Essential Knobology for Ultrasound-Guided Regional Anesthesia and Interventional Pain Management

Abstract

The safety and efficacy of ultrasound (US)-guided nerve blockade relies heavily upon a comprehensive understanding of machine “knobology” [1-3]. Despite differences in appearance and layout, all US machines share the same basic operative functions that users must appreciate in order to optimize the image. While modern US machines offer an abundance of features, the basic functions that all operators should be familiar with are frequency and probe selection, depth, gain, time gain compensation (TGC), focus, preprogrammed presets, color Doppler, power Doppler, compound imaging, tissue harmonic imaging (THI) (on some models), and image freeze and acquisition. Once the physical principles of US are understood, it becomes clear that creating the “best” image is often a series of trade-offs between improving one function at the expense of another. Each of the aforementioned functions is presented in turn below, following the sequence we use when performing any US-guided intervention.