EEG Instrumentation and Calibration 4

Question 1

What is the primary purpose of the 'biological calibration' signal used in EEG systems?

Accepted Answer

To verify the amplifier gain using a known physiological signal

Answer

Biological calibration uses a known physiological signal (such as eye blink artifact) to verify that amplifier gain and channel balance are consistent across all channels.

Question 2

A technologist notices that channel 3 shows a 50% smaller deflection than all other channels during the calibration square wave. The most likely cause is:

Accepted Answer

Gain set too low on the channel 3 amplifier

Answer

When one channel shows a consistently smaller deflection than others during a known calibration signal, the amplifier gain for that channel is set too low.

Question 3

Which electrode placement system uses 10% and 20% distances from skull landmarks to determine electrode positions?

Accepted Answer

The International 10-20 system

Answer

The International 10-20 system divides skull circumference into intervals of 10% and 20% from fixed bony landmarks to standardize electrode placement.

Question 4

When performing a square wave calibration, the 'tilt' or slant on the flat top of the square wave most likely indicates a problem with:

Accepted Answer

The low-frequency filter (time constant) setting

Answer

A tilted or slanted flat top on a square wave calibration signal indicates the low-frequency filter (time constant) is cutting off low-frequency components and distorting the sustained DC portion.

Question 5

The standard paper speed used in routine clinical EEG recording in the United States is:

Accepted Answer

30 mm/sec

Answer

30 mm/sec is the standard paper speed for routine clinical EEG in the US, providing optimal visualization of typical brain wave frequencies.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Instrumentation and Calibration 4