Tan Kristy, Jugé Lauriane, Hatt Alice, Cheng Shaokoon, Bilston Lynne E
Neuroscience Research Australia, Randwick, NSW, Australia.
University of New South Wales, School of Medical Sciences, Kensington, NSW, Australia.
NMR Biomed. 2018 Oct;31(10):e3925. doi: 10.1002/nbm.3925. Epub 2018 Apr 19.
It is important to measure the large deformation properties of skeletal muscle in vivo in order to understand and model movement and the force-producing capabilities of muscle. As muscle properties are non-linear, an understanding of how the deformation state affects the measured shear moduli is also useful for clinical applications of magnetic resonance elastography (MRE) to muscle disorders. MRE has so far only been used to measure the linear viscoelastic (small strain) properties of muscles. This study aims to measure the shear moduli of human calf muscles under varying degrees of strain using MRE. Nine healthy adults (four males; age range, 25-38 years) were recruited, and the storage modulus G' was measured at three ankle angle positions: P0 (neutral), P15 (15° plantarflexed) and P30 (30° plantarflexed). Spatial modulation of magnetization (SPAMM) was used to measure the strain in the calf associated with the ankle rotations between P0 to P15 and P0 to P30. SPAMM results showed that, with plantarflexion, there was a shortening of the medial gastrocnemius and soleus muscles, which resulted in an expansion of both muscles in the transverse direction. Strains for each ankle rotation were in the range 3-9% (in compression). MRE results showed that this shortening during plantarflexion resulted in a mean decrease in G' in the medial gastrocnemius (p = 0.013, linear mixed model), but not in the soleus (p = 0.47). This study showed that MRE is a viable technique for the measurement of large strain deformation properties in vivo in soft tissues by inducing physiological strain within the muscle during imaging.
为了理解和模拟运动以及肌肉的发力能力，在体内测量骨骼肌的大变形特性很重要。由于肌肉特性是非线性的，了解变形状态如何影响所测量的剪切模量对于磁共振弹性成像（MRE）在肌肉疾病临床应用中也很有用。到目前为止，MRE仅用于测量肌肉的线性粘弹性（小应变）特性。本研究旨在使用MRE测量不同应变程度下人小腿肌肉的剪切模量。招募了9名健康成年人（4名男性；年龄范围25 - 38岁），并在三个踝关节角度位置测量储能模量G'：P0（中立位）、P15（跖屈15°）和P30（跖屈30°）。利用磁化空间调制（SPAMM）测量在P0到P15以及P0到P30之间踝关节旋转时小腿的应变。SPAMM结果显示，随着跖屈，腓肠肌内侧头和比目鱼肌缩短，导致这两块肌肉在横向方向上扩张。每次踝关节旋转的应变范围为3 - 9%（压缩状态）。MRE结果显示，这种跖屈过程中的缩短导致腓肠肌内侧头的G'平均下降（p = 0.013，线性混合模型），但比目鱼肌没有下降（p = 0.47）。本研究表明，MRE是一种可行的技术，可通过在成像过程中在肌肉内诱导生理应变来测量软组织在体内的大应变变形特性。
