Category: 5. Ultrasound Knobology and Settings

If you went through the previous steps then you should have a really good and optimized image. Here are just some other buttons you may encounter that may be useful if you need to freeze, measure, or capture your ultrasound image.

Freeze

Just like the world implies, the “freeze” button freezes a frame for you so you have time to view it in more detail. The ultrasound machine will usually store a 10-30 seconds of data and you can scroll back to see previous frames as well.

Calipers (measure)

Calipers are an important feature of ultrasound machines that allows you to measure the distance of specific structures of interest.

Image/Video Capture

All ultrasound machines will allow you to save an image and/or video clip of your ultrasound scan. This is important if you are trying to archive, bill, or use any ultrasound images/videos as teaching files.

Video example of Freeze, Measure, Image Capture:

Below is a quick video demonstrating how to use all of these functions (freeze, measure, image capture) by measuring the LVOT (left ventricular outflow tract) diameter. You can use this same technique to measure any other structure of interest.

The last ultrasound setting you can use to optimize your image is by adjusting the focus. When you adjust your focus you are simply concentrating your ultrasound waves at a specific depth of the image to maximize the resolution at that depth.

Some machines like the Sonosite don’t allow adjusting the focus since the machine has auto-focus built in.

However, if a machine does allow you to adjust the focus, it is very important to place the focus cursor to the depth of the area of interest. Usually, the focus is indicated by a small arrow (or hourglass) superimposed on the depth markings.

Most ultrasound machines will have settings that allow you to fine-tune and adjust the gain at specific depths of your greyscale ultrasound image. These will be termed Near/Far field gain or Time Gain Compensation (TGC).

Near Field and Far Field Gain (Sonosite)

The commonly used Sonosite M-Turbo or Edge machines allow you to adjust the “Near field” and “Far field” gain of your ultrasound images. The near field refers to the top half of the ultrasound screen and the far field refers to the bottom half of the ultrasound screen. The overall gain is just called “Gain” and is on the bottom left-hand corner of the Sonosite machine buttons.

Time Gain Compensation (TGC)

Most other ultrasound machines will allow you to further adjust the gain in even more specific areas of your ultrasound screen. This ultrasound setting is called “Time Gain Compensation” or TGC.

Adjusting the Time Gain Compensation (TGC) allows you to adjust the gain at almost any depth of your ultrasound image, not just the near and far-fields. The top rows of the Time Gain Compensation control the nearfield gain and the bottom rows control the far-field gain.

Here is an example of decreasing the TGC of the middle of the image with a corresponding absence of echoes on the middle of the ultrasound screen.

After optimizing your depth, the next ultrasound setting you should adjust is your gain.

Ultrasound gain simply means how bright or dark you want your image to appear. It increases or decreases the strength of the returning ultrasound signals that you visualize on the screen.

All ultrasound machines will have an “Overall” Gain setting that, when increased or decreased, will make the entire ultrasound image brighter or darker. This is good to use when your entire imaged is too dark (under-gained) or too bright (over-gained).

(Note: Regarding this section, we are referring to Gain in the setting of B-mode/greyscale. You can also change the gain in your Doppler modes which we will discuss in the following section on “Advanced Modes.” Lastly, some machines have an “Autogain” button that I rarely use because I find it typically undergains your image.)

Now the application preset will usually give you a decent image right when you place the ultrasound probe on the patient. However, there are some ultrasound settings that may need to be adjusted to optimize your ultrasound settings further.

The first of these ultrasound settings you should adjust is the depth. The ultrasound depth setting is simply how deep you want the ultrasound machine to be able to scan.

The rule of thumb is to only use as much depth that is necessary to see your structure of interest. Often times for beginning users, their depth will be too high and there is a lot of wasted “Ultrasound Real Estate” on the bottom of the screen.

The right side of the screen will have dots or lines that correspond to the depth in centimeters. This can give you an estimation of how deep your structures are as well. As you INCREASE the depth setting on your machine, you will see the numbers increase on the right side of the screen to correspond to the depth of penetration.

Here is an example of increasing the ultrasound depth to visualize a deeper structure:

Conversely, if you decrease the depth you will be visualizing more superficial structures. Here is an example below of decreasing depth:

After switching to the correct ultrasound probe, the next step is to select the correct application preset for that transducer.

Each transducer will have a different list of application presets based on its frequency and footprint. The ultrasound device companies will create application presets that make sense for those specific probes.

Think of selecting the ultrasound application preset like how you would select the correct preset for your point and shoot camera. You would use a different setting for day mode versus light mode. The camera will help adjust the settings to optimize for those specific conditions.

Selecting the correct application preset is similar in that it will automatically select the ideal frequency, depth, and gain for that application (i.e. cardiac vs abdominal). This gives you a great starting point to further fine-tune your image with the other knobs/buttons (depth, gain, focus, TGC, etc). In addition, the ultrasound will always start in B-mode or “greyscale” mode by default.

If you read the beginning of this post, you should already know what ultrasound probe you need to use based on the application you are performing. So after turning on the ultrasound machine, the next most important step is to switch to the correct ultrasound transducer you will need.

This seems like common sense but I’ve seen many learners just want to jump in and start scanning with the wrong transducer. Unfortunately, understanding all of the ultrasound knobs won’t mean much if you have the wrong ultrasound probe to start off with!

Every machine will have a way to for you to switch between transducers.

(Note: for the Butterfly. You don’t actually have to switch between transducers because it is an “all-in-one” device. When you switch the application preset it will automatically simulate the correct transducer settings for you)

Yes the most important button of all is the power button! Simple enough!

This is an interesting fact: the on and off buttons were derived from a binary numbering system where “0” was for OFF and “1” was for ON. So to create the universal symbol for Power the “0” and “1” were combined to make the following symbol:

This power symbol applies to almost all ultrasound devices as well. Just look for it when you want to turn on your machine.

Starting to use an ultrasound machine can feel really intimidating since they seem to have so many knobs and buttons!

The good news is that all ultrasound machines have the same basic settings and once you understand them you can start using any ultrasound device with ease.

I would suggest approaching any ultrasound machine in with the following order using the step-by-step approach below. I’ve found doing it in this order prevents you from forgetting to optimize basic ultrasound settings that can drastically improve your image quality.