Vibration Fatigue of FDM 3D Printed Structures: The Use of Frequency Domain Approach

Additive manufactured structures are replacing the corresponding ones realized with classical manufacturing technique. As for metallic structures, 3D printed components are generally subjected to dynamic loading conditions which can lead to fatigue failure. In this context, it is useful, and sometimes mandatory, to determine the fatigue life of such components through numerical simulation. The methods currently available in literature for the estimation of fatigue life were originally developed for metallic structures and, therefore, it is now necessary to verify their applicability also for components fabricated with different materials. To this end, in the current activity three of the most used spectral methods for the estimation of fatigue life were used to determine the fatigue life of a 3D printed Y-shaped specimen realized in polylactic acid subjected to random loads with the aim of determining their adaptability also for this kind of materials. To certify the accuracy of the numerical prediction, a set of experimental tests were conducted in order to obtain the real fatigue life of the component and to compare the experimental results with those numerically obtained. The obtained outcomes showed there is an excellent match between the numerical and the experimental data, thus certifying the possibility of using the investigated spectral methods to predict the fatigue life of additive manufactured components.     

急性中心性浆液性脉络膜视网膜病变视网膜外层的SD-OCT表现

目的 探讨急性中心性浆液性脉络膜视网膜病变(central serous chorioretinopathy,CSC)视网膜外层组织的频域相干光断层扫描(spectral domain optical coherence tomography,SD-OCT)视网膜外层组织表现特征。设计回顾性病例系列。研究对象首次发病、荧光素眼底血管造影检查(FFA)表现为单眼单个明确渗漏点(LP)的急性CSC患者55例(55眼)。方法 分析FFA和SD-OCT同步检查图像对应LP及黄斑中心凹、视网膜神经感觉层脱离(NSRD)区域的视网膜色素上皮(RPE)光反射带及视网膜外层组织形态结构。主要指标SD-OCT中色素上皮层脱离(PED)形态特征、视网膜外层组织形态结构特征。结果 41眼(74.5%)LP表现为PED,其中拱形PED(DSPED)15眼(27.3%),扁平不规则PED(FIPED)26眼(47.2%)。与DSPED相比,FIPED更多见于墨渍状渗漏(χ²=11.116,P=0.001)和黄斑中心无血管区外(χ²=4.432,P=0.035)。黄斑中...     

光谱核型分析技术在染色体异常诊断中的应用

目的建立稳定的光谱核型分析技术,并评价其在染色体异常诊断中的应用价值。方法应用光谱核型分析技术对16例外周血和1例羊水细胞染色体样本进行诊断,并与G-显带诊断结果进行比较。结果所建立的光谱核型分析技术不但成功地对全部15例G-显带诊断结果为正常或平衡易位的样本进行了正确诊断,而且对G-显带无法识别的1例外周血样本的衍生染色体片段和1例羊水样本的标记染色体亦明确了来源。结论光谱核型分析技术对染色体异常的诊断具有很高的敏感性和特异性,并且在明确传统核型分析技术不能分析的标记染色体或衍生染色体片段的来源方面具有重要应用价值。     

Imaging the effective networks associated with cortical function through intracranial high‐frequency stimulation

Direct electrical stimulation (DES) is considered to be the gold standard for mapping cortical function. A careful mapping of the eloquent cortex is key to successful resective or ablative surgeries, with a minimal postoperative deficit, for treatment of drug‐resistant epilepsy. There is accumulating evidence suggesting that not only local, but also remote activations play an equally important role in evoking clinical effects. By introducing a new intracranial stimulation paradigm and signal analysis methodology allowing to disambiguate EEG responses from stimulation artifacts we highlight the spatial extent of the networks associated with clinical effects. Our study includes 26 patients that underwent stereoelectroencephalographic investigations for drug‐resistant epilepsy, having 337 depth electrodes with 4,351 contacts sampling most brain structures. The routine high‐frequency electrical stimulation protocol for eloquent cortex mapping was altered in a subtle way, by alternating the polarity of the biphasic pulses in a train, causing the splitting the spectral lines of the artifactual components, exposing the underlying tissue response. By performing a frequency‐domain analysis of the EEG responses during DES we were able to capture remote activations and highlight the effect''s network. By using standard intersubject averaging and a fine granularity HCP‐MMP parcellation, we were able to create local and distant connectivity maps for 614 stimulations evoking specific clinical effects. The clinical value of such maps is not only for a better understanding of the extent of the effects'' networks guiding the invasive exploration, but also for understanding the spatial patterns of seizure propagation given the timeline of the seizure semiology.     

CT灌注联合能谱成像评价射频消融治疗肺癌近期疗效

目的 探讨动态容积CT灌注联合能谱成像在射频消融(RFA)治疗肺癌近期疗效观察中的应用价值.方法 收集已经病理结果证实并拟行治疗的肺腺癌患者30例,术前1～2 d和术后30～40 d均行病灶部位灌注扫描,根据原始图像重建出能谱图像,并对比术前、术后灌注参数血流量(BF)、血容量(BV)、平均通过时间(MTT)、表面通透性(PS)及能谱参数碘(水)基值、水(碘)基值的变化,分析灌注参数及能谱参数对评价RFA治疗肺癌近期疗效的意义.结果 RFA后,全组患者的CT灌注参数及能谱参数值均值均下降,BF(t=7.34,P＜0.001)、BV (t=4.721,P＜0.001)、PS (t=2.224,P=0.034)、动脉期碘(水)基值(t=8.622,P＜0.001)、静脉期碘(水)基值(t=6.608,P＜0.001)及动脉期水(碘)基值(t=4.627,P＜0.001)术前、术后近期差异有统计学意义.RFA前后,缓解组的各参数变化差值均大于复发组,但只有BF(Z=-2.806,P=0.005)、动脉期碘(水)基值(Z=-2.806,P=0.005)及静脉期碘(水)基值(Z=-4.208,P=0.014)变化差值有统计学意义.结论 CT灌注联合能谱成像是一种评价RFA治疗肺癌近期疗效的有效方法.     

多体素MRS在星形细胞瘤中的应用价值

目的探讨多体素MRS在不同级别星形细胞瘤术前诊断的应用价值。方法搜集22例病理证实的脑星形细胞瘤,分为高、低级别2组,行MR常规、增强扫描及MRS检查,比较Cho/Cr、NAA/Cr、Cho/NAA比值及Lac、Lip情况。结果高级别组表现为Cho明显增高,NAA及Cr明显降低,低级别组表现为Cho轻到中度不等增高和NAA不同程度的降低,高、低级别组间Cho/Cr、NAA/Cr以及Cho/NAA比值差别有意义。肿瘤周边水肿区与对侧正常脑组织间Cho/Cr、Cho/NAA比值差别有意义,NAA/Cr比值差别无统计学意义。高级别组中有11例出现Lac峰,7例出现Lip峰,低级别组中仅有2例出现Lac峰,无Lip峰出现。结论多体素H-MRS在术前全面评价星形细胞瘤不同级别间的鉴别诊断及确定肿瘤边界形态方面有重要的临床意义。     

SPIR扫描在诊断骨胳肌肉系统疾病中的应用

目的：探讨SPIR脂肪抑制技术在骨胳肌肉系统疾病MRI检查中的诊断价值。材料与方法：对36例骨、关节软组织疾病患者行T1W／SE、T2W／FSE及T2W／SPIR序列扫描，并对后两者进行比较。结果：各种病理性积液呈高信号；损伤性骨髓水肿呈高信号；骨折线呈低信号，如骨折断端出血则呈线状高信号；软组织肿瘤囊性部分呈高信号，实质部分呈中等强度信号；软组织炎症性病变为弥漫性高信号；骨病成骨性改变为低信号；骨髓病变为高信号或混杂等高信号；椎管内占位性病变及半月板损伤SPIR显示不清。结论：SPIR能提高正常组织与病变组织间的对比度，清晰地显示病变组织，作为T1W／SE、T2W／FSE序列的辅助检查，有助于提高骨胳肌肉系统疾病的诊断水平。     

宝石CT能谱成像在胃癌诊断中的初步应用研究

目的:探讨宝石CT能谱成像(gemstone spectral imaging,GSI)检查在胃癌术前分期中的价值。方法:经胃镜诊断的84例胃癌病人,采用GSI检查,对病灶及淋巴结进行能谱成像分析;其结果与术后病理检查作对照。结果:总数为84例的胃癌病人中,37例为管状腺癌,32例为印戒细胞癌;两者的动脉期病灶碘基值比率分别为(0.2252±0.1321),(0.2609±0.1025);门静脉期病灶碘基值比率分别为(0.4713±0.1498),(0.5630±0.1757),门静脉期的差异具有统计学意义(P=0.02)。腺癌的转移淋巴结和非转移淋巴结碘基值比率在动脉期有统计学差异;印戒细胞癌的转移淋巴结和非转移淋巴结在动脉期和门静脉期均有统计学差异。结论:GSI检查可以反映胃癌的不同病理类型,有助于鉴别转移淋巴结,从而提高胃癌术前的分期准确率。     

Optimal spatial field control for controlled release

Most distributed parameter control problems involve manipulation within the spatial domain. Such problems arise in a variety of applications including epidemiology, tissue engineering, and cancer treatment. This paper proposes an approach to solve a state‐constrained spatial field control problem that is motivated by a biomedical application. In particular, the considered manipulation over a spatial field is described by partial differential equations (PDEs) with spatial frequency constraints. The proposed optimization algorithm for tracking a reference spatial field combines three‐dimensional Fourier series, which are truncated to satisfy the spatial frequency constraints, with exploitation of structural characteristics of the PDEs. The computational efficiency and performance of the optimization algorithm are demonstrated in a numerical example. In the example, the spatial tracking error is shown to be almost entirely due to the limitation on the spatial frequency of the manipulated field. The numerical results suggest that the proposed optimal control approach has promise for controlling the release of macromolecules in tissue engineering applications.     

Fourier components of inhomogeneously broadened water resonances in breast: a new source of MRI contrast.

High spectral and spatial resolution (HiSS) MR data were acquired at 1.5 T using echo-planar spectroscopic imaging from patients with suspicious breast lesions. The water resonances in small voxels are inhomogenously broadened and often have distinct components. Images were calculated with intensity proportional to the Fourier components of the water resonance in each voxel at different offsets from the peak frequency. The results demonstrate that in breast the off-peak Fourier component images of water are qualitatively different from those derived from the peak height of the water resonance. These differences most likely reflect underlying anatomy or physiology. In conventional images, the superposition of the various Fourier components of the water signal may cause loss of detail. The synthesis of water Fourier component images from high spectral and spatial resolution data may provide a new form of contrast, and increase sensitivity to subvoxel physiology and anatomy.