MRI Compatible Robotic Needle Insertion System
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On this page 4 sections
Related concepts 1 concepts
Key Takeaways
- Development of an MR-safe, table-mounted robot that avoids the operational interference associated with traditional pneumatic or piezoelectric systems.
- Implementation of a hybrid serial-parallel robot design that achieves remote needle angulation via elastomeric-sealed fluid cylinders.
- Utilization of a multi-master control architecture allowing both bedside manual inputs and control-room digital signals to synchronize for collaborative tasks.
- Achievement of a 2.25 Hz motion transmission bandwidth for the insertion axis across a 15-foot fluid line.
Summary & Methodology Analysis
The system utilizes a P-RRR-P (prismatic-revolute-revolute-revolute-prismatic) serial-parallel kinematic structure mounted on an arch fixed to the MRI table. To maintain safety in the magnetic field, the researchers opted for fluid-based actuation instead of electromagnetic or metallic components. The remote needle angulation is managed by long-stroke elastomeric-sealed fluid cylinders, while the needle insertion axis relies on a low-friction graphite piston to facilitate force feedback. The architecture enforces a fixed center-of-motion at the skin entry point using a spherical pivot point to ensure precise guidance during the procedure.
The control stack features a multi-master approach that aggregates fluid volume inputs from a bedside manual joystick and a control-room digital motorized master. This allows operators to perform collaborative tasks effectively. Because the elastomeric seals introduce stiction, the system implements feedforward high-frequency dithering, a technique of adding small, controlled oscillations to a signal to prevent static friction from locking the mechanism, to ensure the reference waveform is accurately tracked. The overall system is designed to meet the safety requirements defined in ASTM F2503.
Despite the mechanical design, the paper identifies several performance limitations. The elastomeric-sealed actuators are susceptible to a dead-zone that impacts precision during small displacements. Additionally, the robot experiences a reduced reachable workspace when handling oblique needle entry paths. The inherent friction within the actuators presents a challenge for force transparency, which is a critical metric for maintaining the fidelity of tactile feedback to the operator. The paper does not specify the latency impact of the dither signal beyond the reported 2.25 Hz bandwidth.
Interactive System Flowchart
Cross-Examination & FAQs
A deeper dive clarifying mechanics, constraints, and baseline evaluations.
Q1. What is the primary purpose of this robot?
The robot is designed to perform percutaneous needle interventions within closed-bore MRI scanners.
Q2. Why is this system better than previous approaches?
It avoids the bulk and operational interference found in traditional pneumatic, piezoelectric, or ultrasonic systems.
Q3. Is this device safe for MRI environments?
Yes, it is designed as an MR-safe system following the standards defined in ASTM F2503.
Q4. How is the needle movement controlled?
The system uses a combination of elastomeric-sealed fluid cylinders for 2-DoF angulation and a graphite piston for 1-DoF needle insertion.
Q5. How does the system handle the friction of the seals?
It uses feedforward high-frequency dithering to the reference waveform to overcome stiction in the elastomeric actuators.
Q6. What is the bandwidth of the insertion axis?
The motion transmission bandwidth is 2.25 Hz through a 15-foot fluid line.
Q7. Does the system allow for multiple operators?
Yes, it uses a multi-master control architecture to sum fluid volume inputs from both a bedside manual joystick and a control-room digital motorized master.
Q8. Are there any known precision issues with the actuators?
Yes, the elastomeric-sealed actuators exhibit a dead-zone that can affect small displacement precision.
Q9. Does the robotic arm have full mobility for all needle paths?
No, the reachable workspace is reduced for oblique needle entry paths.