The history of ultrasound.

Diagnostic medical ultrasound may have a brief history, but its roots date back to the early nineteenth century. From its modest beginnings in military institutions where ultrasound was used to examine pathologic specimens, to the routine evaluation of the fetus, injured patients, and those with cerebrovascular disease, ultrasound has secured a position as a key diagnostic test both currently and in the future. Its ability to diagnose valvular and congenital heart disease has reduced the need for invasive cardiac angiography with its attendant risks. Furthermore, endoluminal, transvaginal, transrectal, and transesophageal ultrasound have expanded physicians' diagnostic armamentarium and ability to "look inside" their patients. Notwithstanding all these advancements, ultrasound research and development continue to be fostered, and the ideas of today will be the technology of tomorrow (Fig. 5).