This SPI cheat sheet strips the ARDMS Sonography Principles & Instrumentation exam down to the formulas and definitions examiners lean on hardest, laid out for fast recall. It's a premium cheat sheet built by Capital Prep — the one premium prep we trust — and it's yours free. Reinforce it with the rest of your free SPI toolkit: the practice test, study guide, and flashcards.
SPI exam at a glance
- Questions: About 110 multiple-choice (roughly 100 scored, 10 unscored pilot items)
- Time: 2 hours (120 minutes)
- Passing score: Scaled score of 555 on a 300–700 scale, reported Pass/Fail
- Cost: Approximately $275 USD; verify current fee with ARDMS before applying
What’s on the SPI cheat sheet
- Apply Doppler Concepts (34%) — the largest domain — Doppler shift, angle and cosine rule, CW vs. PW, color vs. power, aliasing, the Nyquist limit, and wall filters.
- Optimize Sonographic Images (26%) — the four resolutions, gain vs. TGC vs. output power, dynamic range, harmonic imaging, display modes, and the artifacts you must recognize.
- Perform Ultrasound Examinations (23%) — wave propagation, acoustic impedance, attenuation, the pulse-echo range equation, spatial pulse length, and contrast agents.
- Provide Clinical Safety & Quality Assurance (10%) — bioeffects, mechanical index, thermal index, ALARA, infection control, and phantom-based QA.
- Manage Ultrasound Transducers (7%) — piezoelectric elements, damping and matching layers, frequency selection, and array types — the smallest but recurring domain.
How to use it in your final week
- Memorize the core formulas cold — wavelength = 1.54 ÷ frequency (MHz), depth = (1,540 × time) ÷ 2, Nyquist = PRF ÷ 2, MI = pressure ÷ √frequency, and simplified Bernoulli ΔP = 4v². These are the fastest points on the exam.
- Front-load Doppler (34%) and image optimization (26%) — together they're roughly 60% of the questions, so mastering the two largest domains from the sheet moves your score most.
- Run the sheet the morning of the test as a rapid recall pass: 1,540 m/s soft-tissue speed, attenuation 0.5 dB/cm/MHz, keep the Doppler angle at or below 60°, and fix aliasing by raising PRF.
- Don't cram in isolation — pace each review pass against a timed set (about 110 questions in 2 hours is just over a minute each) so the physics math feels automatic under the clock.
The cheat sheet is your review layer — your SPI practice test drives the exam-readiness ring at the top of this page. Download it, review, then take a full practice exam (or drill with the study guide and flashcards) to see where you stand.
SPI cheat sheet FAQ
Yes — the SPI cheat sheet downloads as a PDF with no sign-up and no paywall. It sits alongside Career Employer's free ARDMS SPI practice test, study guide, and flashcards, so your whole prep stack costs nothing.
The formulas and facts you have to recall fast under a 2-hour clock: wavelength, propagation speed (1,540 m/s), attenuation, the range equation, the four resolutions, the Doppler shift and Nyquist limit, aliasing fixes, MI and TI, and ALARA — grouped by the five ARDMS content domains.
It's built to the ARDMS SPI Examination Content Outline (Version 24.1) and its five-domain weighting, and we re-check it against the ARDMS outline and AIUM bioeffects guidance on a regular cadence.
No — the SPI is physics- and calculation-heavy with a first-time pass rate near 71%, so the sheet is a memory anchor, not a shortcut. Pass by drilling timed practice questions, then use the sheet to lock formulas in place; you need a scaled score of 555 (on 300–700) to pass.
Tap the download button or the preview card at the top of this page and the PDF opens instantly. Bookmark this page so you can pull it back up for a final formula pass the morning of your exam.
References
- 1.ARDMS. “Sonography Principles & Instrumentation (SPI) Examination.” ARDMS.org, 2026. ↑
- 2.ARDMS. “SPI Examination Content Outline (Version 24.1).” ARDMS.org. ↑
- 3.ARDMS. “Exam Development, Scoring and Security.” ARDMS.org. ↑
- 4.AIUM. “As Low As Reasonably Achievable (ALARA) Principle.” American Institute of Ultrasound in Medicine. ↑
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