Become a Better 4D Tech
For this installment of this 4D ultrasound training series, I explain the more technical aspects of learning 4D ultrasound scanning.
To grasp the concepts here, you'll need a basic understanding of ultrasound physics and how to use the 4D imaging features on your ultrasound machine, including how to save 4D ultrasound image presets. If you purchased your 4D ultrasound from Probo Medical, your presets should already be on the machine. I also recommend reading my Perfecting 4D Imaging: 4D Imaging Ultrasound Basics blog and my Step-by-Step Guide for a Clear "Babyface" Image blog if you're new to 4D ultrasound imaging.
Learn by Making Mistakes
You can't break your ultrasound machine simply by adjusting controls, so don't be afraid to try out various controls to see what they do. Since there was really no guide to making adjustments (until now) this is how I learned.
If you make too many mistakes, most ultrasounds have a button that will change it back to the initial settings. On the Voluson, it is labeled “INIT”. If you can't find such a button on your machine, go back to 2D, then reselect the 4D preset when you enter 4D mode for the first time. By doing this, you will restore the machine to its original settings.
Free Scan = Free Training
Something simple that has also been incredibly useful to me is my network. I have provided people a free 4D session in exchange for allowing me to play with the machine and see what the various controls to do, and how they can improve my image. This is what I do to test all new ultrasound machines. Find a friend who will help you improve your skills.
Quality is an Actual Adjustment Control
Presets are your friend, but they are just a starting point. To get the best image, you need to start getting into the technical controls.
Most 4D ultrasound machines have a way of improving 4D image quality with the switch of a toggle or twist of a knob. On a Voluson ultrasound, this control is labeled “Quality”. There are multiple settings, and the default is typically “High 1”. This is not an optimal setting. You’ll want to go to the highest quality possible... which is "Max" on most Voluson systems.
While the "Quality" control will slow down your frame rate, the difference in the 4D image is really dramatic when you choose higher "Quality". You'll get much better resolution with a slight loss of frame rate. And let's face it, frame rate doesn't matter if the image quality is poor.
Master 4D Probe Dexterity
The more time you practice your coordination and dexterity with the probe in 4D mode, the more efficient and better your images will be. With enough practice, you should be able to move the probe to a better making position without thinking.
To help adjust coordination, some people find it helpful to imagine the probe as a flashlight, moving it around the belly trying to aim it best at the baby’s face. This allows you to think in "4D mode" rather than in a traditional 2D ultrasound "slice".
MOVE THE PROBE: One of the biggest mistakes I see is when people don’t move the probe around enough. Simply placing the probe in the middle of the belly and turning knobs will NOT yield good results. Use the whole belly, both sides, top and bottom, to get the best angle on the face. This will result in some weird contortions on your part, but believe me, it’s worth it.
Gain, The Advantage
USE THE GAIN. Gain will help you find the perfect balance between shadows and highlights, while also reducing artifact within the image.
The Mysterious Mix/Texture/Smoothness Controls
Nearly every 4D ultrasound has some sort of "Mix" control that allows you to adjust smoothness/texture of the image. Unfortunately, these controls are sometimes buried deep within a system, but it's very important to find this on your machine.
The "Mix" is what makes the baby’s face look less like a bunch of blisters, or something that is so smooth there’s no definition in the face. You're looking for something in-between that will find a balance between a textured surface and smoothened skin.
There is no "Magic Number" because some people prefer more texture in the image, others prefer smoothness.
Reduce Speckle and Smooth the Image
Speckle Reduction Imaging is also known as SRI, SRIHD, XRES, and simply Speckle Reduction. If your machine has it, use it.
On some machines, you can enable SRI in 4D imaging, but on most machines you'll need to activate it when you're performing 2D imaging.
Which Speckle Reduction Imaging setting? You'll want to keep the settings relatively low. When SRI is turned up high, the image can look unnaturally smooth and also give a wrinkled paper look. It's not pretty.
Axis Power: The X, Y, Z's of Image Rotation
A cool trick to really help get the baby's face right-side up and into view is to use the X, Y, and Z Controls. These are usually not marked clearly on the controls, as you can see the how they're highlighted in yellow in the image on the left. Other machines have them also inconspicuoulsy placed.
These controls will rotate the image up/down, left-right, and clockwise/counterclockwise. It can help an upside-down face right-side up, help turn the baby to make it appear it's looking your way, and even have it pick its chin up.
Because it’s a volume 3D image, you can rotate the image on those three different axes. This is helpful on the particularly difficult scans where the probe simply can’t get the best angle.
Do NOT overuse this. When you adjust these too far, you’ll lose image resolution. Small adjustments won’t have much impact, but if you’re trying to turn the face 90-degrees up/down/left/right, you’ll get a really bad image. (This does not apply to the control that moves the baby’s face clockwise-counterclockwise, you can spin that baby to your heart’s content.)
Tissue Harmonics is one the oldest yet most valuable image optimization tools.
In 4D, it's rare to find a situation in which Tissue Harmonics will not help your overall image. The tool is so ubiquitous that it's rare to find a case where it's not used.
Ninety percent of the time, you’ll want Harmonics “on.” The exception is with difficult-to-image ( patients where you simply can’t get a good 2D image. Turning off Harmonics will give you better penetration at the cost of image resolution. The result is a grainier image, but sometimes it’s all you can do to get an image at all.
The Mysterious "Threshold" or "TH.Low"
Every machine has this setting, but it also has the most wide variety of names. Typically “Threshold” is in the name somewhere. On Volusons, it’s often seen as “TH Low” or “Thresh” followed by a number.
The threshold essentially tells the machine how to handle weak and strong echoes. A high setting typically tells the machine to delete weak signals and amplify strong ones. This results in a bright face, but any subtle details (darker parts of the image) are eliminated from the image. A low setting results in a grainy, fuzzy, darker image. You’ll want to find a nice balance that shows details in the face, but still eliminates artifact in the image. Volusons typically have a pretty good default setting.
The "Curve" is the green line shown in the image on the left. While all machines have this yellow or green line, some machines allow you to "bend" that line around a baby's face to help remove objects from the image (such as an arm, placenta, or other).
You may not even know you have this option, because it hides in plain sight..
The curve is part of the horizontal line in the Region of Interest box.
This allows you to “bend” the horizontal line of the ROI box when you first enter 4D. In the old days, this was simply a horizontal line that could not be adjusted. The Curve allows you to contour this line around an obstruction and/or help you get a clearer image of the baby’s face.
The Wide-Angle Shot
This Affects Frame Rates! While some may not think this is much of an image optimization tool, it's a bigger deal than you think. The Volume Angle determines how wide of an angle the probe will sweep. The smaller the angle, the faster the frame rates. So, you can trade frame rates for volume angle. After 28 weeks, however, you’ll want a wider angle.
Once you’ve made all these adjustments and have found that you like what you see, it’s time to save your personal preset. Presets are often in the Tools, Utilities, or System Setup menus. Check your user manual on how to get to these settings. Note: on Chison settings, your 4D user preset will be saved as part of the 2D preset. The two are tied together and you cannot save individual 4D presets.
About the Author
Brian Gill is Probo Medical’s Vice President of Marketing. He has been in the ultrasound industry since 1999. From sales to service to customer support, he has done everything from circuit board repair and on-site service to networking and PACS, to training clinicians on ultrasound equipment. Through the years, Brian has trained more than 500 clinicians on over 100 different ultrasound machines. Currently, Brian is known as the industry expert in evaluating ultrasounds and training users on all makes and models of ultrasound equipment, this includes consulting with manufacturers with equipment evaluations during all stages of product development.