数字实时成像(DR)与X射线胶片成像对比分析

本文简要介绍了数字实时成像技术与X射线胶片成像技术的基本原理,从几个方面对两种技术的特点做了比较分析,并初步讨论了X射线成像技术的发展动向。     

Novel Diagnostic of Shock Fronts in Low-Z Dense Plasmas

We performed an experiment using high-energy protons to characterize in situ the spatial and temporal evolution of a laser-driven shock propagating through a low-Z material. Radiography of the shock propagating through the low-Z transparent material (Lexan, quartz, diamond) enabled estimation of density under compression. In order to discriminate the influence of the shocked matter on the protons trajectory, a Monte-Carlo simulation was developed. This code describes the protons trajectory through the matter, calculating the scattering angle and the loss of energy.     

肺癌的胸片体层片与CT、BAG的X线表现和诊断价值比较

目的：探讨胸片，体层片和CT，支气管动脉造影（BAG）对肺癌的诊断价值并对其进行比较，方法：对照病理检查结果对101例患者的胸片、体层片和CT、BAG的X线表现和诊断价值进行回顾性分析，结果：61例肺癌、胸片、体层片诊断正确43例（70．5％）；定性困难16例（26．2％）；误诊8例（13．1％（）。CT诊断正确57例（93．4％）；误诊4例（6．6％；40例肺癌：BAG中有肿瘤血管改变者35例（87．5％）。特征性造影表现有肿瘤血管（27例、67．5％）；肿瘤染色（20例、50％）；肿瘤包烧（835例、87．5％）。结论：胸片，体层片和CT对肺癌具有很高的诊断价值。以CT为优，胸片，体层片显示段以上支气管情况和肿块整体形态较好，CT显示肿瘤的内部结构，轮廓、瘤周、纵隔胸膜转移和纵隔旁及脊柱旁区病灶具有明显优势。BAG对肺癌有一定的诊断价值。     

Infiltration through series of soil aggregates: Neutron radiography and modeling

Soils are often structured as fine-porous aggregates separated by large inter-aggregate pores. Under unsaturated conditions, water is mostly stored in the aggregates and water flow depends on the properties of the aggregates as well as on those of the contacts between aggregates. The goal of this study is to model and evaluate the hydraulic properties of the contacts. We used neutron radiography to monitor the infiltration of water through series of aggregates. The flow process was numerically simulated by considering the hydraulically conducting contact area between aggregates as a variable that depends on the capillary pressure. This contact area was evaluated by matching the observed and simulated water flow across aggregates. We determined the conductivity of the contacts assuming that it scales with the contact area. We also measured the equivalent conductivity of series of aggregates. We found that during drainage the hydraulically conducting contact area drastically decreases and the conductivity of the contacts becomes much smaller than that of the aggregates. We also found that the equivalent conductivity of the aggregate series decreases as the conductivity of the contacts. We concluded that the contacts control the flow: they are highly conductive when wet, but act as bottle-necks under drained conditions. The abrupt transition between these two limiting cases indicates that the contact region is more rapidly drained than the aggregate interior. Our findings might be extended to describe water transfer to an evaporating boundary, infiltration and storage of water in unsaturated aggregated soils.     

MSCT与DR诊断肋骨骨折的对比研究

目的：比较数字X线摄影（DR）和多层螺旋CT（MSCT）在肋骨骨折诊断中的确诊率,评价其在法医临床鉴定中的作用。方法：观察80例肋骨骨折患者的DR正、斜位片,MSCT容积再现（VR）、最大密度投影（MIP）、多平面重组（MPR）及薄层轴位图像,对比分析两种影像学检查方法在肋骨骨折确诊率、漏诊率和疑诊率方面的差异。结果：...     

腕骨脱位或骨折并脱位的影像分析

目的:分析腕骨脱位及骨折并脱位的影像,探讨外力在腕关节传播的过程。方法:对129例腕骨脱位患者行X线和多层螺旋CT检查,分析腕骨脱位或骨折并脱位的类型。结果:月骨脱位32例,腕中关节脱位2例,月骨周围型脱位95例。95例中经舟状骨月骨周围脱位50例,经桡骨茎突月骨周围脱位23例,经头状骨月骨周围脱位4例,经三角骨月骨周围脱位7例,经尺骨茎突月骨周围性脱11例。在合并其他腕骨骨折的病例中。经桡骨茎突及经舟骨骨折病例X线检查均得到确诊,其余56例中,X线漏诊6例则是通过多层螺旋CT薄层扫描及重建才做出正确诊断,单纯月骨周围型脱位较少见(仅3例),有5例X线检查为单纯月骨周围脱位的病例在CT扫描发现合并腕骨撕脱性小骨折。结论:X线检查对腕关节节损伤的程度有可能低估,多层螺旋CT薄层扫描及重建可作出准确、直观诊断。分析外力损伤腕关节的过程对腕骨脱位或骨折并脱位的影像诊断有重要价值。      

中子照相转换屏的角度响应研究

在定量中子照相散射校正时需要考虑中子转换屏对不同角度入射中子的响应,中子转换屏的角度响应研究在中子照相散射校正中具有很重要的意义。本文在理论上推导中子转换屏的角度响应的解析式,并利用蒙特卡罗程序MCNP5对该解析式进行验证。利用蒙特卡罗方法对中子转换屏角度响应的影响因素进行研究。给出中子转换屏的角度响应与转换屏厚度以及入射中子能量之间的关系,中子转换屏的角度响应随着转换屏的厚度增大而增大,随着入射中子能量的增大而减小,并得到6LiF-ZnS(Ag)转换屏的最佳厚度为0.3mm。      

MSCT在邻关节骨囊肿诊断中的应用价值

目的：探讨邻关节骨囊肿的MSCT表现,提高对该病的术前诊断能力。方法：回顾性分析经手术病理证实的32例邻关节骨囊肿的临床及CT薄层扫描、多平面重组（MPR）表现。男20例,女12例,平均年龄42岁。结果：32例均为单发病变,共32个病灶,其中股骨头8个,胫骨近端8个,距骨6个,胫骨远端3个,腕月骨3个,股骨远端、髋臼、肱骨近端和腕舟骨各1个。病灶均位于骨内邻近关节面,病灶大小介于0.8cm×1.2cm～2.5cm×2.9cm之间。单房型26例,CT表现为圆形、类圆形或不规则形囊样低密度区,边缘清晰,均有薄层完整硬化边,相邻关节间隙无明显改变;多房型6例,病灶内有粗细不等的骨性间隔。病灶CT值20～60Hu,3个病灶内见细小气体密度影。穿透型18例,表现为病灶通过邻关节面裂隙与关节腔相通或病灶与关节旁软组织腱鞘囊肿相连;特发型14例,表现为骨内单一病灶,骨外结构正常。结论：邻关节骨囊肿有其特殊发病部位,CT表现典型,结合发病年龄和临床症状,可以作出正确的术前诊断。     

Measurement of fluid contents and wetting front profiles by real-time neutron radiography

Few methods exist for measuring rapidly changing fluid contents at the pore scale that simultaneously allow whole flow field visualization. We present a method for using real-time neutron radiography to measure rapidly changing moisture profiles in porous media. The imaging technique monitors the attenuation of a thermal neutron beam as it traverses a flow field and provides measurements every 30 ms with an image area >410 cm² and a spatial resolution 0.05 cm. The technique is illustrated by measuring the variation in moisture content across a wetting front moving at constant velocity through SiO₂ sand. The relative contributions of the hydraulic conductivity and diffusivity terms in Richards' equation to the total fluid flux within the wetting front region were also measured. The diffusivity was found to rise from zero to a peak value within the wetting front region before falling off while the conductivity was found to rise monotonically. The reliability of the technique was checked via mass balance.     

Distribution of radon sources and effects on radon emanation in granitic soil at Ben Lomond,California

The abundance and distribution of radioelements on bulk and microscopic scales were investigated in residual granitic-derived soil at a facility for investigating the movement of radon into structures. In bulk soil samples, Ra concentrations range from 0.6 to 1.3 pCi/g, and variations in Ra, Th, and K appear to be controlled mainly by heterogeneities inherited from the parent granitic rock, which contains abundant dikes and inclusions. U in soil and parent rock is concentrated in primary minerals (mainly zircon and sphene), and in secondary sites that are of greater importance for Rn emanation. The main U-bearing secondary sites are weathered sphene, grain boundary coatings, weathered biotite and plagioclase, as well as dense Fe-rich coatings and a REE-phosphate mineral present in near-vertical fracture zones in saprolite underlying shallow loam. Elevated U in these sites generally correlates with high Ti, Al, Fe, and/or P. Preferential distribution of U and Ra on grain boundaries and porous weathered minerals is reflected in relatively high Rn emanation rates in the soil. Highest emanation occurs between 1.3 and 2.3 m depth, where fine pedogenic phasesgibbsite and amorphous silica and Fe-OOH—are most abundant; it is related to fixation of Ra by these phases, which precipitate close to the surface and accumulate at these depths by illuviation. Separation of Ra from U may occur locally, given remobilization of U-series elements from secondary sites, and large differences between Ra and U sorption capabilities of several phases present in the soil. Concentration of U along permeable fracture zones in saprolite suggests that contribution of soil-gas Rn from depth (> 2 m) could be significant to Rn availability near the surface.