Board Prep - Trusted Neurodiagnostic Academy - Digital Instrumentation

Digital calibration

Each individual electrode is compared to a system reference

Analog calibration verifies the 70 Hz high filter standard setting by assessing which of the following?

The sharpness of the tip of the calibration signal

Performing square wave and biological calibration on a digital EEG instrument does which of the following?

Verifies standard instrument settings are correct before beginning the recording

The energy internal to the EEG instrument used to perform square wave calibration is called ____________.

Input voltage

If the activity of input 1 is more negative than input 2:

The EEG deflection will go up

If the EEG amplitude is high, you should

Decrease your sensitivity

The purpose of the differential amplifier is:

cancel out external noise in both inputs

The bandwidth is the...

The frequencies inside the set filter settings

The function of the HFF is:

Attenuate the high frequencies without affecting the low frequencies

What causes Phase Lead?

Low Frequency Filter

What causes Phase Lag?

High Frequency Filter

The cutoff frequency

the frequency at which there will be a 30% reduction in amplitude of the signal

The time constant in the HFF

the time it takes for the calibration signal to rise 63%

A notch filter

removes only the frequency inside the notch filter

Lowering the HFF could result in:

decrease muscle artifact

To better visualize spikes:

increase the LFF

What is called a sensor on a digital EEG system?

the scalp electrode

A signal that is continuous without breaks is called:

an analog signal

The second component of the digital EEG system is:

an analog amplifier

The purpose of the analog amplifier is to:

boost the waveform for further processing

The purpose of the ADC circuit is to:

transform the signal into a number

The introduction of a virtual signal into the waveform is called

aliasing

Current EEG systems have a _____ ADC processor.

16 bit

The benefit to having a large range of amplitude for a digital EEG system is:

you can see all high and low amplitude signals with good resolution

Dwell time is:

the length of time between to sample points

The Nyquist Theorem

the fastest signal that can be recorded is the frequency that is half the sampling rate of the digitizer.

What happens when you record a signal faster than the Nyquist frequency?

your signal has less peaks than the original signal

ACNS recommends a sampling rate of at least:

256

Extra receptacles in the jackbox may used to record _____________.

any signal of cerebral or artifactual origin

If the inputs of the differential amplifier are equipotential what do you expect the output signal to be?

no output signal (flat line)

If the inputs of the differential amplifier are in phase, but not equipotential what do you expect the output signal to be?

A small output signal

Reducing (going to a lower number) the high filter setting does which of the following?

attenuates fast frequencies

Changing the low filter setting to a lower number is the equivalent of which of the following?

changing to a longer time constant

Reducing the setting of the low pass filter will affect which of the following?

attenuates spikes

Which of the following frequencies is most attenuated by a high filter setting of 35 Hz?

100 Hz

Which of the following is NOT affected by a high filter setting of 15 Hz?

theta

Which of the following is affected by the Notch Filter?

60 Hz

Time Constant

square wave calibration

Which of the following accentuates focal slow activity?

long time constant

What is the standard paper speed for the recording of EEG?

10 pages per second

Which of the following is NOT a reason to use fast (5 seconds per page) paper speed?

better visualize periodic activity

The EEG is being recorded with standard sensitivity and filter settings. When excessive muscle cannot be reduced or eliminated by patient relaxation the technologist should do which of the following?

change the high (low pass) filter from 70 Hz to 35 Hz or to 15 Hz