Determining the position of an electrode relative to an insulative cover
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.
1. A method of determining that an instrument is exposed to a conductive medium, comprising:
determining a first position at a first time of a first position element and a second position element both connected to the instrument within a volume;
determining a second position at a second time different than the first time of the first position element and the second position element connected to the instrument within the volume;
comparing the determined first position and the determined second position; and
determining whether map data collected with the instrument is valid on the basis of whether at least one of the first position element and the second position element is insulated from the conductive medium in the volume by an insulator of the instrument.
2. The method of claim 1 , providing an output to a user identifying that at least one of the first position element and the second position element is insulated.
3. The method of claim 2 , wherein the output includes displaying an icon on a display device relative to a map of the volume in a color to illustrate that at least one of the first position or the second position element is sheathed.
4. The method of claim 3 , wherein the significance threshold is a determination that a current observed distance traveled is at least 4.5 times that of an immediately previous distance traveled raised to the fourth power.
5. The method of claim 1 , wherein comparing the determined first position and the determined second position includes comparing a distance traveled by at least one of the first position element and the second position element between two successive time steps;
wherein determining whether at least one of the first position element and the second position element is insulated includes determining that at least one of the first position element and the second position element traveled a distance past a significance threshold between two successive time steps.
6. The method of claim 1 , wherein comparing the determined first position and the determined second position includes determining a first direction traveled of the first position element and a second direction traveled of the second position element.
7. The method of claim 6 , wherein determining whether at least one of the first position element and the second position element is insulated includes determining that the first direction of the first position element and the second direction of the second position element are different to a direction threshold value greater than a dot product of the vectors of the first position element and the second position element.
8. The method of claim 6 , wherein the dot product threshold is about 0.25.
9. The method of claim 1 , wherein comparing the determined first position and the determined second position includes comparing a distance traveled of the first position element and the second position element in a single timestep.
10. The method of claim 9 , wherein determining whether at least one of the first position element and the second position element is insulated includes determining that the compared distance traveled of the first position element and the second position element is significantly different.
11. The method of claim 10 , wherein the significantly different distance is at least three times.
12. The method of claim 1 , wherein comparing the determined first position and the determined second position includes determining whether a distance between the first position element and the second position element on the instrument has changed.
13. The method of claim 12 , wherein determining whether at least one of the first position element and the second position element is insulated includes determining that the distance between the first position element and the second position element has changed by a spacing amount.
14. The method of claim 1 , further comprising:
generating a map of the volume based on the first determined positions and the second determined positions;
wherein the generated map is based on determined positions only when the first position element and the second position element are not within the insulator.
15. A method of determining that an instrument is exposed to a conductive medium, comprising:
positioning the instrument within a volume;
determining a maximum valid position the instrument can have in the volume;
determining whether the determined position of the instrument is past the maximum valid position; and
marking the instrument as sheathed when the instrument is determined to be outside of the maximum valid position.
16. The method of claim 15 , wherein marking the instrument as sheathed includes displaying an icon on a display device in a color to illustrate that at least one of the first position or the second position element is sheathed.
17. The method of claim 15 , further comprising:
generating a map of the volume based on a determined plurality of positions of the instrument;
wherein the generated map is based on positions determined only when the instrument is not marked as sheathed.
18. A method of determining that an instrument is exposed to a conductive medium, comprising:
determining a first position of a first position element connected to the instrument within a volume;
determining a second position of the first position element connected to the instrument within the volume, wherein determining the second position occurs after determining the first position;
comparing at least one of a distance or a position between the determined first position and the determined second position relative to a time step between the determining the first position and determining the second position; and
determining whether a map data collected with the instrument is valid based on the comparison of the first position and the second position.
19. The method of claim 18 ,
wherein comparing at least one of a distance or a position between the determined first position and the determined second position includes determining if the first position element has traveled further between two successive timesteps, than the first position element did between two previous successive timesteps.
20. The method of claim 18 , further comprising:
determining a third position of a second position element, wherein the first position element and the second position element are associated with the instrument;
comparing at least one of the first position or the second position with the third position to determine if at least one of:
the first position element and the second position element have traveled in very different directions,
the first position element and the second position element have traveled different amounts,
the first position element and the second position element have changed positions relative to one another;
wherein determining whether the map data collected with the instrument is valid is further based on the comparing at least one of the first position or the second position with the third position.