Progress Report:A Wearable TMS

System for Ambulatory Use

By: Ben SassGroup 19: Beller, Kahan, Sass

Client: St. Jude MedicalDate 10/25/2014

Project Scope and Need

TMS – Transcranial Magnetic Stimulation

AC current through a coil creates a magnetic field.

This magnetic field alters neuronal activity in the brain.

Need: Therapy + TMS

Need: Future Home Therapy

Wearable TMS System

Maintaining Coil Position

Material

Polystyrene

Polycarbonate Urethane

Thermoplastic Elastomer

Headgear

Hemispherical shell

Modular Plate System

3D printed bonnet

Coil Interface

Manipulator

Track System

Direct attachment

Targeting Mechanism

Anatomical Landmark

MRI Marker

Stereotactic Tracking

Design Overview

Design: Material

NinjaFlex®: Thermoplastic Elastomer

Polycarbonate Urethane

Polystyrene

Manufacturing3D Printing

(moderate-difficult)3D printing (easy-

moderate)Extrusion (easy)

Ease of CleaningMild soap Mild soap Mild alcohol

Hardness85A 75D M60-90

Elongation>500% 241% 3-4%

Young's Modulus15.2 M-Pa (2200 psi) 260 M-Pa

300-350 M-Pa (43500-50800 psi)

Ultimate Tensile Strength

34.5 M-Pa (4000 psi) 63.2 M-Pa (9171 psi)30-100 M-Pa (4350-

14500 psi)

Density0.88-1.02 g/cc 1.21-1.22 g/cc 0.96-1.04 g/cc

Table 1: Properties of Materials for Headgear Design http://www.goodfellow.com/E/Polystyrene.html http://www.engineeringtoolbox.com/young-modulus-d_417.html http://www.ninjaflex3d.com/support/using-ninjaflex/technical-specifications/ http://www.dsm.com/content/dam/dsm/medical/en_US/documents/bionate(r)-pcu-product-sheet.pdf http://www.matweb.com/search/datasheettext.aspx?matguid=677752e8e6bf4727b917c242bfc665ef

Pugh Chart: Part A  Weight Material    Polyurethane NinjaFlex® Styrofoam

Cost 4 8 5 10Portability 8 9 10 10Durability 5 10 9 7

Reprocessing Rate 6 10 10 9

Spatial Resolution 10 10 10 8

Lightweight 8 8 10 8Patient

Comfort 8 6 9 9

Target Precision 10 10 10 3

Ease of Setup 7 10 10 10

    596 627 525

Headgear: Hemispherical Shell

Hemisphere system with TrackHemisphere system with grid

Headgear: Modular Plate System

More individualized

Good fit for variety of head sizes

Velcro® is used to connect plates

Grid system

A manipulator will be used for fine coil placement

Headgear: 3D Printed Bonnet

Highly Individualized

Expensive

Time Consuming

Steps:

1. Scan/image the head

2. Convert images to model

3. Convert surface model of head to model of bonnet

4. Print the bonnet

http://www.ablesw.com/3d-doctor/images.html

Pugh Chart: Part B

  Weight Headgear Design

    Hemi Shell Plate System Custom Bonnet

Cost 4 10 10 1

Portability 8 10 10 10

Durability 5 8 5 5Reprocessing

Rate 6 8 5 5

Spatial Resolution 10 4 8 10

Lightweight 8 5 10 10

Patient Comfort 8 4 10 10Target

Precision 10 8 10 10

Ease of Setup 7 10 8 10

    470 571 569

Coil Interface: Grid & Track System

Hemisphere system with TrackHemisphere system with grid

Coil Interface: Motorized Manipulator

The coil manipulator is a 2 stage linear rail system.

Biaxial Movement (normal to the head surface)

Feedback to maintain optimal coil position

Magnetic or potentially piezoelectric

http://www.pimicos.com/web2/en/1,6,250,lps22.html

Pugh Chart: Part C  Weight Manipulator    Motorized Manual Track System

Cost 4 3 6 4Portability 8 10 10 7Durability 5 5 7 2

Reprocessing Rate 6 10 9 10

Spatial Resolution 10 10 9 6

Lightweight 8 8 8 6Patient

Comfort 8 9 9 6

Maximum Operation

Time7 10 10 9

Target Precision 10 10 6 8

Ease of Setup 7 9 6 8

646 591 497

Targeting: Anatomical Landmarks

Anatomical Landmarks

Locate target based on:

Target correlation with observable patient function

Approximate distance from one of the ‘Reporter Regions’

Not very accurate

Fitzgerald, Paul B., et al. "A randomized trial of rTMS targeted with MRI based neuro-navigation in treatment-resistant depression." Neuropsychopharmacology 34.5 (2009): 1255-1262.

Targeting: MRI-Marker System

fMRI to locate areas of abnormal activity

Contrast agent attached to coil in ‘V’ shape.

Trivial computational analysis leads to correlation between coil position and orientation of the marker

More accurate, but confined to MRI machine

Yau, Jeffrey M., et al. "Efficient and robust identification of cortical targets in concurrent TMS–fMRI experiments." NeuroImage 76 (2013): 134-144.

Targeting: Frameless Stereotactic Tracking Mechanism

Fixed collection of cameras placed to track coil position in relation to an fMRI image

Allows for construction of a 3D model of marker position

Interacts well with live feedback positioning

Limited within a visual field

Schönfeldt-Lecuona, Carlos, et al. "Accuracy of stereotaxic positioning of transcranial magnetic stimulation." Brain topography 17.4 (2005): 253-259.

Pugh Chart: Part D

  Weight Tracking

    MRI MarkerStereotactic

CameraAnatomical Landmark

Cost 4 10 3 10

Portability 8 3 7 10

Durability 5 10 9 10

Spatial Resolution 10 10 10 1

Target Precision 10 7 10 7

Ease of Setup 7 7 7 10

    333 362 320

Final Solution Modular Plate System

NinjaFlex®

Motorized Coil Manipulator with Screw Interface Commercially available

stages

Grid System ~1.25 cm

Stereotactic Targeting system

http://www.adafruit.com/product/1691

Acknowledgements I’d like to thank

Mr. Rosenberg and Dr. Venkatesan

Zach and Lindsey

Professor Mell

Dr. Klaesner

Rebecca Gilson

for their help with this presentation.

Thank you! Any questions?