In vivo elasticity measurements of extremity skeletal muscle with MR elastography

Abstract

MR elastography (MRE) has been shown to be capable of non-invasively measuring tissue elasticity even in deep-lying regions. Although limited studies have already been published examining in vivo muscle elasticity, it is still not clear over what range the in vivo elasticity values vary. The present study intends to produce further information by examining four different skeletal muscles in a group of 12 healthy volunteers in the age range of 27-38 years. The examinations were performed in the biceps brachii, the flexor digitorum profundus, the soleus and the gastrocnemius. The average shear modulus was determined to be 17.9 (+/- 5.5), 8.7 (+/- 2.8), 12.5 (+/- 7.3) and 9.9 (+/- 6.8) kPa for each muscle, respectively. To ascertain the reproducibility of the examination, the stiffness measurements in two volunteers were repeated seven times for the biceps brachii. These examinations yielded a mean shear modulus of 11.3 +/-.7 and 13.3 +/- 4.7 kPa for the two subjects. For elasticity reconstruction, an automated reconstruction algorithm is introduced which eliminates variation due to subjective manual image analysis. This study yields new information regarding the expected variation in muscle elasticity in a healthy population, and also reveals the expected variability of the MRE technique in skeletal muscle.

Shear wave group velocity inversion in MR elastography of human skeletal muscle

“…Using group velocity inversion, it is possible to adapt the spatial sector of wave inversion to a boundary-free ROI. This can be particularly important for evaluating MRE experiments of thin muscle layers or less separated muscle groups (21)(22)(23)36). As Fig.…”

Changes in calf muscle elasticity in hypogonadal males before and after testosterone substitution as monitored by magnetic resonance elastography

“…For the reconstructions, the local frequency estimation (13) technique was used to determine shear wavelength and from this to estimate the shear modulus of the muscle (7,14). The underlying principle is based on the fact that the wave propagation velocity is higher in stiffer materials.…”

“…Magnetic resonance elastography (MRE) is a novel approach for measuring muscle stiffness during contraction (6,7). For image contrast, this technique utilizes the elastic properties of tissue, which vary between different tissues or between different affections of one tissue.…”

“…Muscle stiffness has also been shown to vary between muscle groups, gender (7), and degree of muscle load (11). A preliminary study comparing healthy subjects to a small group of patients with neuromuscular dysfunction in the lower extremities with varying etiology (6) demonstrated differences in muscle stiffness between the two groups.…”

Non-identifiability of the Rayleigh damping material model in Magnetic Resonance Elastography

“…Magnetic Resonance Elastography (MRE) can directly visualise and measure tissue elasticity [5][6][7][8], and has been applied to resolve stiffness characteristics of a variety human tissues and organs, such as muscle [9][10][11][12], breast [13][14][15][16][17], liver [18][19][20] and the brain [21][22][23][24][25][26][27][28][29]. MRE acquisition requires application of mechanical waves to tissue within the MRI, phase-contrast MR pulse sequence extended with motion encoding gradient (MEGs), and sophisticated inverse problem methods to identify an elastic modulus map of the tissue.…”