fmri compatible mechatronic ankle device presented by: danielle doane, ben foss-michaelis, brendon...
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fMRI Compatible Mechatronic Ankle
DevicePresented by: Danielle Doane, Ben Foss-Michaelis, Brendon Reedy, Karina Snow, and Brandon Teller
Advisors: Professor Constantinos Mavroidis PhDAzadeh Khanicheh PhD
Sponsor: NU Robotics Lab
Project Statement
Develop a novel device that measures force and position in a functional magnetic resonance imaging (fMRI) environment in order to analyze the cortical response to dorsiflexion and plantarflexion ankle movements
www.mritoday.net
Project Need
Lack of technology preventing research fMRI ankle studies exist, but no device is currently available
Benefits of device Allows for novel approaches in rehabilitation research Correlates data and cortical response Standardizes study and test conditions
Background: fMRI
Functional Magnetic Resonance Imaging Blood Oxygen Level Dependent (BOLD)
Monitors activity by comparing relative amounts of oxygenated and deoxygenated blood
B.H. Dobkin et al./NeuroImage 23 (2004) http://psychcentral.com/lib/img/fmri_bold.jpg
Background: fMRI Brain Studies
fMRI studies of BOLD during limb movement
Hand/Wrist - utilize devices Isometric Dynamic
Ankle No device Predetermined movements
Design Specifications
MRI Compatible Size- 11in wide by 26 in long Weight- 25lbs Functions
Controlled Dorsiflexion and Plantarflexion Free Dynamic, Isometric force sensing
Ranges of Motion and Force Dorsiflexion- 0-10°, 26lb Plantarflexion- 0-40°, 100lb
ROM Increments- 5° Dynamic Ranges of Speeds or Frequency- up to 25°/s
Expert Interviews: Paul Canavan, Northeastern University, PhD, PT, ATC, CSCS Paolo Bonato, Spaulding Rehabilitation, PhD Joel Stein, Spaulding Rehabilitation, MD
Concept Selection Criteria
fMRI Compatibility of Materials (25%)
Ability to Perform Desired Exercises (20%)
Minimal Head Migration (15%)
Resistance in Plantarflexion (10%)
Modulated Design/Ease of Assembly (10%)
Foot and Lower Leg Restraints (10%)
Overall Size/Weight of Device (10%)
Detailed Design
Detailed Design:Material Selection/Manufacturing Plan
Delrin®
Material Strength Easily Machined Low Coefficient of Friction
Manufacturing Plan All components machined at
Northeastern Sensors custom made for fMRI compatibility
wwww.renco.com
wwww.jr3.com
Sensors Aluminum with brass
bolts
Detailed Design:Component Analysis
Analyzed all components for maximum force application of 100lbs CosmosXpress
Deflection and maximum stress Critical Points
Foot Pedal/Base Deflection Max Deflection=.001”
Component Joints - Pins Failure analysis
Detailed Design:Assembled Prototype
Detailed Design:Foot Pedal Assembly
Multi-Axis Load Sensor Attached using Brass
Bolts Foot Straps hold foot in
place Maximum material
displacement of 1.312e-4”
6 Axis Load Sensor
Ankle Strap Location
Detailed Design:Slider/Track Assembly
Dynamic Pins (3 Pins .375 dia X3in) Limit range of motion Incremental hole locations
on top of base Isometric Pin
(.375 dia x 7in) Lock device for isometric
exercise Incremental hole locations
on side of base Factor of Safety of 4.315
Visual Feedback System:Isometric and Dynamic
LabView Interface Promotes normalized test
execution Patient Interaction
Movement dictation Performance feedback Conduct a variety of
exercise programs
Device Function
Testing
System Performance Verification Visual Feedback Ease of use Data output
fMRI Compatibility All components previously
validated for use in fMRI
Conclusions
Conclusions Achieved project goal of designing and prototyping a mechatronic
ankle device for use in fMRI
Device unsuccessfully measures isometric force in the plantarflexion and dorsiflexion direction
Problems arise at the sensor-pedal interface The hypothesis is misalignment and the large area of force
application generate significant torques These torques are compromising the data
Potential solutions include: Redesigning the pedal to reduce area of force application Applying a strain gauge to the Dogbone as the means of force
measurement
Future Work
Potential solutions include: Redesigning the pedal to reduce area of force application Applying a strain gauge to the Dogbone as the means of force
measurement Pedal Redesign Solutions:
Questions???
Acknowledgements: Professor Mavroidis,
Northeastern University Azadeh Khanicheh,
Northeastern University Professor Canavan,
Northeastern University Paolo Bonato,
Spaulding Rehabilitation
www.dkimages.com
Cost Analysis:Cost for one Ankle Device
Cost Analysis:Total Project Cost
Future Work:Testing Plan
Testing Outside fMRI
Performance Verification Isometric- Sensor Readings Dynamic- Different Speeds
Testing Inside fMRI (Phantom Testing)
Sensor Testing Force Sensor Position Sensor
Test Plan No Device Device in room, All power off Device in room, Power On, Phantom in Place, Device not moving Device in room, Power On, Phantom in Place, Device in motion
http://www.medical.siemens.com/webapp/
Design Specifications:Sensing Components Force
Max Force- 100lbs (will amplify down from 250lbs) Position
Range- 360° Static Error- <.02° Resolution- 13 bits
Frequency Range- 120°/s Resolution- 13 bits
Background: Ankle Analysis
Fundamental gait mechanics Dorsiflexion
The upward extension of the ankle, 10~15˚
Plantarflexion The downward extension
of the foot, 25~45˚
Liu et al./ Int. Conf on Intelligent Robots and Systems (2006)
Detailed Design:Geometric Calculations
A design program, SAM, was used to calculate the corresponding displacements to set angles
The program employed a 2-D drawing and a corresponding graph to represent the angle, displacement, and position of the pedal and slider when in motion
Background: Ankle Mechanics
Ankle can support 1.5 to 6 times persons body weight
Primary forces Gastrocnemius muscle force
(Fm)
Ankle joint reaction force (Fj)
Background: fMRI-Compatible Devices and Studies
Gait Rehabilitation Study
Lower Limb Movement Brain Function Studies
Background: fMRI-Compatible Devices and Studies
Isometric Wrist Device Dynamic Hand Device Robotic Arm Device
J. Hidler et al./Journal of Neuroscience (2006)
J. Diedrichsen et al./ Neuroscience (2005)
Khanicheh et al./ IEEE Int Conf on Rehab Robotics (2005)
Background: Existing Ankle Devices
Non MRI-Compatible Devices Platform Type
Devices-Rutgers Ankle
MRI-Compatible Devices Ergometer
-Different Indication
-Not suitable for fMRI
http://www.caip.rutgers.edu/vrlab/projects/ankle/ankle.htmlG.H. Raymer et al./ Med Eng Phys (2006)
Design Concepts: Isometric Device Static testing
Incremental test positions throughout dorsiflexion/plantarflexion range of motion
Force sensing/Data collection
Isometric Force Sensor Locations within Device
Design Concepts: Dynamic Device Range of Motion
Dorsiflexion Plantarflexion
Speed/frequency Position
40°
10° 5°
30°
0°15°
Design Concepts: Visual Force Feedback Used during Isometric and Dynamic exercise
Promotes normalized test execution Patient Interaction
Movement dictation Performance feedback allows researchers to conduct a variety of exercise
programs
Potential Design Concepts: Enclosed Boot
Design
Four Bar PedalDesign
Potential Design Concepts: Slider Pedal Design I (Slider Crank)
Slider Pedal Design II