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Key Facts: SPI Exam
~110
Total Items
ARDMS
2 hrs
Exam Time
ARDMS
$275
Exam Fee
ARDMS
555/700
Passing Scaled Score
ARDMS
5 yrs
Window for SPI + Specialty
Both must be passed within 5 years
ARDMS SPI is the REQUIRED physics prerequisite for all RDMS, RDCS, RVT, RMSKS specialty credentials. ~110 MCQ items, 2 hours, $275 fee, scaled passing 555/700. Must pass SPI + specialty within 5 years. Master Doppler equation, Nyquist limit (PRF/2), range equation, axial vs lateral resolution, transducer construction, ALARA principle with TI/MI thermal/mechanical indices, and the six core artifacts (reverberation, mirror, comet tail, shadowing/enhancement, refraction, aliasing).
Sample SPI Practice Questions
Try these sample questions to test your SPI exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 124+ question experience with AI tutoring.
1What is the average propagation speed of ultrasound in soft tissue?
2Ultrasound waves used in diagnostic imaging are best classified as what type of mechanical wave?
3If frequency doubles in soft tissue, what happens to wavelength?
4What is the wavelength of a 5 MHz ultrasound beam in soft tissue?
5Which acoustic variable describes the concentration of energy in a beam?
6If pressure amplitude is doubled, by what factor does intensity change?
7Acoustic impedance is the product of which two properties?
8What is the typical attenuation coefficient in soft tissue?
9A 4 MHz beam travels 6 cm one-way through soft tissue. What is the total one-way attenuation?
10Which is the largest contributor to attenuation in soft tissue?
About the SPI Exam
ARDMS Sonography Principles and Instrumentation — REQUIRED physics prerequisite for ALL ARDMS specialty credentials (RDMS Abdomen/OB-GYN/Breast/Pediatric, RDCS Adult/Pediatric/Fetal, RVT, RMSKS). Must pass SPI + specialty within 5 years for full credential. Validates expertise in ultrasound physics (wave propagation, attenuation, range equation), transducer construction and beam, pulse-echo instrumentation (TGC, dynamic range, postprocessing), Doppler principles (PW, CW, color, power), QA/bioeffects/safety (ALARA, MI, TI), and artifact recognition.
Questions
110 scored questions
Time Limit
2 hours
Passing Score
Scaled 555/700
Exam Fee
$275 (ARDMS)
SPI Exam Content Outline
Physical Principles
λ=c/f, Z=ρc, attenuation 0.5 dB/cm/MHz, reflection, propagation, wave interactions, range equation
Ultrasound Transducers
PZT crystal, matching layer, types (linear, curvilinear, phased, endocavitary), axial/lateral/elevational resolution
Imaging Principles and Instrumentation
TGC, dynamic range, compression, scan converter, postprocessing; artifacts (reverberation, mirror, comet tail, shadowing/enhancement, refraction)
Doppler Imaging Concepts
Doppler equation, 60° angle rule, Nyquist limit, aliasing, PW vs CW vs color vs power Doppler
Clinical Safety, Patient Care, and Quality Assurance
ALARA, TI (TIB/TIC/TIS), MI, prudent use, bioeffects; QA/phantoms; obstetric scanning
How to Pass the SPI Exam
What You Need to Know
- Passing score: Scaled 555/700
- Exam length: 110 questions
- Time limit: 2 hours
- Exam fee: $275
Keys to Passing
- Complete 500+ practice questions
- Score 80%+ consistently before scheduling
- Focus on highest-weighted sections
- Use our AI tutor for tough concepts
SPI Study Tips from Top Performers
Frequently Asked Questions
Why is SPI required for all ARDMS specialty exams?
ARDMS requires SPI as a separate physics prerequisite to ensure all sonographers — regardless of clinical specialty — have a foundational understanding of ultrasound physics, instrumentation, and safety. Candidates must pass SPI + their specialty exam (e.g., AB, OB/GYN, RVT, RMSKS, BR, PS) within 5 years to receive the full credential. SPI alone does not grant a clinical credential.
What is the Doppler equation?
Doppler frequency shift Δf = (2 × f₀ × v × cos θ) / c, where f₀ = transmitted frequency, v = blood velocity, θ = angle between sound beam and flow vector, c = speed of sound (1540 m/s in soft tissue). Angle correction: 60° is the maximum acceptable angle (cos 60° = 0.5; smaller angle gives higher accuracy). Angle 90° gives no Doppler shift (cos 90° = 0).
What is the Nyquist limit?
Nyquist limit = PRF/2 — the maximum Doppler frequency shift PW Doppler can accurately measure without aliasing. If the Doppler frequency exceeds Nyquist, aliasing occurs (color wraps around or spectral wraps to the other side of baseline). Solutions for aliasing: increase PRF (raise scale), lower transmit frequency, increase angle (closer to 90°), shift baseline, or switch to CW Doppler (no aliasing because CW has no PRF).
How should I study for SPI?
Plan 40-60 hours over 6-8 weeks. Doppler Imaging Concepts (31%) and Imaging Principles and Instrumentation (28%) are the two largest domains — nearly 60% of the exam — so prioritize them, then Ultrasound Transducers (16%), Physical Principles (15%), and Clinical Safety/QA (10%). Master core formulas: λ = c/f, range equation depth = c×t/2, the Doppler equation, axial resolution = SPL/2, near-zone length = D²/(4λ). Understand the common artifacts and their causes.