Body-mounted MR-HIFU Robotic System: Mechanical Design and Accuracy Evaluation

Magnetic Resonance Image-Guided High-Intensity Focused Ultrasound (MR-HIFU) is a technology that enables non-invasive MRI-guided ablation of anatomy, such as benign and malignant tumors and pain-causing nerves. In recent years, MR-HIFU has been widely used for various applications, such as treating uterine fibroids, bone metastases, and prostate and brain cancer, among other diseases. However, the current clinical MR-HIFU systems have shortcomings, such as limited or impossible patient positioning options for targets in the extremities, torso, and neck areas. These shortcomings stem from integrating the ultrasound transducer into the MRI table. This study aims to develop a body-mounted, MRI-compatible robotic positioning system for in-bore procedures for treating musculoskeletal lesions in the extremities. The proposed system aims to improve patient positioning options and increase the accuracy of MR-HIFU for these procedures. A 5-DOF (degrees of freedom) body-mounted MRI-compatible robotic system was designed, and its workspace and kinematics were analyzed using MATLAB and Simulink. A mechanical prototype was fabricated using 3D printers and other manufacturing tools using non-ferromagnetic materials. The targeting accuracy of the prototype was measured using an optical tracker in two benchtop studies. The proposed body-mounted MRI-compatible robotic positioning system has the potential to address the limitations of current clinical MR-HIFU body systems. We propose improving patient positioning and accuracy by using a novel vacuum-pad-based mounting system that conforms to the local body shape and stabilizes both the target anatomy and the robot. The system's high modularity also allows using various probes or needle-based MRI-guided percutaneous interventions by removing the HIFU probe and placing a needle guide tool. As opposed to a table-integrated robot, our proposed robot is patient-mounted and can potentially be integrated with different MRI scanners from different manufacturers.