Which Gel Pad & Commonly Encountered Artefact

Experience would suggest no clear cut first best choice. Horses for courses, Gel Pads the same. It simply comes down to having the gel pads available and selecting to suit purpose.

Looking at a lump hidden deep to hair on the head.

The THICK gel pad (10mm thick) appears to present the best solution short of shaving the space being examined – often not possible nor practical

When coupled with a slightly lower frequency probe than might otherwise be first choice, this gel pad, with a lower frequency linear probe, presents excellent imaging outcome with minimal artefactual disturbance from the overlying hair depth. 

Flexor tendons in a finger, The SQUARE or even the ROUND Gel pad, both 5mm thick. These gel pads, when utilised with a small footprint higher frequency probe will certainly best examine very superficial tissues however, in this instance – flexors in the finger, a larger footprint probe with lower frequency, presents good long length tendon overview.

Artefactual dropout will occur along the length of the finger with the lower frequency, longer footprint probe due to varying angles of insonation along the length of the finger. 

Application heel-toe effect with the probe, whilst scanning, will overcome and enable good long length overview. Should it be necessary, you may certainly then swap to higher frequency smaller footprint probe for any areas focal concern noted during the overview or identified by the patient during the scan.

Ring down artefact, another commonly encountered artefact when utilising a standoff Gel Pad. If encountered, this often just requires a small amount of increased probe pressure, probe heel-toe, or change in angle of insonation. Should this be a persisting problem, changing probe, probe frequency also often helps. As do machine factors.

As with all artefacts, machine factors such as equipment settings (i.e. Gain, TGC, depth, focus, and dynamic range), cannot be ignored. It is not simply a matter of coupling a probe with a gel pad and an area of concern and whizz bang we have an amazing image (sometimes we do). To achieve a desired clinical outcome machine factors really are quite important as well.

Quick side note 

Ultrasound standoff Gel Pads, such as these, depressure focal areas of trauma or tenderness whilst scanning. Permitting a better level of access with the probe/probe pressure than may otherwise be tolerated or permitted.