Abstract: A system includes a processor and an output device. The processor is configured to: (a) receive electrical signals indicative of measured positions of (i) one or more chest position sensors attached externally to a chest of a patient, and (ii) one or more back position sensors attached externally to a back of the patient; (b) compare between (i) a first shift between the measured positions and respective predefined positions of the one or more chest position sensors, and (ii) a second shift between the measured positions and respective predefined positions of the one or more back position sensors; and (c) produce an alert in response to detecting a discrepancy between the first and second shifts. The output device is configured to output the alert to a user.

Abstract: A system includes multiple electrically-conductive channels and a processor. The processor is configured to receive, over the electrically-conductive channels, (i) respective first electric currents from a probe, which is within a body of a patient, via a plurality of first electrodes, which are attached to skin of the patient at a region of the body, and (ii) a second electric current from the probe via a second electrode, which is attached to the skin and is connected to one of the channels. The processor is further configured to ascertain respective first electric-current values of the first electric currents and a second electric-current value of the second electric current, and to calculate a position of the probe between the region and the second electrode, based on the first electric-current values and the second electric-current value. Other embodiments are also described.

Abstract: A method includes computing a position of an intrabody probe, which includes one or more electrodes and an electromagnetic sensor, within a heart of a subject, based on an induced signal received from the electromagnetic sensor, ascertaining a set of properties of signals passed between the electrodes and multiple reference electrodes located at respective reference positions, based on the set of properties, deriving an estimated position of the probe from a position map that maps multiple sets of properties to respective estimated positions, in response to a distance between the computed position and the estimated position being greater than a predefined threshold, ascertaining whether an electrocardiographic signal from the subject is saturated, and in response to the electrocardiographic signal not being saturated, updating the position map so as to map the set of properties to the computed position. Other embodiments are also described.

Abstract: A method includes computing a position of an intrabody probe, which includes one or more electrodes and an electromagnetic sensor, within a heart of a subject, based on an induced signal received from the electromagnetic sensor, ascertaining a set of properties of signals passed between the electrodes and multiple reference electrodes located at respective reference positions, based on the set of properties, deriving an estimated position of the probe from a position map that maps multiple sets of properties to respective estimated positions, in response to a distance between the computed position and the estimated position being greater than a predefined threshold, ascertaining whether an electrocardiographic signal from the subject is saturated, and in response to the electrocardiographic signal not being saturated, updating the position map so as to map the set of properties to the computed position. Other embodiments are also described.

Abstract: A method uses patches fixed to a surface of a body, the patches including respective electrodes in contact with the surface, and at least one of the patches configured to output a signal in response to a magnetic field applied to the body. Initially, the signal is processed to compute first magnetic locations and first electrical locations of the at least one of the patches. Subsequently, the signal is processed to compute second magnetic locations and second electrical locations of the at least one of the patches. A first relation is computed between the first magnetic and the first electrical locations, a second relation is computed between the second magnetic and the second electrical locations, and upon detecting a difference between the second and the first relations, a magnetic location correction is computed and then applied to track a position of a magnetic sensor inside the body.

Abstract: A system includes multiple electrically-conductive channels and a processor. The processor is configured to receive, over the electrically-conductive channels, (i) respective first electric currents from a probe, which is within a body of a patient, via a plurality of first electrodes, which are attached to skin of the patient at a region of the body, and (ii) a second electric current from the probe via a second electrode, which is attached to the skin and is connected to one of the channels. The processor is further configured to ascertain respective first electric-current values of the first electric currents and a second electric-current value of the second electric current, and to calculate a position of the probe between the region and the second electrode, based on the first electric-current values and the second electric-current value. Other embodiments are also described.

Abstract: Catheterization is carried out by inserting a sheath into a human patient and moving a catheter having an electrode through the sheath lumen. A variation between a first threshold value and a second threshold value in electrical current through the electrode is identified. Responsively to the variation, it is reported that a portion of the catheter has transitioned between an in-sheath condition and an out-of-sheath condition. The sheath is defined and identified by the historical data of the readings of the magnetic sensor during its movements.

Abstract: A system includes a processor and an output device. The processor is configured to: (a) receive electrical signals indicative of measured positions of (i) one or more chest position sensors attached externally to a chest of a patient, and (ii) one or more back position sensors attached externally to a back of the patient; (b) compare between (i) a first shift between the measured positions and respective predefined positions of the one or more chest position sensors, and (ii) a second shift between the measured positions and respective predefined positions of the one or more back position sensors; and (c) produce an alert in response to detecting a discrepancy between the first and second shifts. The output device is configured to output the alert to a user.

Abstract: Catheterization is carried out by inserting a sheath into a human patient and moving a catheter having an electrode through the sheath lumen. A variation between a first threshold value and a second threshold value in electrical current through the electrode is identified. Responsively to the variation, it is reported that a portion of the catheter has transitioned between an in-sheath condition and an out-of-sheath condition. The sheath is defined and identified by the historical data of the readings of the magnetic sensor during its movements.

Abstract: Catheterization is carried out by inserting a sheath into a human patient and moving a catheter having an electrode through the sheath lumen. A variation between a first threshold value and a second threshold value in electrical current through the electrode is identified. Responsively to the variation, it is reported that a portion of the catheter has transitioned between an in-sheath condition and an out-of-sheath condition. The sheath is defined and identified by the historical data of the readings of the magnetic sensor during its movements.

Abstract: A method, using patches fixed to a surface of a body, the patches including respective electrodes in contact with the surface, and at least one of the patches configured to output a signal in response to a magnetic field applied to the body. Initially, the signal is processed to compute first magnetic locations and first electrical locations of the at least one of the patches. Subsequently, the signal is processed to compute second magnetic locations and second electrical locations of the at least one of the patches. A first relation is computed between the first magnetic and the first electrical locations, a second relation is computed between the second magnetic and the second electrical locations, and upon detecting a difference between the second and the first relations, a magnetic location correction is computed and then applied to track a position of a magnetic sensor inside the body.

Abstract: A method, consisting of receiving respective electrocardiograph (ECG) signals from body-surface electrodes at respective locations in proximity to a heart of a subject. The ECG signals may be processed to generate respective signal parameters characteristic of positions of the body-surface electrodes with respect to the heart, and the respective locations may be adjusted so as to achieve a specified geometrical relationship between the body-surface electrodes and the heart in response to the respective signal parameters.

Abstract: A method, consisting of receiving respective electrocardiograph (ECG) signals from body-surface electrodes at respective locations in proximity to a heart of a subject. The ECG signals may be processed to generate respective signal parameters characteristic of positions of the body-surface electrodes with respect to the heart, and the respective locations may be adjusted so as to achieve a specified geometrical relationship between the body-surface electrodes and the heart in response to the respective signal parameters.