Ultrasound imaging and muscle function

There is a growing trend in the physical therapy profession to use conventional gray scale brightness (B) mode ultrasound imaging (USI) as a tool to assess the morphological (form and structure) and morphometric (measures of form) characteristics of muscle and then using these findings to draw conclusions regarding muscle function. This trend is reflected in numerous investigations published in the physical therapy literature. As physical therapists typically lack training in the principles and instrumentation underlying USI use it is critical that therapists gain a clear understanding of the information that USI can, and cannot, provide about muscle function, before employing the technique for either research or clinical applications. Failure to do so may result in the propagation of inaccurate terminology and beliefs. This paper aims to clarify the role that USI has in the assessment of muscle function, firstly by briefly reviewing how conventional grey scale B-mode ultrasound images and clips are generated, and secondly by summarizing the types of information that these images can provide. It will then go on to discuss the various factors that need to be considered when interpreting a dynamic USI assessment of muscle, specifically as it relates to the assessment of muscle function