锥度固位结合数字化技术在后牙连续多牙种植即刻修复中的应用

目的:评价口内扫描技术、计算机辅助设计/加工(computer-assisted design/computer-assisted manufacturing, CAD/CAM)技术结合锥度固位方式在种植即刻修复连续多牙缺失中的应用。方法: 选取2017年3月至2018年2月于北京大学口腔医院种植科就诊的连续多个后牙缺失的患者,在种植体植入即刻安放预成锥度固位帽,通过口内扫描制取数字化印模,以CAD/CAM技术制作聚甲基丙烯酸甲酯 (polymethyl methacrylate, PMMA) 临时联冠,临时联冠戴入后即刻负重;6个月后更换为CAD/CAM技术制作的氧化锆永久联冠,临时冠及永久冠戴入时分别拍摄平行投照牙片。通过种植体和修复体存留率、种植体颈部边缘骨水平变化、种植体和修复体并发症等指标评价临床效果,永久修复前用视觉模拟评分 (visual analogue score, VAS) 量表评价患者对即刻修复的满意度。结果:共计10例患者(男4例,女6例,平均55.5岁)纳入本研究,共植入34枚种植体,分别制作14件即刻PMMA修复体和14件永久氧化锆修复体,观察时间4~14个月;种植体及修复体存留率100%,种植体颈部骨水平在种植即刻为(1.06±0.97) mm,即刻修复后6个月时为(0.96±0.82) mm,两者差异无统计学意义(P>0.05);观察期内所有种植体和修复体均未发生并发症;患者满意度VAS评分87.2。结论:对于连续多牙缺失,在种植即刻以数字化流程制作,并结合锥度固位方式的联冠修复体,具有良好的临床效果和患者满意度。     

以苄索氯胺和异丙醇为主要有效成分的消毒剂对牙科印模精度的影响

目的:探究以苄素氯胺和异丙醇为主要有效成分的消毒剂(Cavicide)对于牙科印模精度的影响。方法:体外试验评价Cavicide消毒剂对藻酸盐、聚醚橡胶和硅橡胶3种印模材料消毒后对印模精度的影响。应用高精度模型扫描仪(IScan D103i, Imetric)将标准模型数字化,使用藻酸盐、聚醚橡胶和硅橡胶材料分别制取标准模型的印模各30个,并将每种印模材料的30个印模随机平均分为3组,每组10个印模。在印模制取完成后,3组分别采用仅清水冲洗15 s(空白对照组,BC组)、2%(质量分数)戊二醛溶液浸泡30 min(戊二醛组,GD组)、Cavicide溶液表面喷洒5 min(Cavicide组,CC组)。采用模型扫描仪扫描印模,获得印模的数字化模型。在三维分析软件中,将印模扫描图像与标准模型的数字化模型进行配准,采用RMS作为评价印模与标准模型间偏差的参数。采用单因素方差分析比较3组间偏差,保存偏差的色谱图进行可视化分析。结果:聚醚橡胶及硅橡胶印模材料,3组间差异均无统计学意义(P=0.933,P=0.827);藻酸盐印模材料,GD组与BC组、GD组与CC组间差异均具有统计学意义(GD与 BC,P=0.001,GD与CC,P=0.002), BC组与CC组间差异无统计学意义(P=0.854)。结论:Cavicide喷洒消毒对聚醚橡胶、硅橡胶和藻酸盐印模的精度均未见影响。     

新时代图书馆文献资源共建共享的挑战与机遇

通过调研国内外图书馆文献资源共建共享现状和梳理当前图书馆资源建设的资源海量化和多样化、内容服务智慧化、获取去中心化、技术智能化、传播泛在化、保存战略化等新特征,分析了文献资源实现共建共享在资源数量、规范、存储和服务等方面的挑战和机遇,从政策和资金、资源和技术、理念和信任、机制和沟通等方面提出了开展共建共享工作的相关建议,为有效推进图书馆资源建设、提高文献资源服务能力提供参考。     

黄芪多糖对人肺癌顺铂耐药株A549/DDP细胞耐药性的影响及其机制

探讨黄芪多糖（APS）对人肺癌顺铂（DDP）耐药A549/DDP细胞耐药性的影响,并阐明其可能的作用机制。     

腹腔镜肝切除术与射频消融术对原发性肝癌患者肝功能和免疫功能及3年无瘤生存率的影响

【摘要】目的 探究腹腔镜肝切除(LH)与射频消融术(RFA)治疗对原发性肝癌(HCC)患者肝功能、免疫功能及3年无瘤生存率的影响。方法 回顾性分析2014年3月~2016年1月我院122例HCC患者临床资料,其中行LH术治疗68例（LH组）,行RFA术治疗54例（RFA组）。记录两组手术相关指标（手术时间、术中出血量、输血率、术后住院时间）及围术期并发症发生情况,比较两组术前及术后1周肝功能［谷丙转氨酶(ALT)、谷草转氨酶(AST)］、免疫功能［T淋巴细胞亚群(CD3+、CD4+、CD8+)］差异,并采用Kaplan Meier法绘制3年无瘤生存曲线,使用Log rank法比较两组3年无瘤率。结果LH组手术时间、术中出血量、输血率及术后住院时间均高于RFA组（P＜005）。两组围术期并发症发生率比较差异无统计学意义（P＞005）。术后1周时,两组肝功能指标（ALT、AST）、CD8+均较术前升高（P＜005）,且LH组高于RFA组（P＜005）;两组部分免疫功能指标（CD3+、CD4+）较术前降低（P＜005）,且LH组低于RFA组（P＜005）。术后3年时,LH组无瘤生存42例（6176%）,RFA组无瘤生存19例（3519%）,且LH组3年无瘤生存率明显高于RFA组（P＜005）。结论 RFA术与LH术治疗HCC各有优劣,RFA术在微创方面更具优势,但无瘤生存情况不及LH术,临床应根据实际情况,为HCC患者制定个性化的治疗方案。     

唐县2018年恶性肿瘤发病及死亡情况分析

目的 分析2018年唐县主要恶性肿瘤发病及死亡情况。方法 根据全国肿瘤登记中心制定的审核方法和评价指标,计算恶性肿瘤的发病率、死亡率以及顺位。结果 2018年唐县共报告恶性肿瘤发病1 292例,恶性肿瘤发病率为236.43/10万,中标率为184.60/10万。2018年报告死亡病例621例,粗死亡率为113.64/10万,中标率为74.91/10万。恶性肿瘤发病前5位依次是肺癌、乳腺癌、胃癌、食管癌、结直肠肛门癌。死亡前5位的依次为肺癌、胃癌、肝癌、食管癌、脑神经系统癌症。结论 肺癌、乳腺癌是唐县常见恶性肿瘤,应有针对性地开展防治工作。     

Anatomical accuracy of brain connections derived from diffusion MRI tractography is inherently limited

Tractography based on diffusion-weighted MRI (DWI) is widely used for mapping the structural connections of the human brain. Its accuracy is known to be limited by technical factors affecting in vivo data acquisition, such as noise, artifacts, and data undersampling resulting from scan time constraints. It generally is assumed that improvements in data quality and implementation of sophisticated tractography methods will lead to increasingly accurate maps of human anatomical connections. However, assessing the anatomical accuracy of DWI tractography is difficult because of the lack of independent knowledge of the true anatomical connections in humans. Here we investigate the future prospects of DWI-based connectional imaging by applying advanced tractography methods to an ex vivo DWI dataset of the macaque brain. The results of different tractography methods were compared with maps of known axonal projections from previous tracer studies in the macaque. Despite the exceptional quality of the DWI data, none of the methods demonstrated high anatomical accuracy. The methods that showed the highest sensitivity showed the lowest specificity, and vice versa. Additionally, anatomical accuracy was highly dependent upon parameters of the tractography algorithm, with different optimal values for mapping different pathways. These results suggest that there is an inherent limitation in determining long-range anatomical projections based on voxel-averaged estimates of local fiber orientation obtained from DWI data that is unlikely to be overcome by improvements in data acquisition and analysis alone.The creation of a comprehensive map of the connectional neuroanatomy of the human brain would be a fundamental achievement in neuroscience. However, despite the numerous efforts to date (for a historical review, see ref. 1), creating this map remains a challenge. A major limitation is that the current gold-standard technique for mapping structural connections, which requires the injection of axonal tracers, cannot be used in humans. The introduction of diffusion-weighted MRI (DWI) (2–4) and the subsequent advent of diffusion tensor MRI (DTI) (5) opened the possibility of exploring the structural properties of white matter in the living human brain (6). Local DWI measures are used clinically for the early detection of stroke and for the characterization of neurological disorders such as multiple sclerosis, epilepsy, and brain gliomas, among others (7). In addition, tractography approaches (8–12) that can infer structural brain connectivity based on brain-wide local DWI measurement have been developed (for reviews, see refs. 13 and 14). The success of DWI tractography as a method for studying fiber trajectories has led to a systematic characterization of large white-matter pathways of the living human brain (e.g., ref. 15), and now it is used routinely to provide a structural explanation for aspects of human brain function (16).A major limitation of DWI tractography is that its characterization of axonal pathways is based on indirect information and numerous assumptions. Local white matter orientation profiles are based on the statistical displacement profile (i.e., diffusion propagator) of water molecules in brain tissue on the coarse scale of a voxel, and fiber trajectories are inferred based on the adjacency of similar diffusion profiles. This approach differs fundamentally from conventional tract-tracing approaches in animals, which involve the physical transport of traceable molecules through the cells’ axoplasm over a large distance. Because these molecules occupy positions within the axon, it sometimes is possible to reconstruct the trajectory of individual neurons through the white matter (e.g., ref. 17). Given the inherent coarseness of DWI tractography, it can be argued that the prospect of using this method to reconstruct complex axonal pathways accurately in the human brain, in a manner similar to that used for molecular tracers in animals, is likely to be intrinsically problematic. Indeed, the limitations of DWI tractography techniques have been noted since their inception (8), and the anatomical accuracy of results from tractography based on the tensor model has been shown to be mixed (18). This inaccuracy has been attributed to two main factors. The first relates to the assumptions underlying tractography algorithms. For example, it has long been recognized that a simple tensor model (19) of local diffusion leads to problems in certain white matter regions where fibers cross within individual voxels. As a remedy, high angular resolution diffusion imaging (HARDI) methods (e.g., refs. 20–24) have been developed to enable better characterization of the diffusion displacement profile and to improve the accuracy of tractography. The second factor limiting accuracy stems from the low quality of clinical DWI data because of various sources of noise. Eddy current distortions, subject motion, physiological noise (see ref. 25 for a review), and susceptibility artifacts from echo planar imaging (EPI) (26) all lead to poor local characterization of diffusion and, consequently, to incorrect tractography results. Continuing advances in sequence design, MRI gradient hardware, and postprocessing correction schemes have overcome many of the initial problems (27) and have led to the belief that further acquisition improvements will result in more precise mapping of structural connections in the human brain (28). In fact, the assumption underlying many recent initiatives to map structural brain connectivity from DWI data is that improved image data quality and sophisticated diffusion modeling approaches will result in anatomically accurate maps of white matter connections (29). The goal of the present study is to investigate the validity of this assumption.To achieve this goal, we acquired high angular resolution DWI data from a normal adult rhesus macaque brain, ex vivo, at a spatial resolution of 250 microns (isotropic). This dataset is ideal for exploring the limits of DWI tractography because of its high signal-to-noise ratio (SNR) (for SNR computation, see SI Materials and Methods) and the almost complete absence of experimental confounds and artifacts such as those originating from patient motion, noise, cardiac pulsation, and EPI distortion that are typically encountered in in vivo studies. Using the axonal tracer results from a well-known atlas (17) as reference, we measured the sensitivity (i.e., the ability to detect true connections) and specificity (i.e., the ability to avoid false connections) of several DWI tractography implementations representative of the current state of the art. This approach allowed us to investigate whether sophisticated diffusion modeling techniques, when applied to DWI data of exceptional quality, would yield accurate maps of axonal connections.