11

Portable HeartPortable HeartAttack DetectorAttack Detector

(PHAD)(PHAD)Final PresentationFinal Presentation

Nov 27, 2005Nov 27, 2005

Technion - Israel Institute of TechnologyDepartment of Electrical Engineering

High-Speed Digital Systems Lab

SupervisorSupervisorDaniel AlkalayDaniel Alkalay

System architecturesSystem architecturesNir GluzmanNir GluzmanAlexei IolinAlexei Iolin

22

AGENDAAGENDAProject objectiveSystem block diagramECG signal analysis algorithmFirmware block diagramLabVIEW development platformVI blocks and GUISummary and conclusionsSystem demonstration

33

Develop a system that detects R characteristic point and measures ST-elevation and QRS duration.

Implement the system on National-Instrument(*) Real-Time FPGA development environment using LabVIEW graphical programming language.

Project objectiveProject objective

(*)(*) website: http://ni.comPXI-7831RPXI-1042Q

44

Basic ECG complex

R

P

Q

S

T

55

ST Elevation

66

System block diagramSystem block diagram

77

ECG signal analysis ECG signal analysis algorithmalgorithm

ECG characteristic points are detected with DWT (Discrete Wavelet Transform). DWT is implemented with “Algorithme à trous” (implementation without decimation).

Source: “A wavelet-based ECG delineator: evaluation on standard databases”,IEEE Transaction on biomedical engineering, April 2004.

88

Algorithm Algorithm (cont.)(cont.)

The Wavelet transform (WT) is proportional to the derivative of the filtered version of the signal.

Zero-crossing of the WT corresponds to the local maxima or minima of the filtered signal.

Maximum absolute values of the WT are associated with the maximum slopes in the filtered signal.

Why can ECG characteristic points be detected with Wavelet transform?

99

Algorithm Algorithm (cont.)(cont.)ECG waves are composed of slopes and local maxima or minima.

Therefore, QRS complex produces an unique pattern (max-min-max).

5.7 5.8 5.9 6 6.1 6.2 6.3 6.4 6.5-400

-300

-200

-100

0

100

200

time [sec]

d4

ECG signalQ

R

S

T

J

1010

ECG characteristic pointsdetection flow chart

Detection of Q

Detection of R Detection of S

Detection of J

Calculation ofST level

Calculation ofQRS duration

1111

Q, S detection

Wavelet Decomposition

d4

RMS condition?

ECG sampling

NO

Globalmax. point?

YES

NO

Q characteristic point

Start R search

Globalmin. point?

NO

S characteristic point

YES

Stop R search

YES

1212

R detectionStart R search

d4 zerocrossing?

R characteristic point

Stop Rsearch?

YES

Next QRS complex

YES

1313

Firmware block diagramFirmware block diagramAlgorithm has been implemented in VHDL.Firmware includes 3 main blocks:

Wavelet decomposition. d4 signal processing for QRS complex detection and

calculation of QRS duration. ST elevation calculation.

1414

Firmware Firmware (cont.)(cont.)Top level

1515

LabVIEW developmentLabVIEW developmentplatformplatform

Graphical programming language with built-in functions for I/O, control, analysis and data presentation.LabVIEW advantages:

Intuitive graphical development similar to flowcharting. Bulit-in tools for design, control, data acquisition and

data presentation.

What is LabVIEW?

1616

LabVIEW developmentLabVIEW developmentplatform platform (cont.)(cont.)

Platform includes two independent modules: LabVIEW for Windows (Host):

Floating-point calculations. Data presentation. Off-line data acquisition.

LabVIEW for FPGA: Fix-point signal processing. Real-time data acquisition. VHDL integration.

Synchronizationvia

interrupts

1717

VI blocks and GUIVI blocks and GUI

Data trans-ceiving between FPGA (signal processing) and host (data presentation) is based on synchronization interrupts.FPGA synchronization interrupts demands sequential framing operations:FPGA VI includes three frames:

I/O and signal processing modules (VHDL core). Sampling time delay. IRQ to host.

HDL clock is synthesized from ‘while loop’ index’s LSB.

FPGA

1818

VI blocks and GUI VI blocks and GUI (cont.)(cont.)FPGA VI

1919

VI blocks and GUI VI blocks and GUI (cont.)(cont.)Host

Host includes two independent sub VIs: Test mode for system verification (off-line ECG

analyzing). Real-time controlling mode for analyzing on-line ECG

signals.

Host’s GUI graphically presents both sub VIs outputs and controls FPGA module.

2020

VI blocks and GUI VI blocks and GUI (cont.)(cont.)Test mode VI

2121

VI blocks and GUI VI blocks and GUI (cont.)(cont.)Real-time controlling mode VI

2222

VI blocks and GUI VI blocks and GUI (cont.)(cont.)System’s GUI

2323

Summary and conclusionsSummary and conclusionsProject involves a system development for a medical application.The system is based on a firmware implementation for a sophisticate signal processing algorithm (DWT).ECG real-time DWT analysis is feasible for HW implementation.This project has familiarized us with new development tools and techniques, such as: LabVIEW, HDL designer, ModelSim, Matlab/Simulink. Real-time system development. HW-SW integration.

2424

Summary and conclusionsSummary and conclusionsSystem performance

Both QRS complex and R characteristic point FP (False Positive = false alarm) rates are very low.QRS complex TP (True Positive) rate is very high (>95%).R characteristic point TP rate is lower than in Matlab/Simulink model, because implemented algorithm doesn’t use d2 and d3 (in addition to d4).

System can be used as STEMI detector, because QRS complex TP rate is high enough to detect irregular ST level variations on time.

2525

Summary and conclusionsSummary and conclusionsLabVIEW platform advantages

Rapid prototype system.Dedicated hardware and software.I/O easy access.

2626

Summary and conclusionsSummary and conclusionsLabVIEW platform disadvantages

Development environment is non-conventional - design extraction to other non NI environments is NOT possible.VHDL code is hidden from user.

Lack of debugging tools.

Unfriendly VHDL interface.

Emulator supports FPGA simulations but doesn’t support IRQ simulation (FPGA-Host data trans-ceiving).

2727

System demonstrationSystem demonstration

The faculty ofmechanical engineering

2828

Questions?Questions?