Equipment Operation & Data Interpretation Flashcards
7 cards from real ABEM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Equipment Operation & Data Interpretation flashcards as text
What is the primary purpose of a notch filter set at 60 Hz in EMG/NCS equipment?
Answer: Eliminate electrical interference from AC power lines
A 60 Hz notch filter selectively attenuates electrical noise introduced by AC power line interference without significantly affecting the biological signal.
When performing nerve conduction studies, a 'stimulus artifact' that obscures the early response is best reduced by:
Answer: Reducing the distance between stimulating cathode and anode
Increasing the distance between cathode and anode reduces the voltage gradient at the recording electrodes, minimizing stimulus artifact.
In needle EMG, the term 'insertional activity' refers to:
Answer: Electrical activity generated by mechanical displacement of muscle fibers during needle movement
Insertional activity is the brief burst of electrical potentials produced when the needle mechanically depolarizes muscle fibers during insertion or movement.
The impedance of recording electrodes should ideally be kept below what value to ensure signal quality in electrodiagnostic studies?
Answer: 5,000 ohms (5 kΩ)
Electrode impedance should be kept below 5 kΩ (with matched impedances between electrodes) to maximize signal-to-noise ratio and minimize artifact.
A nerve conduction study shows a prolonged distal latency with normal conduction velocity in the proximal segment. This pattern is most consistent with:
Answer: Focal demyelination at or near the distal recording site
Focal demyelination at the distal segment slows conduction specifically there, prolonging distal latency while leaving proximal velocity intact.
During F-wave studies, the minimum F-wave latency is used rather than the mean because:
Answer: It reflects the fastest-conducting motor axons and is most reproducible
The minimum F-wave latency reflects the fastest-conducting motor fibers and is the most reproducible and clinically meaningful value.
When calibrating an EMG machine, sensitivity is expressed in:
Answer: Microvolts per division
Sensitivity (gain) on EMG equipment is expressed as microvolts (µV) or millivolts (mV) per division on the vertical axis of the display.