Medical ultrasound imaging consists of using high pitched sound bouncing off tissues to generate images of internal body structures.
Frequency refers to the number of cycles of compressions and rarefactions in a sound wave per second, with one cycle per second being 1 hertz. While the term ultrasound generally refers to sound waves with frequencies above 20,000 Hz (the frequency range of audible sound is 20 to 20,000 Hz), diagnostic ultrasound uses frequencies in the range of 1-10 million (mega) hertz.
The principal modes of ultrasound in echocardiography are:
This is the default mode that comes on when any ultrasound / echo machine is turned on. It is a 2 dimensional cross sectional view of the underlying structures and is made up of numerous B-mode (brightness mode) scan lines. This is the most intuitive of all modes to understand. The field of view is the portion of the organs or tissues that are intersected by the scanning plane. Depending on the probe used, the shape of this field could be a sector - commonly seen with Echo and abdominal ultrasound probes or rectangular or trapezoid - seen with superficial or vascular probes.