The Sonography Principles & Instrumentation (SPI) examination is administered by ARDMS and serves as a prerequisite for all ARDMS specialty credentials. It tests knowledge of ultrasound physics, instrumentation, image formation, Doppler principles, artifacts, bioeffects, and quality assurance. Passing the SPI is required before sitting for RDMS, RDCS, or RVT specialty exams. Most sonography programs incorporate SPI preparation into their curriculum.