Needle Insertion Mechanism for Robot Assisted Biopsy

Doherty, James

Student Work

Needle Insertion Mechanism for Robot Assisted Biopsy

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This project aimed to investigate the use of robotic platforms to increase accuracy and improve patient outcomes in ultrasound-guided biopsy procedures. The specific procedure chosen for investigation was percutaneous renal biopsy because it represents an increasing category of in-office guided procedures performed by a single physician. I present the design of an end effector and procedures for using a generic articulated arm to serve as a collaborative guide for a physician to take ultrasound-guided biopsies of the kidneys. Surgical robotics has obvious application to more significant procedures; the advantages of comprehensive imaging and a sedated patient allow for more automated movement, which increases dexterity precision, and ultimately patient outcomes. However, imagery-intensive partially or fully sedated procedures represent only a minority of medical interventions. Through this project, I intended to investigate the potential for robotic assistance in more minor procedures carried out in-office by an individual physician using less comprehensive imaging tools. In the context of more minor procedures, a robot must serve as a minimally disruptive collaborative tool for its user. The overall system I designed consisted of an end effector mounted on a generic industrial 6DOF articulated arm and an optical tracking system to localize the ultrasound probe. The ultrasound probe is tracked by a single camera mounted in the robot's end effector; an April tag mounted to the probe allows for a transformation matrix to be calculated between the probe and the current position of the robotic arm. Using this transformation along with the kinematics of the robot arm itself, the physician can identify biopsy targets and plan approaches in the 2D image space of the ultrasound probe, and the system can use the inverse kinematic model of the arm to calculate poses and trajectories in the 3d workspace. The robotic arm is a small industrial robot unsuitable for surgical use. I chose the industrial arm due to availability; thus, it lacks many features necessary for collaborative operation. This hardware limitation meant that certain aspects of the system's implementation had to remain theoretical with the ABB industrial arm used. However, the system was designed with the assumption of its hypothetical replacement with an articulated arm more suitable to the application. An external IK and path planning tool is used to calculate safe paths around the workspace, ultimately bringing the robot to a minimum safe distance from the patient from which a physician could safely bring the tool head up to the patient. The end effector is a guide for the needle insertion axis; it is constructed around a set of linear bearings and contains sensors for linear position and on-axis load applied to the biopsy needle. While the actuation of the insertion axis is in the hands of the physician, the axis does implement force control through the use of a pneumatic cylinder with a variable flow rate, the purpose of which is to provide both haptic feedback to the physician and to be able to hold the axis in position if necessary. Overall, this project represents a potential approach for using robotics as a collaborative tool for ultrasound-guided procedures.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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