Tweaking the Gain Sliders

The gain on your ultrasound is, in effect, the volume of sound being driven from your ultrasound probe. The higher the gain — the more sound — the brighter the image. The lower the gain — the less sound — the lighter the image.

You want just enough gain to see what you need to see (otherwise it’s too dark for the details to stand out) . . . yet without too much gain, which would wash out the image.

In general, if your overall image is too dark, you should try increasing the gain. On the other hand, if the overall image is too bright, you will want to try decreasing the gain.

You have two ways of adjusting your Gain:

1.) The “B” Gain dial (just to the left of the New ID button) adjusts your overall gain. You’re going to want this set fairly high, and then you’ll mostly let it be.

2.) The TGC Gain Sliders over on the right side of your console allow you to selectively control the gain in each part of your image. The top slider controls the gain at the top of the screen, the next slider down the gain a little lower, etc. Moving a slider to the right brightens that part of the image; moving a slider to the left darkens that part of the image. Think “Right – Bright” and you’ll have it.

When you are first starting out, simply position all of the sliders right down the middle . . . then, with an image taking shape before you on the screen, selectively adjust the sliders in the region you are focusing on to make that portion of the image brighter or darker as needed.

You may want to try deliberately darkening the portions of the image you aren’t concerned with. For example, with podiatry you rarely need to look more than about 4 cm deep . . . so might as well take your bottom three sliders (corresponding to the bottom portion of the screen) and fade them off to the left. No need to send sound down that far if there’s nothing down there you’re trying to see.

But most importantly, take a moment with every exam to adjust the sliders corresponding to your region of interest (which also happens to be where your Focus Pointers are pointed, remember). This will enable you to finesse the image and bring out the greatest detail.

Scanning For the Image

With your settings more or less where you want them, now you will turn to actually scanning for an image. The most important points to remember here are these:

 

  • Use plenty of gel.
  • Orient yourself so that the probe is facing the correct direction (see the tip below).
  • Be sure to apply sufficient pressure.
  • Keep the probe moving (don’t just slap it on there and hope you’re in the right spot).
  • Always be adjusting the angle of the probe until you find just the right angle.
  • Once you have the image mostly where you like it, you may want to fine-tune the gain sliders further.

A few additional tips:

  • Concentrate on the anatomy … Really think about what you’re looking at and the angle at which it should lie with relation to the surface of the probe. Think of the ultrasound beam as “slicing” through the patient’s foot, giving you an image of what lies directly below the probe. Move the patient’s foot or ankle to see known anatomical structures move. All of this is part of learning to “see in ultrasound,” and at some point things simply begin to click.
  • Generally keep the probe oriented with the little dot to your left (so that everything on your left is on the left side of the screen). Two common exceptions: First, in scanning the plantar fascia, where you will scan longitudinally, coming up over the calcaneous, with the dot-end of the probe pointed distal toward the toes. Second, in scanning the Achilles tendon, where you will usually scan longitudinally along the back of the heel, with the dot-end of the probe pointed toward the patient’s head.
  • If you are scanning the ankle or looking for anything especially superficial, try using a stand-off probe attachment. This will have a substantial impact on your results, by moving the region of interest a little lower on the screen, bringing it into a better plane of focus.
  • Remember that each part of the anatomy, or each pathology, might entail a small learning curve in and of itself. As you go through a number of similar instances, you will begin making clearer and clearer distinctions, and pretty soon it will become part of your working repertoire. Just takes practice!

Note on Guided Injections:

You don’t need to actually see the needle during an injection. Once you begin your injection, you can count on seeing the liquid. That’s what you really need to capture for the image you will save.

Still, it’s nice to see the needle. And tweaking your TGC Gain Sliders is one of the best ways to pull in the needle on your image.

Another tweak you might want to try when trying to catch the needle involves Steering the image (think of it as slanting it). With a live image, press your Enter button, pulling up a white pointer arrow. Scroll this over to the left and highlight the word “Steer” near the bottom of the list of settings. Now use your “Menu” dial to adjust the angle. This can make it easier for the sound coming from the probe to catch the edge of the needle you are trying to image. Scroll back over into the image after you’ve adjusted the Steer setting and press your Escape button to go back to imaging.

Just remember, if you use this method, you will want to repeat the steps to change the Steer setting back to 0 degrees before moving on to your other exams.

 

 

At this point, you will scan … and eventually press FREEZE to capture the image you want to save. Now we move into the Post-Capture steps. Click here …