Biomedical NMR, Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.
NMR Biomed. 2019 Jun;32(6):e4087. doi: 10.1002/nbm.4087. Epub 2019 Mar 21.
The current state-of-the-art diagnosis method for deep tissue injury in muscle, a subcategory of pressure ulcers, is palpation. It is recognized that deep tissue injury is frequently preceded by altered biomechanical properties. A quantitative understanding of the changes in biomechanical properties preceding and during deep tissue injury development is therefore highly desired. In this paper we quantified the spatial-temporal changes in mechanical properties upon damage development and recovery in a rat model of deep tissue injury. Deep tissue injury was induced in nine rats by two hours of sustained deformation of the tibialis anterior muscle. Magnetic resonance elastography (MRE), T -weighted, and T -mapping measurements were performed before, directly after indentation, and at several timepoints during a 14-day follow-up. The results revealed a local hotspot of elevated shear modulus (from 3.30 ± 0.14 kPa before to 4.22 ± 0.90 kPa after) near the center of deformation at Day 0, whereas the T was elevated in a larger area. During recovery there was a clear difference in the time course of the shear modulus and T . Whereas T showed a gradual normalization towards baseline, the shear modulus dropped below baseline from Day 3 up to Day 10 (from 3.29 ± 0.07 kPa before to 2.68 ± 0.23 kPa at Day 10, P < 0.001), followed by a normalization at Day 14. In conclusion, we found an initial increase in shear modulus directly after two hours of damage-inducing deformation, which was followed by decreased shear modulus from Day 3 up to Day 10, and subsequent normalization. The lower shear modulus originates from the moderate to severe degeneration of the muscle. MRE stiffness values were affected in a smaller area as compared with T . Since T elevation is related to edema, distributing along the muscle fibers proximally and distally from the injury, we suggest that MRE is more specific than T for localization of the actual damaged area.
目前，肌肉深部组织损伤（压疮的一个亚类）的最先进诊断方法是触诊。人们认识到，深部组织损伤通常是生物力学特性改变的结果。因此，非常需要定量了解在深部组织损伤发展之前和发展过程中生物力学特性的变化。在本文中，我们在大鼠深部组织损伤模型中定量了损伤发展和恢复过程中机械性能的时空变化。通过对胫骨前肌持续变形两小时，在九只大鼠中诱导深部组织损伤。在压痕之前、直接压痕后以及 14 天的随访期间的多个时间点进行磁共振弹性成像（MRE）、T -加权和 T -映射测量。结果显示，在第 0 天，在变形中心附近有一个局部的剪切模量升高热点（从 3.30±0.14kPa 升高到 4.22±0.90kPa），而 T 升高的区域更大。在恢复过程中，剪切模量和 T 的时间过程有明显的差异。尽管 T 逐渐恢复到基线水平，但从第 3 天到第 10 天，剪切模量降至低于基线水平（从 3.29±0.07kPa 降至第 10 天的 2.68±0.23kPa，P<0.001），然后在第 14 天恢复正常。总之，我们发现两小时损伤诱导变形后直接出现剪切模量增加，随后从第 3 天到第 10 天剪切模量降低，然后恢复正常。较低的剪切模量源于肌肉的中度至严重退化。与 T 相比，MRE 硬度值受影响的区域较小。由于 T 升高与水肿有关，沿着损伤近端和远端的肌肉纤维分布，我们建议 MRE 比 T 更能定位实际的损伤区域。
