Echocardiogram System Architecture and Design 2 — Questions and Answers
Question 1: Which component in a modern echocardiography system is responsible for converting electrical signals into ultrasound waves?
- Analog-to-digital converter
- Piezoelectric crystal transducer (Correct answer)
- Digital scan converter
- Time-gain compensation circuit
Correct answer: Piezoelectric crystal transducer
Piezoelectric crystals in the transducer convert electrical energy into mechanical (ultrasound) vibrations and vice versa.
Question 2: In phased array transducer design, steering the ultrasound beam in different directions is achieved by:
- Mechanically rotating the transducer face
- Applying sequential time delays to individual elements (Correct answer)
- Varying the frequency of all elements simultaneously
- Changing the transducer's focal depth manually
Correct answer: Applying sequential time delays to individual elements
Phased arrays steer the beam electronically by introducing precise time delays across individual transducer elements to create constructive interference at the desired angle.
Question 3: The digital scan converter in an echocardiography system serves primarily to:
- Amplify weak returning echo signals
- Convert polar scan data to a Cartesian display format (Correct answer)
- Filter harmonic frequencies from the raw signal
- Synchronize transducer firing with the ECG R-wave
Correct answer: Convert polar scan data to a Cartesian display format
The digital scan converter maps sector-format (polar) ultrasound data into the rectangular pixel grid of a video display.
Question 4: Harmonic imaging improves image quality primarily because harmonics:
- Travel faster through tissue than fundamental frequencies
- Are generated within tissue and have less near-field artifact (Correct answer)
- Require lower transmit power reducing patient heating
- Penetrate deeper tissue planes than fundamental waves
Correct answer: Are generated within tissue and have less near-field artifact
Tissue harmonic signals are generated progressively as the wave propagates, building up away from the transducer face, resulting in fewer near-field reverberation artifacts.
Question 5: Spatial compounding in echocardiographic system design refers to:
- Averaging images acquired from multiple steering angles to reduce speckle (Correct answer)
- Using two transducers simultaneously for biplane imaging
- Stacking multiple frequency harmonics to broaden bandwidth
- Applying compound lenses to widen the acoustic aperture
Correct answer: Averaging images acquired from multiple steering angles to reduce speckle
Spatial compounding averages frames acquired at several beam angles, which reduces speckle and improves tissue boundary definition.
Question 6: In a Doppler echocardiography system, the wall filter (high-pass filter) is used to:
- Eliminate high-velocity aliasing artifacts
- Remove low-frequency, high-amplitude signals from cardiac walls (Correct answer)
- Increase the pulse repetition frequency ceiling
- Separate color flow from B-mode imaging channels
Correct answer: Remove low-frequency, high-amplitude signals from cardiac walls
The wall filter rejects strong, low-velocity Doppler signals from slowly moving myocardium and valves so that blood-flow signals can be clearly displayed.
Question 7: Which system parameter most directly determines the maximum unambiguous depth in pulsed-wave Doppler echocardiography?
- Transmit power
- Pulse repetition frequency (PRF) (Correct answer)
- Dynamic range setting
- Receiver gain
Correct answer: Pulse repetition frequency (PRF)
The PRF sets the time window between pulses; a lower PRF allows echoes from greater depths to return before the next pulse is transmitted, increasing maximum depth.
Echocardiogram System Architecture and Design 2
Which component in a modern echocardiography system is responsible for converting electrical signals into ultrasound waves?