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Brainatics

Our industrial partner was to develop the hardware for EEG data acquisition.

Micromed_HiRes.bmp

Four main tasks need to be accomplished:

  1. the development of a high speed, high number of channels, low power EEG recorder (LTM-EU)
  2. the development of a state-of-the-art acquisition interface for data link over cable (BQPCIe)
  3. the set-up of a wide area, low-power wireless connection for monitoring purposes
  4. the development of a software suite to manage the acquisition and the data (prior the database feeding)
The deadline was set by the commission officers to 20 months for the hardware and 24 months for the software from the beginning of the project (1st of January 2008). This was requested to provide the partners for a suitable hardware to be used in the last year to evaluate the effectiveness of prediction algorithms. ltm-eu-poster35dpi.png PCIe35dpi.png

This short time, yet, forced us to develop the hardware carefully trying to find the best trade-off between innovation and consolidated solutions.

The EEG recorder (LTM-EU) requirements were discussed in and defined by the EPILEPSIAE consortium. They were quite challenging considering the low energy budget available (a couple of alkaline AA batteries):

Number of channels >= 64
Sampling rate 2048 (channels)
Communication Wire and wireless
Power consumption < 0.4 W
On-board memory 4 GB
Power supply Cable / Batteries (2xAA)

Number of channels >= 64 Sampling rate 2048 (channels) Communication Wire and wireless Power consumption < 0.4 W On-board memory 4 GB Power supply Cable / Batteries (2xAA)

We used the available technology of our commercial device (SD-LTM) to develop the new one.

At the end of the development period the following improvements were achieved:

  • new input amplifiers
  • new controller for high-end functions (display and operator interface)
  • new programmable logic (higher cells density and lower power)
  • new memory support (SD-MMC vs CompactFlash)
  • new communication physical layer
  • expandable capability: now it is possible to wire up to 8 LTM-EU on the same cable, keeping the high sample rate speed

To have an updated acquisition interface, available for a reasonable amount of time in the PC market, we decided to adopt the PCIe (express) solution.

Nevertheless, the “start-from-zero” development time were believed to be too long and not compatible with the deadline. Hence we sought for a different approach. Luckily, a chip manufacturer, released near the decision deadline a component which could fit the requirements of:

  • easy of hardware design
  • easy of software driver design
  • low cost (for future mass production)

This solution allowed us to design a flexible PCIe (BQPCIe) interface capable to manage data at a speed of 15Mb/s over two independent channels and compatible in Windows and Linux OS.

Wireless capabilities is a feature that nowadays is almost mandatory. This allows the patient to great improve his/her mobility through environments and let him/her to stand the hospitalization in a better way. Nevertheless, wireless must comply, first of all, with the acquisition of faint electrical signals from the brain, hence, high power transmitters (e.g. WiFi) are not advisable also because they need buckets of energy, not available.

Our choice was, from the beginning, the Bluetooth technology as the power requirements complies with the budget and the range fits the requirement. But if wide areas must be covered, the Bluetooth alone cannot solve the issue, due to the short range capability. Hence we adopted the roaming solution: rather than to have strong power in the transmitter to cover a wide area, we can have less transmitter power (and save batteries) and a number of receiving stations, able to “listen” to the transmitter but spread over the “territory” and interconnected. This experimental solution has successfully been tested in hospital environments by the partners.

All this hardware must be “governed” by the software.

Micromed System-Evolution suite was upgraded to manage the new hardware and new Windows drivers was developed to interface with the PCIe acquisition board.

Also a lot of experiments were made to interface the hardware in Linux OS and a basic platform was settled for further developments.

Though the EPILEPSIAE project was quite challenging, we believe that this gave us also the opportunity to improve a lot the hardware and software performances and allowed us to give our contribution for a better “European Health”.

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