What is Elastography?
Elastography is a cutting edge medical imaging technology that can be used to non-invasively examine tissue material properties in vivo. Elastography was developed in 1991 for the purpose of detecting non-uniform areas in tissue (Ophir et al., 1991). The process uses an imaging technique to measure wave motion through a tissue and calculate tissue material properties based on the mechanics of wave propagation.
Elastography has been applied to study muscle in a variety of different conditions (Ringleb et al., 2007). For example, Magnetic Resonance elastography has been used to examine changes in material properties of muscle associated with aging (Domire et al., 2009). Ultrasound elastography has been shown to be a reliable and repeatable method for determining muscle material properties (Chino et al., 2012), and has been used to determine stiffness of the plantar fascia (Wu et al., 2012).
The picture above demonstrates the elastography process. Ultrasound elastography uses a focused ultrasound pulse to induce tissue deformation and measure the resulting wave using standard B-mode imaging. This figure shows the propagation of ultrasound pulse from the transducer head into the muscle and the propagation of the resulting shear wave. The shear modulus of the muscle is calculated as µ = f2.λ2.ρ where f- frequency, λ- wavelength, and ρ- tissue density.
Ultrasound elastography video clip of the Flexor Hallicus Brevis in a minimalist (barefoot) runner.
Ultrasound elastography video clip of the Flexor Hallicus Brevis in a shod runner.