Though several diagnostic imaging techniques, including X-rays, are available to peer inside the human ultrzsound, they do not offer the soft-tissue images and safety of sonograms. Ultrasound technicians, or diagnostic medical sonographers, earn their pay by using diagnostic equipment that directs sound waves to take images of the human body. Inover 59 percent of the 54, ultrasound technicians worked for general medical and surgical hospitals, making them the largest employer of the profession. One-year certificates are also acceptable, but typically only for those applicants with a related health care background, such as nursing. Most employers also prefer those who have professional certification, which requires an education and passing an exam. California also ranked first for pay among the states. This location was the heart of Silicon Valley, a high-tech center with a high cost of living.