In canine pregnancy scanning, image quality can reveal far more than just the presence of pups—it can provide detailed insights into foetal health, position, and development. In the video below, a late-stage pregnant Cocker Spaniel is scanned using a Vinno D10 with two different transducers: a microconvex and a linear probe. Both deliver strong results, but the difference in clarity is hard to ignore once the linear probe is introduced:

Did You Know…

Foetal canine intestines begin to show movement around 13 to 9 days before whelping? (For comparison, in human foetuses, intestinal activity becomes visible between 22 and 20 weeks before birth.) Remarkably, this movement can be seen on ultrasound—provided you’re using a high-resolution probe such as a linear transducer- and can be a helpful marker when estimating the time window for whelping. Now watch the scan video above again, paying close attention to the pup’s abdominal area. You’ll see the incredible detail of the pup’s intestines; it’s only a small leap to imagine how well you’d be able to see peristalsis occurring at a later gestational stage.

Microconvex Performance: Versatile and Reliable

The first half of the video showcases a scan using a high-quality microconvex probe. This type of transducer is widely recommended for small animal scanning because of its compact footprint, broad field of view, and good penetration depth. The foetal heartbeat is clearly visible, with solid definition of the surrounding anatomy.

This is exactly why microconvex probes are the standard recommendation for those training through the Animal Ultrasound Association. For scanning medium to small breed dogs, microconvex transducers strike an ideal balance between usability, cost and image performance.

A Noticeable Upgrade: Linear Probe Clarity

In the second half of the scan, the switch to a linear probe reveals an immediate improvement in image clarity. Detail becomes crisper, anatomical borders appear more sharply defined. This level of definition is rarely achievable with a microconvex probe.

The improvement is largely due to the higher operating frequency of linear probes, which enhances resolution in the near field—the area closest to the skin surface.

Frequency and Resolution: The Technical Difference

• Linear probes typically operate at higher frequencies (often 3.5–7 MHz or more), which allows for shorter wavelengths and better resolution of superficial structures.
• Microconvex probes, by contrast, use lower frequencies to provide greater depth, which is useful for imaging deeper organs—but at the cost of near-field resolution.

Because Cocker Spaniel puppies are relatively superficial, the extra depth offered by a microconvex probe isn’t necessary in this case. Instead, the linear probe’s high resolution can be used to full effect, resulting in exceptionally clear foetal imaging.

When Should a Linear Probe Be Used?

For most canine and feline pregnancy scans, a microconvex probe is more than adequate. It offers flexibility, ease of handling, and strong image quality—particularly in medium to small breeds. It’s also more cost-effective, making it a sensible choice for paraprofessionals and ultrasound technicians working primarily in animal pregnancy scanning.

However, for veterinary surgeons, registered veterinary nurses (RVNs), or those working in practices with advanced imaging systems like the Vinno D10, adding a linear probe can be a valuable enhancement. While not essential, it enables a much closer look at fine, shallow structures—adding confidence and clarity in certain cases.

The side-by-side comparison shown in the video clearly demonstrates that: Linear ultrasound probes offer superior image quality in the near field compared to even premium microconvex probes.

When imaging small breeds—especially during late-stage pregnancy, where foetuses are positioned near the abdominal wall—a linear probe can reveal extraordinary detail.

For everyday scanning, microconvex probes remain the most practical and widely applicable tool. But for those seeking to maximise image resolution in near-field structures, the linear probe shows its full potential.