Choosing a veterinary ultrasound machine for pregnancy scanning
Choosing your first ultrasound machine can be quite overwhelming. There is now so much choice, with prices ranging from hundreds through to thousands of pounds, all claiming to offer the best possible solution for your needs at the best price.
This short presentation goes through a few examples to help demystify choosing your first ultrasound machine.
So, what is an ultrasound machine?
The machine itself is simply a computer. It will have features such as processing speed, memory, screen and display size, and it may or may not also have a well laid out keyboard for easy use of controls. The most important part of your system, though, is your transducer or probe – yet this is the part of the machine that is least understood by people new to ultrasound.
An ultrasound transducer houses delicate crystals, which convert electrical signals into pressure (or sound) waves, and convert returning echoes back into electrical signals for the computer to process and display on your monitor.
The very first ultrasound transducers used to consist of a single crystal, which was mechanically swung within a fluid-filled housing. The front of the transducer has a lens which focuses the beam at a specific depth. You may have seen sheep scanners, for example, using an old machine with a vibrating or rotating head like the one on the left. This type of ultrasound technology is still available today, sometimes in an updated form – as in the case of the MSU seen on the right – and sometimes not, but regardless of the source, you should expect to pay no more than £1500 for a machine equipped with a mechanical sector probe.
The majority of wrist scanners advertised on sites like eBay use this type of technology, but unlike offerings from specialist ultrasound manufacturers who have improved the technology over time, it provides the same image quality one could have expected from scanners in the 1970s. And why weren’t people scanning their own animals in the 70s? Besides price, it was also because ultrasound was only suitable for use at that time by specialists, who understood the technology in depth and had a highly trained eye. Choosing one of these as your first ultrasound machine if you are not already a very experienced sonographer is setting yourself up for failure. Even on this eBay listing here, I personally can’t discern anything from the scan image they’re using to advertise their machine – and I’m a trained sonographer!
Advances in technology brought us electronic probes. These are filled with multiple crystals, and using electronic firing, the ultrasound beam can be shaped and focused much more effectively. We get much better resolution with these modern transducers, but not all transducers are created equal. The number of crystals and channels within an ultrasound transducer varies widely across manufactures, and has a huge bearing on image quality.
The materials used to construct the probe are also important. To name just a few key components: it needs to be well insulated to protect it from interference, it needs a backing layer to dampen ringing and shorten the pulse length, and it needs a matching layer to preserve sensitivity and ensure effective transmission of the ultrasound waves. All of these components can vary greatly in quality.
So let’s look at some of the choices out there on the Internet right now. This machine here is a bargain £816, with an electronic probe, and even has 3D imaging.
Given that high quality electronic transducers will cost around £1000 alone, alarm bells are already ringing about the quality of this probe. In addition to this, though, can you spot an obvious problem here? Look at the style of the probe, and also read the title: “scanner and rectal probe for vet farm cow dog.” Are you going to be scanning your dog rectally? I sincerely hope not!
Here’s another example of what comes up when you search for “veterinary ultrasound” on eBay. At least the previous listing declared in the title that it was equipped with a rectal probe, despite its declaration that it was suitable for canine scanning being somewhat bewildering. Other listings are not so clear. In this Ebay listing, there is no mention of the probe type – only a picture. Those not familiar with ultrasound might not even notice the problem with the probe here. There is also a picture of a dog and a cat, which leads the buyer to believe this transducer is suitable for small animal use.
Conversely, here’s a scanner decorated with pictures of cows, but sporting an abdominal convex probe! This would be impossible to use for bovine scanning. There seems to be no rhyme or reason to these listings on eBay, and I believe this stems from a complete lack of knowledge from these resellers – who, by the way, are all resellers, despite what their listing may state. There are no ultrasound manufacturers selling on eBay.
If you check out these sellers’ portfolios, they’ll usually be stocking everything from pop-up tents to children’s toys. If you try messaging them a question about their ultrasound machine, they’re invariably unable to answer it.
Did you notice that that scanner also had 3D technology? Just like the first scanner we looked at. And here’s another example. This machine does have a convex probe, and for under £1000 with 3D imaging, it’s very tempting.
But what is 3D?
A standard ultrasound transducer is effectively taking a single slice through the body. Let’s say it has 64 elements. An equivalent 3D transducer is that same number of elements, squared, to be able to take a full volume of these slices. That is why 3D/4D transducers are tens of thousands of pounds.
I have enquired on some of these machines in the past, but the response is always vague.
So what realistic probe options do we have?
First, you need to think about what you are scanning. If they are animals you will scan abdominally like a dog or a goat, you will first of all need to narrow down your search to convex and microconvex only.
These probes have a curved head – never a flat one, as in the bottom image.
Then, how large are those animals? This will influence the footprint – or physical size – of the probe you choose, but also the frequency. Larger animals need to be scanned at lower ultrasound frequencies, so you may wish to look for a probe in the 2 to 5 MHz range. Smaller animals like small to medium sized dogs and Pygmy goats can be scanned at higher frequencies, and a transducer capable to generating frequencies 5MHz and above would be ideal.
Once you know what type of technology you need, be sure to pick a reputable supplier. The safety of your ultrasound machine is your responsibility, and the law states that it is the operator of the equipment who is responsible for proving due diligence in terms of its safety. Importing a cheap machine from China may seem like an attractive option, but if you are going to do this, demand to see their certifications and find out what support they can offer you if anything goes wrong. Ask them if they display thermal or mechanical indices on screen, as these are a legal requirement for use of ultrasound in the European Union, United States and Canada – yet the vast majority of scanners sold on eBay do not show any sign of measuring or displaying outputs.
You can learn more about the safe use of veterinary ultrasound for pregnancy scanning right here on our website, and the AUA is here to support you throughout your ultrasound journey. We can provide you a list of approved suppliers in the UK, Europe and North America, as well as sonographer-led training courses where you can learn how to get the most out of the ultrasound machine you choose. Just get in touch. We are here to help.
September 23, 2018
July 27, 2018