Category: 6. Basic Ultrasound Modes

Ultrasound M-mode is defined as a motion versus time display of the B-mode ultrasound image along a chosen line. The motion is represented by the Y-axis and time is represented by the X-axis. Common applications for M-mode include looking at E point septal separation in cardiac scanning or calculating fetal heart rate for obstetrics. You can also use M-mode in lung ultrasound to evaluate for lung sliding and rule out pneumothorax.

Below is an example of how the M-mode (left side of screen) and B-mode (right side of screen) compare when looking at lung sliding. M-mode simply takes a “slice” of your B-mode image where the cursor line is placed and translates that “slice” over time. It ignores everything else on the B-mode scan except for where you have that cursor line. You can see on the Y-axis how the structures (subcutaneous tissue, muscle, and pleural line) correlate between the M-mode and B-mode images. You can also see the relative motion of these structures over time (X-axis).

Here are the steps to acquiring an M-mode Image:

• M-mode Step 1: Acquire 2D image and Center Structure of Image
• M-mode Step 2: Push the M-mode button to make the M-mode cursor line appear
• M-mode Step 3: Place the M-mode cursor line along the structure of interest
• M-mode Step 4: Push the M-mode button again to activate M-mode
• M-mode Step 5: Push the Freeze Button
• M-mode Step 6: Scroll to the desired image
• M-mode Step 7: Push the Measure Button
• M-mode Step 8: Measure Area of Interest

B-Mode (Brightness Mode) in ultrasound is a setting that creates a two-dimensional (2D) greyscale image on your ultrasound screen and is the most commonly used mode. It is also commonly called 2D mode.

B-mode is the single most important mode you need to master in order to be proficient at point of care ultrasound (POCUS). All of the other modes rely on you getting a good B-mode (2D) image. Fortunately, we already discussed the most common ultrasound settings for B-mode in the ultrasound Knobology section above.

The buttons to get you back to B-mode/2D can be:

• B (just the letter) – GE machines
• 2D (Sonosite and Philips)

Tip: Sometimes, you may be in a different mode or ultrasound machine setting and may wonder how to just reset your settings. Usually pushing the B-mode or 2D button on the ultrasound machine will reset everything and bring you back to the simple B-mode setting.

Now it may seem daunting when thinking about all of the available ultrasound modes available. In this section, the most common and basic ultrasound modes: B-mode and M-mode. In the following section, I will cover the more advanced Doppler Modes.

I would suggest that if you are just starting out, focus on B-mode (greyscale), and get really good at obtaining high-quality 2D images. After you feel comfortable with B-mode start adding on and learning the other more advanced Doppler modes. You can always come back to this post as a reference when you are ready to use the other modes!