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