Diagnostic ultrasound has been in use since the late 1950s. There are no confirmed adverse biological effects on patients from this usage. Although no hazard has been identified that would limit the use of diagnostic ultrasound on patients in education and research, experience from normal diagnostic practice may or may not experience hazards due to extended exposure times and altered conditions. Participants enrolled in this study will be informed about the anticipated exposure conditions and how these compare with normal diagnostic practice (AIUM, 2007).