A Passive Parallel Master-Slave Mechanism for Magnetic Resonance Imaging-Guided Interventions

Area of Science:

• Medical Robotics
• Interventional Imaging
• Biomedical Engineering

Background:

• Magnetic resonance imaging (MRI)-guided interventions require precise instrument manipulation within the scanner bore.
• Existing robotic systems may introduce actuators near the patient, posing safety concerns.
• Needle guidance in pelvic interventions demands dexterity and intuitive control.

Purpose of the Study:

• To present a passive, parallel master-slave mechanism for MRI-guided pelvic interventions.
• To enable physicians to manipulate instruments from outside the MRI scanner.
• To provide five degrees of freedom for natural needle insertion and steering.

Main Methods:

• The mechanism employs two parallel mechanisms based on the Delta robot architecture.
• A two-axis gimbal is integrated for tool angulation.
• An asymmetric design with sliding prismatic joints forming an isosceles triangle was developed for specific access needs.
• Kinematic analysis, friction modeling, and force transmission analysis were performed.

Main Results:

• The asymmetric design demonstrated an improved dexterity index over the desired workspace compared to equilateral designs.
• Simulations accurately predicted the force transmission behavior of prototypes.
• Prototypes, sized for transperineal prostate interventions, withstood necessary insertion forces.

Conclusions:

• The presented passive master-slave mechanism offers a safe and dexterous solution for MRI-guided pelvic interventions.
• The asymmetric design optimizes performance for the specific constraints of MRI environments.
• This technology facilitates precise needle steering using natural physician movements.