Generation of geometry of closed human head and discretisation for finite element analysis

Medical &; Biological Engineering &; Computing -     

Finite-element models of the human head

A review is presented of the existing finite-element (FE) models for the biomechanics of human head injury. Finite element analysis can be an important tool in describing the injury biomechanics of the human head. Complex geometric and material properties pose challenges to FE modelling. Various assumptions and simplifications are made in model development that require experimental validation. More recent models incorporate anatomic details with higher precision. The cervical vertebral column and spinal cord are included. Model results have been more qualitative than quantitative owing to the lack of adequate experimental validation. Advances include transient stress distribution in the brain tissue, frequency responses, effects of boundary conditions, pressure release mechanism of the foramen magnum and the spinal cord, verification of rotation and cavitation theories of brain injury, and protective effects of helmets. These theoretical results provide a basic understanding of the internal biomechanical responses of the head under various dynamic loading conditions. Basic experimental research is still needed to determine more accurate material properties and injury tolerance criteria, so that FE models can fully exercise their analytical and predictive power for the study and prevention of human head injury.     

颅脑组织材料参数对儿童头部冲击响应的影响

目的针对目前对儿童颅脑组织材料参数的不确定性,研究直接冲击载荷条件下颅脑组织材料参数对儿童头部冲击响应的影响。方法应用已验证的3岁儿童头部有限元模型进行冲击仿真实验,采用正交实验设计和方差分析对儿童颅脑组织材料进行参数分析。结果颅骨弹性模量对儿童头部冲击响应具有显著性影响,随着颅骨弹性模量的增加,头部撞击侧颅内压力显著减小(P=0.000),对撞侧颅内压力显著增大(P=0.000),颅骨最大Von Mises应力显著增大(P=0.000)。脑组织的线性黏弹性材料参数对儿童头部冲击响应同样具有显著性影响,随着脑组织短效剪切模量的增加,脑组织最大主应变显著减小(P=0.000),脑组织最大剪应力则显著增加(P=0.000)。结论参数分析结果可为今后儿童头部有限元模型的材料选取提供参考依据,进而提升模型在预测临床上无法通过脑CT影像确诊的脑震荡等脑损伤时的准确性。     

Methodology to determine skull bone and brain responses from ballistic helmet-to-head contact loading using experiments and finite element analysis

The objective of the study was to obtain helmet-to-head contact forces from experiments, use a human head finite element model to determine regional responses, and compare outputs to skull fracture and brain injury thresholds. Tests were conducted using two types of helmets (A and B) fitted to a head-form. Seven load cells were used on the head-form back face to measure helmet-to-head contact forces. Projectiles were fired in frontal, left, right, and rear directions. Three tests were conducted with each helmet in each direction. Individual and summated force- and impulse-histories were obtained. Force-histories were inputted to the human head–helmet finite element model. Pulse durations were approximately 4 ms. One-third force and impulse were from the central load cell. 0.2% strain and 40 MPa stress limits were not exceeded for helmet-A. For helmet-B, strains exceeded in left, right, and rear; pressures exceeded in bilateral directions; volume of elements exceeding 0.2% strains correlated with the central load cell forces. For helmet-A, volumes exceeding brain pressure threshold were: 5–93%. All elements crossed the pressure limit for helmet-B. For both helmets, no brain elements exceeded peak principal strain limit. These findings advance our understanding of skull and brain biomechanics from helmet–head contact forces.     

颅脑有限元模型的研究进展及应用

有限元法(finite element method,FEM)是随着电子计算机的发展而迅速发展起来的一种数值分析方法,同时也是一种比较先进的生物力学研究方法。FEM早期应用于工程科学技术领域,近几年来,生物医学工程领域已经广泛应用FEM进行脑方面的研究。随着交通、运输业的发展,颅脑损伤发生的概率越来越高,严重威胁着人类的身体健康。通过建立颅脑有限元模型,可以很好地研究颅脑损伤的生物力学机制。总结颅脑有限元模型的建立、发展和应用,并对未来的研究方向进行展望。     

颅脑外伤病人脑电地形图的观察与分析

目的：探讨脑外伤病人意识状况与脑电活动慢波频域的关系。方法：对４４例脑外伤病人意识状态进行格拉斯哥昏迷量表（ＧＣＳ）评分，并在伤后不同时期作三次脑电地形图（ＢＥＡＭ）的相关分析。结果：ＧＣＳ评分越低，脑电活动频域就低，ＧＣＳ评分越高，脑电活动频域就高，两者关系密切。结论：ＢＥＡＭ是及时评估病情的有效检查方法     

Effects of head size and morphology on dynamic responses to impact loading

Head responses subjected to impact loading are studied using the finite element method. The dynamic responses of the stress, strain, strain energy density and the intracranial pressure govern the intracranial tissues and skull material failures, and therefore, the traumatic injuries. The objectivity and consistency of the prevailing head traumatic injury criteria, i.e., the energy absorption, the gravity centre acceleration and the head injury criterion (HIC), are examined with regard to the head dynamic responses. In particular, the structural intensity (STI) (the vector representation of energy flow rate) is calculated and discussed. From the simulations, the STI, instead of the gravity centre acceleration, the HIC and the energy absorption criteria, is found to be consistent with the dynamic response quantities. The different local skull curvatures at impact have a marginal effect whereas the locations of the impact loadings have significant effects on the dynamics responses or the head injury. The STI also shows the failure patterns.     

Diffuse axonal injury in head injury: definition, diagnosis and grading

Diffuse axonal injury is one of the most important types of brain damage that can occur as a result of non-missile head injury, and it may be very difficult to diagnose post mortem unless the pathologist knows precisely what he is looking for. Increasing experience with fatal non-missile head injury in man has allowed the identification of three grades of diffuse axonal injury. In grade 1 there is histological evidence of axonal injury in the white matter of the cerebral hemispheres, the corpus callosum, the brain stem and, less commonly, the cerebellum; in grade 2 there is also a focal lesion in the corpus callosum; and in grade 3 there is in addition a focal lesion in the dorsolateral quadrant or quadrants of the rostral brain stem. The focal lesions can often only be identified microscopically. Diffuse axonal injury was identified in 122 of a series of 434 fatal non-missile head injuries--10 grade 1, 29 grade 2 and 83 grade 3. In 24 of these cases the diagnosis could not have been made without microscopical examination, while in a further 31 microscopical examination was required to establish its severity.     

对头部损伤判断准则适用性和可用性的新探索

头部损伤判断准则(Headinjury criterion,HIC)是目前较为广泛被接受的、用来衡量头部在外来载荷下安全性的一种损伤判断准则。它被应用于各国的汽车安全法规中,也是头部损伤防护装置(如头盔)设计的参考标准。然而对它的适用性和可用性也存在着不少的争议。本研究应用人类头部有限元的计算模型,通过分析两个不同大小、不同质量的头部模型在三种不同载荷下所产生的脑组织的应力和相应引出的"头部损伤判断准则"的计算值,识别影响"头部损伤判断准则"的适用性和可用性的因素,为如何更科学地评判头部受载安全性提供新的见解和结论。     

重度颅脑损伤死亡95例临床分析

目的探讨重度颅脑损伤死亡原因。方法对近10年来收治95例因重度颅脑损伤死亡病例进行分析。结果交通事故所致死亡人数明显增加,本文报告病例交通事故高达61.0%,伤后至死亡时间最短20min,最迟伤后254天,平均32.6天,其中开颅手术后植物生存死亡11例,最短80天死亡,最长254天死亡,平均135.6天,伤后至入院时间平均为8.9h,脑疝形成至手术开始时间平均为5.6h。结论重度颅脑损伤患者的死亡原因是多方面的,在临床工作中应积极抢救伤者,多方面寻找原因,以提高重度颅脑损伤诊治水平、降低病死率和致残率。     

Finite element modelling of the tricuspid valve: A preliminary study

The incomplete efficacy of current surgical repair procedures of the tricuspid valve (TV) demands a deeper comprehension of the physiological TV biomechanics. To this purpose, computational models can provide quantitative insight into TV biomechanical response and allow analysing the role of each TV substructure.We present here a three-dimensional finite element model of the tricuspid valve that takes into account most of its peculiar features. Experimental measurements were performed on human and porcine valves to obtain a more detailed TV anatomical framework. To overcome the complete lack of information on leaflets mechanical properties, we performed a sensitivity analysis on the parameters of the adopted non-linear hyperelastic constitutive model, hypothesizing three different parameter sets for three significant collagen fibre distributions.Results showed that leaflets’ motion and maximum principal stress distribution were almost insensitive to the different material parameters considered. Highest stresses (about 100 kPa) were located near the annulus of the anterior and septal leaflets, while the posterior leaflet experienced lower stresses (about 55 kPa); stresses at the commissures were nearly zero. Conversely, changes in constitutive parameters deeply affected leaflets’ strains magnitude, but not their overall pattern. Strains computed assuming that TV leaflets tissue are reinforced by a sparse and loosely arranged network of collagen fibres fitted best experimental data, thus suggesting that this may be the actual microstructure of TV leaflets.In a long-term perspective, this preliminary study aims at providing a starting point for the development of a predictive tool to quantitatively evaluate TV diseases and surgical repair procedures.     

颅脑有限元模型演化规律及其生物力学研究进展

交通事故中头颈部损伤因其较高的致命性,已成为最严重的损伤类型。有限元模型在创伤性脑损伤生物力学机理研究中得到日益广泛应用。回顾头颈部有限元模型的生物力学研究历史和现状,并阐述车辆碰撞交通事故中人体颅脑典型交通伤演化规律和生物力学研究进展,探索头颈部损伤安全防护的方法,以期为车辆碰撞事故中人体颅脑损伤生物力学研究和相应的汽车安全防护装置研制提供理论依据。     

Infections in traumatic brain injury patients

Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose of this cohort study was to delineate the rates, types and risk factors for infection in TBI patients. Retrospective surveillance of infections was conducted for all TBI patients, aged ≥18 years, cared for at the Department of Neurosurgery of the University Hospital of Heraklion, Greece, between 1999 and 2005. A total of 760 patients (75% men) with a median age of 41 years were included. Most (59%) were injured in a motor vehicle accident. One third of them underwent a surgical procedure. Two hundred and fourteen infections were observed. The majority were infections of the lower respiratory tract (47%), followed by surgical site infections (SSI) (17%). Multivariate analysis showed that SSI development was independently associated with the performance of ≥2 surgical procedures (OR 16.7), presence of concomitant infections, namely VAP (OR 5.7) and UTI (OR 8.8), insertion of lumbar (OR 34.5) and ventricular drains (OR 4.0), and cerebrospinal fluid (CSF) leak (OR 3.8). Development of meningitis was associated with prolonged hospitalization (OR 1.02), especially >7 days ICU stay (OR 25.5), and insertion of lumbar (OR 297) and ventricular drains (OR 9.1). There was a notable predominance of Acinetobacter spp. as a VAP pathogen; gram-positive organisms remained the most prevalent in SSI cases. Respiratory tract infections were the most common among TBI patients. Device-related communication of the CSF with the environment and prolonged hospitalization, especially in the ICU setting, were independent risk factors for SSIs and meningitis cases.     

颅脑伤时生长抑素mRNA表达及电针对其影响

目的：探讨电针对颅脑伤的作用机理。方法：采用原位杂交组织化学技术，观察了实验性颅脑伤大鼠脑内生长抑素(SS)变化，并观察了电针治疗颅脑伤时对SS mRNA表达的作用。结果：电针可增加下丘脑室周核SS mRNA表达，而在海马则降低SS mRNA表达。结论：颅脑伤时，电针与SS可能在缓解疼痛方面起协同效应，并且电针可能对海马神经元起保护作用。     

股骨颈内固定系统固定股骨颈基底部旋转截骨的有限元分析

目的 采用有限元分析法比较股骨颈内固定系统（FNS）和空心螺钉作为治疗股骨头坏死的旋转截骨术中内固定装置的生物力学特性。方法 采用虚拟有限元建立中日友好医院分型L2型股骨头坏死模型,模拟前旋90°和后旋180°的旋转截骨术,分别模拟植入FNS（FNS组）及空心螺钉（空心螺钉组）,分析股骨近端截骨块、内固定装置、坏死区的应力分布及位移和股骨的位移。结果 前旋90°和后旋180°模型中,FNS组股骨近端截骨块、坏死区的应力和股骨近端截骨块、内固定装置、坏死区、股骨的位移均小于空心螺钉组。FNS组股骨近端截骨块和坏死区的应力峰值比空心螺钉组减少明显,近端截骨块应力峰值减小47.45%和13.64%,坏死区应力峰值减少44.96%和35.52%。结论 与空心螺钉相比,无论截骨后向前旋90°还是向后旋180°,FNS提供了更好的生物力学稳定性。     

Informational needs in families after their child's mild head injury

OBJECTIVE: When a child is hospitalized due to an illness or injury, the entire family may experience stress and/or anxiety. According to parents who have been in such a situation, providing adequate information is one of the most valuable ways to help the family deal with such feelings. Most mild head injuries suffered by children do not require hospitalisation and in such cases, their families should be provided with appropriate information in connection with their visit to the emergency ward. In the present study, family informational needs are characterized. METHODS: The families of 57 children who had suffered a mild head injury at 0-15 years of age answered one open-ended question. The analysis was carried out using content analysis. RESULTS: This analysis revealed two types of needs, i.e., a need for information concerning the head injury itself and how to provide care, as well as a need for reassurance and support in sharing and coping with the emotional burden. CONCLUSION: Despite differences in the severity of the child's head injury and requirement for hospitalisation, all the families expressed the same informational needs but also the need for emotional support. PRACTICE IMPLICATIONS: In connection with the treatment of children with head injuries, health-care personnel should provide the parents both with information concerning the injury and its treatment and with emotional support.     

CT图像计分在判断颅脑损伤预后的意义

目的:探讨颅脑损伤的CT图像计分与预后的关系。方法:采用521例颅脑损伤病人为研究对象,行头颅10mm层厚CT连续平扫,测量CT图像计分,并分保守治疗组(312例),手术治疗组(209例),进行临床对照分析。结果:依CT图像计分将颅脑损伤分为轻型(≤5分)占22.6％(118例),中型(6～10分)占35.5％(185例),重型(≥11分)占41.8％(218例),各型之间的预后统计学有显著差异(P<0.05)。结论:CT图像计分能较好评估颅脑损伤的预后,为临床判断预后提供重要的客观依据。     

Accidental traumatic head injury in infants and young children

Abstract This article will discuss accidental head injuries in infants and young children. The first category of injury is the crushing head injury. Static forces applied slowly to the head result in multiple fractures of the skull and contusions and lacerations of the brain resulting from the bone fragments striking the brain. This article will discuss the subject of short falls in young children and the resulting head injuries. Because falls are frequent events in early life, many cases have been collected and many papers written on the subject. Study of these cases is informative about the injuries likely to occur in these falls. Most often, only a minor contact injury such as scalp bruise or laceration results. In a 2 to 3% of falls, a simple linear skull fracture occurs and the majority of these are uneventful in terms of neurological deficit or intracranial bleeding. In about 1% of the fractures, an epidural or subdural hemorrhage occurs. Each of these forms of contact hemorrhages will be discussed and illustrated. While these are relatively rare injuries, it is essential that they can be identified as consistent with an accidental mechanism so that an erroneous diagnosis of inflicted injury is not made.     

Extranodal lymphomas of the head and neck

Malignant lymphomas represent approximately 5% of all malignant neoplasms of the head and neck and may involve nodal or extranodal sites. Nodal head and neck lymphomas are similar to other nodal sites and are not further reviewed here. The head and neck region is the second most frequent anatomical site of extranodal lymphomas (after the gastrointestinal tract). Most are non-Hodgkin's lymphomas of B-cell lineage, and overall diffuse large B-cell lymphoma is the most common type. Hodgkin's lymphoma rarely occurs in extranodal sites. Other hematologic neoplasms that commonly involve extranodal sites of the head and neck are also discussed. In this review, we begin by discussing lymphomas involving the head and neck according to anatomical site. Then we discuss specifically the pathological findings of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, plasmablastic lymphoma, extramedullary plasmacytoma, and extranodal natural killer/T-cell lymphoma of nasal type.