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					Measuring Ocular Microtremor
         Thomas Rutkowski
          Vivian Phinney
           Salman Al-Saif
          Mark Hasemeyer
            Steve 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 Module Overview
            System Overview
           Waveform
                                               Bedside Monitor
           Generator
                                              (Philips MP-60/70
                                   Test MUX   or Agilent V24/26)
              OMT
            Simulator                                Philips
                                                    VueLink
             Sensor                                 Module –
           (Provided)                               M1032A
                             Analog Input/     Microprocessor
                             Preprocessing     with Integrated
                               Circuitry -     A/D, UART, and
                                  Amp                DSP
For MCU, currently looking
at Atmel AVR32 with 10-bit
A/D and integrated DSP       Power Supply
functions,50 MHz clock.                       LCD              SD Card
Basic CPU Architecture and Connectivity
           16-bit Parallel Interface    3.5” Graphic
                                            LCD             AVR32UC3B1256 Microcontroller

  Sensor
                                           GPIO
                                         Controller
   Signal                                                UART                MAX3380E
Conditioning                10-bit A/D                                       UART Level
                                                       Controller
                                                                               Shifter

                          16-bit Timer                256kB Flash
                                                                             RealTerm/
                                                                              Bedside
                          PLL – 50 Mhz                                        Monitor
                           CPU Clock              SPI Controller



                              16Mhz
                                                       SD Card            3.3 V Power
                              Crystal
                                                                             Supply
                                                Start Sampling
  Start Sampling       Wait until Buffer 0
                                               Buffer 1, Start FFT
     Buffer 0            Full (1 sec)
                                                  on Buffer 0

      Find OMT
   frequency from                                    Wait until Buffer 1 Full
   FFT output just                                   (1 sec) – FFT on Buffer
      completed                                          0 finishes ~1 ms

   Perform inverse
        FFT on
     frequencies
     within valid
        range.                               Wait until Buffer 0 Full
                                             (1 sec) – FFT on Buffer
   Send frequency                                1 finishes ~1 ms
    and waveform
     samples to
   UART(monitor),                              Start Sampling
  LCD, and SD card.                           Buffer 0, Start FFT
                                                 on Buffer 1
Processing Algorithm   Currently using 1024 sample buffer and
                       1024 kHz sampling frequency, giving 1 second of data in buffer.
Signal Processing – General Overview
 Using FFTs, much faster than DFT algorithms
 Atmel 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 working
    Further testing required to find optimal DSP algorithm
Signal Sampling
 Using 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 sampled
 Frequency components at 15Hz, 90Hz, and 165Hz
Signal recreated with MATLAB
                             Sampled Signal, Frequency Content at 15Hz, 90Hz, 165Hz
                  280


                  270


                  260


                  250
   Voltage [mV]




                  240


                  230


                  220


                  210


                  200
                        0   20    40     60     80    100    120    140    160    180   200
                                                     Time
FFT
 As 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 considering
    After determining the frequency of the OMT signal, a
     sinusoidal wave is generated with varying amplitudes
     proportional to the OMT
    Using wavelet processing
    We 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 above
 We used the FFT algorithms to represent the
  frequency content of the analog signal
 Simple 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
Processed signal
                     Fourier Transform of Processed Signal
            2

           1.8

           1.6

           1.4

           1.2
  Energy




            1

           0.8

           0.6

           0.4

           0.2

            0
                 0        50                      100        150
                                Frequency [Hz]
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 Management
 Utilizing 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




-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.                      http://www.crystalfontz.com/product/CF
                                            AF240320K-T-TS
                      SD Card Socket Board
                                         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.

   Breakout Board for SD-MMC Cards




http://www.sparkfun.com/commerce/produ
ct_info.php?products_id=204
Risks and Contingencies
 Blowing 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
                                                            Current Budget
                                                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.htm
                                            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/594385
                                 LEMO 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                     3,000.00
                                                UROP                        800.00
                                          Northrop Grumman                  200.00
      TOTAL FUNDING                                                                             4,000.00
                  Division of Labor
                                                      Tom   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
                          Expo

Deliverables              • Bedside Monitor Interfaced
                          • LCD on Dongle Functioning
                          • Packaging Finalized



                    Milestone 2
                    • PCB
                      • Sized for Production
                      • SD Card reader Integrated
                    • Signal Processing Implemented
                    • CAD Design sent to Plastic Casing Company




          Milestone 1
          •   Obtain Bedside Monitor and Open Interface Specification
          •   SD Card Interfaced with Microcontroller
          •   Sample the Sensor Signal (save on SD Card)
          •   Finalize which Sampling Algorithm to Use
Timeline
Questions?
In Order of Appearance:
          Tom
         Steve
         Salman
         Mark
         Vivian

				
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posted:8/23/2012
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