Comparison Between Pneumatic and Mechanical Drivers Using Magnetic Resonance Elastography

Principal Investigator: Kai-Nan An, Ph.D.
Project Coordinator: Qingshan Chen — chen.qingshan@mayo.edu

Figure 1: Shear waves induced during MRE scanning.

Magnetic Resonance Elastography (MRE), a non invasive phase contrast MR technique, can visualize small displacements from applied shear waves and quantify the stiffness of soft tissues in vivo. This technique has been applied to soft tissues such as the breast and brain and to skeletal muscles in the lower leg (tibialis anterior and gastrocnemius), arm (biceps), and shoulder (trapezius). In the larger muscles of the quadriceps, inducing shear waves is more challenging than in the smaller muscles and other soft tissues. The purpose of this study was to induce shear waves within the quadriceps muscles with two different drivers (mechanical and pneumatic) in order to measure the stiffness of the vastus intermedius, vastus medialus and sartorius muscles. In healthy volunteers the driver was attached to the lateral size of the thigh and propagating shear waves were applied to the quadriceps muscles with a frequency of 120 Hz (Fig. 1). The elastic properties of all three muscles were similar when measured with both drivers but the pneumatic driver was able to apply shear waves to the deep vastus intermedius in more volunteers than the mechanical driver.