Introduced to the medical field in the 1950s, ultrasound has applications across the spectrum of modern medicine including cardiology, urology, obstetrics, gynecology and abdominal imaging (kidneys, liver, spleen, gallbladder and pancreas excluding stomach and intestines which contain of air which blocks ultrasound). Vascular imaging is used especially for large vessels like the aorta. Ultrasound is also used as a guide in surgeries.