Introduction to Basic Ultrasound principles

To get a good image free of artifacts, sonographers need to have a firm understanding of the basic ultrasound principles. This inculdes ultrasound physics, including common terminology, measurement units, and the fundaments of sound generation.

Sound is generated by a sound source, for exapmle a tuning for or a violin string. When their source vibrates, adjacent partices are displaced.These particles push against other adjacent particles. This constant pushing is known as particle vibration.

Ultrasound refers to sound waves beyond the human audiable range. Diagnostic applications of ultrasound use frequencies of 1 to 10 million cycles/sec, or 1 to 10MHz. Ultrasound is used to examine soft tissue anatomic structures within all areas of the body.

In medical ultrasound, the vibrating source is a ceramic element that vibrates in response to an electrical signal. The vibrating motion of the ceramic elements in the transducer causes the particles in the surrounding tissue to vibrate. As the source vibrates, it periodically presses against and pulls away from the adjacent medium with resultant particle compression and expansion (rarefaction) in the medium. This movement of energy through structures is called a wave. Patients are examined with a transducer that converts electrical energy into mechanical energy. As the sound beam is directed into the body at various angles to the organs, reflection, absorption, and scatter cause the returning signal to be weaker than the initial impulse. Over a short period of time, multiple anatomic images are acquired in a real-time format.