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1.
李晓阳 《CT理论与应用研究》1995,4(3):19-20
本文报道１５７例经ＣＴ诊断的颈椎间盘突出，４例经手术证实。ＣＴ特征表现为：①颈椎间盘后缘局限性软组织块影疝入椎管出；②椎管与硬脊膜间脂肪间隙消失；③硬膜囊受压后移或压迫神经根管。 相似文献
2.
急性颈椎损伤的CT诊断 总被引：2，自引：1，他引：1
本文目的是分析急性颈椎损伤（ＡＣＴ）的ＣＴ征象,评价ＣＴ在ＡＣＴ诊断中的价值及限度。方法：７８例颈椎外伤患者行平片、薄层ＣＴ检查及三维重建,并做对照分析。结果经影像学诊断６０例ＡＣＴ,ＣＴ诊断５９例,１例ＣＴ阴性而由平片确诊 １例。平片与ＣＴ的骨折检出率分别为 ５３． ３％和 ９８．３％。结论：ＣＴ比Ｘ线平片可发现更多的骨折,并能明确骨折块与椎管的关系。这对临床处理严重颈椎损伤起到指导作用。 相似文献
3.
目的：通过观察胸腰段爆裂骨折的ＣＴ表现,探讨其治疗方法。方法：回顾性分析６４例胸腰椎爆裂骨折,研究其ＣＴ表现。结果：胸腰椎前、中、后三柱损伤３１例,前、中柱损伤２２例,中柱损伤１１例;无骨片进入椎管１２例,椎管内骨片占有百分比＜５０％为３６例,＞５０％为１６例。结论：ＣＴ能对椎管损伤准确诊断,对治疗方式的选择有重要参考价值。 相似文献
4.
对４０例隐性椎管闭合不全的患者进行了回顾性研究。此症的临床和放射学诊断曾经是个困难的问题。自ＣＴ和ＭＲ问世后，这个难题已获解决。在隐性椎管闭合不全的患者中，早日进行手术治疗能够阻止神经症状的进展。所以应尽早做影像学检查。 相似文献
5.
本文分析了２３例甲状腺癌和腺瘤的ＣＴ表现，讨论了ＣＴ诊断和鉴别诊断，甲状腺癌呈分界不清的软组织密度包块，密度不均匀，甲状腺腺瘤要据其ＣＴ表现为二个类型：（１）囊性型，（２）实质型。甲状腺癌和囊性型腺瘤鉴别不难，但是在实质型腺瘤的ＣＴ表现相类似，有时鉴别诊断困难。 相似文献
6.
对８０例脊髓型颈椎病作脊髓造影的观察。（１）认为ＣＴＭ能够更准确的显示椎管内横断面影像学资料,及时准确的做出诊断。（２）可以显示脊髓周边情况,能够准确诊断脊髓型颈椎病,显示颈椎部脊髓受压情况,帮助临床医师治疗。 相似文献
7.
动态CTM对腰椎管狭窄症的诊断意义 总被引：4，自引：0，他引：4
本文对２０例有姿势依赖性平状的腰椎管狭窄症病人进行腰椎屈、伸直位动态ＣＴＭ观察表明，当腰椎处在伸直位时中央锥管和侧隐窝的容积均减少，表现为硬膜囊矢状径、硬膜囊最大径、韧带关节间径和黄韧带夹角均有显著减少，关节突向间盘方向突出使得椎管的前外角狭窄、神经袖周围的游离间隙消失，神经根受到挤压、作者从ＣＴ解剖学的角度分析了椎管内各种组织结构的动态变化及其对硬膜囊和神经根的影响，提出脊柱伸展时黄韧短缩性增厚 相似文献
8.
9.
腔隙性脑梗塞的CT诊断及临床特点 总被引：1，自引：1，他引：0
本文回顾性分析了１２０例脑腔隙性梗塞的ＣＴ诊断及临床特点,认为梗塞病灶可被清晰、准确的发现。有助于临床的定性分析,为治疗提供了依据。ＣＴ是目前诊断脑腔隙性梗塞的最有效的检查手段。 相似文献
10.
脊柱神经母细胞瘤误诊思维分析 总被引：1，自引：1，他引：0
脊柱神经母细胞瘤是常发生于幼儿,１０岁以上很少见。我院收治一例罕见的青少年脊柱神经母细胞瘤的患者。虽经Ｘ线照片椎管造影、ＣＴ平扫与增强扫描等多种影像学检查,在我院及外院都是诊断为脊柱结核。该例误诊除客观因素外,主要是由于诊断思维偏差导致误诊。 相似文献
11.
地震土压力评价是挡土墙抗震设计的关键问题之一.以往的研究结果表明,挡墙上地震土压力的大小及分布与墙体的侧向位移或者墙后填土的侧向变形密切相关.经典的物部-冈部地震土压力公式可计算填土处于主动与被动状态的极限平衡条件下的土压力,未考虑挡墙侧向位移或填土侧向变形对土压力的影响.在研究土压力系数随应变增量比变化规律的基础上,本文指出土压力系数与挡土墙位移量之间不存在唯一性关系,发现正常固结填土的土压力系数与以应变增量比表述的填土侧向应变约束条件之间具有良好的唯一性,揭示了压剪耦合效应是土压力形成的物理本质;基于上述的唯一性关系和中间土楔等概念,提出了可考虑填土侧向变形的地震土压力实用计算方法,并通过土压力模型试验结果初步验证了该方法的合理性. 相似文献
12.
在远场地震作用下单桩横向地震响应研究的基础上,引入相互作用因子,研究了远场地震作用下成层地基中桩与桩的横向动力相互作用,得到了桩间距、桩土刚度比、桩顶约束条件、瑞利波入射角度、震动频率是影响群桩横向动力相互作用主要因素的结论,为进一步研究远场地震作用下群桩的横向地震响应打下了基础。 相似文献
13.
Tidal mixing plays an important role in the modification of dense water masses around the Antarctic continent. In addition to the vertical (diapycnal) mixing in the near-bottom layers, lateral mixing can also be of relevance in some areas. A numerical tide simulation shows that lateral tidal mixing is not uniformly distributed along the shelf break. In particular, strong mixing occurs all along the Ross Sea and Southern Weddell Sea shelf breaks, while other regions (e.g., the western Weddell Sea) are relatively quiet. The latter regions correspond surprisingly well to areas where indications for cross-shelf exchange of dense water masses have been found. The results suggest that lateral tidal mixing may account for the relatively small contribution of Ross Sea dense water masses to Antarctic Bottom Water. 相似文献
14.
Jrgen Kisling-Mller 《地球表面变化过程与地形》1992,17(5):501-513
Bedforms and their migration are among the most important features determining bed load transport on point bars in sand-bedded rivers. A case study has been carried out in the Danish river Gels Å in a bend with equilibrium point bar topography. Bedforms (dunes) were repeatedly surveyed to determine the bedform migration on the point bar surface. Bedforms occur in two categories in the bend: primary dunes and secondary dunes migrating transversely in the troughs between primary dunes. The study shows that the migration of these bedforms can account for the entire lateral transport known to concentrate the transport in the convex half of the cross section at the bend exit. The bedform transport is induced by both dune categories, partly by turning of the primary dunes towards the convex bank and partly by the migration of secondary dunes. In certain areas, the two categories operate together and thus make the lateral transport particularly large; it is shown that almost 60 per cent of the entire lateral transport in the bend takes place within less than 30 per cent of the streamwise extent of the point bar. 相似文献
15.
侧脑室室管膜瘤MRI表现特征及其鉴别诊断 总被引：2，自引：0，他引：2
目的:探讨侧脑室室管膜瘤的MRI表现特征.材料和方法:回顾分析经病理证实的38例侧脑室室管膜瘤,所有患者均行了MRI平扫和增强扫描,分析肿瘤部位、大小、生长方式、信号特点及强化方式,有无囊变、出血.结果:大部分肿瘤在T1WI像上呈等或低信号;在T2WI像上呈高信号.约73.7%的肿瘤可见囊变,出血少见.大部分肿瘤边缘不整,22例(57.9%)肿瘤跨脑室壁浸润邻近脑实质,30例(78.9%)肿瘤侵及对侧侧脑室或三脑室.增强扫描大部分肿瘤(89.5%)肿瘤呈不均匀显著强化,4例肿瘤呈轻度不均匀性强化.结论:侧脑室室管膜瘤MR表现具有一定的特征性,了解这些特征,有助于侧脑室室管膜瘤术前诊断和鉴别诊断. 相似文献
16.
As the first part of a sequence focusing on the dynamic response of composite caisson-piles foundations (CCPFs1), this paper develops a simplified method for the lateral response of these foundations. A Winkler model for the lateral vibration of the CCPF is created by joining the two components, the caisson and the pile group, where the four-spring Winkler model is utilized for the caisson and axial–lateral coupled vibration equations are derived for the pile group. For determining the coefficients of the four-spring Winkler model for the caissons, embedded footing impedance is used and a modification on the rotational embedment factor is made for the sake of the geometrical difference between shallow footings and caissons. Comparisons against results from finite element simulations demonstrate the reliability of this modified four-spring Winkler model for caissons in both homogenous and layered soils. The proposed simplified method for the lateral vibration of CCPFs is verified also by 3D finite element modeling. Finally, through an example, the idea of adding piles beneath the caisson is proved to be of great significance to enhance the resistance of the foundation against lateral dynamic loads. 相似文献
17.
通过进行大型模型槽足尺模型试验,根据桩身变形和柱身弯矩的试验结果,分析了水平荷载作用下现浇混凝土大直径管桩（以下简称PCC桩）的水平承栽特性和桩-土共同作用性状。采用大型通用有限元软件ABAQUS对PCC桩的水平承载特性进行了数值模拟,计算结果与试验结果符合得较好,并进一步探讨了PCC桩水平承载特性的主要影响因素。结果表明：表层土体的弹性模量对水平受力性状影响较大,表层土体的厚度对桩身水平位移也有较大影响,因此可以通过改良表层土体来控制桩身水平位移,以达到工程设计要求;土体强度参数对水平承载特性也有影响,尤其是内摩擦角和粘聚力较小时更为明显。 相似文献
18.
大跨双槽渡槽横向地震响应分析 总被引：1，自引：0，他引：1
针对大型渡槽槽身采用薄壁结构的特点,提出大型双槽截面渡槽横向地震响应分析模型。渡槽槽身采用薄壁梁段单元模型,该单元可以考虑渡槽槽身弯曲、自由扭转、约束扭转以及弯曲扭转耦合振动等结构自身特性;渡槽支架采用普通梁单元模拟,渡槽与支架连接所用的盆式橡胶支座,可用集中弹簧模拟。文中采用4种典型地震动计算了双洎河大型渡槽的横向地震响应,给出了该大型渡槽关键部位的地震响应最大值,所得结果可为该大型渡槽抗震设计提供参考。 相似文献
19.
The time-harmonic response of a pile in a poroelastic half space and under lateral loadings is studied. By treating the pile as a one-dimensional structure and the half-space as a three-dimensional poroelastic continuum, the dynamic interaction between a pile and a poroelastic medium is formulated as a Fredholm integral equation of the second kind. Green's functions for a distributed lateral force field acting inside a poroelastic half space is an important ingredient of this paper. Numerical results for lateral dynamic compliance functions are presented to illustrate the dynamic characteristics of a pile in a poroelastic half space. 相似文献
20.
Lateral blasts at andesitic and dacitic volcanoes can produce a variety of direct hazards, including ballistic projectiles which can be thrown to distances of at least 10 km and pyroclastic density flows which can travel at high speed to distances of more than 30 km. Indirect effect that may accompany such explosions include wind-borne ash, pyroclastic flows formed by the remobilization of rock debris thrown onto sloping ground, and lahars.Two lateral blasts occurred at a lava dome on the north flank of Mount St. Helens about 1200 years ago; the more energetic of these threw rock debris northeastward across a sector of about 30° to a distance of at least 10 km. The ballistic debris fell onto an area estimated to be 50 km2, and wind-transported ash and lapilli derived from the lateral-blast cloud fell on an additional lobate area of at least 200 km2. In contrast, the vastly larger lateral blast of May 18, 1980, created a devastating pyroclastic density flow that covered a sector of as much as 180°, reached a maximum distance of 28 km, and within a few minutes directly affected an area of about 550 km2. The May 18 lateral blast resulted from the sudden, landslide-induced depressurization of a dacite cryptodome and the hydrothermal system that surrounded it within the volcano.We propose that lateral-blast hazard assessments for lava domes include an adjoining hazard zone with a radius of at least 10 km. Although a lateral blast can occur on any side of a dome, the sector directly affected by any one blast probably will be less than 180°. Nevertheless, a circular hazard zone centered on the dome is suggested because of the difficulty of predicting the direction of a lateral blast.For the purpose of long-term land-use planning, a hazard assessment for lateral blasts caused by explosions of magma bodies or pressurized hydrothermal systems within a symmetrical volcano could designate a circular potential hazard area with a radius of 35 km centered on the volcano. For short-term hazard assessments, if seismicity and deformation indicate that magma is moving toward the flank of a volcano, it should be recognized that a landslide could lead to the sudden unloading of a magmatic or hydrothermal system and thereby cause a catastrophic lateral blast. A hazard assessment should assume that a lateral blast could directly affect an area at least 180° wide to a distance of 35 km from the site of the explosion, irrespective of topography. 相似文献