Patient-specific modelling of the calf muscle under elastic compression using magnetic resonance imaging and ultrasound elastography

Abstract

Compression therapy is traditionally employed to achieve a variety of therapeutic goals related to venous insufficiency but its mechanisms are neither clearly understood nor conclusively demonstrated. (Avril et al., 2010) have pointed out that the capacity of the treatment to achieve the desired medical goal is closely related to the question of transmission of pressure through the soft tissues, as a result of which biomechanical models have been developed (Dubuis et al., 2012). In these models, the prediction of pressure was made based on the rather strong assumption that the behaviour of soft tissues (muscles and adipose tissues) can be approximated as homogeneous materials. Recent developments in ultrasound imaging can be helpful to improve both our understanding of the effect of medical compression stockings (MCS) on the blood return and on the quality of our predictions. (Bercoff et al., 2004) introduced a new ultrasound based technology called Supersonic Shear Imaging (SSI), for real-time soft tissue elasticity mapping. This transient elastography technique remotely produces a low frequency shear wave inside soft tissue through a radiation force by focusing ultrasonic beams at a supersonic speed. The shear wave motion is captured at a frame rate of 5 MHz. The velocity field of the medium can be mapped an dassuming the medium to be elastic, Young's modulus can be estimated quantitatively. This non-invasive technique allows identifying the material property heterogeneities inside the different compartments of the human leg. Using this experimental technique combined with FE modeling, the present study aims at shedding a light on the influence of those heterogeneities of material properties on the pressure inside the leg under elastic compression.