Fluid is anechoic (black) in ultrasound images.

The “Freeze” button freezes the real-time image.

That allows the operator to perform measurements on the frozen image, or save the image, or scroll through the images sampled e.g. 15 seconds before freezing the image.

M (motion or time-motion) mode displays real-time ultrasound data derived from one single stationary ultrasound beam.

It displays depth along the vertical axis and time along the horizontal axis.

M-mode is primarily used in cardiac and lung ultrasound.

Usually M-mode is displayed together with a 2D greyscale ultrasound image to allow spatial reference.

The 2D image has a graphical M-line superimposed to indicate the position of the M-mode beam that samples the data.

Colour Power Doppler (CPD) like standard colour Doppler detects blood flow through arteries and veins.

CPD does not indicate the velocity or direction of blood flow.

CPD is based on the echo amplitude received from moving cells – not the frequency shifts.

CPD is up to five times more sensitive than colour Doppler in order to detect the velocity of blood flow and can detect low velocity blood flow in veins and within organs. The strong flow sensitivity is the real benefit of CPD.

Colour Doppler displays a real-time 2D cross-section of blood flow.

When the colour Doppler is activated, the cross-section is displayed as a frame on the monitor. The shape of the frame depends on the probe. The position of the frame can be moved around using a touch pad.

Spatial orientation is obtained by overlaying the colour Doppler cross-section on top of a 2D greyscale ultrasound image displaying the soft tissues.

Conventionally, red colour is used for blood moving towards the probe, and blue is used for blood moving away from the probe.

The operator can adjust the intensity of the colour Doppler signal by using the gain user control.

In colour Doppler mode the function of the gain control is switched to colour Doppler.

Colour Doppler is typically activated by pushing a button.

Colour Doppler is used to confirm whether there is flow in a vessel.

The basic imaging mode is B (Brightness) mode, which is the greyscale 2D ultrasound image.

The B-mode button is typically called “B” or “2D” and it also works as a “panic button”. It allows the operator to escape all other modes and return to the default greyscale 2D ultrasound image.

The image of a cardiac phased array probe is shaped as a sector. Adjusting the sector angle is only possible and relevant in cardiac phased array probes.

A narrow sector angle (width) allows either:

1) A higher frame rate (the time required to build the image is reduced by reducing the number of beams for a whole sector)
or
2) A better lateral resolution (the line density can be increased).

Higher frame rate increases temporal resolution.

Higher line density increases lateral resolution.

By using a sector just wide enough to include all relevant details, the ultrasound system capacity is used in the best possible way.