Sonographers specialize in the use of various equipment to scan the human body. X-Rays are only the most familiar mode; sonographers also use other radiation-emitting devices such as MRI and CAT scanners. They also administer ultrasounds, which utilize sound waves to create a three-dimensional picture of the body cavity. There are various certificate programs for medical sonography, ranging from one to four years. Some require an Associate's degree. Most schools of sonography offer a range of specialties ranging from cardiac sonography (heart), mammography (breasts), abdominal sonography, obstetric sonography (fetus), and neurosonography (brain). Many hospitals, vocational schools, colleges, and even the Armed Forces offer schools of sonography. According to the Bureau of Labor Studies the employment prospects are good. As the population gets older, demand for qualified healthcare staff will increase. Sonographers work in hospitals and physicians' offices.