Intra-operative medical imaging enables incorporation of human experience and intelligence in a controlled, closed-loop fashion. Magnetic resonance imaging (MRI) is an ideal modality for surgical guidance of diagnostic and therapeutic procedures, with its ability to perform high resolution, real-time, high soft tissue contrast imaging without ionizing radiation. However, for most current image-guided approaches only static pre-operative images are accessible for guidance, which are unable to provide updated information during a surgical procedure. The high magnetic field, electrical interference, and limited access of closed-bore MRI render great challenges to developing robotic systems that can perform inside a diagnostic high-field MRI while obtaining interactively updated MR images. To overcome these limitations, we are developing a piezoelectrically actuated robotic assistant for actuated percutaneous prostate interventions under real-time MRI guidance. Utilizing a modular design, the system enables coherent and straight forward workflow for various percutaneous interventions, including prostate biopsy sampling and brachytherapy seed placement, using various needle driver configurations. The unified workflow compromises: 1) system hardware and software initialization, 2) fiducial frame registration, 3) target selection and motion planning, 4) moving to the target and performing the intervention (e.g. taking a biopsy sample) under live imaging, and 5) visualization and verification. Phantom experiments of prostate biopsy and brachytherapy were executed under MRI-guidance to evaluate the feasibility of the workflow. The robot successfully performed fully actuated biopsy sampling and delivery of simulated brachytherapy seeds under live MR imaging, as well as precise delivery of a prostate brachytherapy seed distribution with an RMS accuracy of 0.98mm.
Magnetic resonance imaging (MRI) provides high resolution multi-parametric imaging, large soft tissue contrast,
and interactive image updates making it an ideal modality for diagnosing prostate cancer and guiding surgical
tools. Despite a substantial armamentarium of apparatuses and systems has been developed to assist surgical
diagnosis and therapy for MRI-guided procedures over last decade, the unified method to develop high fidelity
robotic systems in terms of accuracy, dynamic performance, size, robustness and modularity, to work inside
close-bore MRI scanner still remains a challenge. In this work, we develop and evaluate an integrated modular
hardware and software system to support the surgical workflow of intra-operative MRI, with percutaneous
prostate intervention as an illustrative case. Specifically, the distinct apparatuses and methods include: 1) a
robot controller system for precision closed loop control of piezoelectric motors, 2) a robot control interface
software that connects the 3D Slicer navigation software and the robot controller to exchange robot commands
and coordinates using the OpenIGTLink open network communication protocol, and 3) MRI scan plane alignment
to the planned path and imaging of the needle as it is inserted into the target location. A preliminary experiment
with ex-vivo phantom validates the system workflow, MRI-compatibility and shows that the robotic system has
a better than 0.01mm positioning accuracy.