How to use your ultrasound machine – 7 tips for vets
At first glance, vet ultrasound machines can appear complicated and the sheer number of buttons, knobs and sliders might seem daunting. Although each veterinary ultrasound machine can look very different, the basic principles are the same. This article will provide you with some helpful tips so that you can obtain the best possible images from your veterinary practice’s ultrasound machine.
1) Pick your probe
The primary probe you will likely have in your vet practice is a microconvex probe. It has a small, curved footprint and produces a wedge-shaped image. Microconvex probes generally have a middle-of-the-range frequency and can penetrate a reasonable depth. They are primarily used for small animal abdominal ultrasound scanning.
Linear probes have a higher frequency but don’t penetrate very far into the animal. They have a large, flat footprint and produce a rectangular image. These are useful for imaging superficial structures such as during ocular scanning and musculoskeletal scanning.
Phased array probes are primarily used for echocardiography and have a small, flat footprint. They have a low frequency and so penetrate deeply and they produce a wedge-shaped image.
Choosing the right probe for your scan will ensure you can achieve the appropriate depth whilst still retaining sufficient frequency to produce a clear image.
2) Adjust overall gain
This is a uniform amplification of all returning ultrasound signals. So, increasing the overall gain will make the entire image brighter, and decreasing it will make the image darker. It is a good idea to adjust this at the very beginning of your exam so it is suitable for that animal. Ideally, you want to alter overall gain until tissues are different shades of grey and fluid is black. Once you have achieved this, you shouldn’t adjust the overall gain too much for the rest of the exam. This is so that you can compare the echogenicity of different organs.
Altering the overall gain or brightness of your image means that you are more likely to visualise pathology, especially if the changes are only subtle.
3) Adjust time gain compensation
The sliders on your ultrasound machine allow you to adjust the gain from the near field to the far field. Returning signals from deeper structures will be weaker than those returning from superficial structures. This means that ordinarily, the image would appear brighter in the near field and darker in the far field. The time gain compensation controls are used to compensate for this and achieve an overall uniform image. You can see the effect they have on the different depths of your image by sliding them from left to right.
As a general rule, you will often need increased amplification in the far field and less amplification in the near field. This means that your sliders should be in a diagonal position whereby they are closer to the left at the top and closer to the right at the bottom. There are exceptions, for instance, if you are scanning the bladder, the area distal to it will appear brighter because there is less acoustic impedance through fluid than there is through tissue. Therefore, you might want to decrease your amplification in the far field to compensate for this.
Adjusting time gain compensation allows you to visualise tissues at a uniform brightness, even if they are situated at different depths.
4) Adjust the focus or focal zone
The region of interest that you are examining should be placed in the focal zone. Usually, there will be a marker (often a small arrow) at the side of the image that moves up and down the screen as you adjust the focal zone. This corresponds to the narrowest part of the beam and the depth where the ultrasound waves are the most concentrated, maximising the resolution and giving the best image at that depth.
Some ultrasound machines have the option to use multiple focal zones. This gives a general improvement in resolution over the depth of the image but also activates a slower frame rate. The slower the frame rate, the more blurry the image will become and there will be a noticeable time lag between the movement of the patient and the movement seen on your screen.
Some vet ultrasound machines have an automatic focal zone placement whereby when you adjust the frequency, it automatically alters the focal zone, optimizing it for that frequency. If this is the case, you won’t have a focal zone marker or arrow displayed on the screen.
Adjusting the focal zone allows you to focus on the specific area of interest and obtain the bet image at that depth.
5) Adjust depth
A good rule of thumb is to adjust the depth so that the organ or area of interest occupies three-quarters of the screen. You then want to set the frequency as high as possible for that depth, which brings us nicely on to the next tip:
6) Adjust the frequency
High frequencies give a high resolution (i.e. a clearer image) but have poor penetration. This is why you should always adjust the depth first and then scan at the highest possible frequency for the depth at which you are scanning. Most probes are multi-frequency and it’s worth noting that most will perform best at the middle of their frequency range.
To get the best images during an exam, you should adjust the depth and frequency for each new organ or area of interest. This means that you will be using these two buttons on your vet ultrasound machine frequently throughout your examination.
Adjusting the frequency means that you can obtain a high-resolution image of the area or organ that you are scanning.
7) Make use of presets
Vet ultrasound machines often come with presets for each of the probes. These can be a good place to start as they’ll predict the required settings for an average scan. There are often presets for different-sized animals, as well as different areas you might be scanning, such as abdomen or cardiac. You can then pick the preset that is most suited to your requirements. They are also helpful if you have manually altered the settings on your machine and feel like you’ve made the image worse, if this is the case, you can just select a preset which will revert to your original image.
Using the presets on your machine can save you time, as well as making scanning easier if you forget any of the above tips!
Other useful considerations for better small animal ultrasonography
Prepare your patient
It might sound obvious but a well-prepared patient can make all the difference when it comes to obtaining good images. Ensure the patient is comfortable and settled – this might require sedation in some circumstances. Clip an area of fur that is appropriate for the type of scan you are performing. Clean the area to remove dirt and then apply a generous amount of ultrasound gel, preferably in advance of the ultrasound scan.
Prepare the environment
Ensure that background light in your scanning room is kept to a minimum to prevent screen reflections and allow maximum visualisation of your screen. Always keep the screen clean from dust and fingerprints and most importantly, clean the probe after every use, according to the manufacturer’s instructions. Be comfortable whilst you are scanning to ensure you can continue scanning for as long as is required and also prevent strain injuries, especially if you are scanning regularly.
Conclusion
Hopefully, these tips have helped you learn how to use your vet ultrasound machine and achieve better images from your patients. To improve your ultrasound scanning skills even further, you could consider taking veterinary ultrasound training.
We offer several options for practical vet ultrasound CPD in our short courses. Or, why not start working towards a recognised postgraduate qualification in diagnostic imaging – the course modules are carefully blended, allowing you the best of both worlds between an online ultrasound course and practical ultrasound training.
