From structural to functional imaging:the developments of clinical ophthalmology optical coherence tomography

Starting with introduction of basic concept of optical coherence tomography(OCT) techniques,this paper focuses on a detailed review of ophthalmic OCT instruments and their clinical applications. As one of the most important inventions of ophthalmology instruments,OCT has become a standard imaging tool for daily ophthalmic diagnosis. The imaging capability has been significantly improved during the past ~ 30 years. In this article,several representing systems which have made significant contributions to OCT developments will be reviewed in details. For each system,the system configuration will be discussed first,follow ed by a brief introduction of their clinical applications. The review concludes with discussions on potential directions of OCT developments and expectations for further improvements of OCT imaging capabilities.

Structural and functional alterations in the brains of patients with anisometropic and strabismic amblyopia:a systematic review of magnetic resonance imaging studies

Amblyopia is the most common cause of vision loss in children and can persist into adulthood in the absence of effective intervention.Previous clinical and neuroimaging studies have suggested that the neural mechanisms underlying strabismic amblyopia and anisometropic amblyopia may be different.Therefore,we performed a systematic review of magnetic resonance imaging studies investigating brain alterations in patients with these two subtypes of amblyopia;this study is registered with PROSPERO(registration ID:CRD42022349191).We searched three online databases(PubMed,EMBASE,and Web of Science) from inception to April 1,2022;39 studies with 633 patients(324patients with anisometropic amblyo pia and 309 patients with strabismic amblyopia) and 580 healthy controls met the inclusion criteria(e.g.,case-control designed,pee r-reviewed articles) and were included in this review.These studies highlighted that both strabismic amblyopia and anisometropic amblyopia patients showed reduced activation and distorted topological cortical activated maps in the striate and extrastriate co rtices during tas k-based functional magnetic resonance imaging with spatial-frequency stimulus and retinotopic representations,respectively;these may have arisen from abnormal visual experiences.Compensations for amblyopia that are reflected in enhanced spontaneous brain function have been reported in the early visual cortices in the resting state,as well as reduced functional connectivity in the dorsal pathway and structural connections in the ventral pathway in both anisometro pic amblyopia and strabismic amblyopia patients.The shared dysfunction of anisometro pic amblyopia and strabismic amblyopia patients,relative to controls,is also chara cterized by reduced spontaneous brain activity in the oculomotor co rtex,mainly involving the frontal and parietal eye fields and the cerebellu m;this may underlie the neural mechanisms of fixation instability and anomalous saccades in amblyopia.With regards to specific alterations of the two forms of amblyo pia,anisometropic amblyo pia patients suffer more microstructural impairments in the precortical pathway than strabismic amblyopia patients,as reflected by diffusion tensor imaging,and more significant dysfunction and structural loss in the ventral pathway.Strabismic amblyopia patients experience more attenuation of activation in the extrastriate co rtex than in the striate cortex when compared to anisometropic amblyopia patients.Finally,brain structural magnetic resonance imaging alterations tend to be lateralized in the adult anisometropic amblyopia patients,and the patterns of brain alterations are more limited in amblyopic adults than in childre n.In conclusion,magnetic resonance imaging studies provide important insights into the brain alterations underlying the pathophysiology of amblyopia and demonstrate common and specific alte rations in anisometropic amblyo pia and strabismic amblyopia patients;these alterations may improve our understanding of the neural mechanisms underlying amblyopia.

Epileptic brain network mechanisms and neuroimaging techniques for the brain network

Epilepsy can be defined as a dysfunction of the brain network,and each type of epilepsy involves different brain-network changes that are implicated diffe rently in the control and propagation of interictal or ictal discharges.Gaining more detailed information on brain network alterations can help us to further understand the mechanisms of epilepsy and pave the way for brain network-based precise therapeutic approaches in clinical practice.An increasing number of advanced neuroimaging techniques and electrophysiological techniques such as diffusion tensor imaging-based fiber tra ctography,diffusion kurtosis imaging-based fiber tractography,fiber ball imagingbased tra ctography,electroencephalography,functional magnetic resonance imaging,magnetoencephalography,positron emission tomography,molecular imaging,and functional ultrasound imaging have been extensively used to delineate epileptic networks.In this review,we summarize the relevant neuroimaging and neuroelectrophysiological techniques for assessing structural and functional brain networks in patients with epilepsy,and extensively analyze the imaging mechanisms,advantages,limitations,and clinical application ranges of each technique.A greater focus on emerging advanced technologies,new data analysis software,a combination of multiple techniques,and the construction of personalized virtual epilepsy models can provide a theoretical basis to better understand the brain network mechanisms of epilepsy and make surgical decisions.

Non-concomitant cortical structural and functional alterations in sensorimotor areas following incomplete spinal cord injury

Brain plasticity, including anatomical changes and functional reorganization, is the physiological basis of functional recovery after spinal cord injury（SCI）. The correlation between brain anatomical changes and functional reorganization after SCI is unclear. This study aimed to explore whether alterations of cortical structure and network function are concomitant in sensorimotor areas after incomplete SCI. Eighteen patients with incomplete SCI（mean age 40.94 ± 14.10 years old; male：female, 7：11） and 18 healthy subjects（37.33 ± 11.79 years old; male：female, 7：11） were studied by resting state functional magnetic resonance imaging. Gray matter volume（GMV） and functional connectivity were used to evaluate cortical structure and network function, respectively. There was no significant alteration of GMV in sensorimotor areas in patients with incomplete SCI compared with healthy subjects. Intra-hemispheric functional connectivity between left primary somatosensory cortex（BA1） and left primary motor cortex（BA4）, and left BA1 and left somatosensory association cortex（BA5） was decreased, as well as inter-hemispheric functional connectivity between left BA1 and right BA4, left BA1 and right BA5, and left BA4 and right BA5 in patients with SCI. Functional connectivity between both BA4 areas was also decreased. The decreased functional connectivity between the left BA1 and the right BA4 positively correlated with American Spinal Injury Association sensory score in SCI patients. The results indicate that alterations of cortical anatomical structure and network functional connectivity in sensorimotor areas were non-concomitant in patients with incomplete SCI, indicating the network functional changes in sensorimotor areas may not be dependent on anatomic structure. The strength of functional connectivity within sensorimotor areas could serve as a potential imaging biomarker for assessment and prediction of sensory function in patients with incomplete SCI. This trial was registered with the Chinese Clinical Trial Registry（registration number： Chi CTR-ROC-17013566）.

Recent progress in the molecular imaging of therapeutic monoclonal antibodies

Therapeutic monoclonal antibodies have become one of the central components of the healthcare system and continuous efforts are made to bring innovative antibody therapeutics to patients in need.It is equally critical to acquire sufficient knowledge of their molecular structure and biological functions to ensure the efficacy and safety by incorporating new detection approaches since new challenges like individual differences and resistance are presented.Conventional techniques for determining antibody disposition including plasma drug concentration measurements using LC-MS or ELISA,and tissue distribution using immunohistochemistry and immunofluorescence are now complemented with molecular imaging modalities like positron emission tomography and near-infrared fluorescence imaging to obtain more dynamic information,while methods for characterization of antibody’s interaction with the target antigen as well as visualization of its cellular and intercellular behavior are still under development.Recent progress in detecting therapeutic antibodies,in particular,the development of methods suitable for illustrating the molecular dynamics,is described here.

Application of modern neuroimaging technology in the diagnosis and study of Alzheimer’s disease

Neurological abnormalities identified via neuroimaging are common in patients with Alzheimer’s disease.However,it is not yet possible to easily detect these abnormalities using head computed tomography in the early stages of the disease.In this review,we evaluated the ways in which modern imaging techniques such as positron emission computed tomography,single photon emission tomography,magnetic resonance spectrum imaging,structural magnetic resonance imaging,magnetic resonance diffusion tensor imaging,magnetic resonance perfusion weighted imaging,magnetic resonance sensitive weighted imaging,and functional magnetic resonance imaging have revealed specific changes not only in brain structure,but also in brain function in Alzheimer’s disease patients.The reviewed literature indicated that decreased fluorodeoxyglucose metabolism in the temporal and parietal lobes of Alzheimer’s disease patients is frequently observed via positron emission computed tomography.Furthermore,patients with Alzheimer’s disease often show a decreased N-acetylaspartic acid/creatine ratio and an increased myoinositol/creatine ratio revealed via magnetic resonance imaging.Atrophy of the entorhinal cortex,hippocampus,and posterior cingulate gyrus can be detected early using structural magnetic resonance imaging.Magnetic resonance sensitive weighted imaging can show small bleeds and abnormal iron metabolism.Task-related functional magnetic resonance imaging can display brain function activity through cerebral blood oxygenation.Resting functional magnetic resonance imaging can display the functional connection between brain neural networks.These are helpful for the differential diagnosis and experimental study of Alzheimer’s disease,and are valuable for exploring the pathogenesis of Alzheimer’s disease.

Brain Mechanisms of College Students’ Social Adjustment: Evidence from Multimodal Magnetic Resonance Imaging (MRI)

This study investigated the neural basis of social adjustment using multimodal brain imaging and social-adjustment measurements to analyze functional and structural brain features during social adjustment in college students. The results showed that, regarding brain function, some dimensions of social adjustment were associated with the insula, and some regions of the frontal and occipital lobes. Self-adjustment and satisfaction required activation of the middle frontal gyrus, while career adjustment and academic adjustment required inhibition of the inferior frontal gyrus and lingual gyrus, respectively. Decreased metabolic activity of the lingual gyrus was beneficial for obtaining satisfaction. Regarding brain structure, the total score and some dimensions of social adaptation were associated with the gray matter of portions of the temporal and parietal lobes. The superior temporal gyrus was associated with the total social adjustment and satisfaction score, the middle temporal gyrus with campus-life adjustment and satisfaction, and the post central gyrus and the inferior parietal lobule with emotional adjustment. The changes in the gray matter volume of these brain regions to a certain extent reflected socially adaptive behaviors. The results suggest that social adaptability is associated with various brain regions dispersed among both hemispheres of the brain, and requires synergistic inter-actions between multiple brain regions and both brain hemispheres.

短周期密集台阵深部地壳结构探测研究进展

由于穿透能力强,天然地震接收函数成为壳幔结构探测中最为广泛使用的方法.随着人们对地球内部结构和动力学过程认识程度的提高,台间距相对较大的宽频带台阵已无法满足壳幔结构高分辨率探测的需求.短周期密集台阵采用频率较高的便携式数字地震仪,通过百米级台间距的密集观测,可在短时间内(1~2个月)获得大量地震数据.其优势主要表现在三个方面:(1)地壳内射线交叉覆盖好,有利于提高分辨率;(2)射线密集分布,通过相干叠加压制噪声,可实现高频接收函数的成像;(3)观测时间短,效率高.因此,短短几年内,短周期密集台阵已经成为地壳深部结构探测的常规手段之一.本文主要介绍短周期密集台阵深部地壳结构探测的由来,以及通过几个典型的探测实例,展示探测效果及其在不同构造域的应用.

基于功能影像学探讨百会治疗失眠的中枢机制

百会为治疗失眠的效穴,临床使用频率高。功能影像学,广义上包括多种成像技术,狭义主要指功能性磁共振成像(fMRI),数据分析方法分为功能分离和功能整合两类,试验设计方案包括任务态(Tb-fMRI)与静息态(Rs-fMRI),静息态因操作简便且能直观反映针刺持续和累积效应而被广泛应用。多项fMRI研究表明,失眠患者在视觉区、感觉运动区、情绪相关脑区等存在局部功能异常,针刺百会单穴或组穴可引起特定脑区如顶叶、额叶、颞叶等的改变,从而改善睡眠。针刺单穴百会主要集中在Rs-fMRI局部一致性(ReHo)、比率低频振幅(fALFF)研究,而针刺百会组穴研究从Rs-fMRI局部一致性(ReHo)、度中心度(DC)、种子连接(FC),以及Tb-fMRI比率低频振幅(fALFF)等方面展开,研究发现不同研究方法和穴位组合下的脑区激活改变存在差异,且针刺百会组穴所调控脑区多于单穴针刺,体现了百会对失眠、认知和情绪的调节作用以及腧穴间的协同作用。然而,针刺百会引起的中枢信号改变复杂,功能影像作为评估失眠的中枢指标虽有潜力,但仍需更规范、深入的研究。

Regional brain structural abnormality in ischemic stroke patients:a voxel-based morphometry study

Our previous study used regional homogeneity analysis and found that activity in some brain areas of patients with ischemic stroke changed significantly. In the current study, we examined structural changes in these brain regions by taking structural magnetic resonance imaging scans of 11 ischemic stroke patients and 15 healthy participants, and analyzing the data using voxel-based morphometry. Compared with healthy participants, patients exhibited higher gray matter density in the left inferior occipital gyrus and right anterior white matter tract. In contrast, gray matter density in the right cerebellum, left precentral gyrus, right middle frontal gyrus, and left middle temporal gyrus was less in ischemic stroke patients. The changes of gray matter density in the middle frontal gyrus were negatively associated with the clin- ical rating scales of the Fugl-Meyer Motor Assessment （r = -0.609, P = 0.047） and the left middle temporal gyrus was negatively correlated with the clinical rating scales of the nervous functional deficiency scale （r = -0.737, P = 0.010）. Our findings call objectively identify the functional abnormality in some brain regions of ischemic stroke patients.

Machine learning for detecting mesial temporal lobe epilepsy by structural and functional neuroimaging

Mesial temporal lobe epilepsy(mTLE),the most common type of focal epilepsy,is associated with functional and structural brain alterations.Machine learning(ML)techniques have been successfully used in discriminating mTLE from healthy controls.However,either functional or structural neuroimaging data are mostly used separately as input,and the opportunity to combine both has not been exploited yet.We conducted a multimodal ML study based on functional and structural neuroimaging measures.We enrolled 37 patients with left mTLE,37 patients with right mTLE,and 74 healthy controls and trained a support vector ML model to distinguish them by using each measure and the combinations of the measures.For each single measure,we obtained a mean accuracy of 74%and 69%for discriminating left mTLE and right mTLE from controls,respectively,and 64%when all patients were combined.We achieved an accuracy of 78%by integrating functional data and 79%by integrating structural data for left mTLE,and the highest accuracy of 84%was obtained when all functional and structural measures were combined.These findings suggest that combining multimodal measures within a single model is a promising direction for improving the classification of individual patients with mTLE.

多模态影像技术在儿童症状性癫痫中的应用进展

儿童是癫痫的好发人群,由于其中枢神经系统处于发育阶段,所以病因更加复杂、表现形式更加多样,早期诊断和及时、有效处理能减少儿童中枢神经损伤,最大程度地保护患儿的脑功能。根据有无明显抽搐可将癫痫分为惊厥性和非惊厥性,而非惊厥性因无明显临床症状,诊断相对比较困难,容易导致误诊而延误治疗,明确诊断需要依靠脑电图(癫痫样或节律性放电)。随着影像检查手段的不断发展,明确癫痫病因、定位癫痫病灶的方式更加多样化,定位更加准确,同时功能成像检查方式也使得早期评估癫痫的脑功能变化成为可能。本文就近年来症状性儿童癫痫的MRI及其与正电子发射计算机断层显像(positron emission tomography,PET)融合应用的研究进展及临床应用进行综述,旨在为今后的相关研究提供参考和借鉴。

改进YOLOv4的遥感图像目标检测算法

为有效解决遥感图像目标检测算法在复杂背景下的检测效果不佳的问题,提出一种改进YOLOv4的目标检测算法。设计一种跨阶段残差结构,替换原主干网络的简单残差结构,降低模型参数量和计算负担;引入CBAM注意力机制,加强CSP模块间有效特征交互;使用跨阶段分层卷积模块重构特征融合阶段对深层特征图的处理方式,防止网络退化和梯度消失;采用Mish激活函数,增强融合网络对非线性特征的提取能力。在RSOD、DIOR数据集上的实验结果表明,改进YOLOv4算法的测试mAP相比原YOLOv4算法分别高出4.5%、7.3%,其检测速度分别达到48 fps、45 fps,在保证实时性的同时检测精度有较大提升。

糖尿病周围神经病变多模态MRI研究进展

糖尿病周围神经病变(diabetes peripheral neuropathy,DPN)是较常见的糖尿病慢性并发症,严重影响患者生活质量。DPN发病机制比较复杂,目前研究表明与神经病理性改变关系密切。近些年多模态MRI获得长足进展,MRI以软组织分辨率高、无创、无辐射等优点著称,成为探索DPN中枢神经及周围神经发病机制的重要方法。本文应用基于体素的形态学测量(voxel-based morphometry,VBM)、弥散张量成像(diffusion tensor imaging,DTI)、功能MRI(functional MRI,fMRI)等技术,对研究DPN脑结构、脑功能改变以及周围神经结构异常的文献进行综述,为临床早期诊断和制订精准治疗方案提供依据。

基于结构功能交叉神经网络的多模态医学图像融合

针对多模态医学图像融合中存在纹理细节模糊和对比度低的问题,提出了一种结构功能交叉神经网络的多模态医学图像融合方法。首先,根据医学图像的结构信息和功能信息设计了结构功能交叉神经网络模型,不仅有效地提取解剖学和功能学医学图像的结构信息和功能信息,而且能够实现这两种信息之间的交互,从而很好地提取医学图像的纹理细节信息。其次,利用交叉网络通道和空间特征变化构造了一种新的注意力机制,通过不断调整结构信息和功能信息权重来融合图像,提高了融合图像的对比度和轮廓信息。最后,设计了一个从融合图像到源图像的分解过程,由于分解图像的质量直接取决于融合结果,因此分解过程可以使融合图像包含更多的细节信息。通过与近年来提出的7种高水平方法相比,本文方法的AG,EN,SF,MI,QAB/F和CC客观评价指标分别平均提高了22.87%,19.64%,23.02%,12.70%,6.79%,30.35%,说明本文方法能够获得纹理细节更清晰、对比度更好的融合结果,在主观视觉和客观指标上都优于其他对比算法。

多层特征融合与语义增强的盲图像质量评价

针对现有盲图像质量评价算法在面对真实失真图像时性能较差的问题,本文提出多层特征融合和语义信息增强相结合的无参考图像质量评价算法。提取图像的局部和全局失真特征,利用特征融合模块对特征进行多层融合;利用多层扩张卷积增强语义信息,进而指导失真图像到质量分数的映射过程;考虑预测分数和主观分数之间的相对排名关系,对L_(1)损失函数和三元组排名损失函数进行融合,构建新的损失函数L_(mix)。为了验证本文方法的有效性,在野生图像质量挑战数据集上进行了验证和对比实验,该算法的斯皮尔曼等级相关系数与皮尔逊线性相关系数指标相比原算法分别提升2.3%和2.3%;在康斯坦茨真实图像质量数据数据集和野生图像质量挑战数据集上进行了跨数据集实验,该算法在面对真实失真图像时表现出了良好的泛化性能。

基于中心对称特征耦合仿射度量模型的图像匹配方法

针对当下较多图像匹配算法利用距离度量法来实现特征匹配,没考虑图像仿射变换的影响,使得匹配结果准确率不高的问题,提出了中心对称特征耦合仿射度量模型的图像匹配算法。首先,引入Forstner算子,利用像素点的GS梯度特征提取特征点;然后,利用图像的Haar小波信息与中心对称像素点的灰度值,求取特征向量;接着,利用特征点之间的旋转、平移以及缩放的仿射特征,构造仿射度量模型,利用其计算出匹配的特征点对;最后,采用结构相似度(SSIM)函数,计算匹配点对的结构相似性,对匹配点对去伪求真,以求取最优匹配效果。实验结果表明,与当下匹配方法相比,所提算法不仅能更准确地实现图像匹配,而且还能够更好地适应具有仿射变换关系图像之间的匹配。

基于rtfMRI-NF技术调控失眠障碍患者杏仁核活性对大脑度中心性的影响

目的 探讨实时功能磁共振成像神经反馈(real-time functional magnetic resonance imaging neurofeedback, rtfMRI-NF调控失眠障碍(insomnia disorder, ID)患者杏仁核活性对大脑度中心性(degree centrality, DC)的影响。材料与方法 本研究采用rtfMRI-NF调控34例ID患者杏仁核活性,结合临床多导睡眠监测(Polysomography, PSG)、匹兹堡睡眠质量指数(Pittsburgh Sleep Quality Index, PSQI)等量表对患者进行干预前后评估。使用配对t检验分析干预前后功能成像数据的DC值差异,并探讨调控前后DC值变化及其与临床量表等数据的相关性。结果 经rtfMRI-NF调控后,ID患者的PSQI、失眠严重程度指数(Insomnia Severity Index Scale, ISI)等量表评分均显著降低(P均<0.05)。此外,右侧海马旁回的DC值显著增高(GRF校正,体素水平P<0.001,团块水平P<0.05),并与睡眠效率差值呈负相关r=-0.478,P<0.05);而右侧背外侧额上回等区域的DC值降低(GRF校正,体素水平P<0.001,团块水平P<0.05),并与干预后ISI评分呈正相关(r=0.488,P<0.05)。结论 rtfMRI-NF技术可重塑ID患者特定脑区的DC值,并有效提高ID患者的睡眠质量。

磁共振成像影像导航及靶区选择在经颅磁刺激治疗中的应用

背景:在经颅磁刺激临床实际应用中,是否能准确瞄准刺激脑区可影响经颅磁刺激的实际治疗效果。近年来,随着神经导航系统、移动式增强现实技术的发展,以及多种不同模态磁共振成像数据分析方法的出现,刺激靶区定位的准确性和靶区选择的优化有望得到进一步的提高。目的:综述基于磁共振成像的影像导航定位原理及在经颅磁刺激中的应用,归纳不同模态磁共振成像数据分析在指导经颅磁刺激靶区选择上的作用。方法:应用计算机在PubMed、中国知网和万方数据库检索相关文献,以“transcranial magnetic stimulation,coil positioning,neuronavigation,augmented reality,magnetic resonance imaging,经颅磁刺激,线圈定位,神经导航,增强现实,核磁共振成像,原理”为主要检索词,最终纳入63篇文献进行分析。结果与结论:①传统经颅磁刺激线圈放置方法中,“5 cm规则”、国际脑电10-20定位法最为常用,这些方法具有简便、经济的优点,但过于依赖操作者的经验,存在不同操作者的技术差异。②基于立体定向技术发展而来的神经导航系统是目前可视化程度及准确度最高的辅助经颅磁刺激线圈放置的引导方式,它通过MRI数据采集、脑三维重建、头模配准及立体几何定位等步骤来实现可视化定位,具有较高的临床治疗及科研应用价值,但因其设备较为昂贵,目前在医疗机构中尚未普及。③对于不同层次的医疗单位,移动式移动式增强现实技术不失为一种经济、高效的神经导航系统替代方案,它通过磁共振成像数据采集、构建二维/三维图像、虚拟图像与真实脑图像叠加来实现头皮下脑组织可视化定位,具有直观性强、成本低廉的优势,可在基层医疗单位推广应用。④尽管相对脑电10-20定位策略,可视化定位的临床疗效优越性目前尚未充分体现,但随着研究者对人脑多种不同模态磁共振成像扫描数据的挖掘,有望进一步优化经颅磁刺激治疗靶区选择的策略,提高经颅磁刺激治疗应答率和个性化程度,这在将来是极具潜力和挑战的研究方向。

脑震荡后综合征的磁共振成像研究进展

脑震荡后综合征(postconcussional syndrome,PCS)是脑外伤后最常见的慢性后遗症。PCS的损伤机制涉及多种神经病理生理过程,目前尚不明确。越来越多的磁共振成像技术,例如,扩散张量成像(diffusion tensor imaging,DTI)、灌注加权成像(perfusion weighted imaging,PWI)、氢质子磁共振波谱成像(hydrogen proton magnetic resonance spectroscopy,1H-MRS)等被用于探究PCS从急性期到慢性期的神经病理生理变化与临床症状的关系。本文根据患者受伤的不同时期及其疾病进展进行纳入,对多种高级MRI手段在PCS中的应用进行综述,从不同角度了解其潜在神经病理机制,更好地服务于疾病的诊疗及预后。