Team Members

1
Team Members

• Mike Wells Team Leader
• Andrew VanDeWeghe BWIG
• Yuk-ki Lam Communications
• Steve Trier BSAC
• Brent Geiger
• Tom Chia

2
Client

• Andrew Alexander Ph.D.
• Assistant Professor of Medical Physics and
  Psychiatry
• Keck Laboratory at the Waisman Center

Advisor

• Mitchell Tyler M.E., P.E.

3
Abstract

• A small movement during an MRI scan causes the
  images to become blurred and gives unusable
  results. The proposed optical motion sensor
  device will serve as a head motion detector and
  feedback mechanism for training patients to
  suppress movement while in a mock MRI
  environment. It is expected that this device
  will reduce head motion during an actual MRI scan
  and will produce better results in fewer scans.
  Ultimately, this will save time, money, and most
  importantly will reduce stress for the patient.

4
Problem Definition

• To design a device that
• detects head movement in an MRI simulator
• quantifies movement on a millimeter scale
• provides feedback
• does not change the simulator environment
• non-invasive to the patient (comfortable)
• easy to operate

5
Motivation

• Reduced head movement in the actual MRI will
• Produce better images in fewer scans
• Save time and money
• Relieve stress on the patient and client
• Only a bite bar is currently available to
  restrict head motion (in the MRI simulator )
• Does not work for all patients

6
Background

• Magnetic Resonance Imaging (MRI) produces an
  image by using strong magnetic fields
• Spin orientations of H atoms align with the
  applied field
• Using a second magnetic field at a
  radio-frequency causes the spin of some H atoms
  to re-align
• Energy is released when these spins return to
  their normal state.
• This energy is what is recorded and is used to
  produce an image

7
The MRI Simulator

• Main purpose is to familiarize patients to the
  enclosed environment of the MRI tube
• Goggles and headphones provide visual images and
  simulate the loud noise of the actual MRI machine
• Especially important for training children,
  elderly, claustrophobic, and exceptionally
  nervous patients

8
Design Criteria

• Ergonomics
• Patient comfort, non-invasive, not dangerous,
  cleaned easily, readily accessible
• Simplicity and Adaptability
• Simple to operate, applicable to all patients, no
  unnecessary complications
• Feasibility
• Working prototype by the end of the semester,
  must be within cost restraints

9
Design Criteria

• Sensitivity/Accuracy
• Must be able to measure movement of 1mm, must be
  consistent
• Price
• Final prototype must be less than 500, final
  device must be affordable by Waisman labs

10
Proposed Designs

• Headband Photosensor
• Focused light source attached to headband worn by
  patient
• Photosensor mounted on head coil above light
  source
• Light/photosensor system measures head movement
  and provides feedback response

11
Proposed Designs

• Strain Gauge System
• Force platform and strain gauges built into
  pillow of MRI simulator
• Strain gauge array measures head motion through
  pressure changes and provides feedback response

12
Proposed Designs

• Optical Image Tracking
• Use basic optical mouse technology
• CMOS sensor, LED, Signal Processor
• Optical sensor mounted in position near patients
  head
• Processor analyzes changes in images (from CMOS
  sensor) and translates pixel movement into head
  motion data

13
Decision Matrix
14
Final Design

• Modified optical image tracking system
• Only one sensor (feasibility)
• Placed on patients forehead
• Forehead is ideal because it is broad, flat, free
  of hair, and transfers all head motion
• Computer analysis
• Based in LabView 6.1
• Variable error setting
• Feedback Light Sound

15
LabVIEW Interface
16
Prototype Design

• Wireless Mouse disassembled
• Separated into RF transmission board and optical
  sensor board
• Optical sensor mounted in small project box and
  connected by wire to RF board mounted in larger
  project box with on/off power switch
• Mock setup of goggles constructed
• Adjustable, full scale

17
Prototype Design

• Optical sensor box mounted on goggles
• Allows vertical motion, rotation, LED is directed
  away from patient
• Interchangeable clear plastic strip between
  sensor and patient
• Patient comfort
• Sanitary needs

18
Testing

• Screen resolution set to 1024 x 768.
• Acceleration of mouse turned off.
• Speed of cursor set to fast for precision.
• Light contact with skin works best.
• 48 trials of varying distance were performed to
  obtain a relationship between distance and cursor
  movement.

19
Calibration
20
Ethical Considerations

• Eye exposure to LED
• Normal usage of AllnGaP II LED (639nm) poses NO
  danger to eyes
• Agilent Technologies
• On/Off switch minimizes LED exposure
• Sensor LED rays directed away from eyes
• Collision of sensor w/ patients head
• Mobile sensor mount moves in response to movement

21
Ethical Considerations

• Sanitation
• Comfortable, sterile, and disposable sensor
  covers
• Possible electrical shock or injury from contact
  with device
• Sharp objects and loose wires contained in
  project boxes

22
Conclusion

• Final design fulfills restraints
• 1 mm resolution
• Notification of excessive movement
• Non-invasiveness
• Addressed safety issues
• LED exposure
• Sanitation

23
Future Work

• Eliminate contact with patient
• Improve LED light to softer color or infrared
• Improve quality of data interpretation
• New options auto-feedback, sampling rate, data
  analysis