Infrared Camera from Wii System to Track Ultrasound Probe and Create 3-D Image

Vanderbilt UniversityDepartment of Biomedical Engineering

 Van GambrellLaura Owen

Steven WalstonJonathan Whitfield

Advisor Dr. Christopher Lee - Department of Neurology

Amyotrophic Lateral Sclerosis

• ALS is a progressive neurodegenerative disease that causes atrophy of voluntary muscles through degradation of motor neurons

 • The size, shape, and

structural makeup of muscles like the bicep can be good indicators of the severity of the disease

 

ALS in the United States

• 20-30 thousand people in the US have ALS

• Doctors diagnose approximately 5,000 new cases every year.

• Once diagnosed, a person with ALS is only expected to live 3-5 years.

• Understanding the effects of the disease should help increase the life expectancy and in time hopefully cure itStephen Hawking

Dr. Christopher Lee

• Vanderbilt University Medical Center, Neurology Department 

• Dr. Lee specializes in evaluating muscle ultrasound in ALS patients

• He uses this information to determine early clinical and electrodiagnostic features of critical illness polyneuropathy and myopathy

Imaging Muscles

MRI• Great images• But expensive, time

consuming, and immobile• Current standard

Ultrasound• Images comparable to MRI• Cheaper• Short imaging time• 2D linear images acquired by

free hando Difficult to make a

reproducible 3D image 

Ultrasound

MRI

Imaging MachineryUltrasound MRI

Cost: • Sonosite Titan: $16,500

Size:• Small laptop• 8" LCD

Mobile:• Portable docking station• 4 hour battery life

Cost:• Typical MRI Machine:

$3 MillionSize:• 490 Square Feet

Mobile:• Not Mobile

Could 3-D Ultrasound be a good alternative to MRI• Can the location and position of the ultrasound probe be

monitored?• Can a three dimensional image of muscle be generated

using the signal from the probe and correlating it with the data of the orientation of the US probe?

• Will an imaging system that fulfills these two questions be effective, portable, and cost efficient?

• Will the monitoring of muscle volume be effective in researching treatments for ALS?

Solution Design• Objective is to use 2 Wii-mote CCD's to track infrared LEDs

o x and y position from each wii mote to calculate position in 3D• Using a triangulation algorithm to determine the position of

the LED in 3 dimensional space using the 2 Wii-motes • Wii-mote can track up to four infrared emitters at one time

o Placement of the LEDs will allow the tracking of the probe in 3-D space

• Using the gyroscope from the Wii Motion Plus we will be able obtain the yaw, pitch, and roll information of the US probe

Status and Results• Wiimote simultaneously tracks 4 infrared LEDs in 2D space • Wrote a triangulation algorithm that computes 3D location

from the 2 sets of data• Determined the camera calibration information, including

focal length and other matrix information• Calculated a centroid to return one data set for 4 IR light

sources• Ordered the WiiMotion Plus, Andruino, and adapter • Have Opensource code to return the Yaw, Pitch and Roll

data from the WM+ and Andruino• Determined sampling rate to be 60 Hz

Data Transfer Schematic

Wii-Motion Plus and Arduino

Arduino is an open source prototyping platform that can interface with the Wii-Motion Plus and the computer to provide angular data from the U.S. probe

Wii-Motion Plus has much more sensitive accelerometers than the wii mote that can provide 6 degrees of freedom to correctly establish the U.S. probe's orientation.

Physical Schematic

Estimated Final Cost of Design

• Wii Motes: $39.99 o X 2 = $79.98

• Wii Motion Plus: $17.96• Adruino: $30.00• Adruino + Wii Motion Plus Adapter: $4.00• Circuit Electronics: $15

o LEDs, Resistors, Battery, Wires• System Mount: ~$20.00• Arm Stabilizer: ~$18.00• Unforeseen Additions: ~$40.00

Final Cost: ~$225.00

• Infrared signals from external sources can interfere with LED signals

• The IR LEDs emit signal in a conical area (limited view)

• Potential accuracy problems• Incorrect centroid calculations

due to blocked IR LED 

Known Problems

Wiimote Sensitivity

• 2 infrared LEDs 30.48cm apart

• Error = -2.46mm ± 2.23 (mean ± std) 

Current Work Plans

• Set up the Wii Motion Plus + Adruino• Use the Opensource Software to obtain working

gyroscope data  • Sync wiimote and ultrasound acquisition rates• Interface the system with the 3-D reconstruction

software

Future Work Plans

By March 1st• Physically attach the WiiMotion+ device to US probe• Create a mounting system for the IR cameras•  Use the position data to tag Ultrasound images and

create a 3 dimensional image Mid March• Begin taking samples for data analysis

April• Have completed data acquisition• Quality assessment