RDMS certification: SPI exam, cost & jobs
RDMS is the ARDMS sonography credential: pass the SPI physics exam plus one specialty exam, budget about $575 to test, and renew on a 3-year CME cycle.
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A diagnostic medical sonographer captures an abdominal ultrasound image at the bedside.
What is RDMS certification?
RDMS stands for Registered Diagnostic Medical Sonographer, the credential issued by the American Registry for Diagnostic Medical Sonography (ARDMS), a Council of Inteleos. You earn it by passing two computer-based exams: the Sonography Principles and Instrumentation (SPI) exam, which covers ultrasound physics, and one clinical specialty exam such as Abdomen or OB/GYN. The SPI is the same first exam behind every ARDMS registry, so passing it once counts toward more than one credential. RDMS is the ARDMS credential for general diagnostic sonography, and US imaging employers routinely ask for it by name. Many postings expect it before they'll interview you.
RDMS vs RDCS, RVT, and RMSKS
All four ARDMS registries share the same SPI physics exam and differ only in the clinical specialty you add on top. Match the credential to the kind of scanning you do.
| RDMS | Registered Diagnostic Medical Sonographer, for general diagnostic imaging. Specialties include Abdomen, OB/GYN, Breast, Fetal Echocardiography, and Pediatric Sonography. |
|---|---|
| RDCS | Registered Diagnostic Cardiac Sonographer, for echocardiography. Specialties are Adult Echocardiography, Pediatric Echocardiography, and Fetal Echocardiography. |
| RVT | Registered Vascular Technologist, for vascular ultrasound of arteries and veins. |
| RMSKS | Registered Musculoskeletal Sonographer, for imaging muscles, tendons, and joints. |
If you scan hearts, the credential you want is RDCS, not RDMS, even though both come from ARDMS. A separate body, the ARRT, also offers a sonography credential, but RDMS is the credential US ultrasound employers usually name, so earn it unless a specific employer asks for the ARRT version.
Who requires RDMS
Hospitals, health systems, and outpatient imaging centers ask for RDMS on sonography roles. In our US listings the role is Diagnostic Medical Sonographer, and it appears under posting titles like ultrasonographer, ultrasound technologist, and echocardiographic technician at employers such as large hospital networks and per-diem staffing pools. Most postings list a current ARDMS credential as required, and some accept a candidate who is registry-eligible and will finish the exams within a set window. New graduates of an accredited program are a common hire, since the program itself sets up the exam eligibility.
Requirements and eligibility
- No prerequisite for the SPI exam. You can sit the physics exam while you're still enrolled in a sonography program, before you have any clinical hours logged.
- One ARDMS prerequisite pathway for the specialty exam. Each pathway pairs an education requirement with documented clinical ultrasound experience.
- The most common route is finishing a program accredited by CAAHEP, which satisfies both the education and the clinical-hours parts in one step.
- An alternative route pairs an associate degree or higher in an allied health field with about 12 months of full-time clinical ultrasound experience, roughly 1,680 hours, recorded on ARDMS Clinical Verification forms.
- No state license is needed to take the exams. Most states don't license sonographers, so employers treat the RDMS itself as the standard.
- A 5-year deadline. Once you pass the SPI, you have 5 years to earn a specialty credential, or you retake the SPI.
Cost, format, and renewal
The figures below reflect ARDMS/Inteleos schedules as of 2026. You pay for the SPI and the specialty exam separately, so budget for both to earn the credential.
| Issuing body | ARDMS, the American Registry for Diagnostic Medical Sonography, a Council of Inteleos |
|---|---|
| Exams required | The SPI physics exam plus one RDMS specialty exam |
| SPI exam | 110 questions, a 2-hour limit, computer-based at a Pearson VUE testing center |
| SPI fee | $275 (ARDMS, 2026) |
| Specialty exam fee | $300 for each RDMS specialty exam (ARDMS, 2026) |
| Specialty areas | Abdomen, Breast, Fetal Echocardiography, OB/GYN, or Pediatric Sonography |
| Time to add a specialty | Within 5 years of passing the SPI, or you retake the SPI |
| Renewal cycle | A 3-year continuing medical education (CME) cycle |
| CME requirement | 30 CME credits per cycle, dropping to 25 for cycles ending on or after December 31, 2026, with the annual SKILLS activity counted for the balance |
| Annual requirement | A specialty-specific SKILLS Knowledge Confirmation each year from January 1, 2026: 40 questions per specialty across four quarterly quizzes, 80% cumulative to pass |
| Annual maintenance fee | About $85 a year to keep the credential active (ARDMS, 2026) |
Choosing a specialty and the 5-year window
Pick the specialty that matches the scanning you actually do, because that's the exam you have to pass to hold the RDMS at all. Someone working in a women's imaging clinic sits the OB/GYN exam; someone in a general radiology department usually sits Abdomen. The order is fixed: pass the SPI first, then the specialty exam. Watch the 5-year deadline. Passing the SPI early, say during school, is fine, but if you let more than 5 years go by without earning a specialty, that SPI pass expires and you pay for it again. If you later add a second specialty, ARDMS waives a block of your required CME credits for that cycle, so adding a specialty is worth doing when your work moves into a new area.
How to get certified
- Enroll in a diagnostic medical sonography program accredited by CAAHEP, which sets up your exam eligibility along with your clinical hours.
- Take the SPI exam. You can sit it during the program, since the physics exam has no prerequisite.
- Choose your specialty exam to match your clinical concentration, such as Abdomen or OB/GYN.
- Confirm which ARDMS prerequisite pathway you meet, and submit any Clinical Verification forms your route requires. Start at the ARDMS get-certified page.
- Schedule and pass the specialty exam at a Pearson VUE center, within 5 years of your SPI pass.
- Download your RDMS credential, then set reminders for the annual SKILLS quizzes and your 3-year CME deadline.
Demand for RDMS on MedJobList
RDMS is named in 115 of the active US openings we track right now. Those are diagnostic medical sonographer roles at hospital systems and imaging centers, posted under titles like ultrasonographer and echo tech. You can browse them in the section below, or filter the full job list by the RDMS credential yourself.
On the job
Keep your credential active before your start date, because imaging departments verify it directly with ARDMS during onboarding and an expired card can hold up your badge. Ask at the interview who covers your continuing education: many hospitals reimburse the annual maintenance fee and give staff paid CME time, since keeping sonographers registered is on the department too. Track your CME credits and your quarterly SKILLS quizzes through the year rather than the week they're due, and if your work shifts into a new area, add that specialty exam while you're still scanning it daily.
FAQ
ARDMS is the certifying body, the American Registry for Diagnostic Medical Sonography. RDMS is one of the credentials it issues, the Registered Diagnostic Medical Sonographer. In short, ARDMS grants you the RDMS. The same body also issues the RDCS for cardiac sonography, the RVT for vascular, and the RMSKS for musculoskeletal.
Plan on $275 for the SPI exam and $300 for the specialty exam as of 2026, so about $575 to test. After you're certified, ARDMS charges about $85 a year to keep the credential active.
The Sonography Principles and Instrumentation exam is the ultrasound physics exam that every ARDMS credential is built on. It has 110 questions and a 2-hour limit, and it's computer-based at a Pearson VUE testing center. Passing it once counts toward the RDMS, RDCS, RVT, and RMSKS, so you only take it a single time.
RDMS offers five specialty exams: Abdomen, Breast, Fetal Echocardiography, OB/GYN, and Pediatric Sonography. You pass the SPI plus one of these specialties to earn the credential, and you can add more specialties later.
You complete continuing medical education on a 3-year cycle and pay an annual maintenance fee of about $85. The CME requirement is 30 credits per cycle, dropping to 25 for cycles ending on or after December 31, 2026. From January 1, 2026, you also complete an annual SKILLS Knowledge Confirmation, four quarterly quizzes for each specialty you hold.
You need to meet one ARDMS prerequisite pathway, and the most common route is finishing a diagnostic medical sonography program accredited by CAAHEP. Another route pairs an allied-health associate degree with about 12 months of documented clinical ultrasound experience. The SPI physics exam itself has no prerequisite, so you can sit it while you're still in a program.