AB vs SPI: ARDMS Exam Comparison
This page compares the ARDMS Abdomen (AB) and Sonography Principles & Instrumentation (SPI) exams side by side. They differ in clinical scope, content focus, career setting, and 2025 pass-rate data.
AB vs SPI: Exam Comparison
| Factor | Abdomen (AB) | Sonography Principles & Instrumentation (SPI) |
|---|---|---|
| Credential earned | RDMS | RDMS/RVT prerequisite |
| Question count | 165 | 110 |
| Exam duration | 3 hours | 2 hours |
| Passing score | 555/700 | 555/700 |
| 2025 first-time pass rate | 73% | 74% |
| 2025 repeat pass rate | 45% | 47% |
| 2025 overall pass rate | 67% | 68% |
| Difficulty level | Moderate | Hard |
Source: ARDMS/APCA Global Exam Performance Summary Report, 2025. First-time and repeat rates describe different candidate groups and do not by themselves establish exam difficulty.
About the Abdomen (AB) Exam
The ARDMS Abdomen (AB) specialty exam covers the liver, gallbladder, biliary system, pancreas, kidneys, spleen, retroperitoneum, and abdominal vasculature. It is one of the most commonly pursued RDMS specialty registrations and rewards systematic, organ-by-organ preparation aligned to the official content outline.
About the Sonography Principles & Instrumentation (SPI) Exam
The ARDMS Sonography Principles and Instrumentation (SPI) exam is the physics prerequisite required before earning any ARDMS specialty credential. It tests sound wave physics, transducer construction, image formation, ultrasound artifacts, Doppler principles, quality assurance, bioeffects, and ALARA safety principles. Unlike specialty exams, the SPI rewards an academic rather than clinical approach.
Key Topics Compared
AB Key Topics
- Liver segmental anatomy
- Hepatic pathology
- Biliary system
- Gallbladder disease
- Pancreatic anatomy
- Splenic pathology
- Renal anatomy
- Urinary system
- Retroperitoneal structures
- Abdominal vasculature
- GI tract sonography
- Thyroid and neck structures
- Scrotum and testes
SPI Key Topics
- Sound wave physics
- Transducer technology
- Image formation
- Spatial resolution
- Artifacts
- Doppler principles
- Hemodynamics
- Bioeffects and safety
- ALARA principle
- Image quality optimization
- Digital signal processing
- Harmonic imaging
Among 2025 candidates, AB first-time and repeat pass rates were 73% and 45% (a 28-point gap); SPI rates were 74% and 47% (a 27-point gap). These are separate groups, not a measure of individual improvement.
Which Exam Should You Take First?
The right choice depends on your clinical background, your current employer's needs, and your long-term career goals. Sonographers with strong clinical experience in abdomen imaging should consider the AB exam first, as applied clinical knowledge transfers directly to board performance. Similarly, those working predominantly in sonography principles & instrumentation settings will find the SPI exam more immediately supported by their daily practice.
- Career goals: The SPI is the physics exam every ARDMS credential shares; the AB exam decides which specialty your RDMS covers. Consider whether that specialty aligns with your desired work environment.
- Where to start: SPI is required for every RDMS and RVT credential, and most candidates take it first. Pass rates compare separate candidate groups, not the inherent difficulty of an exam.
- Clinical experience: Take the exam that aligns with your strongest clinical rotations or work experience. Hands-on scanning experience impacts exam readiness.
- Prerequisite: The SPI physics exam is a prerequisite for earning the RDMS specialty credential. If you have not passed SPI, plan for it before completing the specialty registration.
Both exams reward structured, domain-aligned preparation. The AB first-time pass rate is 73% compared with 74% for SPI; use these cohort results as context rather than a prediction of your individual outcome.