Ultrasound modes
A – Mode:
A, for Amplitude. In the early years of ultrasound before easy access to CT scanners ultrasound was used to monitor midline shifts. Amplitudes over time were used to show structural shifts (Figure 11). However, A-mode is still in use in Eye ultrasound.

B – mode:
Also called 2d mode. Ultrasound signals are send out over whole Ultrasound probe and returning signals are plotted against time delays. The result is a 2d picture showing impedance differences at the right depths.

M – mode:
M, for Motion. Showing the change over time on one line of ultrasound waves. This enables the device to show an area of interest with high resolution moving over time. Uses include cardiac muscle movement and IVC measurements

Doppler:
The Doppler effect describes a change in frequency of sound waves depending on the direction in which they’re travelling (and being recorded). In Figure 14 the pitch (and with that the frequency) changes depending on the relative movement of the ambulance regarding a watching person. If the ambulance travels towards a person the sound is relatively high, gets lower once the ambulance is passing and even lower once the ambulance is moving away.