Welcome to part 2 of your series on how to set up your own neuromuscular ultarsound lab! If you missed part 1 dealing with local settings, you can find it here:
This time we discuss the topic of choosing the right machine and probes for your needs.
This guide will also be uploaded to our Additional Resources in the next weeks – which means you can download and print it there for free.
If you have comments or ideas – we are happy to hear them!
Now let´s get started. Fasten your seatbelts and get ready for our second chapter:
2. THE EQUIPMENT
a. The ultrasound platform
There is an incredible choice of ultrasound platforms out there. However, not all are perfectly fitting for neuromuscular ultrasound. You want to assess very small structures, and therefore you will need higher quality machines.
If you already have a platform, the decision may be easier – just check if your probes are suitable or if there are ones with higher frequencies available.
You will have to spend some thoughts on how you want to use your machine and what are your ideal settings:
1. Classical system:
Comes with a cart, with which you can move it, but can´t just be packed under the arm and taken to another room. Usually they will have the most comfortable features in terms of possibilities in post-processing and documentation. Budget varies, but these are generally pricier than their smaller colleagues. If you are operating in one room and don´t have to move around a lot, plus your budget isn´t too tight, this might be your right choice.
2. Laptop system:
with cart or just put on the table. Depending on how much you want to invest you get a cart as well. These will usually only have a port for one probe, so this is a little bit of a caveat: if you have to change probes often, you have to be careful not to damage it. Image quality might not be as elaborated as in the classical systems, but is surely sufficient in many systems. Plus: they cost less. So whether you expect you have to change sites for you examinations often or have a little bit tight budget – these might be the correct choice for you.
3. Handheld devices:
Technical progress is amazing. We have multiple systems available now that work by connecting a probe to your mobile phone and start scanning. However, at time of publishing the first version of our guide, these systems were not really suitable for assessment of nerve pathology besides CTS. So, at the moment, they may not be the correct choice for you.
4. Combined EMG-Ultrasound-machine:
If your main focus is on electrodiagnostics, you are looking for a new machine anyway and you want to add ultrasound to your workflow, this might be comfortable for you. One compact workstation for the workflow of the future in the EMG-lab. Further this will soon alter your daily work by using ultrasound for EMG studies and US-guided therapy. Also great for assessment of the major nerves. If you plan to frequently scan very small nerves, you might be limited with these systems at the moment.
b. The probes
1. The must-have allrounder:
For most indications, 12-15 MHz linear probes are suitable. You can easily assess the major nerves of upper and lower limb. The proximal sciatic and the small nerves with less than a millimeter in diameter might give you a hard time or even not be possible, though.
Pic 1. The musculocutaneous nerve as an example for a medium sized nerve, lying a little deeper, that can well be assessed with 12-15 MHz. On top you see the coracobrachial muscle, below the biceps and the humerus. You get a reasonable field of view and penetration depth, allowing morphological evaluation.
2. The deep explorer:
9 Mhz or less, maybe with curved array, give you the possibility to also examining the deep lying sciatic in every situation.
Pic 2. The sciatic nerve as THE example for a deep lying, thick nerve, covered by the biceps femoris. You need a low frequency to get a good penetration depth and see beneath subcutaneous tissue and muscle.
3. The detail checker:
With 18 MHz or higher you are in the territory of assessing the tiniest nerve with a diagnostic accuracy. Get lateral resolutions of 60 µm and less. Keep in mind that the higher you go, the less is your penetration depth! With 18 MHz about 2 cm of depth can be reliably assessed.
Pic 3. The lesser occipital nerve as an example for a tiny nerve with a diameter of about one mm, yet being situated quite superficially. This is the domain of the high frequency probes – a narrow field of view, a low penetration depth but a hell of a resolution.
Finally: don´t be shy and try as many machines as you can. Getting on the next bigger meeting for radiologists or neurologists in your area is surely a good start. There you have a lot of companies assembled and can get a first impression. We suggest you prepare kind of your own protocol what you would like to see with your future machine. Check out different nerves at different sites. If you are really doing it for the first time, we recommend to simply look for the median nerve at the wrist. Get a first impression of the work-flow with the machine. How is a new patient entered? How to start scanning? How to adjust scanning parameters? How to safe pictures and videos? How to measure? What are the possibilities for starting/stopping a video? In which ways data can be exported? Is there a panoramic view (in case you want that)? Which presets are installed and how do you add new ones?
After checking some machines, you may chose some with the best workflow for yourself. Deciding on the image with one try is difficult. It is better to announce your interest to the local representatives of the company and arrange a demo. Depending on how much time you can use for NMUS in your daily practice, we suggest two weeks minimum. Use that time wisely. If possible, have some time left after work.
Make your co-workers and family members your models.
Get people of different statures and ages, so you get a real-life impression on how the machine works. Check out the most frequently requested nerves and muscles. Play with image optimization and get help from the company on how to achieve the best image.
We hope that was helpful for you. If you have anything to add or comment – we are happy to hear!
See you soon.
Your Sonocampus Team