Basic ultrasound physics, instrumentation, and knobology

This chapter will discuss basic ultrasound physics in a simple practical approach that is relevant to non-radiologists. Medical ultrasound machines generate and receive ultrasound waves through the transducer. Waves are sent vertical to the surface of the transducer. By curving the surface of the transducer, it is possible to widen the area of the studied field. B mode (brightness mode) is the main mode that is used in trauma patients. This mode gives black and white images. It produces two-dimensional (2D) images depending on the site of the anatomical section. The denser the studied tissue is, the more it reflects ultrasound waves and the brighter it is on the image. Fluid will be black, soft tissue will be gray, fibrous tissues will be white without shadow, and solid material will be white with an acoustic shadow. Imaging one line over time is called the moving mode (M mode). Common artifacts encountered by the sonographer include shadow artifact, enhancement artifact, edge artifact, mirror artifact, and reverberation artifact. The operator should be familiar with their ultrasound machine, the type of transducers used, how to control its outcome by using basic buttons, and, more importantly, how to correlate sonographic findings with clinical findings.