Ultrasound echo is related to stress and strain in tendon

Abstract

The mechanical behavior of tendons has been well studied in vitro. A noninvasive method to acquire mechanical data would be highly beneficial. Elastography has been a promising method of gathering in vivo tissue mechanical behavior, but it has inherent limitations. This study presents acoustoelasticity as an alternative ultrasound-based method of measuring tendon stress and strain by reporting a relationship between ultrasonic echo intensity (B mode ultrasound image brightness) and mechanical behavior of tendon in vitro. Porcine digital flexor tendons were cyclically loaded in a mechanical testing system while ultrasonic echo response was recorded. We report that echo intensity closely follows the applied cyclic strain pattern in time with higher strain protocols resulting in larger echo intensity changes. We also report that echo intensity is related nonlinearly to stress and nearly linearly to strain. This indicates that ultrasonic echo intensity is related to the mechanical behavior in a loaded tissue by an acoustoelastic response, as previously described in homogeneous, nearly incompressible materials. Acoustoelasticity is therefore able to relate strain-dependent stiffness and stress to the reflected echo, even in the processed B-mode signals reflected from viscoelastic, inhomogeneous material such as tendon, and is a promising metric to acquire in vivo mechanical data noninvasively.

Ultrasound Assessment of Ex Vivo Lung Tissue Properties Using a Fluid-Filled Negative Pressure Bath

“…As anticipated, ultrasound echo intensity measurements likewise demonstrated volume-dependent changes. Volume-dependent echo intensity changes that are related to pressure changes in inflating lung tissue are analogous to strain-dependent echo intensity changes that are related to stress changes in the stretching tendon [7], and the stiffness-related changes in echo intensity first seen in tendon [9] are here confirmed as compliance-related changes in lung echo intensity.…”

“…Ultrasound imaging has previously been used in connective tissues to not only provide visual information about a tissue but also quantitatively describe its mechanical properties (i.e., by relating tissue mechanical properties to changes in echo intensity, or the grayscale brightness in the ultrasound image) [7][8][9][10]. Ultrasound is highly portable, inexpensive, noninvasive, and requires no radiation or contrast injection.…”

“…This makes it especially attractive in pediatric patients, pregnant women, patients who are sedated and mechanically ventilated, or those who have advanced kidney disease [11]. A relationship between tissue stress and strain and ultrasonic echo intensity (grayscale brightness in the ultrasound 1 image) has previously been defined in tendons [7], demonstrating a correlation between tissue stiffness and echo intensity. However, the use of pulmonary ultrasound has been limited to guidance for pleural thoracentesis and the diagnosis of pulmonary hypertension, great vessel abnormalities, pneumothorax, and pleural effusion.…”

Effects of repeated eccentric contractions with different loads on blood circulation and collagen fiber orientation in the human Achilles tendon

“…3A and B). A previous in vitro study reported that the mean echogenicity of tendons was non-linearly related to the applied tendon stress 32) . Nevertheless, the mean echogenicity of tendons increased during the relaxation period of a stress-relaxation test 33) .…”

Assessment of digital flexors tenorrhaphy in equine: a review

“…The alteration in tendon echogenicity reflects changes in the cellular and extracellular composition of injured tendons along with the repair tissue, it ranged from a barely perceptible decrease in echogenicity with mild loss of fibre pattern as in mild tendonitis, to complete disruption of fibre pattern seen with fibre rupture accompanied with haemorrhage or with serious fluid accumulation and oedema (Denoix et al 2005;Duenwald et al 2011).…”