实时剪切波弹性成像杨氏模量最大值诊断甲状腺乳头状癌BRAF V600E基因突变的价值

目的:探究实时剪切波弹性成像（SWE）杨氏模量最大值诊断甲状腺乳头状癌（PTC）鼠类肉瘤滤过性毒菌致癌同源体B1（BRAF）V600E基因突变的价值。方法:回顾性分析2018年1月~2019年6月宿迁市第一人民医院收治的110例PTC患者共124个结节的临床及超声影像学资料。患者经病理学检查均确诊为PTC,并完成了BRAF V600E基因检测以及SWE检查,临床资料完整。通过比较V600E基因突变型与野生型PTC的SWE检查结果,并绘制患者Emax值的ROC曲线,分析Emax值对PTC患者BRAF V600E基因突变的诊断效能。结果:BRAF基因检测结果显示:124个PTC结节BRAF基因检测V600E野生型共37个,V600E突变型共87个。野生型PTC结节的SWE图像多以蓝色为主,而突变型主要表现为红橙相间彩色混杂的图像。突变组PTC结节Emax、Emean、Eratio值均明显大于野生组,比较差异具有统计学意义（P<0.05）,ROC曲线分析显示:Emax值诊断V600E突变的AUC=0.846>0.5（95%CI:0.808~0.885, P<0.01）;Cut-off值为43.65 kPa,此时敏感度为91.45%,特异性为68.23%。以Emax≥43.65 kPa为临界值对124个结节进行诊断,结果显示:SWE诊断PTC结节为V600E基因突变型90个,野生型34个,正确率为86.29%;SWE诊断结果与基因检测结果一致性显著（Kappa值=0.665, P<0.01）。结论:PTC BRAF V600E基因突变型与野生型的SWE影像学特征具有明显差异,应用SWE的Emax值诊断PTC结节V600E基因突变的正确率和敏感性均较高,诊断价值显著,值得在临床上推广应用。     

Elastic and viscoelastic characterization of microcapsules for drug delivery using a force-feedback MEMS microgripper

This paper reports a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper and its application to micro-scale compression testing of swollen hydrogel microcapsules at wet state during manipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5 nN) and the other for gripping force measurements (force resolution: 19.9 nN). With the capability of resolving gripping forces down to 19.9 nN and material deformations with a 20.5 nm resolution, the system quantified Young’s modulus values and viscoelastic parameters of alginate microcapsules (15–25 μm), demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials.     

超声弹性成像仿真的有限元分析

本文利用有限元分析的方法，用弹性力学的理论计算得到软组织在不同情况下的应变分布。这对于弹性成像的理论分析具有重要的辅助作用，可以研究软组织的不同状态和各种力学参数对弹性成像的影响，以及从理论上估计弹性成像的局限性。有限元分析的结果说明，弹性成像比较适于检测较硬的肿块，另外，还可能判断乳腺肿瘤的一些性质，这在临床上有很大的参考价值。     

门静脉高压症猪肝动脉的生物力学特性

目的：建立猪门静脉高压症模型,探讨门静脉高压症对肝动脉的生物力学特性的影响。方法：猪以四氯化碳、苯巴比妥、乙醇,配合高脂、低蛋白、低胆碱饮食进行混合饲养。通过脾静脉插管测压,取肝动脉在生物软组织力学试验机上测定其压力-直径关系,计算机图像分析测量肝动脉两端血管环的张开角及其几何形态学指标。结果：实验组门静脉压(4．17±1．03)kPa明显大于对照组(1．51±0．79)kPa,肝动脉的各向同性增量弹性模量、血管容积弹性模量和血管压力-应变模量均随压力的上升而增大,在相同压力下明显大于对照组。肝动脉的顺应性显著低于对照组,而张开角显著增加。结论：门静脉高压症时,肝动脉的生物力学特性发生了显著变化。     

Ultrasound evidence of altered lumbar fascia in patients with low back pain

Different hypotheses have been proposed about the role of lumbar connective tissue in low back pain (LBP). However, none of the previous studies have examined the change in the elastic behavior of lumbar fascia in patients with LBP. The present study aimed to evaluate the changes in the elastic behavior of lumbar fascia in patients with chronic non-specific LBP based on ultrasound imaging. The sonographic strain imaging assessed the thoracolumbar fascia (TLF) of 131 human subjects (68 LBP and 63 non-LBP). Assessments were done at L2–L3 and L4–L5 levels bilaterally. The points were located 2 cm lateral to the midpoint of the interspinous ligament. There were no significant differences in age, sex, and BMI between LBP and healthy individuals. There is a strong inverse relationship between pain severity (r = −0.76, n = 68, p = 0.004) and the TLF elastic modulus coefficient. No significant relationship were observed between age (r = 0.053, n = 68, p = 0.600), BMI (r = −0.45, n = 68, p = 0.092), and gender (r = −0.09, n = 68, p = 0.231) with the TLF elasticity coefficient. The LBP group had a 25%–30% lower TLF elastic modulus coefficient than healthy individuals. The present study is the first to evaluate the elastic coefficient of TLF using the ultrasound imaging method. The study results showed that the TLF elastic coefficient in patients with LBP was reduced compared to healthy individuals and directly related to LBP severity.     

Stress analysis between implant prostheses with different moduli and surrounding bones北大核心

背景:应力遮挡效应会导致植入假体修复骨缺损手术失败,其主要原因是由于植入假体的弹性模量大于骨组织弹性模量。目的:分析植入假体弹性模量对应力分布的影响,寻求消除应力遮挡现象的方法。方法:通过CT扫描的方式获取实验犬与人体骨组织的模型,分别对其优化后进行梯度赋值,建立较为可靠的骨骼力学模型,并与植入假体组合后进行有限元仿真。首先,通过对比格犬骨骼模型和人体骨骼模型及其对应的植入假体进行有限元仿真,模拟了不同弹性模量对植入假体修复术后的应力和位移分布情况;其次,分析了较小弹性模量差仍会形成应力遮挡现象的原因,建立了骨骼模型及植入假体模型,确立了材料属性赋予方法;最后,验证了该模型及材料属性赋予方法的可行性,并通过随机选取受力点的方式,定量分析植入假体弹性模量与骨骼弹性模量之间的关系对应力遮挡形成的影响。结果与结论:通过梯度赋值法建立与骨骼力学性质更加接近的实验犬骨骼模型和人体骨骼模型,该方法重建的力学模型与真实骨骼的力学性质更为接近;通过有限元仿真力学测试证明,不同弹性模量植入假体对假体本身与周围骨骼间相对位移的影响较小;另外量化弹性模量对假体植入骨骼后对应力分布的影响,可为后续的相关研究提供帮助。     

Plasticity of skeletal muscle phenotype: mechanical consequences

Muscles are complex biological machines that perform a wide variety of mechanical activities. Over the past 30 to 40 years, a large amount of effort has been devoted to understanding cellular/molecular responses of skeletal muscle to various altered physiological states (e.g., altered loading state induced via immobilization/spaceflight, resistance training). Many cellular/molecular adaptations brought about by such interventions act on underlying processes that regulate activation, force and velocity of shortening/lengthening, and relaxation. In this context, measurements of mechanical properties (e.g., force-velocity relationship) are important, because they can provide insight into the physiological consequences of such adaptations. During the course of the past 10 to 15 years, a number of investigators have employed the work-loop technique to provide a more realistic approach toward understanding muscle function. Additionally, the work-loop technique provides a unique conceptual perspective that integrates: (1) the length-tension relationship, (2) activation kinetics, (3) the force-velocity relationship in the shortening domain, (4) relaxation kinetics, (5) the force-velocity relationship in the lengthening domain, and (6) the compliance of the passive elastic elements. A discussion of those factors (i.e., factors 2-5) that appear to be highly malleable forms the basis of this paper.     

Biomechanical properties of the rat oesophagus in experimental type-1 diabetes

The gastrointestinal tract remodels its morphology and circumferential stress-strain properties in diabetes mellitus. This study adds one more piece of mechanical knowledge, namely the oesophageal shear modulus and its dependence on the circumferential and longitudinal stresses and strains of oesophagus in diabetic rats and control rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg kg(-1) body weight). The diabetic rats lived up to 28 days after the induction of diabetes. The oesophagus was studied in vitro using a triaxial machine. Stepwise elongation and inflation plus continuous twist were carried out with measurement of the resultant forces. Circumferential and longitudinal stresses and strains were computed from steady-state values of longitudinal force, outer diameter and the applied pressure. The shear modulus was computed from the twist angle-torque relationship. The circumferential and longitudinal stress-strain relationships were exponential. The circumferential stiffness increased 1 week after induction of diabetes (P < 0.001). The longitudinal stiffness increased in the 4-week diabetic rats (P < 0.001). The shear modulus varied as function of longitudinal strain and pressure. The oesophagus became stiffer in shear 4 weeks after the induction of diabetes (P < 0.001).     

A Microstructural Hyperelastic Model of Pulmonary Arteries Under Normo- and Hypertensive Conditions

This work represents the first application of a statistical mechanics based microstructural orthotropic hyperelastic model to pulmonary artery mechanics under normotensive and hypertensive conditions. The model provides an analogy between the entangled network of long molecular chains and the structural protein framework seen in the medial layer, and relates the mechanical response at macro-level to the deformation (entropy change) of individual molecular chains at the micro-level. A finite element approach was adopted to implement the model. Material parameters were determined via comparing model output to measured pressure–stretch results from normotensive and hypertensive trunks and branches obtained from a rat model of pulmonary arterial hypertension. Results from this initial study show that this model appears reasonable for the study of hyperelastic and anisotropic pulmonary artery mechanics. Typical tangent modulus values ranged from 200 to 800 kPa for normotensive arteries—this increased to beyond 1 MPa for hypertensive vessels. Our study also provokes the hypothesis that increase of cross-linking density may be one mechanism by which the pulmonary artery stiffens in hypertension.