肝脏多房环形强化病变的影像分析?

目的：分析肝脏多房环形强化的影像学特征,探讨肝脓肿、肝内胆管细胞癌、肝转移瘤的鉴别诊断要点。方法：回顾性分析31例肝脏病变表现为多房环形强化的影像学特征,其中肝脓肿15例,肝内胆管细胞癌7例,肝转移瘤9例。13例行上腹部 CT 平扫和三期增强检查,7例行 MRI 平扫及 LAVA 多期增强检查,11例同时行 CT 和 MRI 检查。结果：3种病变在环壁及分隔的强化征象有差异。肝脓肿环壁及分隔均匀、完整（P <0.05）,可见病灶缩小征（P <0.05）。胆管细胞癌环形强化呈向心性充填（P <0.05）,或出现肝包膜回缩（P <0.05）和扩张胆管壁的局限性增厚。环壁不规则中断或见强化的壁结节,是诊断转移瘤较有价值的征象。结论：肝脓肿、肝内胆管细胞癌、肝转移瘤 3种病变各有其影像特点,CT 及 MR 检查对三者的诊断与鉴别诊断有重要价值。     

致密砂岩储层CO2驱油特征的核磁共振实验研究

利用核磁共振技术对致密砂岩储层不同渗透率级别基质岩心和裂缝基质岩心不同驱替压力下CO2驱油特征进行了研究,简述核磁共振原理及实验方法。表明:致密砂岩储层特低、超低渗透基质岩心在初始CO2驱替压力下,岩心毛细孔隙和微毛细孔隙区间的油不同程度被采出,随着CO2驱替压力增大,特低、超低渗透基质岩心毛细孔隙区间油的采出程度不断增加且累积采出程度不同。裂缝致密砂岩储层岩心,裂缝和毛细孔隙区间的油在初始CO2驱替压力下,岩心裂缝中的油及毛细孔隙中的部分油被驱替出来,CO2驱替压力提高毛细孔隙、微毛细区间油的采出程度和累积采收程度较小。致密砂岩储层特低、超低渗透基质岩心和裂缝致密砂岩储层岩心,随着CO2驱替压力增大毛细孔隙区间的部分剩余油成正比增加进入到微毛细孔隙区间改变储层剩余油分布。核磁共振技术能够深入研究致密砂岩储层CO2不同驱替压力阶段,岩心裂缝、毛细孔隙区间、微毛细孔隙区间油的采出程度和剩余油分布情况,对于研究致密砂岩储层微观驱油机理具有较重要的价值。      

Using wavelet‐domain adaptive filtering to improve signal‐to‐noise ratio of nuclear magnetic resonance log data from tight gas sands

In tight gas sands, the signal‐to‐noise ratio of nuclear magnetic resonance log data is usually low, which limits the application of nuclear magnetic resonance logs in this type of reservoir. This project uses the method of wavelet‐domain adaptive filtering to denoise the nuclear magnetic resonance log data from tight gas sands. The principles of the maximum correlation coefficient and the minimum root mean square error are used to decide on the optimal basis function for wavelet transformation. The feasibility and the effectiveness of this method are verified by analysing the numerical simulation results and core experimental data. Compared with the wavelet thresholding denoise method, this adaptive filtering method is more effective in noise filtering, which can improve the signal‐to‐noise ratio of nuclear magnetic resonance data and the inversion precision of transverse relaxation time T₂ spectrum. The application of this method to nuclear magnetic resonance logs shows that this method not only can improve the accuracy of nuclear magnetic resonance porosity but also can enhance the recognition ability of tight gas sands in nuclear magnetic resonance logs.     

含脂肪原发性肝癌的影像诊断及鉴别诊断

目的：探讨CT与MRI对含脂肪原发性肝癌的诊断及鉴别诊断价值。方法：回顾性分析我院病理证实的22例含脂肪原发性肝癌的CT、MRI表现。结果：22例含脂肪肝癌中,巨块型16例,结节型4例,弥漫型2例。肿瘤单发17例,多发5例;5例多发肿瘤内均只有1个含脂肪病灶,共有含脂肪肿瘤22个。18例肿瘤以实质成分为主,肿瘤内脂肪呈散在、小簇状分布;4例肿瘤以脂肪成分为主,瘤内脂肪呈球状表现,实质成分较少。CT显示肿瘤内斑片状、球状脂肪密度影,MRI脂肪抑制序列及化学位移梯度回波序列正反相位均明确显示脂肪的存在。22例动态增强扫描均较好地显示“快进快出”的影像强化特征,其中15例显示肿瘤假性包膜。结论：CT、MRI能较好显示原发性肝癌的影像特征及肿瘤内所含的脂肪组织,对诊断与鉴别诊断具有重要价值。     

弥散加权成像评价直肠癌淋巴结转移的价值

目的：探讨MR弥散加权成像诊断直肠癌淋巴结转移的价值。方法：62例经病理证实直肠癌患者行MRI常规序列扫描及DWI,测量淋巴结ADC值,根据病理结果将MRI检出的淋巴结分为转移性和良性淋巴结两组,将盆腔淋巴结MRI诊断结果与手术病理结果相对照,比较两组淋巴结的ADC值差异是否有统计学意义。结果：共测量225个淋巴结ADC值,b值为800s／mm2,转移性淋巴结组平均ADC值为（0．76±0．15）×10^-3mm2／s,良性淋巴结组平均ADC值为（1．16±0．14）×10^-3mm2／s,两组平均ADC值差异有统计学意义（P〈0．05）。ADC值以1．0×10×10^-3mm2／s为阈值,判断转移性淋巴结与良性淋巴结时,灵敏度、特异度及准确度分别为：94．53％、91．62％和93．45％。结论：弥散加权成像诊断直肠癌淋巴结转移具有较大临床价值。     

核磁共振与瞬变电磁三维联合解释方法

传统核磁共振地下含水量解释多采用基于均匀半空间或层状导电模型的一维反演,分层给出地下含水信息.然而,这些方法忽略了地下复杂电阻率分布信息对结果的影响,也不能很好地反映局部三维含水构造.本文从三维电介质中核磁共振响应的正演理论出发,提出首先利用瞬变电磁数据进行基于等效导电平面法的快速电阻率成像,然后将成像结果作为核磁共振三维反演的电性模型,进行联合解释.激发磁场的分布采用有限元法直接求解,通过引入伪δ源实现电流源的加载,并强加散度条件排除了三维磁场模拟中"弱解"的影响.针对核磁共振灵敏度矩阵的病态性和数据中存在的干扰信号,提出考虑罚项的非线性拟合目标函数,利用线性化方法进行核磁共振反演.模型数据表明该方法能较准确反映地下三维含水构造,实测算例进一步证明了方法的有效性.本研究将促使核磁共振方法在岩溶、裂隙水、孤立水体等复杂水文地质条件及隧道、矿井灾害水源探测等方面得到有效应用.     

Numerical investigation of oscillations induced by submerged sliding masses within a harbor of constant slope

Oscillations within a rectangular harbor of constant slope induced by submerged sliding masses are investigated numerically based on Boussinesq-type equations and results are used to reveal the characteristics of the generated oscillations. The numerical result of each transverse eigenfrequency is very close to the theoretical prediction and the spatial structure of each mode of the oscillations may also be well captured by the existing analytical solutions based on shallow water equations. The investigation shows that relatively small-scale sliding masses whose width is small compared with the harbor width may induce obvious transverse oscillations. The predominant transverse components are those with small mode numbers when the solid slides start moving from the backwall. In comparing the oscillations induced by the slides of constant velocity and those accelerated by gravity force with bottom friction, it is observed that the movements accelerated by gravity force may facilitate the development of very low transverse oscillation modes while those with constant velocity may also be in favor of the higher ones. The augmentation of the sliding velocity along the constant slope may shift the amplitudes of the oscillation components to smaller values, which corresponds to the physical understandings of the waves generated by underwater sliding masses or landslides. While the sliding masses may not act on an isolated point of the bottom but follow a certain trajectory along the harbor, the transverse oscillations induced by them are sensitive to their position of departure in both the cross-harbor direction and the offshore direction. Longitudinal oscillations may be induced by relatively large sliding masses of harbor width on a constant slope within the harbor. Although the longitudinal oscillations may not reach a steady state without forcing terms at the entrance of the harbor, some patterns of several low-mode ones occur and wavelet spectra are used to analyze their evolutions and comparisons are made with theoretical predictions. It is revealed that the longitudinal oscillations are also sensitive to the moving velocity and initial location of the sliding masses.     

On natural modes in moonpools with recesses

The theoretical model of Molin [6] is extended to the case of rectangular moonpools with one or two recesses, as can be found in some drillships. Obtained natural frequencies and modal shapes of the piston and first sloshing modes are compared with experimental results available in literature, with good agreement. An approximation easy to implement is proposed for the natural frequency of the piston mode. Further illustrative results are presented when some geometrical parameters of the moonpool are being varied.     

地面核磁共振方法在大坝安全检测中的试验研究

地面核磁共振方法是一种直接探测地下水信息的地球物理勘查方法,本文将该无损探测技术用于土石坝的渗流安全评估试验。由于探测的核磁共振信号源于地下水中的氢质子,则可以确保核磁共振响应仅与地下水信息有关。利用地面核磁共振方法直接找水的技术优势,探测堤坝的浸润面,以判断堤坝的渗流(漏)隐患,为堤坝尤其是小型病险水库堤坝、易发事故的堤防的病险诊断提供一种便捷、高效和可重复利用的方法。通过NUMISPOLY多道核磁共振探测系统在某原体大坝检测中的试验,得到原体大坝的浸润面,进而对土石坝进行渗流(漏)隐患的评估,该方法为堤坝渗流(漏)隐患探测提供了一种有效而可靠的新方法。      

致密砂岩储层流体参数核磁共振实验研究

利用核磁共振技术对致密砂岩储层岩心流体参数进行研究,简述致密砂岩储层流体参数核磁共振测量原理及计算岩心流体参数方法。实验确定了岩心流体动用参数T2截止值方法,进行了可动流体致密砂岩储层分类评价研究。油田矿场核磁共振测量岩心含油饱和度、可动流体饱和度,并对可动流体饱和度、含油饱和度识别油水层方法进行研究。表明:实验测定红河区块岩心T2截止值为4.06ms,利用致密砂岩储层岩心可动流体等级划分标准,对致密砂岩储层岩心单井及不同层位、多井之间进行储层比较分类评价。油田矿场核磁共振技术测量计算的含油饱和度结果与常规方法测量的含油饱和度结果对比,表明油田矿场核磁测量含油饱和度是可行且可靠的。岩心含油饱和度与可动流体饱和度比值大小可识别油水层。