Ultrasound Imaging Guide
A quick and easy guide for optimizing ultrasound images
With 20+ years of training and technical support for our customers, we have created this ultrasound image optimization guide to provide you with a plain-English manual to understanding your ultrasound machine and how to get the best images. Keep in mind that manufacturer presets are often not “optimal” for your needs, and learning how to adjust your ultrasound machine’s parameters will help you get the best image, become more efficient, and achieve better clinical results.
- Dynamic Range (Compression)
- Ultrasound Gray Maps
- Line Density
- Frame Average/Persistence
- Edge Enhance
Your first look at an ultrasound can be an intimidating experience. Physicians are quickly finding out that using an ultrasound machine isn’t as easy as it appeared. In my experience, it’s been a tough pill to swallow, which is why I’ve created this guide. Physicians frequently express their frustrations to me; they open the box, see a bunch of foreign buttons and knobs, and confusion sets in. The user manual is often poorly designed, which only adds to their confusion. Then they turn it on, stare at a screen, and feel lost.
Over the last 15 years, I’ve found the solution to be simple. Learn where to start and understand which buttons and knobs actually matter.
Physicians and clinicians typically do not receive formal training for the ultrasound. This guide is for those folks. You can quickly master image optimization through a basic understanding of ultrasounds and by testing a few controls.
In this guide, I’ll start by covering the key functions and controls for optimizing ultrasound images. Deeper in this guide, we’ll cover more advanced technologies to help you fine-tune and truly understand your ultrasound.
Grab your user manual for reference
Each user manual has a section in the front which outlines the location of different controls. Find that page and leave it open. If you don’t have a hard copy of the manual, try pressing the F1 key on the keyboard. This typically opens the electronic manual. Take a picture of it with your phone or tablet to use as a reference.
Good image quality is fairly subjective. It’s also relative to the capabilities of the machine. Frequently, two people looking at the same image will have a different perspective on what is “good.” Those who have used an ultrasound machine before often want the images to be similar to the images from their old machines. New users want images that fits their brain’s perspective of what they think the anatomy should look like. It’s up to you to decide, and your opinion may change as you master the ultrasound.
I’ll refer to musculoskeletal imaging (which includes needle guidance) because it’s the most common type of user I speak with, but these steps apply to all modalities.
This is one of the most important steps, particularly with CRT (non flat-panel LCD) monitors. On machines with CRT monitors, most user manuals list their recommended steps.
Most manufacturers suggest you start with 90-100% contrast, then adjust the brightness. The greyscale bar (shown on the right) shows the ultrasound’s current greyscale from white to black. Start by setting the lighting in the room to match the lighting you’ll use when scanning. Next, turn the brightness to its highest point, then concentrate on the very bottom of the greyscale bar; it will be the darkest point. Slowly turn the brightness down until the darkest level is black and no longer visible. The top should be white, but not over-saturated. If you have a contrast adjustment (many portable machines do not), you can set this to your liking. However, note that adjusting the contrast will have an impact on your brightness setting.
Setting the brightness is the only adjustment that remains consistent with each new exam. All of the settings below are not saved on the ultrasound machine unless you go through specific steps to save a custom preset. In other words, feel free to play around, you can always start over by re-selecting the preset.
Tip: Be ambidextrous or get some help
For the following steps, you’ll need to see what happens with a live image. If you don’t have a helper, take the probe in your right hand, put some gel on, and place the probe on your left arm or wrist. Make adjustments with your left hand (usually the opposite for lefties). As you make adjustments, you’ll see what happens on a live image. Don’t worry about getting a perfect image.
Many factory presets are poorly set up. On older machines, MSK and needle guidance/nerve settings were not common studies. In those cases, you’ll have to try out other settings.
For MSK and needle guidance, you can generally skip OB/GYN, abdominal, cardiac, and urology settings when using a linear probe. Instead, look for any preset associated with superficial imaging such as small parts, breast, venous, peripheral vascular, thyroid, nerve, default, and different user settings (user 1, user 2, user 3, etc). Go through these a few times so you have some reference points. Take a note of your favorites. For purposes of the next steps, choose one and stick with it. You can go back to the others after you’ve gone through other controls.
Note: Calculations are affected by the presets you choose. In MSK, it’s generally not an issue, but in other modalities, measurement and analysis packages (M&A) are associated with the preset. You can set the M&A package to a custom preset, but because it’s unique to each machine, it’s beyond the scope of this series.
Getting started, everyone must know these basic controls. You’ll use these most often no matter how advanced you get. In this section, you’ll learn the controls that you’re most likely to use in all of your exams.
The gain knob will likely be your most-used imaging control. This adjusts the overall brightness of the ultrasound image. You’ll find yourself going to this control on nearly every scan. Get in the habit of adjusting it, you’ll be surprised at how a simple twist can make a world of difference in your image quality.
With the exception of SonoSite and many tablets, each machine has 5-10 slide controls grouped together. These are TGC or Time Gain Compensation controls. They adjust gain in specific areas of the image (near-, mid-, and far-field). The best way to see what a control does is to slide one of the controls all the way to the right, then all the way to the left while looking at a live image. You’ll see that a certain section of the image turns very bright, then very dark.
When you receive the ultrasound, the TGC controls appear as they do in the image on the left, in a straight line down the middle. Most techs adjust these to left-of-center for the nearfield (top), and slowly move to right-of-center as image quality decreases deeper in the image. The idea is to have lower gain in the nearfield, and higher gain deeper in the image where image quality is weaker.
SonoSite users: The general equivalent of TGC are two separate gain knobs that control nearfield gain and farfield gain.
These are two often-overlooked image optimization features. The focal position tells the ultrasound the depth at which you’d like the highest resolution. As you move the focal position up and down, you’ll see a triangle or dot move up or down the left or right side of the image. You’ll see the image resolution improve in the area of the selected focal position.
Focal zones allow you to have multiple focus points. As you increase the number of focal zones, your frame rate will decrease and the image will refresh slowly.
Adjusting the frequency allows you to increase resolution at the expense of penetration, or increase penetration at the expense of resolution. Because most transducers are broadband, adjusting the frequency will typically display a frequency range, not a single frequency. Some machines will show the actual frequency range (represented by MHz),;others don’t show the frequency and offer one of three choices: “Res”, “Gen”, or “Pen” (I will address “HARM” or “Harmonics” later in this guide).
“Res” translates to the highest frequency band available on the transducer. These settings are used for superficial imaging. “Gen” represents mid-range frequencies that are often the default setting. “Pen” represents the transducer’s lowest range of frequencies and is for deeper tissue or difficult-to-image patients. Try the different settings in each image you take. You’ll want the highest possible frequency setting that allows you to see the anatomy you’re viewing.
Other machines will show a specific frequency or range of frequencies. In this case, use lower frequencies when you need penetration in the image. Use higher frequencies when you are looking at superficial imaging. High frequencies provide the best resolution, but you lose penetration. Low frequencies provide the best penetration at the expense of image resolution.
Many ultrasounds come with a feature that automatically optimizes the gain and overall contrast of the image. This feature analyzes the tissue in the image and attempts to provide you with the most optimized image. This feature is usually called one of the following variations: Auto Optimize, Auto Tuning, or Tissue Equalization. Most people forget this button exists, but it’s often a great starting point once you get your presets, frequency, depth, and focus dialed-in.
Words of comfort:
- If you’ve made a disaster of the image, reset to the original preset you selected. Simply go back to the exam or preset screen, and select the preset which you originally chose. This will reset all of your changes, allowing you to start over.
- If you’ve made adjustments you like, nearly every machine allows you to save your own custom imaging preset. However, they’re all different and can’t be covered here, so check your user manual. Be sure to write down the settings you prefer.
In the last 20 years, three technologies have hit the mainstream market that have had the most dramatic impact on ultrasound image quality. These are: Tissue Harmonics Imaging, Compound Imaging, and Speckle Reduction Imaging.
Knowing they exist is one thing, but learning how to use them is a very important step in getting the best image quality out of your ultrasound machine. Here I’ll point out the basic concepts, what the technologies do, and how to use them.
Note: I call these by their common names. Most manufacturers use some form of the name “harmonics,” however, Speckle Reduction and Compound Imaging are given different names by every manufacturer. Consult your user manual to find these on your machine.
This is the most common advanced imaging technology and is found on about 90% of available new and refurbished ultrasound machines.
What is it? Harmonics imaging allows the ultrasound to identify body tissue and reduce artifact in the image. It does this by sending and receiving signals at two different ultrasound frequencies. For example, with harmonics on, a probe would emit a frequency of 2MHz, but it would only “listen” for a 4MHz frequency. This improves image quality because body tissue reflects sound at twice the frequency that was initially sent, which results in a cleaner image that better displays body tissue without extra artifact. The following image shows a demonstration of a signal sent at 7 Mhz and received at 14Mhz. You can see how body tissue is better defined and image artifact is reduced.
Why use it? Harmonics is useful in most situations, particularly on difficult-to-image patients where there’s a lot of “noise” in the image. Note, however, that it doesn’t always help for very superficial tissue or very deep tissue (it varies depending on the transducer). The best way to see what harmonics does is to turn it on and off in different situations to see what helps. You’ll find many presets on your machine that have harmonics enabled and disabled. Be sure to try them all.
How do you use it? A machine with harmonics will have a “THI,” “Harm,” “HI,” or similar button/control on the machine. When it’s enabled, it is typically adjusted via the Frequency control. The frequency display will likely change from displaying frequency range (in MHz) to Low, Mid, and High or Pen, Gen, and Res. “Low” and “Pen” are for deep tissue while “High” and “Res” are for superficial imaging.
Drawbacks? Deep penetration. The image can outright disappear completely when looking at deep tissue. In this case, you’ll want to turn it off for the most difficult-to-image patients (particularly obstetrics).
What is it? Speckle Reduction Imaging (SRI, uScan, XRES, etc) uses an algorithm to identify strong and weak ultrasound signals. By evaluating the image on a pixel-by-pixel basis, it attempts to identify tissue and eliminate “speckle.” Weak signals that seem to be astray are eliminated, while strong signals are enhanced/brightented. It provides a smoother, cleaner image. The image below demonstrates an image with Speckle Reduction enabled.
Why use it? You can identify tissue better. It makes measurements easier and provides a much cleaner image. Most machines with Speckle Reduction have it “on” for nearly all of their presets. Rarely will you have it “off.”
How to use it: Most machines offer varying levels of Speckle Reduction. The lowest levels reduce small amounts of artifact and lightly enhance tissue, while the strongest levels can look over-processed. Most often it is set near mid-level. This is a post-processing technology, which means you can adjust its level after the image is frozen. I recommend you take an image, freeze it, then adjust its Speckle Reduction levels to see its effect on the image.
Drawbacks? When set too high, the image can look like crumpled paper. Also, this is solely dependent on the internal computer and results in slower frame rates.
Here are the different names manufacturers use for the technologies:
|Speckle Reduction||SRI, SRI HD, XRes, iClear, Adaptive Speckle Reduction, MView, SCI, SonoHD, ApliPure+, TeraVision, SRF|
|Compound Imaging||CrossXBeam, CRI, SonoCT, iBeam, OmniBeam, XView, SonoMB, ApliPure, Spatial Compounding|
What is it? Compound Images combines three or more images from different steering angles into a single image. Traditionally, transducers send ultrasound signals in a single “line of sight.” This means it sends a sound signal perpendicular to the probe head, then listens for the echo. With compound imaging, the ultrasound sends signals at multiple angles, allowing it to “see” tissue from multiple angles and eliminate artifact. The following image best represents what’s really happening:
Why use it? Compound imaging increases image resolution by using the multiple lines of site to eliminate artifacts, shadows, and increase edge detail.
How to use it: Some manufacturers included this as a retrofit option and you may need check the user manual (F1 opens the user manual on most ultrasound machines). Many systems offer different levels of Compound Imaging. The number or level typically refers to how many lines of sight the transducer is using… 3, 5, 7, etc.
Drawbacks? It’s not always effective in extreme superficial imaging. It isn’t available for sector transducers. The deeper the penetration, the less effective it is. The more lines of sight, the slower your frame rate. Compound Imaging is available only on linear and convex transducers.
Extra bonus: Some machines allow you to use it for 2D “Beam Steering” which can make a large difference in needle visualization because the beam will reflect perpendicular to the needle. The result is a very bright image of the needle.
Settings or “presets” that come on your ultrasound machine are created by a group of engineers and sonographers, or possibly just a single sonographer. Regardless, those people are creating settings for what they think is the best possible image. In many cases, creating factory presets involves the manufacturer copying general settings from previous machines, or imitating a different manufacturer’s settings.
Considering this, if you really want the best image, it’s in your best interest to dig deep and learn what you like. Earlier parts of this guide gave you the basics and knowledge behind the technology, but here we’re going to dig into the secondary controls, some of which have a very dramatic impact on how the image is displayed.
Don’t worry, adjusting these settings won’t permanently affect your machine unless you specifically go through the steps to save a preset. You can always reset to the default by reselecting the exam preset from your exam or transducer menu. Worst case, reboot the machine.
These secondary controls are available on nearly every machine (SonoSite and some tablet ultrasounds may not have these). They’re not special technologies, these are seemingly cryptic functions that determine how the ultrasound interprets/displays the image. As you’ll see, dramatic changes can occur when using these controls. Note that there is no “perfect” image. That’s purely in the eyes of the beholder.
Dynamic Range (also known as Compression) allows you to tell the ultrasound machine how you want the echo intensity displayed as shades of gray. A broad/wide range will display more shades of gray and an overall smoother image. A smaller/narrow range will display fewer shades of gray and appear as a higher contrast with a more black-and-white image.
To make things confusing, some manufacturers (for example: GE) call it Dynamic Range on a live image, then change it to Compression when the image is frozen.
Dynamic Range and Gray Maps affect one another. If you change one, you may want to adjust the other.
Adjusting gray maps on your image has a similar effect on an ultrasound image as changing the dynamic range., but they are different. While Dynamic Range adjusts the overall number of shades of gray, a gray map determines how dark or light you prefer to show each level of white/gray/black based upon the strength of the ultrasound signal.
Simply put, dynamic range increases or decreases the number of gray shades displayed, while gray maps adjust the brightness of each shade of gray.
Although they may appear to have a similar effect, they are very different. It often helps to adjust them in conjunction with each other to get the best image.
Line density adjusts the number of scan lines in your ultrasound image. A higher level provides better resolution in the image (more scan lines), but reduces the frame rate. Use this to get the best possible image with the most acceptable frame rate.
Frame averaging, or persistence, are similar functions in which multiple image frames are combined, or “averaged” into a single image. Its effect is similar to that of Speckle Reduction, in which the image appears smoother and noise is reduced in the image.
Reject or rejection filter tells the machine the minimum level of echo displayed. For example, if you have a lot of noise in the image, you can increase the Reject level to eliminate the weaker signals, which cleans up the image and suppresses the weakest signals.
With Edge Enhancement, the ultrasound attempts to make a sharper image by combining adjacent signals. This will show higher contrast and brighter edges of structures.
Creating Custom Presets
Nearly all modern ultrasounds have some way of saving your own custom presets (except most SonoSites and some handheld portable systems). This will be in the system settings, but it’s best to go to your user manual (press F1 on most systems), because it is different on every machine.
Using these adjustments to optimize your ultrasound image
Learning these adjustments will let you set your own custom presets or allow you to make adjustments on-the-fly while acquiring an image. With a little practice you’ll quickly become an expert on optimizing your ultrasound.
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