Registering probe and sheath images on a display
A method, including calculating locations of first sensors attached to a probe that has been inserted into a human patient, and calculating positions of second sensors attached to a sheath via which the probe is inserted. The method also includes calculating respective shapes of the probe and the sheath, to achieve a best fit to the calculated probe sensor locations and sheath sensor positions, while restricting the probe to pass through the sheath. The calculated respective shapes of the probe and the sheath are used to present an image of the sheath aligned with the probe.
1. A method for correcting image misalignment between a sheath and probe inserted into a body, comprising:
calculating locations of first sensors attached to a probe that has been inserted into a human patient;
calculating positions of second sensors attached to a sheath via which the probe is inserted;
calculating respective shapes of the probe and the sheath, to achieve a best fit to the calculated probe sensor locations and sheath sensor positions, while restricting the probe to pass through the sheath, wherein calculating the respective shapes of the probe and the sheath comprises minimizing a cost function to determine a best match between a calculated location and a measured location, the cost function is a weighted combination of intrinsic energy, position error and orientation error and incorporating a slide variable having a value related to a distance between distal ends of the probe and sheath into the cost function;
correcting image misalignment between the sheath and the probe using the calculated respective shapes of the probe and the sheath; and
presenting a corrected image of the sheath accurately aligned with the probe and having no discrepancies in the image of the probe relative to the sheath.
2. The method according to claim 1 , wherein calculating the locations of the first sensors attached to the probe comprises positioning at least one magnetic sensor on the probe, and calculating the locations using a magnetic tracking system.
3. The method according to claim 1 , wherein calculating the positions of the second sensors comprises positioning at least one electrode on the sheath, generating a plurality of currents from the at least one electrode, and calculating the positions in response to the plurality of currents in a current tracking system.
4. The method according to claim 1 , wherein calculating the respective shapes of the probe and the sheath comprises modeling the probe and the sheath as a single shaft.
5. The method according to claim 4 , wherein the first sensors are fixed on the shaft.
6. The method according to claim 4 , wherein the second sensors are free to slide on the shaft.
7. The method according to claim 1 , wherein a minimum value of the slide variable corresponds to a distal tip of the probe being inside the sheath.
8. The method according to claim 1 , wherein a maximum value of the slide variable corresponds to the first sensors and the second sensors being separated by no more than a preset distance.
9. An apparatus for correcting image misalignment between a sheath and probe inserted into a body, comprising:
a probe configured to be inserted into a human patient;
first sensors attached to the probe;
a sheath via which the probe is inserted;
second sensors attached to the sheath; and
a processor, configured to:
calculate locations of the first sensors attached to the probe,
calculate positions of the second sensors attached to the sheath,
calculate respective shapes of the probe and the sheath, to achieve a best fit to the calculated probe sensor locations and sheath sensor positions, while restricting the probe to pass through the sheath, wherein calculating the respective shapes of the probe and the sheath comprises minimizing a cost function to determine a best match between a calculated location and a measured location, the cost function is a weighted combination of intrinsic energy, position error and orientation error and incorporating a slide variable having a value related to a distance between distal ends of the probe and sheath into the cost function, and
correct image misalignment using the calculated respective shapes of the probe and the sheath to present an image of the sheath accurately aligned with the probe and having no discrepancies in the image of a probe relative to a sheath.
10. The apparatus according to claim 9 , wherein calculating the locations of the first sensors attached to the probe comprises positioning at least one magnetic sensor on the probe, and calculating the locations using a magnetic tracking system.
11. The apparatus according to claim 9 , wherein calculating the positions of the second sensors comprises positioning at least one electrode on the sheath, generating a plurality of currents from the at least one electrode, and calculating the positions in response to the plurality of currents in a current tracking system.
12. The apparatus according to claim 9 , wherein calculating the respective shapes of the probe and the sheath comprises modeling the probe and the sheath as a single shaft.
13. The apparatus according to claim 12 , wherein the first sensors are fixed on the shaft.
14. The apparatus according to claim 12 , wherein the second sensors are free to slide on the shaft.
15. The apparatus according to claim 9 , wherein a minimum value of the slide variable corresponds to a distal tip of the probe being inside the sheath.
16. The apparatus according to claim 9 , wherein a maximum value of the slide variable corresponds to the first sensors and the second sensors being separated by no more than a preset distance.