Abstract This report describes three prototypes for a device that can rotate and flex/hyperextend the neck in CT and MRI scanners. This device must situate the head in positions of a known degree of rotation. Positions must be reproducible, allowing for accurate rescanning. The chosen design provides continuous isocentric rotation that can be isolated at any given angle. A reliable measuring system allows for the positions of the head to be replicated in future scans. At the current stage, half of the device is built, but more pieces are needed.

Background and Motivation Focus One Background: –Nerve roots run through the neural foramen –Cervical motion may compress the neural foramen and shear the nerve roots Goal: –To measure the degree of compression in the neural foramen in order to detect the pinching of the nerve roots during rotation

Background and Motivation Focus Two Background: –Degree of rotation of each vertebra differs among patients Goal: –Compare the stability of segmented motion in the vertebrae of normal patients with that of patients with instability (Neck Reference)

Background and Motivation Focus Three Background: –A disorder called Chiari I malformation –The cerebellum alters the flow waveform of CSF Goal: –Analyze the effect of flexion and hyperextension on the flow rate of CSF in patients with Chiari I malformation (The Chiari Clinic)

Rotation in the cervical vertebrae

Imaging The foci of this study can be evaluated with magnetic resonance imaging (MRI) and computed tomography (CT) MRI will be used for a high degree of resolution in detecting vascular significance CT will be used more often because of its ability to image bone MRI Scanner

MRI Takes images by sending radiofrequency pulses into the body and detecting the signal off of the body’s protons Because of the large magnetic field, ferromagnetic materials—iron, cobalt, and nickel—cannot be brought close to the scanner Electrical wires and non-ferromagnetic materials can act as antennae and distort the images The MRI scanner being used is a GE Signa 1.5 T

CT Transmits x-rays into the body in a radial fashion Metallic objects are not hazardous, but can cause blurring in the images The CT scanner being used is a GE Lightspeed

Design Criteria Design a device that: Allows for isocentric movement –Flexion/hyperextension about the temporo- mandibular joint –Left/right rotation about spinal axis Has the ability to reproduce positions Is made of MRI- and CT-compatible material Is light and portable Looks aesthetically pleasing

Decision Matrix DesignRotating Arm Helmet Design U-shape design Continuous rotation 321 Isocentric Left/right rotation 321 Isocentric flexion/extension 231 Ergonomics 231 Patient Adaptability 321 Compatible material 231 Total =Best rating2=Second best rating3=Third best rating

Preliminary Design Advantages –The helmet design featured a rotating locking hinge (Design 1) –Head cradle shaped like a helmet –Easily compatible with both MRI and CT scanner stretchers Disadvantage –It could not achieve isocentric flexion/hyperextension.

Intermediate Design Advantages –Based on client feedback and suggestions –U-shaped bar enables isocentric flexion/hyperextension (Design 2) –A pin joint allows for simple rotation –Both flexion/hyperextension and device elevation adjust with a single joint –Improved shape of head cradle Disadvantages –Excessive stress on the U-shaped bar –The design has an imbalanced weight distribution

Final Design Advantages –Consulted stresses and stability of design with professors and within the team –Performed a basic finite element analysis on the back pin with CosmoWorks, a sub-program of SolidWorks –Added a back support for the reinforcement of the U- shaped bar (Design 3) –Can now adjust the degree of flexion/hyperextension at the back support –Added clamp around rotation pin for stationary positioning Disadvantage –No reliable method for attaching to both the MRI and CT stretchers

Final Design: Results Continuous motion with stationary positioning Compatible with CT and MRI Material selection –Polyvinyl chloride (PVC) –Nylon screws Basic finite element analysis Detailed Solid Works ® drawings Video presentation Prototype representation

Finite Element Analysis Performed FEA on the head cradle On the restraint, the support rod was immovable (no translation) at the clamp Given a force of 8 lb orthogonal to the head cradle surface Used a solid mesh, 8998 elements, and nodes Used a von Mises stress analysis Minimum factor of safety = 19

Final Design: Progress Milled side supports Constructed U-shaped bar with PVC glue Back of the head support Clamp over the rod through the U-bar Back joint support Makeshift base Future head cradle

The Building Process

Future Work Continue research on materials Insert a support mechanism for the side supports Accommodate prone scans Perform an advanced finite element analysis Improve manufacturing capabilities Scan patients and evaluate the accuracy of reproducible positions

A Special Thanks to: Professor Osswald -Material Selection Professor Manner -Finite Element Analysis Professor Fronczak -Joint design

References Chiu, L.C., Liteamon, B.S., Yiu-chiu, B.S Clinical Computed Tomography for the Technologists. Raven Press, New York. Hashemi, R.H., Bradley, W.G MRI The Basics. Williams & Wilkins, Baltimore, MD. “Hospital for Joint Diseases.” Spine Center. Accessed: 5 Oct URL: “Spine Universe.” Accessed: 4 Oct URL: “The Center for Spinal Disorders.” Accessed: 4 Oct “The Chiari Clinic.” Accessed: 7 Oct URL: “The Neck Reference.” Accessed: 4 Oct URL: