Ultrasound is an invaluable tool for performing biopsies, guiding vascular access, and performing nerve blocks. It is best performed with a high resolution linear array transducer. For most veterinary ultrasound machines, these will fall in the £3000 – £3500 price range.
Mounted needle guides are available (but expensive), and whilst they offer some practical advantages, perfecting a freehand technique will ultimately give you more freedom and flexibility. It is difficult, for example, to use needle guided systems to biopsy superficial structures, due to the fixed angle of insertion.
Practice makes perfect
When you are first learning, an uncooked chicken breast and some stuffed olives as targets can be an inexpensive way of familiarising yourself with the technique. Identify your target with ultrasound first, and then see if you can successfully guide your needle to biopsy the filling.
Another idea is to use ultrasound for procedures you wouldn’t perhaps normally use it for – for example, draining ascitic fluid or pleural effusions – because you may already be very confident with these procedures so it gives you more of an opportunity to practice the hand-eye coordination required in combining your needle guidance with your ultrasound imaging.
- The probe orientation marker corresponds to the marker on your display. Make sure you know which way you are orientated, so that movements of your needle will correspond anatomically to your ultrasound display.
- Set your focal zone at or just below the level you wish to sample, to maximise your resolution in this area.
- Optimise your depth control so that the area of interest fills as much of the display as possible.
- Reducing your gain can often help in visualising the bright needle.
- The more parallel your needle is to the ultrasound beam, the better you will visualise it. Freehand technique, whilst more difficult to perfect, gives you an advantage in this respect.
- When a perpendicular approach is unavoidable, the shaft may not be seen, but the needle tip should still be visible due to its rougher surface (causing ultrasound scattering). You may also see black shadowing below the needle (as you may be used to seeing when scanning over rib, for example), or bright reverberation/ring down (you may have seen this when imaging over gas in the bowel). These ultrasound artefacts are very useful in seeing the trajectory of your needle.
- It’s normal to feel that you don’t have enough hands when you first start practicing! Have someone to assist you until you become confident with the technique.
An excellent paper on needle visualisation with ultrasound is available here: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2044.2005.04475.x – it’s written from a human perspective, but the principles are the same.
For help with transducer or needle guide pricing for your veterinary ultrasound system, email contact at animalultrasoundassociation.org