Data acquisition

Webinar: https://www.biopac.com/events/how-to-get-high-quality-optical-brain-imaging-data/

Introduction

fNIR Signal Processing slide:

Top left: bad optode contact; there is hair trapped under the optode. You can try to resolve this by placing a headband over the optode to keep it closer to the skin or make the strap tighter. Optode 1 and also a little bit 5 and 3 in this example shows the effect of hair. The sharp change towards the end of the x-axis shows an adjustment where the hair was moved out of the way.

Makeup needs to be removed because it reflects a lot of light and will distort the signal.

Top right: Saturated signals mean the signal is larger than the machine can handle and this signal cannot be recovered. We want a maximum of 3,500 mV. Therefore, we need to make sure we prevent this issue. This can be done prior to the experiment by reducing the gain or the light intensity. If this issue remains undetected until after the experiment, the optode where there is saturation will need to be eliminated from the analysis.

Lower left: spike from motion artifact. Can either eliminate (preferred) or correct for it. Try to prevent by tightening the strap without tension but less possibility to move.

Lower right: good signal.

Acquisition and setup

To start, tell COBI Studio which device you are using. Go to Device → select device and select your device (in the webinar it’s the “USB” device”) → click “select” → “close”.

Synchronize your markers with your data: select either serial or parallel port.

Change light intensity of emitters and receivers and change gain:

For most participants, the default should work, but some might need adjustments.

Make sure all the boxes under “Input source” are checked, this records the ambient light information. This is important to subtract the ambient light artifacts during the analysis.

If you are in a room with very bright ambient light, you can cover the headband with a hat to protect it from the effects of the light.

Select channel layout

Visualize → Operations → Load/Save Layout → Load Layout → select as desired → click “open”

COBI Studio already has a list of preset configurations we can choose from, you can select one here.

In this example, a 16 channel-3 wavelength setup is selected.

This means

oxygenated hemoglobin
deoxygenated hemoglobin
ambient light

Back on the properties screen, you can select “Layout editor” and there you see your 16 optodes listed

If you click on an optode → “Raw channel data – Enter the channel – 0,1,2, - v”, you can see under the optode number what wavelengths are selected for wavelengths 1, 2 and 3.

We can scale each channel separately by selecting:

Properties → Display format → Apply individual graph settings

Can also customize the display format in terms of the width and height of the channels

You can add manual markers. E.g., you can hit the number “1” and a marker is added immediately. In addition, you can select other manual markers under “Manual Markers”.

If you want to end the experiment, press the stop button (this is different in our software):