Engineering Medical Devices @ MIT 2.75 Part I

With the goal of engaging graduate students and accelerating ideas into prototypes, teams of MIT graduate engineering students spend a semester collaborating with clinicians in CIMIT-affiliated hospitals to develop innovative medical devices. Clinicians (physicians, nurses, and scientists) present clinical problems and initial ideas. Students form teams to work with the clinicians to turn these ideas into reality. The goal is for the students to deliver a working prototype and a journal-quality article in one semester. In its fifth year, the course has been a great opportunity for clinicians to test out new ideas and to stimulate new collaborations. For example, Robopsy, a robotic device to assist radiologists performing tumor biopsies was invented by an MIT team led by Rajiv Gupta, MD, in 2004. The team was awarded the 2007 MIT $100K prize, the world's leading entrepreneurship competition and the 2008 ASME Innovation Showcase.

Moderator: Alex Slocum, PhD, Pappalardo Professor of Mechanical Engineering and MacVicar Faculty Fellow, MIT, slocum@mit.edu

A Novel Catheter Navigation System 
Clinician: Rajiv Gupta, MD, PhD, Director, VCT Lab and Assistant Radiologist, Department of Radiology, Massachusetts General Hospital, rgupta1@partners.org  
MIT Student Team: Jean Chang, Ellen Chen, Kenny Cheung, Alison Greenlee

 
 

There no techniques that allow doctors to quickly and accurately maneuver a catheter during an extravascular procedure. Presently utilized techniques restrict catheters to simple paths and therefore limit a doctor's ability to position the catheter in a poorly constrained environment. The proposed catheter navigation system overcomes these limitations and positions the catheter tip while the overall catheter shape is maintained. The system consists of a disposable set of "Tension Stiffening Guide-Wires," a double-lumen catheter, and an external reusable control system that is used to remotely maneuver the catheter. The "Tension Stiffening Guide-Wires" are composed of a set of beads with spherical bearing surfaces so that when the beads are held in tension, a friction lock forms between each bead. Mathematical analysis was performed to predict contact forces between beads, change in guide-wire conformation due to external forces, tip deflection, and failure modes. The catheter navigation system is not path limited and can make a number of three-dimensional turns inside the body. The goal of this prototype is to present doctors with a working catheter positioning system that will enable faster and accurately extravascular procedures to be conducted faster and more accurately.

Design and Prototyping of a Head Fixation Device for Transcranial Magnetic Stimulation 
Clinician: Alvaro Pascual-Leone, MD, PhD, Professor of Neurology, Harvard Medical School; Director of the Berenson-Allen Center for Noninvasive Brain Stimulation and Attending Neurologist and Director of Research, Behavioral Neurology Unit, Beth Israel Deaconess Medical Center, apleone@bidmc.harvard.edu 
MIT Student Team: Dodd Gray, Lawrence Maligaya, Adam Paxson

 
 

For applications of transcranial magnetic stimulation (TMS) and other cranial procedures involving relatively small instruments, this team will present a device for fixturing these instruments relative to a patient's head. The device consists of an ergonomic base table in which the patient rests face-down. The patient's head is supported by a custom-molded face restraint compliantly fixed to the base table. Indexing of the patient's skull is accomplished with a molded dental insert. Each stage of the design process is discussed with emphasis on a systematic approach based on structural analysis and bench-level experimentation. The performance of the final prototype is evaluated using digital image analysis. Our device achieves a positioning repeatability of 2.5mm, with a maximum displacement of 1.3mm over a five-minute period once the device has been affixed.

Interbody Device and Procedure for Endoscopic Lumbar Fusion 
Clinician: Kevin McGuire, MD, MS, Chief, Orthopaedic Spine Service, Beth Israel Deaconess Medical Center; Co-director, Comprehensive Spine Center and Combined Spine Fellowship Program; Instructor, Harvard Medical School, kjmcguir@bidmc.harvard.edu 
MIT Student Team: Nadia Cheng, Sourabh Kumar, Ryan Slaughter, Maria Telleria 
 
 
 
This team designed an interbody device and procedure that allows for performing minimally invasive lumbar fusion operations. Minimally invasive fusion techniques are currently limited due to non-availability of suitable interbody devices which can pass through an endoscopic tube and still obtain and maintain the required disc height for fusion. Here, a balloon based expandable device is presented which fulfills all the requirements of an interbody device used for lumbar fusion. It consists of an open-ring shaped balloon which is inserted into the disc space through the endoscopic cannula in the deflated state. The disc space is propped open by filling in pressurized saline into another balloon placed inside the ring. Once properly placed in the disc space, the ring shaped balloon is filled with fast solidifying bone cement slurry causing it to expand into the final ring structure. The saline balloon is eventually removed out of the disc space allowing for a large central space for packing bone graft material. The entire technique is described here, highlighting the essential features of the device. A successful device can be designed with a suitable choice of bone cement and balloon material. Available values for material properties suggest that the designed device would successfully allow for a complete lumbar fusion. Future in-vivo studies are needed to fully assess the success of the device.