Measuring Ocular Microtremor. The Brainstem Has 3 components 4 cranial nerves on each section.
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Transcript of Measuring Ocular Microtremor. The Brainstem Has 3 components 4 cranial nerves on each section.
Measuring Ocular Microtremor
The Brainstem
• Has 3 components
• 4 cranial nerves on each section
Assessing Brainstem Activity• “High Tech”
BIS Technology Expensive (sensors & trained technicians) Can’t use if swelling from head injuries
Glasgow Coma Scale
• “Low Tech”
Cranial Nerves
Unconscious Patients
Very uncomfortable procedures to assess intactness of cranial nerves
Flush 60 oz. of ice cold water in ear
Ocular Microtremors (OMT)OMT have been shown in clinical studies
to accurately reflect brainstem activity
Ocular motor nerves originate in the brainstem where sensory signals are pre-processed and sent to the cerebrum
Oculo-motor nerves originate in the brainstem
These signals are necessary for consciousness
Packaging & Architecture
• Incorporate a disposable element into the sensor mounting apparatus. • Redesign and re-package the electronics for miniaturization and packaging for in-line dongle-type element on the cable.
Objective 1
Objective 2
SignalProcessing
- Signal processing for signal amplification and/or noise reduction
Objective 3Integration Into
Patient Overhead Monitor
• Research and understand the standard(s) used to integrate into this technology • Implement in software with potential hardware modifications for the physical interface.
Current Trend Analysis Software
Component OverviewWaveform Generator
OMT Simulator
Sensor (Provided)
Power Supply
Analog Input/
Preprocessing Circuitry
- Amp
Test MUX
XRAM
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 12-bit A/D and integrated DSP functions,50 MHz clock.
OMT Sensor
Composed of a piezoelectric transducer, and a surface mount IC amplifier
The sensor generates voltage when it undergoes stress, in this case eye movement
The piezoelectric transducer was designed to be really sensitive to slight amounts of stress
Power ManagementThe current “Blackbox” is powered by a
medical grade power supply which provides ±12V for the sensor, and 5V for the processing unit
The Atmel AVR32 processor has a maximum voltage rating of 3.6V
The interface module to the bedside monitor will be powered by the monitor itself
Originally the bedside monitor was going to be used to power both the processor and sensor
Power optionsDual PS/2 – output voltage 5V ±10%Dual MIB/RS232 – output voltage 5V ±5%USB 2.0 – low power mode, output voltage 4.4V
It is more convenient to construct our own custom power supply that is capable of powering both the sensor and processor
Power Management continued
Power Flow
Sensor
Power supply
Signal processing unit
Monitor interface
Bedside monitor
Sample Signal until XRAM Buffer Full
Perform DSP Algorithm on Buffer
Contents
Extract Necessary Data From DSP Output
Send Wave Samples, Freq,
and Amp. to UART(Monitor)
Broad Overview of Software
Sampling Sampling will be interrupt driven, and will continue until a buffer a buffer is filled. Buffer must be large enough for an adequate analysis of signal.
When the first buffer is full, the DSP algorithm will be started on the signal and sampling will continue to a secondary buffer of equal size. Sampling and DSP will alternate between buffers so no data is lost.
The buffer size and sampling rate will be configurable over the UART.
A/D
DSP
Buffer 1
Buffer 2
XRAM
DSP Output
Bus
FFT – Generate
Output Array in XRAM
Search Valid Range of Array for
Max Energy
Zero Out Locations
Outside of OMT Range (Filter)
Inverse FFT to Obtain Filtered
Waveform in Time Domain
FFT Method
Amplitude/
Frequency
Output
Filtered Waveform Output
-An FFT is performed on the contents of the sample buffer, with spectrum data saved to an array.
-The array locations corresponding to the valid OMT range are searched for the maximum energy, giving the Frequency and Amplitude of the OMT signal.-An inverse FFT on only the valid OMT frequency range is required to reconstitute a time-domain waveform that can be sent to the bedside monitor.
Digital HPF/LPF/Not
ch Filter Routines
Modify Buffer
Filtered Wavefor
m Output
Peak-Count and
Amplitude-Averaging Algorithm
Amplitude/
Frequency
Output
Peak-Detection Method
-Digital filter routines modify the contents of the buffer, giving a filtered signal that could be sent to the bedside monitor.
-Positive-to-negative changes in slope are counted, giving the frequency. The amplitudes at which this occurs are averaged.
Wavelets – Short Oscillations of a given frequency. Can be compared to our signal to determine if energy at that frequency is present.
Bedside Monitor InterfacePhilips VueLink Module
1032ARS-232 Input – Open
Interface ProtocolAllows 1 Waveform (OMT
Signal), 2 Numerics (Amplitude and Frequency), Diagnostic Messages (ex. OMT out of valid range), and Alarms (ex. OMT below certain value)
http://www.sentec.ch/fileadmin/documents/manuals/EN-HB-005928-b-SDM_VueLink_Installation_Manual.pdf
Testing and Data MiningImportant in order to determine the pattern
and/or trend of OMT signalsDetermining a pattern is vital to the signal
processing componentThe process involves a subject (one of us) to
lie down and have the sensor mounted on a closed eyelidusing surgical sensitive tape
Due to a lack of FDA approval and other required certification, we will not be able to gather data on a large scale basis
Vivian’s OMT
Mark’s OMT
Division of LaborMark Tom Vivian Salman Steve
PowerPower Supply x xPowering Sensor x xMCUSignal Sampling - A/D x xDSP of Signal x xInterfaceAnalog Sensor x xOutput Interface (monitor) x xManufacturingPCB x x xDongle x x xAdministrativeMediary to EyeTect x xMediary to medical experts xDocumenatationTechnical Manual xUser's Manual xUROP/EEF xExtra (if time)Data Mining/Trend Evaluation x xBedside Monitor x x
Schedule
First Milestone Second Milestone Pre-Expo
Grants Throughout Semester
BudgetExpenses
Product Unit Cost Amount Total Cost ProviderProcessing/Manufacturing
Atmel AVR32 Development Kit 179.00 1 179.00 http://mouser.com/2-layer PCB 33.00 3 99.00 http://www.4pcb.comPackaging 20.00 1 20.00
InterfaceVuelink M1032A 300.00 1 300.00 http://www.hp.com
Philips M3 Bedside Monitor 2,650.00 1 2,650.00 http://www.dotmed.comMedical Grade Power Supply
Capacitors 10 30.00Diodes 10 30.00
Power MOSFET Transistor 4.25 10 42.50Cooling Fan/Heat Sink 42.00 1 42.00
Power MCU 74.00 1 74.00Packaging 20.00 1 20.00
Administrative CostsPrinting Manuals 40.00 1 40.00
Poster 75.00 1 75.00Shipping/Handling Fees 200.00 1 200.00
Margin7% 266.11
Total 4,067.61
FundingOutside Funds
EyeTect 3,000.00UROP ?
Interference Concerns
Accidental patient movementElectrical noise from other equipment in
the ICU roomNoises in excess of 95 dBHeartbeat
ContingenciesSoftware implementation of display if
bedside monitor is not able to be acquired
Scaling number of processors to ensure proper operation
Purchasing additional components to ensure minimal downtime especially before expo
RisksDuring application of sensor patients’
eye may be agitated
Additional cord is hanging off of patient
Possibility of dongle removing sensor from patients’ eye if too heavy
Components may be destroyed if wired incorrectly
Extension possibilities
Add through connections in order to minimize hanging cables
Adding accelerometer to measure patient movement to find bad samples
Questions?