Transcript Neck Rotator Final PowerPoint Presentation

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 temporomandibular 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
Design
Rotating
Arm
3
Helmet
Design
2
U-shape
design
1
Isocentric Left/right
rotation
3
2
1
Isocentric
flexion/extension
2
3
1
Ergonomics
2
3
2
3
2
3
1
1
1
15
15
6
Continuous
rotation
Patient Adaptability
Compatible
material
Total
1=Best rating
2=Second best rating
3=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 Ushaped 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
17114 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 Manner
-Finite Element Analysis
Professor Osswald
-Material Selection
Professor Fronczak
-Joint design
References
Chiu, L.C., Liteamon, B.S., Yiu-chiu, B.S. 1995. Clinical Computed
Tomography for the Technologists. Raven Press, New York.
Hashemi, R.H., Bradley, W.G. 1997. MRI The Basics. Williams &
Wilkins, Baltimore, MD.
“Hospital for Joint Diseases.” Spine Center. Accessed: 5 Oct. 2003.
URL:
http://www.hjd.org/hospitals/hjd/hjdspine/muscleandligaments.htm.
“Spine Universe.” Accessed: 4 Oct. 2003. URL:
http://www.spineuniverse.com/displayarticle.php/article1442.html.
“The Center for Spinal Disorders.” Accessed: 4 Oct. 2003.
http://www.centerforspinaldisorders.com/disorders.htm.
“The Chiari Clinic.” Accessed: 7 Oct. 2003 URL:
http://tribble.missouri.edu/ns/chiari/.
“The Neck Reference.” Accessed: 4 Oct. 2003. URL:
http://www.neckreference.com/anatomy.html.