Measuring Ocular MicrotremorThomas

RutkowskiVivian PhinneySalman Al-Saif

Mark HasemeyerSteve Carroll

Ocular Microtremors (OMT)

-Low-amplitude, high-frequency tremors of the eye. (20-100Hz)

-Caused by random, ground-state signals on oculo-motor nerves

-Oculo-motor nerves originate in brain stem. OMT indicates brainstem health.

-OMT correlated with patient’s level of consciousness.

-Gives strong indication of the chances of recovery for coma patients.

System OverviewWaveform Generator

OMT Simulator

Sensor (Provided)

Power Supply

Analog Input/

Preprocessing Circuitry

- Amp

Test MUX

Microprocessor with Integrated A/D, UART, and

DSP

Bedside Monitor (Philips MP-

60/70 or Agilent V24/26)

Philips VueLink Module – M1032A

For MCU, currently looking at Atmel AVR32 with 10-bit A/D and integrated DSP functions,50 MHz clock.

System Module Overview

LCD SD Card

16-bit Timer

10-bit A/DUART

Controller

256kB Flash

AVR32UC3B1256 Microcontroller

16Mhz Crystal

PLL – 50 Mhz CPU Clock

Signal Conditioni

ng

Sensor

RealTerm/ Bedside Monitor

3.3 V Power Supply

MAX3380E UART Level

Shifter

SPI Controller

3.5” Graphic LCD

16-bit Parallel Interface

SD Card

Basic CPU Architecture and Connectivity

GPIO Controller

Start Sampling Buffer 0

Wait until Buffer 0 Full (1 sec)

Start Sampling Buffer 1, Start FFT

on Buffer 0

Wait until Buffer 1 Full (1 sec) – FFT on Buffer

0 finishes ~1 ms

Start Sampling Buffer 0, Start FFT

on Buffer 1

Find OMT frequency from FFT output just

completed

Currently using 1024 sample buffer and 1024 kHz sampling frequency, giving 1 second of data in buffer.

Send frequency and waveform

samples to UART(monitor),

LCD, and SD card.

Perform inverse FFT on

frequencies within valid

range. Wait until Buffer 0 Full (1 sec) – FFT on Buffer

1 finishes ~1 ms

Processing Algorithm

Signal Processing – General OverviewUsing FFTs, much faster than DFT

algorithmsAtmel studio has several built in FFT

algorithms that require minimal modification But… it’s not working as we had anticipated

Further work in DSP is needed Just recently got sampling, buffers, and FFT

workingFurther testing required to find optimal DSP

algorithm

Signal SamplingUsing the built in ADC in the Atmel processor to

sample data

The input voltage ranges from 0V to 3.3V (adjustable), the signal needs to be scaled and clamped to avoid causing damage to the processor

Use of a 8:1 voltage divider, or an op-amp circuit with gain K = 0.125, assuming a maximum 12V input from the sensor IC

A 3V zener diode is used to clamp the analog input, or a comparator circuit

Signal Sampling (contd.)-Sensor output is in the range ±12 V

-A/D takes 0 - 3.3 V

-First stage inverts and scales sensor output to ±1.5 V

-Second stage adds 1.5V DC offset for new range of 0 – 3 V for A/D

Signal to be sampledFrequency components at 15Hz, 90Hz, and

165Hz

Signal recreated with MATLAB

0 20 40 60 80 100 120 140 160 180 200200

210

220

230

240

250

260

270

280Sampled Signal, Frequency Content at 15Hz, 90Hz, 165Hz

Vol

tage

[m

V]

Time

FFTAs with other things involving signal processing,

we are currently experimenting with the built in FFT functions

The FFT routines functioned properly with minimal modifications

Going forward, two possible solutions to processing that we are consideringAfter determining the frequency of the OMT signal,

a sinusoidal wave is generated with varying amplitudes proportional to the OMT

Using wavelet processingWe will know more once we’ve done more careful

testing, since our sensor is very sensitive, there is a lot of room for error

FFT (contd.)Filtering and Noise Reduction

As mentioned previously in PDR, the OMT frequency range lies between 40Hz and 120Hz

Use of a high pass filter at 20Hz, and a low pass filter at 150Hz

We identified the main source of noise as that coming from various power lines across the room

A notch filter is used (bandstop) for the frequency range 57Hz-62Hz

Sensor is sensitive, picks up the slightest movement, another sensor might be used to provide a differential solution

The other main artifact that affects the signal is heartbeat and voice, we are still considering solutions to both problems

FFT (contd.)The following slide represents an example of

the same signal sampled aboveWe used the FFT algorithms to represent the

frequency content of the analog signalSimple processing was done to filter out

unwanted frequency content (below 20Hz, above 150Hz, and 60Hz)

The slide after that is a capture of Vivian’s OMT frequency content

0 50 100 1500

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2Fourier Transform of Processed Signal

Ene

rgy

Frequency [Hz]

Processed signal

Captured OMT Signal over 1 Second Interval

We believe that thorough testing and experimentation is very important to the success of our project

After CDR, we will continue with OMT processing

Power ManagementUtilizing a medical grade power supply, since

project is not power centric, plus it is safer to go with this option and avoid any risk or harm to the experimental subjects (basically us)

ELPAC MED113TT, provides three regulated outputs, 5V, ±12V

LP2951 voltage regulator from TI will be used to power the Atmel processor

Power Management (contd.)

Bedside Monitor • Leasing from Medelco

• Lease will include:

Philips MP70 Touch Screen Monitor

M1032A Vuelink Interface Module

M8048A FMS (Flexible Module Server)

M3001A MMS (Multiple Monitoring System)

• Possibly:

M1032A#K66 Cable with DSUB-9 connector

VueLink Cable Pinout Showing UART Tx/Rx Lines

VueLink Connector

DB-9 Connector

Backup Plan - Analog Input Signals

LCD Display

http://www.crystalfontz.com/product/CFAF240320K-T-TS

-Parallel or SPI Interface to LCD- 4-Wire Resistive Touch Panel- Will display small waveform and OMT frequency, in addition to bedside monitor display. -Touch-screen menu may allow user to configure data-logging options, sampling rate, and buffer size.

SD Card Socket Board

http://www.sparkfun.com/commerce/product_info.php?products_id=204

Breakout Board for SD-MMC Cards

Routes SD card pads to solder able through-hole connector.

We will use SPI mode to read/write from card.

Card requires 3.3 V

Data Logging can be started using touch screen menu on LCD.

Risks and ContingenciesBlowing the sensor piezo-transistor or integrated IC amp

Eyetect shipped a backup sensor earlier this week The FFT signal processing algorithm is a concern

Waveform spiky and aperiodic Now that we have the sampling, buffers and basic FFT

working, can test other processing strategies: Wavelets FIR Filters on Buffer followed by Peak-Count Algorithm Statistical Analysis

Product Unit Cost Amount Total Cost Provider

PROCESSING/MANUFACTURING Atmel AVR32 Development Kit 179.00 1 179.00 http://mouser.com/4-layer PCB 66.00 3 198.00 http://www.4pcb.com

Packaging 95.00 2 190.00 http://www.firstcut.com/

INTERFACE Philips M3 Bedside Monitor 600.00/mo. 2.5 1,500.00 http://www.medelco.com/patient_monitors.html

Vuelink M1032A - 1 -

M3001A MMS (Multiple Monitoring System) - 1 -M8048A FMS (Flexible Module Server) - 1 -

Vuelink connector to DSUB9 Cable 175.00 1 175.00 http://www.dotmed.com/listing/594385LEMO Circular Push Pull Connectors 24.92 3 74.76 http://mouser.com/2GB SD Flash Card Model CT2GBSD 7.99 1 7.99 http://www.newegg.com/

Breatkout Board for SD-MMC Card BOB-00204 17.95 3 53.85 http://www.sparkfun.com/ LCD Display - CFAF240320K-T-TS 30.74 3 92.22 http://www.crystalfontz.com/

MEDICAL GRADE POWER SUPPLY Voltage Regulator LP2951_33 (3.3V) 0.96 5 4.80 http://www.newark.com/Surface mount bypass capacitors (25

capacitors) 4.50 2 9.00 http://www.ti.com/Surface mount resistors 0.20 30 6.00 http://www.amazon.com/Power Connector (5-pin) 5.50 2 11.00 JB Saunders

ALPS_SKHUQBO56A Switch 2.00 2 4.00 http://www.allelectronics.com

ADMINISTRATIVE COSTS Printing Manuals 40.00 1 40.00 Poster 12.00/ft. 4 feet 48.00

Rider Insurance Policy for Bedside Monitor 250.00 1 250.00 Shipping/Handling Fees 100.00 2 200.00

MARGIN 7% 213.05

TOTAL COSTS 3,256.67 Outside Funds

OUTSIDE FUNDING EyeTect 3,000.00UROP 800.00

Northrop Grumman 200.00TOTAL FUNDING 4,000.00

Current Budget

Division of LaborTom Vivian Mark Salman Steve

Power

Power Supply X

Powering Sensor X X

MCU

Signal Sampling - A/D X X

DSP of Signal X X X

Interface

LCD Interface on Dongle X

Data Capture on SD Card X X

Condition Sensor Output X X X

Patient Bedside Monitor Interface X X

Manufacturing

PCB X X

Dongle X

Documentation

Technical Manual X X

User's Manual X X

UROP X

Extra (if time)

Data Mining/Trend Evaluation X X

Deliverables

Timeline

Questions?In Order of Appearance:

Tom

Steve

Salman

Mark

Vivian