Methods and systems for robot-assisted surgery

1. A method for defining a boundary surface for a robotic surgery system, comprising:

identifying at least a portion of an epidermal surface of a patient in an image dataset of an anatomy of the patient, wherein the image dataset comprises at least one of a three-dimensional x-ray CT reconstruction and a three-dimensional MRI dataset;

generating a boundary surface based on the identified epidermal surface, wherein the boundary surface comprises a virtual three-dimensional surface above the epidermal surface of the patient;

registering the image dataset and the boundary surface within a patient coordinate system;

defining a target location below the epidermal surface of the patient; and

controlling a robotic arm to:

maintain an end effector of the robotic arm pointed along a trajectory intersecting with the target location and with the boundary surface;

allow movement of the robotic arm to advance the end effector along the trajectory toward the target location; and

prevent the end effector from crossing the boundary surface, the end effector configured as a cannula configured to allow one or more instruments to removably pass through the cannula to the target location along the trajectory.

2. The method of claim 1 , wherein identifying at least a portion of an epidermal surface comprises applying an image segmentation process to the image dataset.

3. The method of claim 2 , wherein applying an image segmentation process comprises performing a thresholding operation based on radiodensity values associated with different portions of the image dataset.

4. The method of claim 1 , wherein at least a portion of the boundary surface is extrapolated from the at least a portion of the epidermal surface identified in the image dataset.

5. The method of claim 1 , wherein registering the image dataset and the boundary surface comprises correlating the image dataset and the boundary surface with a patient position that is determined using a motion tracking system.

6. The method of claim 5 , wherein controlling the robotic arm comprises determining at least one of a position and an orientation of the robotic arm within the patient coordinate system by tracking one or more marker devices fixed to the robotic arm.

7. The method of claim 1 , wherein at least one of:

(i) controlling the robotic arm comprises using inverse kinematics of the robotic arm to compute a motion path for the robotic arm that avoids crossing the boundary surface,

(ii) controlling the robotic arm comprises:

monitoring a position of the patient using a motion tracking system; and moving the robotic arm to maintain the end effector of the robotic arm outside of the boundary surface in response to a movement of the patient detected by the motion tracking system, and

(iii) the method further comprises modifying at least one of a velocity, acceleration and torque at one or more joints of the robotic arm as a function of proximity to the boundary surface.