Systems and methods for instrument buckling detection

1. A method comprising:

measuring, with a sensor fixed to an elongated flexible instrument and while a distal end of the elongate flexible instrument is internal to a patient, a shape of a section of the elongated flexible instrument disposed within a shape constraint device configured to remain external to the patient;

comparing the measured shape of the section of the elongated flexible instrument to an expected shape; and

determining whether the measured shape of the section of the elongated flexible instrument differs from the expected shape by a predefined threshold.

2. The method of claim 1 , wherein the shape of the section of the elongated flexible instrument is measured between an anatomical entryway and a proximal instrument portion.

3. The method of claim 1 , wherein the expected shape is based upon the shape constraint device.

4. The method of claim 1 , wherein the expected shape is an expected shape volume.

5. The method of claim 4 , wherein the expected shape volume comprises one of: a substantially straight tubular volume or an arced tubular volume.

6. The method of claim 1 , wherein determining whether the measured shape of the section of the elongated flexible instrument differs from the expected shape comprises determining whether a proximal portion of the section deviates from or along a reference axis more than a distal portion of the section deviates from or along the reference axis.

7. The method of claim 1 , wherein determining whether the measured shape of the section of the elongated flexible instrument differs from the expected shape comprises determining whether a portion of the section moves in a predefined direction.

8. The method of claim 1 , wherein the measuring the shape of the section of the elongated flexible instrument includes measuring a maximum curvature of the elongated flexible instrument.

9. The method of claim 1 , wherein the measuring the shape of the section of the elongated flexible instrument includes determining a total cumulative bend angle for the section.

10. The method of claim 1 , wherein a measured length of the section of the elongated flexible instrument being measured changes in real time as the elongated flexible instrument enters or retracts from an anatomical entryway.

11. The method of claim 1 , further comprising, providing a notification in response to determining that the measured shape of the section of the elongated flexible instrument differs from the expected shape.

12. The method of claim 1 , further comprising, in response to determining that the measured shape of the section of the elongated flexible instrument differs from the expected shape, putting the elongated flexible instrument in a safe state.

13. The method of claim 1 , further comprising, in response to determining that the measured shape of the section of the elongated flexible instrument differs from the expected shape, automatically manipulating the elongated flexible instrument until a portion of the section is within the predefined threshold.

14. A method comprising:

measuring, with a sensor secured to an elongated flexible instrument and while a distal end of the elongate flexible instrument is internal to a patient, a shape of a section of the elongated flexible instrument disposed within a shape constraint device configured to remain external to the patient;

comparing the measured shape of the section of the elongated flexible instrument to an expected shape;

determining whether the measured shape of the section of the elongated flexible instrument differs from the expected shape by a predefined threshold; and

contracting the shape constraint device by advancing the elongated flexible instrument.

15. A system comprising:

an instrument drive system;

an elongated flexible instrument connected to the instrument drive system;

a sensor fixed to the elongated flexible instrument and configured to measure a shape of at least a portion of the elongated flexible instrument between the instrument drive system and a distal end of the elongated flexible instrument;

a shape constraint mechanism extending between an entry port and the instrument drive system to constrain a section of the elongated flexible instrument, the entry port being disposed distally of the shape constraint mechanism; and

a control system configured to manipulate the elongated flexible instrument using the instrument drive system and determine whether the section of the elongated flexible instrument within the shape constraint mechanism buckles beyond a predefined threshold.

16. The system of claim 15 , wherein to determine whether the section of the elongated flexible instrument within the shape constraint mechanism buckles beyond the predefined threshold, the control system is further configured to determine whether the section extends outside a boundary associated with the shape constraint mechanism.

17. The system of claim 15 , wherein to determine whether the section of the elongated flexible instrument within the shape constraint mechanism buckles beyond the predefined threshold, the control system is further configured to determine whether a proximal portion of the section deviates from a reference axis more than a distal portion of the section deviates from the reference axis.

18. The system of claim 15 , wherein to determine whether the section of the elongated flexible instrument within the shape constraint mechanism buckles beyond the predefined threshold, the control system is further configured to determine whether a portion of the section moves in a predefined direction away from a longitudinal axis of the shape constraint mechanism.

19. The system of claim 15 , wherein the sensor comprises at least one of: a fiber-optic shape sensor, an electromagnetic sensor, optical markings, or a video camera.

20. The system of claim 15 , wherein a constrained length of the section of the elongated flexible instrument being constrained changes in real time as the elongated flexible instrument moves.