fMRI Compatible Mechatronic Ankle Device Presented by: Danielle Doane, Ben Foss-Michaelis, Brendon Reedy, Karina Snow, and Brandon Teller Advisors: Professor Constantinos Mavroidis PhD Azadeh 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

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)

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 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

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

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 (F m ) Ankle joint reaction force (F j )

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 G.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 Pedal Design

Potential Design Concepts: Slider Pedal Design I (Slider Crank) Slider Pedal Design II