ARDMS SPI EXAM LATEST EXAM 2025 | ALL QUESTIONS
AND CORRECT ANSWERS (GRADED A+) | VERIFIED
ANSWERS | LATEST VERSION
Sonography Principles & Instrumentation | Key Domains: Ultrasound Physics, Transducers & Beam
Formation, Instrumentation & Image Processing, Doppler Principles & Hemodynamics, Artifacts,
Bioeffects & Safety (ALARA), Quality Assurance, and Ergonomics | Expert-Aligned Structure |
Exam-Ready Format
Introduction
This structured ARDMS SPI (Sonography Principles & Instrumentation) Exam for 2025 provides
110 high-quality exam-style questions with correct answers and rationales. It emphasizes core
ultrasound physics concepts, equipment operation, image optimization techniques, Doppler physics,
artifact recognition, and the application of safety principles critical for clinical practice and board
certification.
Answer Format
All correct answers must appear in bold and cyan blue, accompanied by concise rationales
explaining the underlying physical principle, instrumentation function, clinical implication, and why
alternative options are scientifically or practically incorrect.
1. Which of the following is a mechanical index (MI) used to estimate?
A. Thermal effects of ultrasound
B. Risk of cavitation
C. Spatial peak temporal average intensity
, D. Beam width
Rationale: The Mechanical Index (MI) is a dimensionless number displayed on ultrasound machines
that estimates the likelihood of non-thermal bioeffects, specifically inertial cavitation. It is
calculated as peak rarefactional pressure divided by the square root of frequency. A higher MI
indicates greater cavitation risk.
2. In Doppler ultrasound, aliasing occurs when:
A. The Doppler angle is 90 degrees
B. The velocity exceeds the Nyquist limit
C. The transducer frequency is too low
D. The wall filter is set too high
Rationale: Aliasing is a sampling error in pulsed-wave Doppler that occurs when the blood velocity
exceeds half the pulse repetition frequency (PRF), known as the Nyquist limit. This causes the
waveform to "wrap around" the baseline. Solutions include increasing the PRF, using a lower
frequency transducer, or shifting the baseline.
3. Which transducer type produces a rectangular image format?
A. Phased array
B. Linear array
C. Curvilinear array
D. Annular array
,Rationale: A linear array transducer has elements arranged in a straight line and produces a
rectangular (or square) field of view. Phased arrays produce a sector image; curvilinear arrays
produce a blunted sector; annular arrays produce a sector with dynamic focusing along the beam
axis.
4. The primary advantage of harmonic imaging is:
A. Increased penetration depth
B. Reduction of near-field and side-lobe artifacts
C. Higher frame rate
D. Improved Doppler sensitivity
Rationale: Harmonic imaging uses frequencies that are integer multiples (usually the 2nd
harmonic) of the transmitted frequency. Since harmonic signals are generated primarily in the focal
zone and not in the near field, this technique reduces near-field clutter and side-lobe artifacts,
resulting in improved image contrast and clarity.
5. The thermal index (TI) is a measure of:
A. Cavitation potential
B. Estimated tissue heating
C. Beam intensity in water
D. Pulse duration
, Rationale: The Thermal Index (TI) is a real-time display on ultrasound systems that estimates the
maximum temperature rise in tissue due to ultrasound absorption. TI = 1 indicates a potential 1°C
temperature rise; TI > 1 suggests greater heating risk, especially in sensitive tissues like fetal brain
or eye.
6. Which of the following artifacts causes a structure to appear deeper than it actually is?
A. Mirror image
B. Speed error (range error)
C. Refraction
D. Reverberation
Rationale: Speed error (also called range error) occurs when ultrasound travels through a medium
at a speed different from the assumed 1540 m/s (e.g., through fat or fluid collections). If sound
travels slower than 1540 m/s, the machine assumes it took longer to return, placing the reflector
deeper than its true location.
7. The pulse repetition frequency (PRF) is primarily limited by:
A. Transducer frequency
B. Imaging depth
C. Beam width
D. Gain setting
AND CORRECT ANSWERS (GRADED A+) | VERIFIED
ANSWERS | LATEST VERSION
Sonography Principles & Instrumentation | Key Domains: Ultrasound Physics, Transducers & Beam
Formation, Instrumentation & Image Processing, Doppler Principles & Hemodynamics, Artifacts,
Bioeffects & Safety (ALARA), Quality Assurance, and Ergonomics | Expert-Aligned Structure |
Exam-Ready Format
Introduction
This structured ARDMS SPI (Sonography Principles & Instrumentation) Exam for 2025 provides
110 high-quality exam-style questions with correct answers and rationales. It emphasizes core
ultrasound physics concepts, equipment operation, image optimization techniques, Doppler physics,
artifact recognition, and the application of safety principles critical for clinical practice and board
certification.
Answer Format
All correct answers must appear in bold and cyan blue, accompanied by concise rationales
explaining the underlying physical principle, instrumentation function, clinical implication, and why
alternative options are scientifically or practically incorrect.
1. Which of the following is a mechanical index (MI) used to estimate?
A. Thermal effects of ultrasound
B. Risk of cavitation
C. Spatial peak temporal average intensity
, D. Beam width
Rationale: The Mechanical Index (MI) is a dimensionless number displayed on ultrasound machines
that estimates the likelihood of non-thermal bioeffects, specifically inertial cavitation. It is
calculated as peak rarefactional pressure divided by the square root of frequency. A higher MI
indicates greater cavitation risk.
2. In Doppler ultrasound, aliasing occurs when:
A. The Doppler angle is 90 degrees
B. The velocity exceeds the Nyquist limit
C. The transducer frequency is too low
D. The wall filter is set too high
Rationale: Aliasing is a sampling error in pulsed-wave Doppler that occurs when the blood velocity
exceeds half the pulse repetition frequency (PRF), known as the Nyquist limit. This causes the
waveform to "wrap around" the baseline. Solutions include increasing the PRF, using a lower
frequency transducer, or shifting the baseline.
3. Which transducer type produces a rectangular image format?
A. Phased array
B. Linear array
C. Curvilinear array
D. Annular array
,Rationale: A linear array transducer has elements arranged in a straight line and produces a
rectangular (or square) field of view. Phased arrays produce a sector image; curvilinear arrays
produce a blunted sector; annular arrays produce a sector with dynamic focusing along the beam
axis.
4. The primary advantage of harmonic imaging is:
A. Increased penetration depth
B. Reduction of near-field and side-lobe artifacts
C. Higher frame rate
D. Improved Doppler sensitivity
Rationale: Harmonic imaging uses frequencies that are integer multiples (usually the 2nd
harmonic) of the transmitted frequency. Since harmonic signals are generated primarily in the focal
zone and not in the near field, this technique reduces near-field clutter and side-lobe artifacts,
resulting in improved image contrast and clarity.
5. The thermal index (TI) is a measure of:
A. Cavitation potential
B. Estimated tissue heating
C. Beam intensity in water
D. Pulse duration
, Rationale: The Thermal Index (TI) is a real-time display on ultrasound systems that estimates the
maximum temperature rise in tissue due to ultrasound absorption. TI = 1 indicates a potential 1°C
temperature rise; TI > 1 suggests greater heating risk, especially in sensitive tissues like fetal brain
or eye.
6. Which of the following artifacts causes a structure to appear deeper than it actually is?
A. Mirror image
B. Speed error (range error)
C. Refraction
D. Reverberation
Rationale: Speed error (also called range error) occurs when ultrasound travels through a medium
at a speed different from the assumed 1540 m/s (e.g., through fat or fluid collections). If sound
travels slower than 1540 m/s, the machine assumes it took longer to return, placing the reflector
deeper than its true location.
7. The pulse repetition frequency (PRF) is primarily limited by:
A. Transducer frequency
B. Imaging depth
C. Beam width
D. Gain setting
