Basford Jeffrey R, Jenkyn Thomas R, An Kai-Nan, Ehman Richard L, Heers Guido, Kaufman Kenton R
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, 200 SW Second Street, Rochester, MN 55905, USA.
Arch Phys Med Rehabil. 2002 Nov;83(11):1530-6. doi: 10.1053/apmr.2002.35472.
To investigate whether a new tissue-imaging technique, magnetic resonance elastography (MRE), offers a viable, noninvasive way to study healthy and diseased muscle.
Convenience sample.
A magnetic resonance imaging (MRI) laboratory.
Eight control subjects (4 men, 4 women), between the ages of 24 and 41 years, with normal neuromuscular examinations and histories, and 6 subjects (3 men, 3 women), ages 17 to 63 years, with lower-extremity neuromuscular dysfunction (1 with childhood poliomyelitis, 2 with flaccid, 3 with spastic paraplegia).
Subjects lay supine with their legs within the coils of a 1.5T MRI machine, with their feet strapped to a footplate positioned so that the axes of rotation of their ankles coincided with the apparatus. All subjects were tested in a no-load (0 torque) condition. Control subjects were also evaluated as they isometrically resisted ankle dorsi- (20.2Nm, 40.5Nm) and plantar- (8.2Nm, 16.4Nm) flexion moments. Subjects with neuromuscular dysfunction were evaluated in the same manner, except 1 individual with residual lower-extremity strength who could only be tested in the resting and passive ankle dorsiflexion modes. Shear waves were induced with a 150-Hz electromechanic transducer located over the belly tibialis anterior. MRE images were collected with a gradient-echo technique gated to the transducer's motion. Wave-phase propagation was visualized with 8 equally offset images across 1 vibration-cycle.
Changes in shear-wave wavelength (lambda) and muscle stiffness (as expressed by the shear modulus [G]) in the tibialis anterior and gastrocnemius muscles.
Wavelength and G differed between the groups in all the muscles studied, and increased as the load increased. Moreover, lambda and G in the neuromuscular disease group at rest (eg, 3.88+/-0.48cm; range, 2.87-4.91cm; 38.40+/-00.77kPa; range, 22.35-59.67kPa) and in the lateral gastrocnemius were, respectively, more than 1.5 and 2.4 times larger than they were in the same muscle in the control group (2.56+/-0.28cm, 16.16+/-00.19kPa; P=.0002) (1Pa=1N/m(2)).
Shear-wave wavelength and muscle stiffness increased with load in healthy muscle. In addition, at least for our sample, these quantities differed significantly between muscles with and without neuromuscular disease. In summary, MRE appears to provide in vivo physiologic information about the mechanical properties of muscle at rest and during contraction that is not otherwise available. The potential of this technique for monitoring the effects of treatment and exercise on both healthy and diseased muscle merits further research.
研究一种新的组织成像技术——磁共振弹性成像（MRE），是否能提供一种可行的、非侵入性的方法来研究健康和患病肌肉。
便利抽样。
磁共振成像（MRI）实验室。
8名对照受试者（4名男性，4名女性），年龄在24至41岁之间，神经肌肉检查及病史正常；6名受试者（3名男性，3名女性），年龄在17至63岁之间，患有下肢神经肌肉功能障碍（1例小儿麻痹后遗症，2例弛缓性，3例痉挛性截瘫）。
受试者仰卧，双腿置于1.5T MRI机器的线圈内，双脚绑在一个脚板上，脚板的位置使踝关节的旋转轴与仪器重合。所有受试者均在无负荷（0扭矩）条件下进行测试。对照受试者还在等长抵抗踝关节背屈（20.2牛米、40.5牛米）和跖屈力矩（8.2牛米、16.4牛米）时接受评估。患有神经肌肉功能障碍的受试者以相同方式进行评估，但有1例下肢有残余力量的个体只能在静息和被动踝关节背屈模式下进行测试。用一个150赫兹的机电换能器在胫骨前肌肌腹上方诱发剪切波。采用与换能器运动同步的梯度回波技术采集MRE图像。通过1个振动周期内8幅等距偏移图像观察波相位传播。
胫骨前肌和腓肠肌中剪切波波长（λ）和肌肉硬度（以剪切模量[G]表示）的变化。
在所研究的所有肌肉中，两组之间的波长和G值存在差异，且随负荷增加而增加。此外，神经肌肉疾病组静息时（如3.88±0.48厘米；范围2.87 - 4.91厘米；38.40±00.77千帕；范围22.35 - 59.67千帕）和外侧腓肠肌中的λ和G值，分别比对照组同一肌肉中的值大1.5倍和2.4倍以上（2.56±0.28厘米，16.16±00.19千帕；P = 0.0002）（1帕 = 1牛/米²）。
健康肌肉中，剪切波波长和肌肉硬度随负荷增加而增加。此外，至少对于我们的样本，有无神经肌肉疾病的肌肉之间这些量存在显著差异。总之，MRE似乎能提供关于静息和收缩状态下肌肉力学特性的体内生理信息，而这些信息是其他方法无法获得的。该技术在监测治疗和运动对健康和患病肌肉的影响方面的潜力值得进一步研究。
