Ultrasound probes, or transducers, are a necessary part of any veterinary ultrasound system. Without a good quality probe, veterinarians would have difficulty producing high-resolution images with their ultrasound machine. 

But since probes can also be a big financial investment, it’s important to select one that’s a good fit for your practice.

How Do Veterinary Ultrasound Probes Work?

These devices have piezoelectric crystals built into the probe’s working surface, which convert electrical energy into sound waves. These sound waves interact with tissues at different depths within an animal’s body, reflecting back to be picked up by those same crystals. The information is transmitted back to the ultrasound machine to produce an image for interpretation. 

However, not all probes are created equally. Different probes work better than others for different patients or types of studies.

Goals for Your Veterinary Ultrasound System

What will the doctors, specialists, technicians, or other team members be using the ultrasound for? 

If specialty ultrasounds, like echocardiograms and detailed abdominal studies, are performed frequently, it probably makes sense to invest in high-quality probes. On the other hand, if the ultrasound is used primarily for cystocentesis, the fanciest probe on the market might not be a great investment.

Some practices might want to invest in handheld or portable veterinary ultrasound units that connect to a smartphone or tablet. This is probably best in scenarios like triage with a focused check for fluids (A-FAST or T-FAST).

Of course, another important consideration is the type of patients your practice sees. A feline-only practice might have different needs than a practice that sees large dogs.

Goals may change over time and with additional experience. It’s not necessary to buy all the probes upfront, before practitioners are ready to use them. But it might make sense to select an ultrasound machine with additional functionalities that offer room to grow, so more probes can be added in the future when they are needed. 

Veterinary Ultrasound Probe Types and What They’re Used For

Here are some important factors to consider when choosing a transducer…

• Frequency and depth. Frequency is measured in MHz. Higher frequency probes offer better image resolution. 

Depth refers to how deeply the sound waves penetrate into tissue.

While each of these factors are important in their own right, they are often grouped together because they are inversely related: a higher frequency probe has shallower penetration, and vice versa.

Thankfully, newer technology means many probes offer an adjustable range of frequencies and depths, so a single probe can be used on a variety of patients. There are even some that auto-adjust when viewing different depths.

• Size. Probe size generally refers to the “footprint,” or the area of the probe in contact with a patient. For cats and small dogs, a smaller probe is more easily placed under the ribs, which offers an advantage for seeing certain organs. Footprint is also relevant for cardiac studies since the probe must be placed between ribs.

• Shape. This refers to the shape of the footprint of the probe, and properties that tend to be associated with that category. The most commonly used probes in small animal medicine typically fall into one of these categories…

  • Linear. A linear probe has a footprint in a straight line. This creates a square or rectangular image with less distortion at the edges. Typically, these probes are higher frequency and low depth. Ideal for surface structures (like muscles, joints, and ligaments), some practitioners prefer linear probes for abdominal studies in cats and small dogs. A smaller, hockey stick-shaped version is also available, which may be a good fit for exotics or small structures like the eyes.

  • Convex and microconvex. Convex probes have a curved footprint. They vary in frequency and can be used for a variety of studies. They create a more triangular image, with some distortion at the edges.

Microconvex probes, which have a smaller footprint, are probably the most commonly used, versatile probe in small animal medicine. They’re often a good fit for those who want to invest in a good “all around” probe for cats and most dogs, for abdominal and basic cardiac exams.

However, a standard convex probe might be needed to see deep structures in very large dogs. 

• Phased array. This is considered a more “advanced” probe. It’s a common choice for echocardiography. It facilitates easier passage of the beam between ribs, while still generating high-quality images. Phased array probes also offer a higher frame count, for documenting small changes with the heart’s movements. They typically have several functions, including Doppler. 

Additional Considerations

As with any equipment investment, it’s important to research the equipment itself and consider factors like financing, tax advantages, warranties, and service plans. 

Talk to veterinary ultrasound suppliers. Ask to try out the machine you’re considering. Many offer a sample or demo machine that you can keep in the clinic for a short period of time, or at least can offer a demo in your office. Speak to colleagues or check veterinary forums for recommendations, too.

And of course, remember to protect your investment. Dropping a probe can cause permanent damage. Have a system to prevent this, including proper storage, as well as a tie or leash to hold the probe to the operator’s arm in case of accidental drops, so it won’t hit the floor.

All things considered, an ultrasound probe can be a great investment in patient care and generating income for the practice. But since they can be pricey, it’s important to choose wisely and find a probe that’s a good fit for your practice’s needs.

Written by: Dr. Tammy Powell, DVM