镍钛形状记忆合金骨植入物镍离子释放的体外测试方法

目的 镍钛形状记忆合金骨植入物临床使用过程中存在镍离子析出的风险，植入物镍离子释放在体内很难直接测试，为此本文建立一种镍钛形状记忆合金骨植入物镍离子释放的体外测试方法。方法 选用磷酸盐缓冲盐溶液(phosphate buffer salt solution,PBS)作为测试液，用于植入物镍离子的浸提，将植入物置于带盖容器中，容器中装有PBS，将容器静置在温度稳定控制的恒温培养箱内(37±1)℃下，静置相应设置的时间点，每个时间点设1组空白试验和3个相同平行试样进行镍释放量测定，分别用石墨炉原子吸收光谱仪(atomic absorption spectrometer,AAS)和电感耦合等离子体质谱仪(inductively coupled plasma mass spectrometry,ICP-MS)设备测试溶液中镍离子浓度。结果 随时间推移从器械中释放出来的镍离子浓度整体呈下降趋势，镍离子释放时点为4周时，释放周期结束，AAS测得镍离子释放量平均值为0.37×10^-3μg/(cm²·d)，累计释放量平均值为10.22×10^-3     

镍钛形状记忆合金表面改性后的血液相容性

背景：镍钛形状记忆合金植入人体内必需要有很好的生物相容性和生物安全性。 目的：观察分析镍钛形状记忆合金表面改性后对其生物相容性的影响。 方法：将镍钛形状记忆合金随机分为两组,经阴极电沉积法处理的材料为实验组,未经处理的为空白组,通过扫描电镜观察实验组材料表面的变化,并测定材料的溶血率和动态凝血时间。体外培养骨髓基质干细胞,与两组材料复合培养,通过MTT法检测两组材料中细胞存活数量。 结果与结论：镍钛形状记忆合金表面改性后,表面出现由很多的纳米级颗粒紧密聚集形成的Ti-O膜,实验组材料的溶血率下降,凝血时间延长,两组材料与骨髓基质干细胞复合培养第2,4,6天,实验组吸光度比空白组明显增高(P < 0.05)。说明镍钛形状记忆合金经阴极电沉积法表面改性后具有较好的生物相容性和生物安全性。     

镍钛形状记忆合金材料在骨科的应用

背景:目前镍钛形状记忆合金使用广泛,已应用于骨科内固定物、牙科心血管材料、神经外科、泌尿外科、胃肠外科、肝胆外科以及生殖医学等医学诸多领域。目的:就镍钛形状记忆合金在骨科各方面的应用作一综述,以阐明其在骨科的应用现状。方法:由第一作者分别以"镍钛形状记忆合金,骨折"和"Nickel titanium(NiTi)shape memory alloys,fracture"为关键词进行检索,CNKI数据库的检索时限为2002/2009,PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed)的检索时限为1963/2009,检索内容为镍钛形状记忆合金在骨科的应用。结果与结论:计算机初检得到57篇文献,阅读标题和摘要进行筛选,保留符合纳入标准的17篇归纳总结。结果显示,镍钛记忆合金不仅仅使用在四肢骨折中,近年来也使用在脊柱和股骨头骨折中。镍钛记忆合金生物相容性好,并具有超弹性、低磁性、耐磨损、耐疲劳、抗腐蚀的特性,已作为一种新型内固定材料被广泛使用。     

TiNi形状记忆合金在接骨中的应用

目的将具有形状记忆效应和生物相容性的TiNi合金用于接骨件.方法先将TiNi合金设计成接骨扒钉、接骨板、骨髓波形针和接骨环,然后进行形状记忆处理.根据TiNi形状记忆合金件的形状进行变形,将变形后的TiNi状形记忆合金件与断骨进行连接.之后,随着体温或体外热源对合金的加热,温度达到合金的Af点后,变形后的TiNi状形记忆合金接骨件便可自动恢复原来的形状或尺寸,将断骨紧固在一起.结果结合牢固、不易变形和松动,性能优于不锈钢.结论TiNi形状记忆合金接骨扒钉、接骨板、骨髓波形针和接骨环可以用于接骨手术中.     

腰椎椎体间镍钛记忆合金支架的生物力学分析

目的 测试镍钛记忆合金支架的力学性能及用于腰椎间融合术的体外生物力学性能。方法 通过力学测试机测试支架的力学性能,并在新鲜腰椎标本上模拟腰椎间融合术,对比分析镍钛记忆合金支架及其配套的骨粒-可吸收骨水泥混凝物浇注植骨方法、传统盒状融合器用于腰椎间融合术的生物力学性能。结果 镍钛记忆合金支架最大抗压强度为(12 964±962) N,记忆特性有效范围内最大形变为(4.68±0.03) mm,形状恢复率为99.86%。相比于正常腰椎模型,单独使用镍钛记忆合金支架植入模拟腰椎间融合术后手术节段稳定性在前屈、后伸、侧屈、旋转方向上均有增加,与采用传统盒状融合器相当(P>0.05)。而在复合使用配套设计的自体骨粒-可吸收骨水泥混凝物植骨后,手术节段活动度进一步降低(P<0.05),节段稳定性与附加椎弓根螺钉内固定组相当(P>0.05)。镍钛记忆合金支架植入后的抗拔出强度弱于传统盒状融合器(P<0.05),在配合使用自体骨粒-可吸收骨水泥混凝物植骨时的抗拔出强度显著强于传统盒状融合器(P<0.05)。结论 本研究的镍钛记忆合金支架同时配套设计了相匹配的骨粒-骨水泥混凝...     

表面改性TiNi记忆合金棒的回复力学实验研究

采用直径为6~7 mm钛铌涂层T iN i记忆合金棒与未经表面改性的T iN i记忆合金棒,相变温度平均为33.0℃,低温下在三点弯卡具上进行预弯,挠度分别为5.0、10.0、15.0和20.0 mm,保持位移恒定,分别在37℃及50℃的生理盐水溶液恒温水浴箱中测量其三点弯回复力变化特性。结果表明,T iN i记忆合金棒的回复力随回复温度、棒直径、变形量增加而增加;经钛铌表面喷涂后6 mm及6.5 mm棒的回复力有一定降低,但7 mm棒回复力没有显著性差异。依照以上数据可以为临床设计脊柱侧弯矫形棒提供参考。     

卵磷脂单分子膜表面张力系数和温度关系的实验研究

很多物质的表面张力系数α均随温度的升高而降低,卵磷脂是肺表面活性物质的主要成份,通过对该膜在27℃、37℃和42℃三个不同温度下表面张力系数的测定,了解其α与温度间的关系.实验发现:温度从27℃增加到37℃时,同一表面浓度下,α随温度升高而减小,温度升到42℃且表面浓度较大时,α值反而相对变大,这可能是由于41℃以上,碳氢链较长的卵磷脂发生相变(从胶体转变为液晶态)所致.     

自由成形制备氧化锆全瓷牙种植体的初步研究

目的探索陶瓷自由成形制备全瓷牙种植体的工艺,并研究烧结温度对氧化锆陶瓷主要性能的影响。方法采用固相含量为55vol%的氧化锆陶瓷浆料,通过自由成形的方法制备试样,并用无压烧结方法在1 100℃、1 200℃、1 300℃和1 400℃下烧结试样,保温2 h,随炉冷却。对烧结试样的致密化程度、抗弯强度、微观形貌及相组成进行测试。结果试样最大收缩率为16.83%,致密度可达98.36%;1 300℃试样3点抗弯强度达到480 MPa;1 400℃试样X射线衍射检测出单斜相氧化锆的衍射峰,抗弯强度有所下降。结论陶瓷自由成形技术在牙科修复体制造领域具有广阔的发展前景,1 300℃烧结温度下试样综合性能最优,为最佳烧结温度。     

非聚焦超声对溶液中不同肺腺癌细胞株及永生化支气管上皮细胞系杀伤作用的实验研究

目的:探讨非聚焦超声(none focused ultrasound,NFU)对悬液中癌细胞的杀伤是否具有普遍性及是否存在差异,为设计NFU灭杀癌性胸腹水的治疗方案提供实验依据.方法:以肺腺癌细胞株(GLC-82、LLC)及永生化支气管上皮细胞系(HBE)为实验对象,将其分为GLC-82、LLC及HBE3个细胞组.采用的NFU剂量为30W/cm2×5 s.分别测试比较O℃及37℃条件下NFU作用后细胞的即刻及24 h存活率、24 h细胞的增殖率及凋亡率.台盼蓝拒染法测细胞存活率;MTT法检测增殖率;流式细胞仪检测凋亡率.结果:(1)3组细胞经NFU辐照后,即刻及实验24 h其存活率、增殖率及凋亡率在3组细胞间差异均无显著性.而实验24 h时细胞的周期变化在3组细胞之间差异有显著性,GLC-82、HBE2组的G1期细胞所占比例多于LLC组,而s期细胞所占比例少于LLC组;(2)Control、NFU 0℃和NFU 37℃3种不同处理方式的细胞其存活率、增殖率、凋亡率差异均有显著性,即NFU 0℃组和NFU 37℃组两组细胞存活率、增殖率明显低于Control组,且NFU 37℃组低于NFU 0℃组;NFU 0℃组和NFU 37℃组两组细胞凋亡率均高于Control组,且NFU 37℃组略高于NFU 0℃组;实验24 h时细胞的周期变化在3种不同处理方式间差异无显著性.结论:NFU对悬液中上述3种细胞均具杀伤作用,提示其对悬液中癌细胞的杀伤具有一定的普遍意义;其灭杀效果与温度环境有关,37℃时具有较好的灭杀效果;超声对悬液中肿瘤细胞的灭杀既有瞬时灭杀作用同时也具持续性灭杀效应.     

镍钛聚髌器治疗髌骨骨折的电测分析

应用电阻测度应变技术,得到镍钛聚髌器这一记忆合金内固定器的应力-应变关系曲线,较为精确地测定了镍钛聚髌器动态聚合加压髌骨于解剖位的生物力学力值,结果表明:镍钛聚髌器可从9个方向产生向心聚合力,纵向为主,记忆加压力值为13.67Kg,侧向为辅,永加压力值为5.19Kg,并具有一定的耐疲劳性.本实验为临床使用及指导病人术后功能锻炼提供了科学的依据,并为研究动态记忆力学下的骨愈合机理提供了实验基础.     

Reproducibility of the bladder shape and bladder shape changes during filling

The feasibility of high precision radiotherapy to the bladder region is limited by bladder motion and volume changes. In the near future, we plan to begin treatment delivery of bladder cancer patients with the acquisition of a cone beam CT image on which the complete bladder will be semi-automatically localized. Subsequently, a bladder shape model that was developed in a previous study will be used for bladder localization and for the prediction of shape changes in the time interval between acquisition and beam delivery. For such predictions, knowledge about urinary inflow rate is required. Therefore, a series of MR images was acquired over 1 h with time intervals of 10 min for 18 healthy volunteers. To gain insight in the reproducibility of the bladder shape over longer periods of time, two additional MRI series were recorded for 10 of the volunteers. To a good approximation, the bladder volume increased linearly in time for all individuals. Despite receiving drinking instructions, we found a large variation in the inflow rate between individuals, ranging from 2.1 to 15 cc/min (mean value: 9 +/- 3 cc/min). In contrast, the intravolunteer variation was much smaller, with a mean standard deviation (SD) of 0.4 cc/min. The inflow rate was linearly correlated with age (negative slope). To study the reproducibility of the bladder shape, we compared bladder shapes of equal volume. For all individuals, the caudal part of the bladder was the most reproducible (variations<0.3 cm in all cases). The cranial and posterior parts of the bladder was much less reproducible, with local SD values up to approximately 1.2 cm for bladders with a volume of 200 cc. These large long-term variations were primarily caused by changes in position and filling of the small bowel and rectum. However, for short time intervals, the rectal filling was (nearly) constant. Therefore, the reproducibility of urinary inflow, combined with the previously developed shape model gives us an excellent tool to predict short-term shape changes. We intend to use this tool for further improvement of image-guided radiotherapy for bladder cancer patients.     

How expectations shape pain

Pain is highly modifiable by psychological factors, including expectations. However, pain is a complex phenomenon, and expectations may work by influencing any number of processes that underlie the construction of pain. Neuroimaging has begun to provide a window into these brain processes, and how expectations influence them. In this article, we review findings regarding expectancy effects on brain markers of nociception and how expectations lead to changes in subjective pain. We address both expectations about treatments (placebo analgesia and nocebo effects) and expectations about the environment (e.g. expectations about pain itself). The body of work reviewed indicates that expectancies shape pain-intensity processing in the central nervous system, with strong effects on nociceptive portions of insula, cingulate and thalamus. Expectancy effects on subjective experience are driven by responses in these regions as well as regions less reliably activated by changes in noxious input, including the dorsolateral prefrontal cortex and the orbitofrontal cortex. Thus, multiple systems are likely to interact and mediate the pain-modulatory effects of expectancies. Finally, we address open questions regarding the psychological processes likely to play an intervening role in expectancy effects on pain.     

RNA shape space topology

The distinction between continuous and discontinuous transitions is a long-standing problem in the theory of evolution. Because continuity is a topological property, we present a formalism that treats the space of phenotypes as a (finite) topological space, with a topology that is derived from the probabilities with which one phenotype is accessible from another through changes at the genotypic level. The shape space of RNA secondary structures is used to illustrate this approach. We show that evolutionary trajectories are continuous if and only if they follow connected paths in phenotype space.     

Device based left ventricular shape change: validation of conductance technology in shape changed hearts

We have reported that device based left ventricular (LV) shape change, accomplished by Myosplint, improved LV systolic function by three-dimensional echocardiography (3-D echo). However, evaluation of this device using the pressure-volume relationship is still important. This study was conducted to validate the use of conductance technology for this evaluation in shape-changed hearts. An ex vivo study using excised ovine hearts (n = 11) and an in vivo study using a canine pacing-induced heart failure model (n = 11) were performed. Three Myosplints were implanted. Before and after the shape changes, volumes measured by a conductance catheter were compared with volumes measured by the amount of saline in the ex vivo study or by 3-D echo in the in vivo study. The conductance volumes were linearly correlated with the saline volumes (r2 = 0.961+/-0.046; p < 0.0001) in the ex vivo study and with 3-D echo volumes (r2 = 0.757+/-0.220; p < 0.0001) in the in vivo study. The conductance volumes were linearly correlated with LV volumes even in the shape-changed hearts. This technology can be used to evaluate pressure-volume loops in the shape-changed hearts as long as the conductance volume is calibrated by a reliable method.     

Training models of anatomic shape variability

Learning probability distributions of the shape of anatomic structures requires fitting shape representations to human expert segmentations from training sets of medical images. The quality of statistical segmentation and registration methods is directly related to the quality of this initial shape fitting, yet the subject is largely overlooked or described in an ad hoc way. This article presents a set of general principles to guide such training. Our novel method is to jointly estimate both the best geometric model for any given image and the shape distribution for the entire population of training images by iteratively relaxing purely geometric constraints in favor of the converging shape probabilities as the fitted objects converge to their target segmentations. The geometric constraints are carefully crafted both to obtain legal, nonself-interpenetrating shapes and to impose the model-to-model correspondences required for useful statistical analysis. The paper closes with example applications of the method to synthetic and real patient CT image sets, including same patient male pelvis and head and neck images, and cross patient kidney and brain images. Finally, we outline how this shape training serves as the basis for our approach to IGRT/ART.     

Grasping reveals visual misjudgements of shape

There are many conditions in which the visually perceived shape of an object differs from its true shape. We here show that one can reveal such errors by studying grasping. Nine subjects were asked to grasp and lift elliptical cylinders that were placed vertically at eye height. We varied the cylinder’s aspect ratios, orientations about the vertical axis and distances from the subject. We found that the subjects’ grip orientations deviated systematically from the orientations that would give the mechanically optimal grip. That this is largely due to misjudging the cylinder’s shape (rather than to selecting a comfortable posture) follows from the fact that the grip aperture was initially more strongly correlated with the maximal grip aperture (which is related to the expected contact positions) than with the final grip aperture (which is determined by the real contact positions). The correlation with the maximal grip aperture drops from 0.8 to 0.6 in the last 1% of the traversed distance (11% of movement time), showing that the grip aperture was anticipated incorrectly (it is automatically “corrected” at contact). The grip orientation was already strongly correlated with the grip orientation at the time of maximal grip aperture, half way through the movement (R≥0.7), showing that the suboptimal grip orientations were planned that way. We conclude that subjects plan their grasps using information that is based on the misperceived shape.     

Still-unknown determinants of the cranial shape

Although the shape of the neurocranium has long attracted the attention of anthropologists, the causes and mechanism of its formation have yet to be fully elucidated. At least from medieval times to the present, the superior view of the human skull has changed from an anteroposteriorly long shape to a short one. This is called "brachycephalization." Why does such a phenomenon occur? Does the cranial shape have a functional meaning? Main investigations, especially statistical, which have been carried out on these problems up to now, will be presented here. Reviewing the results of the investigations, they suggest, at least, that the shape of the neurocranium is correlated not only with the muscles of mastication and the jaws but also with the vertebrae, ribs and pelvis inside of the body, and, outside of the body, associated with environmental factors such as temperature, wealthiness, etc. In order to determine the concrete causes and mechanism for the formation of the cranium, it is emphasized in particular that not only human skeletal remains but also the paleoenvironmental data that are accompanied with them should intensively be collected in the future.