Each type of probe has its own frequency range that can be set.
Frequency is usually set at mid range as a default when turning on.
It can be adjusted according to purpose of scanning.
Toggle up allow better resolution, i.e. when using flat-linear array probe for placing intravenous peripheral line.
Toggle down allow better penetration, i.e. when performing DVTscanning in obese patient.
Some ultrasound companies referring to the frequency range indicating the higher end first, i.e. 12-6 MHz.
Function to be able to scroll though several saved images that occurred when hitting freeze button.
Trackball or touchpad are used for reviewing theses images and select the best one available.
This button allow you to take measurement on the image.
Freeze the image first before measuring on the page with calliper function.
A crosshair will appear on the screen when hitting the calliper button.
Use trackball or touchpad to move a crosshair to the point that you want to begin measuring. Hitting a select button to fix the first crosshair and the second crosshair will appear automatically.
Move the second crosshair to the other endpoint then hit a select button again to fix the second crosshair.
The machine will automatically generate measurement that you want on the screen, i.e. distance.
Useful for magnifying a small object that locate deep into the body.
It enlarge the object that you are interested in but the image will become grainier.
You can adjust the depths of image that you want to be displayed on the screen.
Increase the depth of you want to find a deep object in the body. And vice versa a shallow object.
The lesser the depth the greater the magnification (appear larger).
The more number of hash marks the greater depth it is. Hash marks usually represent in centimetre.
In general start  with the maximum depth to locate the object. After that decreasing the depth for greater magnification.
This allow modulation of the signal strength that return to the probe.
The more energy is coming back the brighter the image appear on screen. And vice versa for less energy.
This also modulate sensitivity to detect object of interest.
Increase the gain if you are looking at echogenic object and decrease the gain if object is anechoic.
The darker image at the deeper level occurs due to energy attenuation by surrounding tissue.
The ultrasound machine auto compensated for this by automatically increasing the gain at deeper levels.
TGC allows you to manually adjust the amount of gain (brightness) at certain depth of the image while leaving the rest of the field unaffected.
Attenuation occur while ultrasound waves travel through tissues.
Increase power will push ultrasound waves through tissues to reach the object of interest which position deeper.
The machine analyse various tissue densities that appear on screen and automatically adjust parameters, including focus, gain, and frequency.
This function is expected to improve image quality but sometimes it does not so turning this function on and off and make comparison is recommended.
For each transmitted ultrasound wave tissue generate more than one echoes that return to the probe.
Harmonic waves have double frequency and less artefacts, especially edge artefact, than original echo.
Tissue harmonic helps improving image especially in structures with reflective properties, i.e. bone and membrane, by visualising only the harmonic frequency echo.
There are many varieties of echogenicity of ultrasound waves returning to the probe.
High dynamic range include wide range of echogenicity from weak to strong, which provide a lot of detail.
If you are scanning structure with reflective properties surrounded by layers of soft tissue you may want to lower dynamic range. By doing so the one with strong echogenicity will standout.
There is an optimum depth that object of interest will have the best lateral resolution on screen.
Lateral resolution is the ability to distinguish two small objects at the same depth.
This depth can be adjusted by manipulating the focus control. It is usually shown as a small arrow near the hash marks.
Activate focus function and then use trackball or touchpad to adjust the arrow to the same depth with area of interest.
The machine applies colours over the B-mode image to indicate motion.
Doppler sends out ultrasound waves and detects changes in energy of returning waves affected by motion.
In general, ultrasound default red indicates motion towards the probe, and blue indicates motion away from the probe.
When the ultrasound beam is close to 90 degree to the probe it will generate poor Doppler signal because motion hardly effects the wave energy at that angle.
Angling the probe helps visualize motion better.
Motion of the probe can also create colour through the image. Hand must be very still while using colour doppler mode.
Control sensitivity of the machine to motion.
Start with gain high and lower it down until there is no "speckle" and there is no colour in static tissue.
When activating colour Doppler mode the box will appear on B-mode image. Flow is only measure in this area.
The bigger the box is more information is processing. The image on screen may become slow or jammed.
Adjust the box size just to be big enough to cover area of interest.
Measure motion of tissue at all depths intersect by the line created by each crystal in the probe.
This is measured over time and generate a graph on screen.
For emergency<unk> an this is used for assessing lung tissue, heart valve movements, and velocities.
Presets optimise all parameters suitable for different purposes of scanning.
Minimimal adjustment of parameters are required if you select appropriate preset.
Ultrasound: physics and knobology
Ultrasound: Signs
Ultrasound: Probe selection
Nerve Block: Median
Ultrasound: Probe orientation
Ultrasound: Tendons
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