= Digitize EEG Sensors and Head Shape =
== Getting Started ==
The Brainstorm Digitize application allows for a connection to a Polhemus device and collection of digitized head points and/or EEG sensor locations.

The connection to the device is made via a serial port connection. This can be accomplished using a direct serial connection or with a USB-to-Serial cable connection to the host computer.

{{attachment:polhemus.png}} Figure 1. Polhemus system with two receivers and one transmitter

{{attachment:typical_polhemus_setup.png}} Figure 2. Typical Polhemus setup

The application is designed for two receivers (i.e. the stylus and reference) one transmitter.

The '''stylus''' is used by the operator to point to the desired position for collection

The '''reference''' is fixed to the subject’s head, typically with glasses or headband. While the subject’s head can move during the collection, the reference sensor should not move from the starting position relative to the head.

The '''transmitter''' is fixed behind the subject, typically to a non-metal chair or table. The orientation is shown here, with X+ pointing up and Y+ point to the right. {{attachment:transmitter.png}} Figure 3. Transmitter orientation
****Care should be taken when setting up this system to ensure accurate collection. Thorough testing should be performed using known head coordinates (phantom) to determine accuracy.

The head coordinate system used in the Digitize application is based on the CTF head coordinate system, see /CoordinateSystems.

To start the Digitize application, start Brainstorm. Then select ‘Digitize’ from the File Menu.
{{attachment:bst_menu_digitize.png}} Figure 4. Starting Digitize

The Brainstorm GUI will be hidden during the use of the Digitize application and will reappear after exiting Digitize.