When you’re starting out with bedside ultrasound, it’s tempting to save yourself a few seconds and use the probe that’s set as the default probe for whatever you want to scan. This is a rookie error. The reason there are different probes is that any single probe design and its corresponding frequency range represents a series of trade-offs. The biggest trade-off is between resolution and depth of view. The other is between scope (the size and shape of the sound beam) and resolution. For more depth, for example to see the back of the liver, you need a lower-frequency probe but this limits the image resolution or detail that is seen. High-frequency probes are great for detail work, for example with tendons or vessels, but have limited depth of penetration and are therefore limited to superficial structures.

With scope, the wider or more fan-shaped the beam, the lower the resolution. The higher resolution seen with linear beam arrays comes with a smaller lateral field of view or scope.

Therefore when scanning abdomens, use the low-frequency, curved probe (good depth, wide scope, lower detail). When scanning superficial structures such as vessels or for foreign bodies, use the high-frequency, linear probe (shallow depth, high detail, narrow scope). When scanning the heart use the small-footprint, wide-scope probe with the lower frequency. This allows you to get between the ribs (small footprint) and see all the cardiac chambers (greater depth) but does compromise on the detail which is an acceptable tradeoff with cardiac sonography.