signal. A detector determines signal features arising from the first particle in the first signal and in the second signal.

Abstract: An arrangement for influencing and/or detecting magnetic particles includes a selector for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in the region of action. A driver changes the position in space of the two sub-zones in the region of action by a magnetic drive field so that the magnetization of the magnetic particles changes locally, and a receiver acquires signals. The signals depend on the magnetization in the region of action, and the magnetization is influenced by the change in the position in space of the first and second sub-zone. The receiver has first and second compensators, each including a compensation coil.

Abstract: A method for influencing and/or detecting magnetic particles in a region of action includes generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in the region of action. The method further includes changing the position in space of the two sub-zones in the region of action by means of a magnetic drive field so that the magnetization of the magnetic particles change locally, and acquiring signals that depend on the magnetization in the region of action. The magnetization is influenced by the change in the position in space of the first and second sub-zone. The magnetic drive vector of the magnetic drive field is rotated in at least one rotation plane.

Abstract: A system and method enables data to be communicated from a position within a human body to an external data device. The system includes a wireless communication module that is electrically coupled to an implant component having a metal surface so that the implant component operates as an antenna in response to the application of a modulated carrier wave being applied to the implant component. The wireless communication module may be coupled to the implant component so that the implant component operates as a monopole or dipole antenna. When the monopole configuration is used, the system further includes a ground plane so that the electromagnetic field emitted by the implant component is reflected and the emitted and reflected fields resemble the emitted field of a dipole antenna for the carrier frequency.

Abstract: A system for navigating a catheter probe through a body cavity includes a sensing coil affixed to a distal end of the probe. Magnetic fields are projected into the body cavity to induce voltage signals in the sensing coil that are sufficient to describe the orientation and position of the probe. A set of magnetic coils each generates a substantially uniform field in a single respective dimension. The orientation angles of the sensing coil may be determined from known values of the unidirectional fields and the measured induced voltage signals. Gradient magnetic fields with components in two dimensions are projected into the body cavity to induce another group of voltage signals. The geometrical intersection of constant voltage surfaces developed by certain gradient fields that produce the measured induced voltage signals is a set of lines on which the catheter is located. The point of intersection of such lines yields the positional coordinates.