**1.2 Brief history**

Since the 1940s there have been pioneers (physicians, biologists, physicists) who intuited that acoustic energy, at that time used only in war industry to detect submarines, could have applications in medical diagnosis. The first ultrasound images contained information about the density of tissues displayed along an axis ("A- mode" ultrasound). Later, "sectional" ultrasound was invented, which detailed echoes in a plane ("B-mode" ultrasound with applications in obstetrics). In the '60s the procedure had an accelerated development by diversifying examination techniques, identifying more clinical applications and increasing access to a large number of specialties. In the '70s clinical specialties such as obstetrics and cardiology "claimed" the method, using as the main argument its clinical character arising from the direct relationship between the examining physician and the patient. After the '90s, emergency physicians requested the presence of miniature, portable ultrasound equipment in the emergency room proving that ultrasound, using accordingly well defined algorithms, contributed to saving lives. Today, ultrasonography is used by clinicians in more than 50% of cases. Although there is still an ongoing "battle" between clinicians and radiologists for the monopoly over the ultrasound method, the final outcome is an exceptional dynamic of the method, considered today the most common diagnostic imaging procedure in the world (Derchi & Claudon, 2009). In the near future the ultrasound examination will be unrestrictedly generalized with the introduction of the procedure as basic training for medical students, as part of clinical examination.
