An Introduction to Small Animal Veterinary  Ultrasound Probes

An Introduction to Small Animal Veterinary Ultrasound Probes

Tim Perks of BCF Technology

My old man always said, “Right tool for the right job”. Diagnostic ultrasound imaging can be a tricky business if you aren’t a confident scanner, and if you aren’t using the right probe your job can become even more difficult. At BCF, we understand your need to be able to get the most out of the equipment you purchase for your practice – so here is our advice on the range of ultrasound probes available to make your job easier.

Ultrasound Frequency Range

Let’s begin by explaining ultrasound image quality related to frequency. As you choose a frequency, there is always a trade-off between resolution and penetration.

A higher frequency produces a higher resolution image, but the ultrasound wave will not penetrate as deeply into the patient. A lower frequency means that you will get a decrease in image resolution, but the ultrasound beam will be able to penetrate to a greater distance into the patient. It is important to strike a balance between these two factors to achieve the best image of the area of interest.

Most small animal ultrasound scans are performed at a depth of 2 – 15 centimetres. A frequency range of 4 – 10 MHz should allow you to scan within these depths.

Modern electronic probes scan at multiple frequencies while older, mechanical probes often only operate at a single, fixed frequency.

Micro-Convex Veterinary Ultrasound Probe

This is the main probe that is used for small animal abdominal scanning. A smaller footprint provides improved surface contact, resulting in great image quality. Imaging through small rib spaces and underneath the costal arch is also easier. These probes usually offer a high frequency range.

Convex Veterinary Ultrasound Probe

A convex probe has a large point of contact with the skin surface, with the ultrasound beam spreading to a wider field of view within the patient. These probes are less useful for small animal imaging as they don’t fit into areas like the intercostal spaces, the xiphisternum or under the costal arch. They typically have a lower frequency range (3.0-5.0 MHz), therefore the resolution you can achieve will be less than with other types of probe. However, large convex probes can be useful for scanning the liver in extremely large dogs or in large animal practice as they allow for deeper penetration within the patient.

Linear Veterinary Ultrasound Probe

Linear probes are primarily used for superficial abdominal structures, especially in cats, such as the small intestine and the kidney. They are also excellent for ophthalmic imaging. Linear probes offer a higher resolution image than convex probes as they have higher frequency capabilities and the ultrasound beam does not diverge as it leaves the probe.

One limitation is that they often have quite large footprints, so for small animals and exotics a hockey stick linear probe is preferable.

Hockey Stick Veterinary Ultrasound Probe

Hockey stick probes are linear probes with an ultra-small footprint. They operate at a higher frequency range, but the penetration ability is poor. They are designed as an intra-operative probe, meaning that it would be used directly on an organ during surgery. These features make it a superb choice for scanning exotic species, musculoskeletal scanning in small animals (such as the biceps tendon) and for ophthalmology.

Phased Array Veterinary Ultrasound Probe

A Phased array probe would be the probe of choice for echocardiography.

The footprint is very small and the ultrasound beam comes from a smaller point of origin, making it easier to pass between the rib- spaces of the patient. The probe can generate a very high pulse repetition, which allows an extremely high frame rate.

The benefit of this is that when scanning a rapidly moving heart, the image can be played back frame by frame and small changes in position can be observed and detected. Phased array probes can also perform high quality Doppler scans.

Matrix Veterinary Ultrasound Probes

Matrix Probes are a relatively new addition to ultrasound scanning. The crystals in the probe are arranged in several linear arrays forming a matrix. This improves lateral and axial resolution and allows focus in two dimensions rather than just one. In other words, these probes produce a very high quality, high resolution image!

Final Thoughts and Advice

The most important thing to remember is to not drop the probe! They house the piezoelectric crystals that produce the ultrasound waves. Not only do they break easily, they are almost impossible to repair. Furthermore, the probe is normally the most expensive part of a scanner, with the price of a probe ranging from R50k to more than R170k. Also consider the compatibility of a probe when upgrading your ultrasound unit. This could save you money if you keep your probe in good condition.

Keeping the probes clean and always following the cleaning guidelines from the product manual (with a list of approved cleaning agents) is also important. Probes do not like spirits, so restrict the use of spirit to biopsies and FNAs. Prolonged exposure to spirits can cause the surface of the probe to dry out, harden and crack/peel which will affect the image quality. We recommend thinking of the surface of the probe as you would a camera lens!

Lastly, build confidence in your scanning! Practice makes perfect, and attending our regular BCF CPD ultrasound training courses is a fun and practical way to develop your skills further. Great imaging is an excellent way to generate regular cash flow revenue into your business.

For more information on veterinary ultrasound probes and scanners or other imaging equipment, contact Tim Perks at BCF Technology South Africa on +27 82 616 4685 www.bcftechnology.co.za

Figure 1: 8C-RS 4-10 MHz 11mm radius micro-convex probe
Figure 2: 4C-RS 2-5 MHz 60mm radius convex probe
Figure 3: 12L-RS 5-13 MHz 47mm footprint linear probe
Figure 4: L8-18i-RS 6.7 – 18 MHz 25mm footprint linear hockey stick probe
Figure 5: 6S-RS 2.5-7.0 MHz 16.8×23.5mm footprint phased array probe
Figure 6: ML6-15 5–13 MHz 16x61mm linear matrix probe

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