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
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.
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
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