Reconfigurable Fiducial-Integrated Modular Needle Driver for MRI-Guided Percutaneous Interventions

摘要

Needle-based interventions are pervasive treatments in Minimally Invasive Surgery (MIS), which can be used in a number of diagnostic and therapeutic procedures, including biopsy, radioactive seed implantation, delivery of therapeutic agents, and thermal therapy. Intra-operative medical imaging promises high precision and improved workflow for interventional procedures, by offering intuitive anatomic structure of the tissue in situ. Magnetic Resonance Image (MRI) can provide high quality, real time, high soft tissue contrast imaging without ionizing radiation, and therefore is an ideal guidance tool for image-guided therapy (IGT). To date, a variety of robotic devices for image-guided interventional procedures have been developed such as these described in [1–4]. However, most of these devices are driven manually or by the actuators that are not compatible with MRI, and thus not suitable for MRI-guided therapy.In this study, we designed and evaluated a compact, reconfigurable MRI-compatible needle driver, using modular design approach, to support various needle-based interventions (e.g. straight needle insertion, asymmetric tip-based needle steering, and concentric-tube needle deployment). Integrated with an imaging coordinate registration fiducial frame concentric with the needle, the needle driver could be visualized and localized in the image space directly, and therefore enable the real-time MRI-guided percutaneous interventions with high precision and reliability.A modular design approach is utilized in the design of the needle driver to enable universal and multipurpose needle intervention. This driver is designed to couple with an existing base platform described in [5], or a variety of other existing and yet to be developed platforms such as [6]. The needle driver consists of multiple actuation units, which are essentially identical and have independent, decoupled motion, as show in Fig. 1. Each individual actuation unit drives a single needle, cannula, or tube, and offers 2 degrees of freedom (DOF) motion - 1 DOF linear translation and 1 DOF axial rotation, as show in Fig. 2. The actuation units ride on a common lead screw and linear guide which is firmly fixed on the base, and the nut is rotated by a timing belt drive mechanism, enabling linear translation (DOF #1). The needle clamping mechanism is attached to a pulley which is driven by similar timing belt drive mechanism, implementing axial rotation of the tube (DOF #2). The needle is gripped by a universal collet supporting varying sizes of standard needles from 25 Gauge (0.51 mm) to 16 Gauge (1.65 mm). An insert may be used to ensure sterility of all needle-contacting components. An eccentric belt tensioner is utilized to adjust the center distance between the motor and the tube clamping mechanism, by twisting the motor housing to varying angles with respect to the tube clamping mechanism, and thus guarantee the effective and smooth power transmission [5]. Nonconductive materials were utilized to build the majority of the components of the needle driver, non-ferrous aluminum is chosen for linear guide and lead screw, which require high stiffness, to maintain MRI compatibility. Piezoelectric motors (PiezoMotor actuators, Uppsala, Sweden) are selected as the actuators, for its high accuracy, dynamic performance and robustness as well as MRI compatibility utilizing the custom-developed MRI-compatible piezoelectric drive system described in [7]. Optical encoders with shielded, filtered differential signaling (US Digital, Vancouver, Washington) are utilized as the position feedback sensors.The most import feature of the design is modularity, which makes it possible to readily add more concentric needles, tubes, or cannulas, and thus enables more complex controlled motion profiles for procedures such as biopsy, brachytherapy, interstitial ablation, and concentric-tube needle deployment. The needle driver can also potentially be lengthened or shortened based on the requi