ARDMS SPI Exam: The Complete Guide (2026)
Last Updated: January 2026 | Reading Time: 18 minutes
Quick Summary: The ARDMS SPI (Sonography Principles & Instrumentation) exam is a 110-question, 2-hour test required for every ARDMS credential. With a 71% first-time pass rate, proper preparation is essential. This guide covers everything you need: exam format, content domains, 10 free practice questions, registration steps, and proven study strategies.
Table of Contents
What is the SPI Exam?
Why the SPI is Challenging
The SPI is often considered one of the more challenging exams because:
- Abstract concepts: Unlike clinical exams where you can rely on anatomy knowledge, physics requires understanding mathematical relationships and wave behavior
- Broad scope: Topics range from basic acoustics to advanced Doppler principles and bioeffects
- High stakes: You cannot earn any ARDMS credential without passing the SPI
SPI Exam Format & Structure
Understanding the exam format helps you prepare strategically:
| Aspect | Details |
|---|---|
| Total Questions | Approximately 110 multiple-choice |
| Time Limit | 2 hours (120 minutes) |
| Passing Score | 555 (on a 300-700 scale) |
| Format | Multiple choice and hotspot questions |
| Testing Centers | Pearson VUE (in-person or online proctoring) |
| Exam Fee | $275 (as of 2026) |
Understanding the 5 Content Domains
The SPI exam is divided into 5 content domains, each weighted differently. Knowing these weights helps you prioritize your study time.
Content Domain Weights
Question estimates based on total question count. Focus study time proportionally.
Study tip: Spend the most time on the largest domain—it makes up the biggest portion of your exam.
Domain 1: Perform Ultrasound Examinations (23%)
Approximately 25 questions
Domain 2: Manage Ultrasound Transducers (7%)
Approximately 8 questions
Domain 3: Optimize Sonographic Images (26%)
Approximately 29 questions
Domain 4: Apply Doppler Concepts (34%)
Approximately 37 questions
Domain 5: Provide Clinical Safety & Quality Assurance (10%)
Approximately 11 questions
Speed = Frequency × Wavelength
c = 1540 m/s in soft tissue
Wavelength (mm) = 1.54 / Frequency (MHz)
1. Doppler shift = (2 × transmitted frequency × velocity × cos θ) / c
2. Nyquist limit = PRF/2
3. Aliasing occurs when Doppler shift > Nyquist limit
4. CW Doppler: No range resolution, no aliasing
5. PW Doppler: Has range resolution, subject to aliasing
Free SPI Practice Test Questions
Test your knowledge with these sample SPI exam questions. Answers and explanations are provided below.
Question 1
What is the speed of sound in soft tissue?
Question 2
Which resolution is determined by pulse duration?
Question 3
A sonographer increases the PRF. What effect does this have on aliasing?
Question 4
Which transducer type is best suited for cardiac imaging through the intercostal spaces?
Question 5
What does the Mechanical Index (MI) indicate?
Question 6
In pulsed wave Doppler, what determines the maximum detectable velocity without aliasing?
Question 7
Which artifact results from sound traveling through a fluid-filled structure?
Question 8
The piezoelectric effect describes:
Question 9
What happens to axial resolution when frequency is increased?
Question 10
A Doppler angle of 90 degrees results in:
Answer Key with Explanations
The assumed speed of sound in soft tissue is 1540 m/s (or 1.54 mm/μs). This value is used by ultrasound machines to calculate depth. Sound travels at 330 m/s in air and about 1480 m/s in water.
Axial resolution equals spatial pulse length divided by 2 (SPL/2). Since SPL depends on wavelength (and thus frequency) and number of cycles in the pulse, axial resolution is determined by pulse characteristics. Lateral resolution depends on beam width.
Increasing PRF raises the Nyquist limit (PRF/2), allowing higher Doppler shifts to be detected without aliasing. This is a primary method for reducing aliasing in pulsed wave Doppler.
Phased array transducers have a small footprint, making them ideal for imaging through narrow acoustic windows like intercostal spaces. They electronically steer the beam to create a sector-shaped image.
The Mechanical Index indicates the likelihood of cavitation (mechanical bioeffects). Higher MI values suggest greater cavitation risk. The Thermal Index (TI) indicates thermal bioeffect risk.
The Nyquist limit equals PRF/2. This is the maximum Doppler shift that can be accurately measured without aliasing in pulsed wave Doppler. Higher PRF = higher velocity detection capability.
When sound passes through a low-attenuation structure (like a cyst), more sound reaches deeper tissues, causing them to appear brighter. Shadowing occurs behind highly attenuating or reflective structures.
Piezoelectric crystals convert electrical signals to mechanical vibrations (sound waves) and vice versa. This bidirectional conversion is fundamental to ultrasound transducer operation.
Higher frequency = shorter wavelength = shorter spatial pulse length = better (smaller) axial resolution. The tradeoff is decreased penetration at higher frequencies.
When the Doppler angle is 90°, cos(90°) = 0, making the Doppler shift equation equal zero. This is why Doppler imaging requires angles less than 90° (ideally 30-60°) to the direction of flow.
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SPI Exam Scoring & Pass Rate
Current Pass Rates
According to official data, the SPI first-time pass rate is approximately 71%. This makes it one of the more challenging exams.
Why Pass Rates May Be Lower
- Underestimation: Students focus on specialty exams and don't dedicate enough time to physics
- Abstract concepts: Physics is less intuitive than anatomy-based exams
- Math component: Calculations can be time-consuming and error-prone
- Broad scope: The exam covers a wide range of topics
Understanding Your Score Report
Your score report includes:
- Overall scaled score (pass/fail)
- Performance breakdown by content domain
- Percentile ranking compared to other examinees
What If You Don't Pass?
First, know that you're not alone—many examinees don't pass on their first attempt.
- Waiting period: 60 days before you can retake
- Maximum attempts: 3 attempts per 12-month period
- Re-application: You must submit a new application and fee for each attempt
How to Register for the SPI Exam
Step 1: Create an ARDMS Account
Visit myARDMS.org, create a new account or log in, and complete your profile information.
Step 2: Verify Your Eligibility
ARDMS offers several pathways to SPI eligibility:
- Pathway 1: Graduate from a CAAHEP-accredited sonography program
- Pathway 2: Currently enrolled in final semester of accredited program
- Pathway 3: Hold ARRT, CCI, or equivalent credential (or MD/DO with sonography training)
- Pathway 4: Documented clinical sonography work experience
Step 3: Submit Your Application
Select 'SPI Examination' from available exams, choose your eligibility pathway, upload required documentation, and pay the application fee ($275 as of 2026).
Step 4: Receive Your Authorization to Test (ATT)
ARDMS reviews applications within 2-4 weeks. Upon approval, you'll receive an ATT via email. Your ATT is valid for 90 days.
Step 5: Schedule with Pearson VUE
Visit Pearson VUE, choose in-person or online proctoring, select your preferred date and time, and confirm your appointment.
What to Expect on Exam Day
For In-Person Testing
Before arrival:
- Get 7-8 hours of sleep
- Eat a balanced meal
- Arrive 30 minutes early
- Bring two forms of valid ID (one with photo and signature)
At the testing center:
- Check in with the test administrator
- Store personal belongings in a locker (no phones, watches, or notes)
- Palm vein scan or photo may be taken for security
During the exam:
- You'll receive scratch paper and a basic calculator
- Breaks are permitted but count against your time
- Raise your hand if you need administrator assistance
For Online Proctoring
System requirements:
- Reliable high-speed internet
- Webcam and microphone
- Windows or Mac computer (no tablets)
- Quiet, private room
Environment requirements:
- Clear desk (remove all items except computer)
- No dual monitors
- Well-lit room
How Long Should You Study?
The ideal study timeline depends on your background:
| Situation | Recommended Study Time |
|---|---|
| Currently in school (physics fresh) | 4-6 weeks |
| Recent graduate (< 1 year) | 6-8 weeks |
| Working sonographer (1-3 years) | 8-10 weeks |
| Returning after break (3+ years) | 10-12 weeks |
Sample Study Schedule
Week 1-2: Foundation
- Review basic physics: waves, sound properties
- Study Domain 1 (Performing Examinations)
- Complete 100-150 practice questions
Complete 100-150 practice questions
Week 3: Transducers & Image Optimization
- Study Domain 2 (Transducers)
- Study Domain 3 (Image Optimization)
- Focus on artifact recognition
Complete 150-200 practice questions
Week 4: Doppler (Most Critical)
- Dedicate full week to Domain 4
- Master Doppler equation and Nyquist limit
- Practice spectral and color Doppler concepts
Complete 200+ practice questions
Week 5: Safety & Comprehensive Review
- Study Domain 5 (Safety)
- Review weak areas from practice tests
- Take first full-length mock exam
Complete 200 practice questions
Week 6: Final Preparation
- Take 2-3 timed mock exams
- Review missed questions
- Light review of formulas and key concepts
- Rest the day before your exam
Free Video Lessons
Free Video Lessons
Watch these free video lessons to help you prepare for the SPI.
Tips to Pass the SPI Exam
1. Understand, Don't Just Memorize
Physics concepts build on each other. Don't just memorize "higher frequency = better axial resolution." Understand WHY: Higher frequency → shorter wavelength → shorter SPL → better axial resolution.
2. Master Doppler First
Since Doppler accounts for 34% of the exam, start early and practice calculations repeatedly. Understand the relationships between PRF, Nyquist limit, and aliasing.
3. Practice Under Real Conditions
Complete 110 questions in 2 hours with no interruptions. Simulate the testing environment and review thoroughly to understand why you missed questions.
4. Focus on Weak Areas
After each practice test, calculate your accuracy by domain. Spend 60% of study time on your lowest-scoring domains.
5. Use Spaced Repetition
Don't cram. Review material at increasing intervals: Day 1 (learn), Day 3 (first review), Day 7 (second review), Day 14 (third review).
6. Don't Self-Evaluate During the Exam
Concentrate on one question at a time. Don't waste mental energy on "what if I fail" thoughts. Answer every question and keep moving.
FAQs
How many questions are on the SPI exam?
The SPI exam contains approximately 110 multiple-choice questions.
What is the passing score for the SPI exam?
You need a scaled score of 555 or higher (on a 300-700 scale) to pass.
How long is the SPI exam?
You have 2 hours (120 minutes) to complete the exam—approximately 65 seconds per question.
What is the SPI exam pass rate?
The current first-time pass rate is approximately 71%.
How much does the SPI exam cost?
The examination fee is $275 (as of 2026).
Can I take the SPI exam online?
Yes, ARDMS offers online proctoring through Pearson VUE if you meet technical and environmental requirements.
How many times can I take the SPI exam?
You can attempt the SPI exam up to 3 times within a 12-month period with a mandatory 60-day waiting period between attempts.
Should I study for SPI or my specialty exam first?
Most students benefit from taking the SPI first while physics concepts are fresh from school.
How do I know if I'm ready for the SPI exam?
Aim for 80-85% accuracy on practice exams under timed conditions before scheduling your test.
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This guide is updated regularly to reflect the latest ARDMS SPI exam information. Last reviewed: January 2026.