Thrust 2: Compactness
Title
2G: Fluid Powered Surgery and Rehabilitation via Compact Integrated Systems
Project Leaders
Prof. Robert Webster (Vanderbilt)
Prof. Jun Ueda (Georgia Tech)
Vito Gervasi, R&D Manager, Rapid Prototyping Center (MSOE)
Statement of Project Goals
The objective of the research is to extend fundamental understanding of the unique characteristics of fluid power that enable precise machines to withstand intense magnetic fields. Toward this end, the project will develop compact systems where cylinders, valves, and sensors are no longer independent entities assembled together, but are a single integrated system that can be manufactured simultaneously. Magnetic Resonance Imaging (MRI) compatible devices are the perfect focusing application for this research. In surgery, MRI provides excellent soft tissue resolution, but robots are required to effectively make intraoperative use of this information. In rehabilitation, functional MRI (fMRI) offers the unique ability to visualize brain activity during therapy. Fluid power can be an essential enabler in both contexts, because traditional electromagnetic actuators fail (or cause artifacts in) intense magnetic fields. This research could open an entirely new industry to fluid power: Medicine (~1/6 of the Gross Domestic Product of the USA).
Project's Role in Support of the Strategic Plan
Fluidic energy transmission holds the promise of being an effective method of transmitting energy during imaging in an MRI where no other method exists today. The major technical barriers that are being targeted relate to 1) compact integrated systems (by designing systems where valves, cylinders, and sensors are not separate entities), and 2) making fluid power systems safe and easy to use in a medical application (new force sensors will ensure human safety when interacting with machines in an MRI). A successful demonstration of the technology will help to break a transformational barrier by applying fluid power in medicine. This aligns with the CCEFP vision "of transforming and fully exploiting fluid power into a compact, efficient and effective source of energy transmission."
Description and Explanation of Research Approach
MRI-compatible Actuators and Surgical Robots (Vanderbilt)
Intraoperative image guidance, and particularly use of MRI images which have far better soft tissue imaging capability than other modalities, has the potential to fundamentally change the fact that the success of any modern surgery relies entirely on the experience, memory, spatial reasoning, judgment, and hand-eye coordination of the surgeon. To break this barrier and move surgical accuracy beyond the limits of human skill and perception, what is needed is real-time image feedback during surgery, combined with precise machines able to accomplish the surgeon's objectives accurately. Such feedback can 1) enable the surgeon to visualize the position of instruments in relation to sensitive subsurface blood vessels, nerves, tumors, etc., before incisions are made, and 2) enable the robot to directly position a tool at a desired target specified in a medical image. Both of these capabilities have the potential to make surgery safer and to improve clinical outcomes by enhancing the accuracy of treatment delivery. MRI is a key enabler of this due to its unique ability to clearly show soft-tissue boundaries and structures which are not visible in other imaging modalities. This makes fluid power essential - it is the only viable technology that can transfer energy to actuate machines without the adverse interference effects associated with by the intense magnetic fields required by MRI or interfering with the imaging itself. MRI is also safer than other imaging modalities like CT, which use ionizing radiation.
fMRI-compatible Sensors and Haptic Device (Georgia Tech)
Magnetic resonance imaging is one of the most useful methods available to study neuroscience, evaluate rehabilitation therapies, and perform image-guided interventions and surgeries. Functional MRI (fMRI) is a new technique that can observe the brain structure activities by measuring blood flow in a certain area such as motor cortex. Actuation and sensing technologies usable in MRI/fMRI would provide a wide variety of applications and research opportunities such as studies on neuroplasticity after stroke, somatosensory and motor functions, and sympathetic nerve activity during motor task learning. A nonmagnetic fluid-powered haptic device that interfaces with a patient during an fMRI procedure is considered suitable.
Approach: This project will explore fundamental pneumatic control problems posed by the MRI environment. This is a different scale, which has different constraints than many existing fluid power systems today. The project will explore closed vs. open loop control of various MRI compatible systems and line dynamics will be interesting topics to study from a theoretical perspective. This project will study the interaction of design and control working to answer the open research questions: Is it possible to design your way out of a control problem using a pneumatic stepper motor for example? Are there particular designs that are more challenging to control, but offer performance benefits if such control is done well? Similarly, the medical environment itself poses interesting problems, as fluid power systems must be designed to be efficient, small, clean, and able to be sterilized, which are unique requirements. Furthermore, we intend to develop an analytical model that efficiently simulates complex dynamics of the integrated system for optimization. The project will develop a design methodology that resolves problems associated with the use in MRI/fMRI, in particular, limitation of space, non-magnetic requirement, and limitation in control/sensing.
Figure 1-1: (Left) Photo of a patient in an MRI machine from the front shows the limited space available for a robot. (Center) A schematic of the MRI bore seen from the side illustrates how the robot and patient will fit within the machine. (Right) The robot deploys a steerable needle called an "active cannula" made from multiple percurved superelastic concentric tubes.