基于改进的时移成像条件的保幅叠前深度偏移研究

为了实现保幅叠前深度偏移,在波动方程保幅偏移方程的基础上详细推导了傅里叶有限差分波动方程延拓算子。由于波动方程叠前深度偏移技术的应用受计算效率的制约,因而,提出了利用大延拓步长进行波场延拓,在延拓层位,利用相关成像条件进行成像。对延拓步长层间的层位,结合含有绕射聚焦项的时移映射函数,对延拓层位上未基于频率叠加的上、下波场的互相关值进行傅里叶逆变换,并结合零时刻成像原理求出延拓层间的成像值。脉冲响应测试和Marmousi模型试算表明该方法可以实现保幅叠前深度偏移,并可以大幅度提高偏移成像效率。

基于非线性Lamb波改进全聚焦成像的板中损伤分类与定位

采用有限元仿真的方法建立三维铝板模型,对板中不同类型损伤的分类与定位问题进行了研究.使用ABAQUS在板中设置了微裂纹和圆孔两种类型损伤,利用来自不同类型损伤区域响应信号传播速度的差异提出了一种适用于不同类型损伤的改进全聚焦成像算法,并以此为基础提出了实现板中损伤分类与定位的方法.此方法使用脉冲反转法从响应信号中提取与微裂纹相关的二次谐波信号,同时利用滤波获得响应信号中的基波信号,然后结合提出的改进全聚焦成像算法分别利用二次谐波信号和基波信号对损伤进行成像.仿真结果表明,利用改进的全聚焦成像算法对脉冲反转提取到的二次谐波成像时可先实现对板中微裂纹损伤的选择成像,然后结合滤波后基波信号的使用可实现对圆孔的定位.相较于传统的全聚焦成像算法,此提出的方法不仅可以给出更准确的损伤位置预测,同时也能实现对不同损伤类型的区分.

逆时偏移在弱振幅储层成像中的研究与应用

结合逆时偏移技术在大港油田孔南王官屯地区孔一段弱振幅储层成像攻关中的实践,以本次攻关采用的关键技术——逆时偏移为核心,以速度建模流程为基础,总结了逆时偏移技术的基本原理、实践流程和应用效果。并结合资料的构造解释与储层预测,初步分析了逆时偏移在本区的应用,取得了良好的效果。

Diagnostic value of gadobenate dimeglumine-enhanced hepatocyte-phase magnetic resonance imaging in evaluating hepatic fibrosis and hepatitis

AIM To evaluate the diagnostic value of gadobenate dimeglumine(Gd-BOPTA)-enhanced hepatocyte-phase magnetic resonance imaging(MRI) in evaluating hepatic fibrosis and hepatitis.METHODS Hepatocyte-phase images of Gd-BOPTA-enhanced MRI were retrospectively evaluated in 76 patients with chronic liver disease. These patients were classified into five groups according to either the histopathological fibrosis stage(S0-S4) or the histopathological hepatitis grade(G0-G4). The relative enhancement ratio(RE) of the liver parenchyma in the T1-vibe sequence was calculated by measuring the signal intensity before(SI pre) and 90 min after(SI post) intravenous injection of Gd-BOPTA using the following formula: RE =(SI post-SI pre)/SI pre. One-way analysis of variance was used to compare the difference between the relative RE in the hepatocyte phase(REh) and the stage of hepatic fibrosis and the grade of hepatitis. Pearson's productmoment correlation analysis was used to evaluate the relationship between the REh and the levels of serologic liver functional parameters.RESULTS According to histopathological hepatic fibrosis stage, the 76 patients were classified into five groups: 16 in S0, 15 in S1, 21 in S2, 9 in S3, and 15 in S4 group. According to histopathological hepatitis grade, the 76 patients were also classified into five groups: 0 in G0, 44 in G1, 22 in G2, 8 in G3, and 2 in G3 group. With regard to the stage of hepatic fibrosis, REh showed significant differences between the S2 and S3 groups and between the S2 and S4 groups(P < 0.05), but no significant difference was observed between the other groups. With regard to the grade of hepatitis, REh showed significant differences between the G1 and G2 groups and between the G1 and G4 groups(P < 0.05), but no significant difference was observed between the other groups. Increased REh showed correlations with decreased serum levels of TB, ALT and AST(P < 0.05). CONCLUSION To some extent, measuring the REh using Gd-BOPTAenhanced MRI might be a noninvasive technique for assessing the stage of hepatic fibrosis. This method is able to differentiate no/mild hepatitis from advanced hepatitis. TB, ALT and AST levels can predict the degree of liver enhancement in the hepatocyte phase of Gd-BOPTA-enhanced MRI.

Role of new endoscopic techniques in inflammatory bowel disease management: Has the change come?

Despite significant therapeutic progress in recent years,inflammatory bowel disease(IBD),which includes Crohn’s disease and ulcerative colitis,remains a challenge regarding its pathogenesis and long-term complications.New concepts have emerged in the management of this disease,such as the"treat-totarget"concept,in which mucosal healing plays a key role in the evolution of IBD,the risk of recurrence and the need for surgery.Endoscopy is essential for the assessment of mucosal inflammation and plays a pivotal role in the analysis of mucosal healing in patients with IBD.Endoscopy is also essential in the detection of dysplasia and in the identification of the risk of colon cancer.The current surveillance strategy for dysplasia in IBD patients indicates white-light endoscopy with non-targeted biopsies.The new chromoendoscopy techniques provide substantial benefits for both clinicians and patients.Narrow-band imaging(NBI)has similar rates of dysplastic lesion detection as whitelight endoscopy,and it seems that NBI identifies more adenoma-like lesions.Because it is used instinctively by many endoscopists,the combination of these two techniques might improve the rate of dysplasia detection.Flexible spectral imaging color enhancement can help differentiate dysplastic and non-dysplastic lesions and can also predict the risk of recurrence,which allows us to modulate the treatment to gain better control of the disease.The combination of noninvasive serum and stool biomarkers with endoscopy will improve the monitoring and limit the evolution of IBD because it enables the use of a personalized approach to each patient based on that patient’s history and risk factors.

The application of DCE-MRI in diagnosing breast cancer

Objective The aim of the study was to further explore the diagnostic value of breast dynamic contrast enhancement (DCE), and improve specificity of breast cancer diagnosis.

Image Restoration of Depth of Field Extension Imaging System Based on Genetic Algorithm

Genetic algorithm is a search algorithm based on genetic mechanism and natural selection. It has been widely applied to research fields including image processing field. The paper improves standard genetic algorithm and improves the arithmetic speed of the algorithm, which achieves better image restoration effect. And the paper compares the image restoration quality of traditional algorithm, standard genetic algorithm and improved genetic algorithm to prove the feasibility of applying genetic algorithm to image restoration.

一种提高海兔神经节成像清晰度的清晰化技术（英文）

无论在脊椎动物还是无脊椎动物中,提高神经环路的成像效果对于神经环路的功能研究都是必不可少的。因此,一种新的基于鼠脑的成像技术——清晰化技术(CLARITY),正吸引越来越多的研究者将它运用到其它物种中。这里我们将改进过的清晰化技术应用于无脊椎动物海兔的神经节的清晰化成像中。改进之处包括为海兔神经节修改了水凝胶溶液配方并设计了一个专用的容器。我们使用预先经过免疫组化处理的神经节,再使用改进的清晰化技术。我们采用荧光和共聚焦成像检查这些技术的相容性以及成像效果的改善程度。结果显示,这种改进过的清晰化技术确实可以使样本更清晰,并且进一步提高了海兔神经节中神经肽CP2免疫阳性神经元的清晰度。例如,这种方法提高了神经节深处的一些弱免疫阳性神经元的可视化效果。这种改良方法使得清晰化技术不仅更适合海兔整体神经节的结构成像,也会对其它的无脊椎动物神经节的成像起到帮助作用。