Development of a phantom mimicking the functional and structural behaviors of the thigh muscles characterized with magnetic resonance elastography technique.

Abstract

Magnetic Resonance Elastography (MRE) is a non invasive technique based on the propagation of shear waves in soft tissues providing the quantification of the mechanical properties [1]. MRE was successfully applied to healthy and pathological muscles. However, the MRE muscle methods must be further improved to characterize the deep muscles. A way will be to develop phantom mimicking the muscle behavior in order to set up new MRE protocol. Thus, the purpose of this study is to create a phantom composed of a similar skeletal muscle architecture (fiber, aponorosis) and equivalent elastic properties as a function of the muscle state (passive or active). Two homogeneous phantoms were manufactured with different concentrations of plastisol to simulate the elastic properties in relaxed (50% of plastisol) and contracted (70% of plastisol) muscle conditions. Moreover, teflon tubing pipes (D = 0.9 mm) were thread in the upper part of the phantom (50%) to represent the muscle fibers and a plastic sheet (8 × 15 cm) was also included in the middle of the phantom to mimic the aponeurosis structure. Subsequently, MRE tests were performed with two different pneumatic drivers, tube and round, (f = 90Hz) to analyze the effect of the type of driver on the wave propagation. Then, the wavelength was measured from the phase images to obtain the elastic properties (shear modulus). Both phantoms revealed elastic properties which were in the same range as in vivo muscle in passive (μ(50%) = 2.40 ± 0.18 kPa ) and active (6.24 ± 0.21 kPa) states. The impact of the type of driver showed higher values (about 1.2kPa) with the tube. The analysis of the wave behavior revealed a sliding along the plastic sheet as it was observed for in vivo muscle study. The wave was also sensitive to the presence of the fibers where gaps were identified. The present study demonstrates the ability of the phantom to mimic the structural and functional properties of the muscle.