Department of Radiology, Charité, Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany; Berlin Institute of Health (BIH), Anna-Louisa-Karsch-Str. 2, 10178, Berlin, Germany.
Department of Radiology, Charité, Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany.
J Mech Behav Biomed Mater. 2021 Sep;121:104645. doi: 10.1016/j.jmbbm.2021.104645. Epub 2021 Jun 18.
Many elastography studies have shown that liver stiffness increases with fibrosis and thus can be used as a reliable marker for noninvasively staging fibrosis. However, the sensitivity of viscosity-related mechanical parameters, such as shear wave dispersion, to liver fibrosis is less well understood.
In this proof-of-concept study, 15 healthy volunteers and 37 patients with chronic liver disease and biopsy-proven fibrosis were prospectively investigated by MR elastography at six drive frequencies of 35-60 Hz. Maps of shear wave speed (SWS, in m/s) and loss angle (φ, in rad), as a marker of stiffness and viscous properties, respectively, were generated using tomoelastography data processing. The Child-Pugh score was used to assess cirrhosis severity.
While SWS increased with fibrosis (F0: 1.53 ± 0.11 m/s, F1-F3: 1.71 ± 0.17 m/s, F4: 2.50 ± 0.39 m/s; P < 0.001), φ remained unchanged during mild to severe fibrosis (F0: 0.63 ± 0.05 rad, F1-F3: 0.60 ± 0.05 rad, P = 0.21) but increased in cirrhosis (F4: 0.81 ± 0.16 rad; P < 0.001). Correspondingly, the slope of SWS-dispersion within the investigated range of vibration frequencies increased from insignificant (F0-F3: 0.010 ± 0.007 m/s/Hz) to significant (F4: 0.038 ± 0.025 m/s/Hz; P = 0.005). Significant correlation with the Child-Pugh score was found for φ (R = 0.60, P = 0.01) but not for SWS.
Although cirrhosis is associated with liver stiffening and, intuitively, transition towards more rigid material properties, the observed increases in φ and slope of SWS-dispersion indicate abnormally high mechanical friction in cirrhotic livers. This biophysical signature might provide a prognostic imaging marker for the detection of pathological processes associated with fibrosis independent of stiffness.
许多弹性成像研究表明，肝脏硬度随纤维化而增加，因此可作为一种可靠的非侵入性分期纤维化的标志物。然而，剪切波速度分散等与粘度相关的力学参数对肝纤维化的敏感性尚不清楚。
在这项概念验证研究中，对 15 名健康志愿者和 37 名经活检证实患有慢性肝病和纤维化的患者进行前瞻性研究，使用 MR 弹性成像在 35-60 Hz 的六个驱动频率下进行检测。使用断层弹性成像数据处理生成剪切波速度（SWS，单位为 m/s）和损耗角（φ，单位为 rad）图，分别作为硬度和粘性特性的标志物。使用 Child-Pugh 评分评估肝硬化严重程度。
SWS 随纤维化程度增加而增加（F0：1.53±0.11 m/s，F1-F3：1.71±0.17 m/s，F4：2.50±0.39 m/s；P＜0.001），而在轻度至重度纤维化期间，φ 保持不变（F0：0.63±0.05 rad，F1-F3：0.60±0.05 rad，P=0.21），但在肝硬化中增加（F4：0.81±0.16 rad；P＜0.001）。相应地，在所研究的振动频率范围内，SWS 分散的斜率从无意义（F0-F3：0.010±0.007 m/s/Hz）变为显著（F4：0.038±0.025 m/s/Hz；P=0.005）。φ 与 Child-Pugh 评分呈显著相关（R=0.60，P=0.01），而 SWS 则无相关性。
尽管肝硬化与肝脏僵硬有关，并且直观上与更刚性的材料特性有关，但观察到的 φ 和 SWS 分散斜率增加表明肝硬化肝脏中存在异常高的机械摩擦。这种生物物理特征可能为检测与纤维化无关的纤维化相关病理过程提供一种预后成像标志物。
