CT球管的选购、日常维护及常见故障

球管是CT机中最昂贵的消耗性核心部件,提供适宜的工作条件,正确合理的使用、维护及保养,既能保证优质的图像,又可以延长球管的使用寿命,从而提高社会效益及医院经济效益。     

多球壳菌素延长裂殖酵母细胞寿命可能机制研究

寻找抗衰老活性分子并研究其作用机制是衰老药物学的研究重点和热点。前期研究发现天然产物多球壳菌素(一种神经鞘脂合成特异性抑制剂)能够延长模式生物芽殖酵母的寿命,而裂殖酵母在进化上更接近哺乳动物,且在形态和遗传上与芽殖酵母有显著差异的另一种模式生物,本研究考察了多球壳菌素对裂殖酵母寿命的影响,并进一步研究了其调控细胞寿命的相关机制。结果显示,多球壳菌素延长裂殖酵母寿命具有保守性,其延长细胞寿命的机制包括:增强细胞压力抗性、促进糖原和海藻糖的积累、降低胞内活性氧的水平,且发现多球壳菌素介导的寿命延长依赖于压力应答类蛋白激酶Sty1。综上,多球壳菌素是一种潜在的抗衰老药物分子,后期有望开发它用于延缓哺乳动物细胞(包括人类)衰老及预防和治疗衰老相关疾病。     

我国第一只全身CTX线管研制成功并通过鉴定

上海医疗器械九厂与协作单位上海交通大学、华东师范大学和核工业部九院六所经过三年多时间的努力,攻克了一系列技术难关,研制出“CT54型全身CTX线管”。最近在上海医药管理局主持下,通过鉴定。 CT54型全身CTX线管经中国上海医疗器械检测中心测试验证,其技术参数与指标均已达到西门子公司Optil51型管等国外同类产品水平。医院临床使用结果表明,摄片清晰,分辨率高,曝光寿命已达40000次以上,能够满足临床使用要求。该管不但能配套于“中华I型CT机”,而且还能配套     

氮肥对水曲柳和落叶松细根寿命的影响

采用微根管技术研究了氮肥对水曲柳和落叶松细根生长、衰老和死亡的影响,探讨两树种细根寿命与氮有效性之间的相关关系.结果表明：林地施氮肥后,两树种细根数量都呈减少趋势,细根总体直径增加,分枝程度降低;氮肥使水曲柳细根存活率提高,细根中位值寿命延长105 d,而落叶松细根存活率对氮肥反应不敏感;施氮肥对细根寿命的延长效应主要体现在直径较小的一级根、表层（0～15 cm)根系和春夏季新生的细根,表明氮肥对高生理活性的细根
影响较强.     

肠道微生物对寿命的影响及其机制*

延长健康寿命的跨度对每个人都有重要意义,百岁老人存在独特的肠道菌群特征,肠道微生物群是许多年龄相关变化的核心,菌群特征以及菌群基因组成改变都能影响机体寿命。一些饮食和药物要发挥延寿效果也离不开微生物的参与,微生物具有重要的介导和转化作用,益生菌和粪便移植等措施在动物模型中已被明确可以影响机体寿命。越来越多的研究表明微生物不仅能产生小分子化合物促进健康寿命跨度的增加乃至延长个体寿命如γ-氨基丁酸、荚膜异多糖酸,还能影响宿主的生物合成代谢如5-羟色胺,甚至间接参与宿主信号通路的调控。目前对于这些微生物的生物学功能以及对宿主寿命的影响还没有系统的总结,对肠道微生物影响寿命的证据以及生理机制进行综述,为改善老年期健康状况的干预措施提供参考。     

热量限制可延长灵长类动物的寿命

热量限制(caloric restriction,CR)是指在提供生物体必要的营养成分,保证生物体不发生营养不良的前提下,限制其每日摄取的总热量.自McCay等于1935年首次报道CR可以延长大鼠寿命至今70余年间,大量实验结果表明CR是除遗传操作以外最有效的延长寿命的方法,已经成为研究衰老机制及干预措施的重要模型,并且已有不少研究探索如何应用CR来研究人类的衰老机制及干预措施.     

四种不同来源的超氧化物歧化酶（SOD）对黑腹果蝇寿命、 繁殖力和抗逆能力的影响

【目的】 评价不同来源的超氧化物歧化酶（SOD）对果蝇延长寿命, 增强繁殖力和抗逆能力的功效。【方法】以黑腹果蝇Drosophila melanogaster为实验材料, 比较研究从家蝇Musca domestica中提取的SOD、 在毕赤酵母Pichia pastoris中重组表达的人hEC SOD、 在酿酒酵母Saccharomyces cerevisiae中重组表达的中国拟青霉Paecilomyces sinensis SOD (ps-SOD)以及商品SOD对果蝇寿命、 繁殖力和抗逆能力的影响。【结果】在饲料中添加4种SOD均能显著延长果蝇的平均寿命, 雌果蝇寿命延长8.09%~12.38%, 雄果蝇寿命延长12.01%~15.86%; F1代雌性子代数量增加25.94%~30.07%, 雄性增加21.75%~39.54%。果蝇的耐高温和抗紫外辐射能力与添加的SOD浓度有关。在饲料中添加较高剂量的SOD, 使热暴露雌性果蝇的寿命延长7.45%~9.88%, 雄性果蝇延长13.46%~15.12%; 受紫外线辐射的雌性果蝇的寿命延长13.47%~20.47%, 雄性果蝇延长16.49%~23.73%。【结论】综合评价认为, 4种SOD均能延长果蝇寿命, 增强其繁殖力和抗逆能力, 但这些功效在本研究供试的4种SOD间无显著差异, 为不同来源SOD的应用提供了重要数据。     

容积减影成像计算机自动化技术与实现

探讨在PC机上对容积CT灌注（CTP）源影像全自动生成减影CTP源影像的方法。首先在WindowsXP操作系统中使用Matlab,对4层螺旋CTP源影像进行DICOM文件格式解析,获得CT成像设备的球管每转一周扫描层数及容积减影方法需要的其它参数信息,然后经过容积的CT值集合读、容积的CT值集合减以及容积的CT值集合写等几个步骤,生成减影CTP源影像的DICOM文件序列。使用该容积减影方法得到的减影CTP源影像,在定性肉眼观察和定量CT值矩阵比对上,与使用CT影像工作站上的减影软件手工逐层半自动减影得到的结果类同。容积减影方法实现了容积CTP源影像的自动化减影处理与成像,为最终形成一个一站式的减影CTP软件奠定了基础。     

衰老过程中行为和认知功能退化的调控机制研究

随着人类预期寿命延长,人口老龄化问题越来越严重.过去几十年关于衰老的研究使人们对长寿的生物学机理有了一定的认识,然而延长寿命应以保持老年个体健康的行为和认知功能为前提,近期研究显示延长寿命不一定延缓衰老过程中的行为和认知功能退化.衰老相关行为退化的调控机制目前知道的还很少,如何实现老年人口健康的衰老是现代社会极具挑战也...     

封面说明

正随着人类预期寿命延长,人口老龄化问题日益严峻。过去的研究使人们对长寿的生物学机理有了一定的认识,然而延长寿命应以保持老年个体健康的行为和认知功能为前提,近期研究显示延长寿命不一定延缓衰老过程中的行为和认知功能退化。衰老相关行为退化的调控机制目前知道的还很少,如何实现老年人口健康的衰老,提高老年人的生活质量是现代社会极具挑战也是迫切需要解决的问题。     

同步辐射在显微CT中的应用

计算机X射线断层成像技术（CT）是利用X射线的穿透能力对物体进行扫描,所得信号经过反投影的算法而得到物体二维分布的一种成像方法,已经在医学诊断、工业探伤等领域广泛应用。但是由于实验室光源的低通量,光源点大小及其单色性等限制了其向高分辨发展,通常其分辨率在0．5mm左右。利用微焦点X射线源作为光源的显微CT分辨率可以达到微米量级,但是由于其光通量低且为非单色光,对不同样品有不同程度的束线硬化,影响了其真实分辨率。同步辐射作为一种新兴的光源有高亮度、高光子通量、高准直性、高极化性、高相干性及宽的频谱范围的特点,配合高分辨的X射线探测器,可以发展同步辐射显微CT,其分辨率可达10μm以下。利用同步辐射的高空间相干性开展位相衬度显微CT的研究,对低吸收物质也可以清晰三维成像。新建的上海光源的X射线成像及生物医学应用线站开展了三维显微CT方面的研究,经过初步试验,得到了较好的结果。     

Low-tube-voltage selection for non-contrast-enhanced CT: Comparison of the radiation dose in pediatric and adult phantoms

PurposeWe used pediatric and adult anthropomorphic phantoms to compare the radiation dose of low- and standard tube voltage chest and abdominal non-contrast-enhanced computed tomography (CT) scans. We also discuss the optimal low tube voltage for non-contrast-enhanced CT.MethodsUsing a female adult- and three differently-sized pediatric anthropomorphic phantoms we acquired chest and abdominal non-contrast-enhanced scans on a 320-multidetector CT volume scanner. The tube voltage was set at 80-, 100-, and 120 kVp. The tube current was automatically assigned on the CT scanner in response to the set image noise level. On each phantom and at each tube voltage we measured the surface and center dose using high-sensitivity metal-oxide-semiconductor field-effect transistor detectors.ResultsThe mean surface dose of chest and abdominal CT scans in 5-year olds was 4.4 and 5.3 mGy at 80 kVp, 4.5 and 5.4 mGy at 100 kV, and 4.0 and 5.0 mGy at 120 kVp, respectively. These values were similar in our 3-pediatric phantoms (p > 0.05). The mean surface dose in the adult phantom increased from 14.7 to 19.4 mGy for chest- and from 18.7 to 24.8 mGy for abdominal CT as the tube voltage decreased from 120 to 80 kVp (p < 0.01).ConclusionCompared to adults, the surface and center dose for pediatric patients is almost the same despite a decrease in the tube voltage and the low tube voltage technique can be used for non-contrast-enhanced chest- and abdominal scanning.     

Relationships between bone mass and micro-architecture at the mandible and iliac bone in edentulous subjects: a dual X-ray absorptiometry, computerised tomography and microcomputed tomography study

doi: 10.1111/j.1741‐2358.2011.00527.x Relationships between bone mass and micro‐architecture at the mandible and iliac bone in edentulous subjects: a dual X‐ray absorptiometry, computerised tomography and microcomputed tomography study Objectives: To compare bone volume, bone mineral density, cortical thickness and bone micro‐architecture in a series of paired mandibular and iliac bone samples analysed by various imagery techniques to see whether relationships exist between the various techniques and between mandibular and iliac bone. Materials and methods: Bone samples from the mandible and ilium were harvested in 20 cadavers and analysed by dual energy X‐ray absorptiometry (DXA), computerised tomography (CT) on a conventional hospital machine and microCT. Results: Significant correlations were found between Hounsfield density obtained by CT, and bone mass determined by microCT but not with DXA values. Cortical thickness measurements were well correlated between CT and microCT. No relationships were found between mandibular and iliac bone, when considering mineral density, cortical thickness, bone volume or micro‐architecture. Conclusion: In clinical practice, CT remains the most appropriate routine means for bone qualitative and quantitative evaluation at the mandible. In this ex vivo study, these results confirm that mandibular bone status does not reflect the axial skeletal one and assist in the placement of implants with dental prostheses in old or osteoporotic patients.     

Micro‐CT X‐rays do not fragment DNA in preserved bird skins

Most zoological systematics studies are currently based on morphological features, molecular traits or a combination of both to reconstruct animals’ phylogenetic history. Increasingly, morphological studies of museum specimens are using X‐ray computed tomography to visualize internal morphology, because of its ‘non‐destructive’ nature. However, it is not known whether CT can fragment the size of DNA extracted from museum specimens, as has been demonstrated to occur in living cells. This question is of paramount importance for collections based research because X‐rays may reduce the amount of data obtainable from specimens. In our study, we tested whether exposure of museum bird skins to typical CT X‐ray energies (for visualization of the skeleton) increased DNA strand fragmentation, a key factor for the success of downstream molecular applications. For the present study, we extracted DNA from shavings of 24 prepared and dried bird skins (100⁺ years) footpads before and after CT scanning. The pre‐ and post‐CT fragmentation profiles were assessed using a capillary electrophoresis high‐precision instrument (Agilent Bioanalyzer). Comparison of the most common strand length in each DNA sample (relative mass) revealed no significant difference unexposed and exposed tissue (paired t‐test p = 0.463). In conclusion, we found no further quantifiable degradation of DNA strand length under standard X‐ray exposure obtained from our bird skins sample. Differences in museum preservation techniques probably had a greater effect on variation of pre‐CT DNA fragmentation.     

Gating in small-animal cardio-thoracic CT

Gating is necessary in cardio-thoracic small-animal imaging because of the physiological motions that are present during scanning. In small-animal computed tomography (CT), gating is mainly performed on a projection base because full scans take much longer than the motion cycle. This paper presents and discusses various gating concepts of small-animal CT, and provides examples of concrete implementation. Since a wide variety of small-animal CT scanner systems exist, scanner systems are discussed with respect to the most suitable gating methods. Furthermore, an overview is given of cardio-thoracic imaging and gating applications. The necessary contrast media are discussed as well as gating limitations. Gating in small-animal imaging requires the acquisition of a gating signal during scanning. This can be done extrinsically (additional hardware, e.g. electrocardiogram) or intrinsically from the projection data itself. The gating signal is used retrospectively during CT reconstruction, or prospectively to trigger parts of the scan. Gating can be performed with respect to the phase or the amplitude of the gating signal, providing different advantages and challenges. Gating methods should be optimized with respect to the diagnostic question, scanner system, animal model, type of narcosis and actual setup. The software-based intrinsic gating approaches increasingly employed give the researcher independence from difficult and expensive hardware changes.     

Using a multiscale image processing method to characterize the periodic growth patterns on scallop shells

The fine periodic growth patterns on shell surfaces have been widely used for studies in the ecology and evolution of scallops. Modern X‐ray CT scanners and digital cameras can provide high‐resolution image data that contain abundant information such as the shell formation rate, ontogenetic age, and life span of shellfish organisms. We introduced a novel multiscale image processing method based on matched filters with Gaussian kernels and partial differential equation (PDE) multiscale hierarchical decomposition to segment the small tubular and periodic structures in scallop shell images. The periodic patterns of structures (consisting of bifurcation points, crossover points of the rings and ribs, and the connected lines) could be found by our Space‐based Depth‐First Search (SDFS) algorithm. We created a MATLAB package to implement our method of periodic pattern extraction and pattern matching on the CT and digital scallop images available in this study. The results confirmed the hypothesis that the shell cyclic structure patterns encompass genetically specific information that can be used as an effective invariable biomarker for biological individual recognition. The package is available with a quick‐start guide and includes three examples: http://mgb.ouc.edu.cn/novegene/html/code.php .     

Technical note: Terahertz imaging of ancient mummies and bone

Ancient mummified soft‐tissues are a unique source to study the evolution of disease. Diagnostic imaging of such historic tissues is of foremost interest in paleoanthropology or paleopathology, with conventional x‐ray and computed tomography (CT) being the gold‐standard. Longer wavelength radiation in the far‐infrared or Terahertz region allows diagnostic close‐to‐surface tissue differentiation of bone morphology while being harmless to human cells. The aim of this study is to show the feasibility and the morpho‐diagnostic impact of THz imaging of historic remains. Images of an artificially embalmed ancient Egyptian human mummy hand, an artificially embalmed ancient Egyptian mummified fish and a macerated human lumbar vertebra were obtained by THz‐pulse imaging and compared with conventional X‐ray and CT images. Although conventional x‐ray imaging provides higher spatial resolution, we found that THz‐imaging is well‐suited for the investigation of ancient mummified soft tissue and embalming‐related substances / wrappings. In particular, bone and cartilaginous structures can be well differentiated from surrounding soft‐tissues and bandage‐wrappings by THz imaging. Furthermore, THz‐pulse imaging also measures the time‐delay of the pulsed signal when passing through the sample, which provides supplementary information on the optical density of the sample that is not obtained by X‐ray and CT. Terahertz radiation provides a completely non‐invasive diagnostic imaging modality for historic dry specimens. We anticipate this modality also to be used for detection of hidden objects in historic samples such as funerary amulets still in situ in wrapped mummies, as well as potentially for the identification of spectral signatures from chemical substances, e.g., in embalming essences.. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Jaw muscles in older overdenture patients

Objective: To determine, using computer tomography (CT), whether the retention of a small number of teeth in the older adult used to support overdentures could affect the cross‐sectional area (CSA) and X‐ray density of two jaw closing muscles. Design: Cross‐sectional study of a group of older patients subdivided into dentate, edentulous and those wearing overdentures supported by two to five teeth. Subjects: The sample consisted of 24 subjects aged 55–68 years. Outcome measures: CSA and X‐ray density of two jaw closing muscles, masseter and medial pterygoid were measured and evaluated using CT. Results: There were no significant differences between left and right jaw muscles, but the CSA of the masseter muscles were significantly larger than the medial pterygoid muscles. The CSA of the masseter and medial pterygoid muscles was significantly smaller in edentulous subjects compared with dentate subjects but no significant difference was observed between subjects wearing overdentures and those with a natural dentition. No significant differences were observed with the X‐ray density between different muscles or dental states. Conclusion: The retention of a small number of teeth in the older adult used to support overdentures appears to sustain the CSA of two jaw closing muscles and therefore could enhance these patients’ masticatory ability compared with those who were edentulous.     

上球管遥控床的智能控制

介绍能隔室遥控操作的上球管遥控床的智能控制系统,包括用VB编制的上位机监控界面,基于AT90S8515的下位机的控制,以及上、下位机的串行通信。本系统具有友好的人机界面,性能良好,易于产品的升级、改进。     

CT 与X线诊断肠梗阻的临床价值探讨

目的：探讨腹部X 线与CT 扫描鉴别急性肠梗阻的准确性,为临床诊断提供参考。方法：选取2011年8 月-2013 年8 月我院 收治的66 例急性肠梗阻患者的临床资料进行回顾分析。所有患者均经手术活检或病理诊断证实为急性肠梗阻。术后患者均行腹 部X 线及CT扫描检查,对两种方法判断肠梗阻的发生、梗阻部位、类型及病因与手术病理结果进行比较,评价并分析两种检查 方法的准确率。结果：66 例肠梗阻患者中,X线检出率为89.39%,CT 检出率为95.45%。X 线诊断小肠梗阻准确率为72.10%,CT 为86.05%;X线诊断结肠梗阻准确率为69.57%,CT 为86.96%。X线诊断肿瘤准确率为69.57%,CT 为86.96%;X线诊断肠粘连 准确率为67.86%,CT 为82.14%;X 线诊断肠套叠准确率为60.00%,CT 为80.00%;X线诊断单纯性机械性肠梗阻准确率为78.72%,CT为82.98%;X线诊断绞窄性肠梗准确率为73.68%,CT 为78.95 %。CT 对肠梗阻部位、病因及类型的诊断准确率高于腹部X 线片,差异具有统计学意义(P<0.05)。结论：腹部X 线与CT 用于诊断急性肠梗阻具有较高的准确率,但CT 对于肠梗阻部位、梗阻类型及梗阻病因的诊断优于X线片。