senior capstone design project real-time electrocardiogram spectral analyzer ryan carnathan, keith...
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BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Senior Capstone Design Project Real-Time Electrocardiogram Spectral Analyzer
Ryan Carnathan, Keith Berry,
Mark Stadick, & Greg MichaelsonElectrical & Computer Engineering
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Requirements
• Apply knowledge
• Solve Real World Problems
• Work in Multidisciplinary Teams
• To become actively involved in a company or community organization.
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Purpose
• Used in conjunction with the HP Merlin bedside monitor
• Real-time spectral analysis of the beat-to-beat variability
• Assess the potential for:– Improved bedside clinical monitoring – Diagnostic and predictive information
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Function
• Graphical interface for the display and analysis of:– ECG Waveforms– QRS Complex Detection– Heart Rate Variability (HRV) Spectrogram
• These functions are performed and displayed in real-time.
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Implementation
• Hardware
• QRS Detection
• Spectral Analysis
• Integration and User Interface
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Definition of terms
• Electrocardiogram (ECG)
• Heart Rate Variability (HRV)
• QRS Complex
• RR v.s. NN
• The ECG Waveform
• The QRS Complex
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Hardware
• Data Acquisition Card (DAQ)
• Laptop Computer
• Accessories
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Data Acquisition Card
• Capabilities– Sample Rate
500 kS/s
– Number of Channels8 Differential16 Single Ended
– Gains0.5, 1, 2, 5, 10, 20, 50,
100
– Voltage Levels±10 V - ±50 mV
• Configuration– Sample Rate
1 kS/s
– Number of Channels1 Differential
– Gain Setting1
– Voltage Levels±5 V
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Laptop Computer
• CPU– Intel 600 MHz
Pentium
– 256 k Level 2 Cache
• Storage– 20 GB Hard Drive
– 3 ½ inch Floppy Drive
• Memory– 512 MB of Ram
• Peripherals– Infrared Transfer
– 10/100 Network Card
– 56k Modem
– (2) PCMCIA Slots1 Taken by DAQ
• Operating System– Windows 2000 SP 1
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Laptop Configuration
• CPU– 600 MHz
– 500 MHz (Battery)
• Hard Drive– 15.4 GB Free
• Ram Used– 128 MB (System)
– 384 MB Available
• DAQ Input– 1 Differential Channel
– 1 kHz Sample Rate
– BNC Connection
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Accessory Box
• Component Box• Connector Block• BNC Connection• Ribbon Cable• Strain Relief Device
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Connections
• Merlin To DAQ– 6.35 mm Audio Cable
To BNC
• DAQ to Laptop– 68 Pin Ribbon Cable
(0.2 M)
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Software Integration
• Program Functions– Initialize DAQ
– Start Acquisition
– Check Buffer
– Transfer Buffer
– Stop Acquisition
• Software– LabWindows CVI
– MatLab 6.0
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Acquisition Sample
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Battery Efficiency
• CPU– Voltage = 1.35V (Full Power)
Average Power < 2.0 Watts
– Voltage = 1.1V (Battery) Average Power < 1.0 Watts
• Battery Life– 3:15 per Battery
2 Batteries Possible
• DAQ Requirements– ±5 VDC (±5%)
280 mA typ400 mA max70 mA unused
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
QRS Detection Overview
• QRS detection algorithm
• Current Status
• Future work
• Summary
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
QRS Detector Algorithm
• Block Diagram
Remove Offset Filter Clip
QRS Peak Detection
PeakAcceptance/Rejection
Output QRSp-p Interval
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
QRS Detector Algorithm cont.
• ECG Input Data
• Remove Offset
• Filter
• Clip
• QRS Peak Detection
• Output QRS N-N Interval
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
QRS Detector Sample Output
0 500 1000 1500 2000
-2
0
2
4
6
8
10Raw ECG
0 500 1000 1500 2000
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Scaled ECG
0 500 1000 1500 2000
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Clipped ECG
0 500 1000 1500 2000
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Detected QRS w/ Scaled ECG
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Current Status
• Operational– Remove d.c. offset– Clip below amplitude threshold– Detect QRS complexes (clean signals only)
• Pending – Integration with graphical user interface– Digital Filter– QRS Accept/Reject function
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Future Work
• 1st Priority– Integration with graphical user interface– Digital Filter– QRS Accept/Reject function– Final report outline– Testing and debugging
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Future Work Continued
• 2nd Priority– Adaptive amplitude threshold function– Final report draft– Speed and performance improvements
• 3rd Priority– Final report– Final presentation
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Heart Rate Variability (HRV)– Inter Beat Intervals (IBI)
variation in the time intervals between beatsassumes irregular beats have been removednormal to normal (NN) beats
– Instantaneous Heart Rate (IHR)variation in consecutive instantaneous heart rates inverse of IBI
Spectral Analysis
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Power Spectral Density (PSD)– Distribution of Variance Over Frequency
• Three Operations– Resample– Filter– Generate Spectrogram
Fast Fourier Transform (FFT)Transforms Time Signal to Frequency
Spectral Analysis
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Resample
Filter
FFT
QRSDetector
GUIPlot
Block Diagram
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Elapsed Time vs Number of Heart Beats
QRS Output
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Re-Interpreted Data From QRS Detector– NN Intervals – Indexed by Heart Beats
NN Intervals
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Interpolate– Generate Continuous Curve– Passes Through Existing Points
• Sample New Series– Constant Time Period– Required for Fast Fourier Transform (FFT)– NN Intervals vs Time
Resampling Overview
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Resampling
– Input Signal from QRS Detector:
– Resampled Signal:
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Filtering
• Spikes in Signal – Missed Beats by QRS Detector– Distort Valid Data
• Filter– Flattens Large Excursions– Modifies Only Large Outlying Data Points
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Filtering
– Resampled Signal:
– Filtered Signal:
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• Estimating Spectral Power– Remove Mean Value– Perform FFT – Power Calculation - |FFT|2
Spectrogram Algorithm
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
• PSD vs Time
Spectrogram Example
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Features
• Implemented– Plots
ECG
– User ControlsStart/StopWindow SizeScrolling
– ModesHistoricalReal Time
• Planned– Plots
Beat to BeatSpectrogramScaleogram
– User ControlsGraph SelectionNotes
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Process Budget
• Limits– Data Acquisition
10-15% of CPULittle Memory
– Beat Detection5-10% of CPULots of Memory
– Spectrogram Calculation30% of CPU
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Completed
• Hardware– Specified Needs– Purchased / Acquired– Built– Software Completed– Tested on Merlin
• GUI– 2 Plots– Scrolling– Integration of Hardware– Real-time ECG Display– Historical Mode
• QRS Detector– Literature Review
– Scaling
– Clipping
– Beat Detection
• Spectrogram– Resampling
– Median Filter
– Spectral Estimation
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Remaining Tasks
• GUI– Spectrogram
Integration
– QRS Detector Integration
– User Notepad
• QRS Detector– Filtering
– Ectopic Beat Rejection
• Spectral Analysis– Filter Refinement
– Higher Resolution Spectrogram Plot
BIOMEDICAL SIGNAL PROCESSING LAB
b s p . p d x . e d u
PORTLANDNIVERSITYU
STATE ELECTRICAL & COMPUTERENGINEERING
Presentation Overview
• Introduction
• Hardware
• QRS Detector
• Spectral Analysis
• User Interface
• Summary and Conclusion
• Demonstration