RDCS (Registered Diagnostic Cardiac Sonographer) is an ARDMS credential for sonographers specializing in cardiac imaging. Candidates must pass the Sonography Principles & Instrumentation (SPI) exam and a cardiac specialty exam. RDCS specialty options include Adult Echocardiography (AE), Pediatric Echocardiography (PE), and Fetal Echocardiography (FE). The RDCS is the standard credential for echocardiographers working in cardiology departments and cardiac imaging centers.