Safety and regulatory procedures for human use

Owned by Christopher Black
Last updated: Apr 09, 2016 by Jakob Voigts
2 min read

The Open Ephys system is currently not considered safe, and is not approved for human use. If you intend to use the system for human EEG, you need approval of your host institution and any applicable regulatory body.

 

A concern of EEG is the introduction of harmful currents through the electrodes that can pass through the participant/patient.  If the EEG system is connected to the mains  a fault or short circuit can cause the mains voltage (~110-240V depending on where you live) to be transposed on the participant via the electrodes.  This would cause a potential difference across the participant and a path for current to flow, which can cause serious injury or death.

We can avoid this problem by isolating the system from the power source. 

Regulatory status / procedures:


The most stringent regulation that we should aim for is the IEC 60601-1, and more specifically the 
IEC 60601-2-26:2012, Medical electrical equipment - Part 2-26: Particular requirements for the basic safety and essential performance of electroencephalographs

links:  general requirements , specific EEG requirements. sadly, it looks like the IEC wants money for the specification documents.

LVDS Isolator Board:

There is an old (and faulty see issues page) design for an isolator for the headstage lvds/spi connection here which should work pretty well, but needs to be redesigned and tested:
https://github.com/open-ephys/headstage-isolation-board

USB isolator:

There are various solutions for electrically decoupling a USB connection - if such a isolator can supply enough DC current to run the board, or can be used with a separate isolation transformer, this could also work pretty well.
Using some transformers (murata technologies NCM6S0505EC) for the 5V supply and isolators (Analog Devices ADUM5000 and ADUM4160) for the USB, we can operate open ephys safely while running human based recordings.

Mains power isolator:

At the 'lowest' level, the entire system can run off a Laptop/portable PC that is running of a battery pack. This still leaves mains voltage on the subject side and in itself is not safe, but should provide protection against mains voltage spikes.