比较二维小波和二维小波包技术在不同压缩模式下的降噪处理

背景：小波和小波包技术是进行时频信号分析的重要方法。医学图像数字化采集后断层多，数据信息量大，易受噪声影响。采用二维小波技术和小波包技术可以实现肝癌图像的完美压缩和降噪。 目的：比较二维小波和二维小波包技术在不同压缩模式下压缩肝癌图像的优劣以及小波降噪的技巧。 方法：选用同一幅动脉期肝癌图像，进行4 层分解，利用二维小波和二维小波包技术分别进行Balance sparsity-norm、Remove near0和Bal.sparsity-norm(sqrt)三种模式的压缩处理，再利用小波函数对含噪声信号的图像进行降噪处理。 结果与结论：对于同一种压缩模式，二维小波包技术压缩肝癌图像优于二维小波技术，3种压缩模式中Bal.sparsity-norm(sqrt)模式和Remove near0 mode模式压缩比例更小，图像清晰度更好；小波降噪能很好地消除噪声信号。提示利用二维小波技术和小波包技术都可以实现肝癌图像的完美压缩和降噪。     

MRI图像的小波融合处理★

背景：小波图像融合是将两幅图像融合在一起，以获取对同一场景的更为精确、全面、可靠的图像描述。 目的：用小波变换图像融合技术融合MRI脑梗死图像，以恢复缺损图像。 方法：图像融合的主要机制是利用二维小波分析法对MRI脑梗死图像进行小波分解，并对高低频信号采用多种融合方式进行融合。通过对比不同融合方式后的效果图，找出最适合本部位MRI图像的融合方法。 结果与结论：不同方式的融合技术能成功修复不同的缺损部位，多种融合方式的合适组合能完全修复多处缺失部位。对于文中给出的MRI脑梗死图像，采用最小值融合方式的融合效果最好。提示使用二维小波分析法处理医学图像，简便快捷，能有效改善图像的视觉效果，辅助临床诊断。     

小波先验在OSL重建算法中的应用***★

背景：MAP(最大后验)统计重建方法可以在重建过程中引入合适的先验知识达到去除噪声的目的。 目的：根据小波系数的统计特性及能量平衡的原理对高频信息做相应的处理，并将多尺度的小波先验应用到OSL重建算法中以去除噪声。 方法：实验从“变换域”的思想出发，在小波域上根据小波系数的统计特性及能量平衡原理对不同尺度的高频信息做相应的处理，并利用处理后的小波系数进行小波重建。 结果与结论：基于小波先验的OSL算法比ML-EM算法重建的图像与测试模型的误差变小、相关性变大、噪声变少，重建图像变得比较平滑，视觉效果较清楚。     

轮廓波及曲波和小波变换用于显微图像消噪的比较*****☆

背景：小波变换只能反映信号的零维奇异性，无法最优表示图像中的线奇异；而且小波变换只存在3个方向，这些都显著影响了它在图像处理领域的应用效果。针对小波变换的缺点，多尺度几何分析理论正在逐步发展，轮廓波变换和曲波变换就是其中的典型代表。 目的：定性、定量地比较轮廓波、曲波和小波变换在图像消噪处理中的效果。 方法：在简要介绍3种变换基本原理的基础上，比较它们在图像消噪领域的应用，以均方误差和峰值信噪比作为定量指标评价消噪效果，并将其应用于显微镜图像的消噪处理。 结果与结论：综合定量评价指标和人眼视觉感受，曲波变换的消噪结果最佳，轮廓波变换效果次之，小波变换效果则不够理想。     

医学图像的零树小波编码

背景：医学数字图像必须是高质量的、高分辨率,所以数据量很大,如此巨大的数据量不利于图像存档与传输系统的运行和数字化医院、远程医疗的实现。因此,图像压缩成为图像存档与传输系统要解决的重要问题。 目的：分析零树小波变编码算法原理并编程实现对医学数字图像的压缩,使之能够满足医学图像的传输和诊断要求。 方法：应用嵌入式零树小波编码算法,探讨小波基和小波变换层数的选择,编程实现对医学数字图像的压缩。 结果与结论：选择双正交小波基对医学图像进行4层小波变换实现压缩,获得了较高的峰值信噪比,取得了较好的压缩效果。 关键词：小波变换;图像压缩;嵌入式零树小波;医学数字图像;数字化医学     

基于B-样条双正交小波R波的标定和QRS波检测

实现心电信号QRS波检测的算法很多，文章给出了一种基于B-样条双正交小波对心电信号R波峰值标定和QRS波波段检测的方法。利用双正交样条小波等效滤波器，对心电信号按Mallat算法进行快速变换；从信号奇异点的李氏指数与模极大值关系的角度，分析心电信号奇异点（R峰值点）与其小波变换模极大值对的零交叉点的关系。用二次B-样条小波滤波器组对心电数字信号进行4个尺度的小波分解，然后根据分解的尺度波形特性求出正负极值对过零点，即R波峰值，并检测出QRS波段。采用Matlab编程实现该算法。从实验结果可以得出，该算法对心电信号中QRS波群的特征提取和几种常见的心电干扰具有较强的鲁棒性，经MIT-BIH标准心律失常数据库验证，QRS波的正确检测率达99.9%。文中给出了程序流程图。     

基于数学形态学人脑MR图像感兴趣区域的提取**★◆

背景：在人脑MRI图像中感兴趣区域提取中，应用数学形态学方法取得了较好的效果，但是在抗噪性能和结构元素选取时存在一些不足之处，使得提取效果有缺陷。 目的：在数学形态学的基础上，采用一系列改进的数学形态学方法，以期清晰完整地提取人脑MR图像中的感兴趣区域如脑脊液部位，为医学诊断提供准确信息。 方法：首先采用复合形态学滤波去除脉冲和高斯噪声，用高低帽变换进行图像增强，然后用形态分水岭阈值分割提取脑部各成分，对分割出的脑脊液图像进行形态开闭滤波、边缘跟踪和灰度填充后，运用抗噪型边缘检测算子检测出清晰完整的脑脊液区域边缘，最后在原图像中用彩色标定，突出感兴趣区域。 结果与结论：综合应用多种数学形态学算法，清晰完整地提取了人脑MRI图像中的感兴趣区域——脑脊液部位。经验证，该方法具有简单、快速、精度高、适用性强等特点。 关键词：图像分割；边缘检测；人脑图像；数学形态学；感兴趣区域；提取     

基于灰度对比和自适应小波变换的X射线图像增强

背景：X射线检查作为常规的检查方式得到了广泛的应用,然而由于现有技术的局限性,使得X射线图像往往具有灰度对比度低和噪声影响等缺点,因此,现有的X射线图像往往达不到医生的要求。 目的：增强和去噪处理对比度较低且含有噪声的X射线图像,以达到易于医生理解和识别的目的。 方法：针对空间域处理和变换域处理增强X射线图像的不足,提出了基于灰度对比和自适应小波变换的X射线图像增强算法。首先,选择需要增强和减弱的灰度范围,并根据八邻域灰度对比增强算法对X射线图像进行灰度变换,并用中值滤波算法对图像进行平滑;然后,对X射线图像进行小波分解,并运用相邻分解层之间相关系数的大小来确定细节信号和噪声。 结果与结论：应用了灰度对比和自适应小波变换相结合的X射线图像增强算法,把基于空间域增强的方法和基于变换域的方法有机地结合起来,比传统的单一增强方法更为优越。实验结果证明它能自适应地增强X射线图像的灰度对比,使得图像细节的显示更加清晰,同时在一定程度上去除了噪声的干扰,对于灰度对比度较低的图像效果更加明显。     

基于小波变换和高斯差分的冷冻电镜生物大分子图像自动分割

冷冻电镜生物大分子图像分割是进行冷冻电镜生物大分子颗粒识别的基础。本文分析了冷冻电镜生物大分子图像的主要特点,提出了基于小波变换和高斯差分（DoG）的冷冻电镜生物大分子图像自动分割方法。该方法利用小波变换得到原图像的低分辨率图像,抑制了噪声,提高了图像的对比度;同时采用DoG算子解决了图像亮度不均匀的问题,并对DoG图像采用基于灰度梯度信息融合的分割方法。实验结果表明该算法能有效的减少噪音对边缘提取的影响,分割效果良好,是一种全新的冷冻电镜生物大分子图像自动分割算法。     

基于交互式数据语言MRI图像直方图增强方法的比较*★

目的：比较不同直方图增强方法对改善MRI图像质量的作用效果。 方法：基于交互式数据语言编程环境，分别采用直方图均衡化、自适应直方图均衡化和直方图规定化对颈髓MRI T2W图像进行增强处理，利用峰值信号噪声比和图像信息熵评价图像暗区细节的表现性能以及图像噪声水平。 结果：直方图均衡化对图像暗区细节的增强效果一般，图像整体对比度反而有所下降；自适应直方图均衡化增强细节的同时放大了图像噪声，并在边缘形成伪影；直方图规定化可选择匹配直方图函数的类型，充分显示图像暗区细节，图像噪声水平低于前两种方法。 结论：应用直方图增强方法处理颈髓MRI T2加权图像，在图像暗区细节表现和图像低噪声水平上，直方图规定化明显优于直方图均衡化和自适应直方图均衡化。     

Hepatic Considerations in the Use of Antiepileptic Drugs

Summary: Virtually all of the major antiepileptic drugs (AEDs) can cause hepatotoxicity, although fatal hepatic reactions are rare. The mechanisms, incidences, and risk profiles for such reactions differ from drug to drug. With carbamazepine and phenytoin, hepatotoxicity may be due to drug hypersensitivity. Although the profiles of patients at risk have not been well-defined for these two antiepileptic drugs, it would appear from reports in the literature that older adolescents and adults are at higher risk than children of developing serious or fatal hepatotoxicity. Once hepatotoxicity develops, mortality rates are 10–38% with phenytoin and 25% for carbamazepine. The risk profile for valproate fatal hepatotoxicity has been more clearly defined. Those at primary risk of fatal hepatic dysfunction are children under the age of 2 years who are receiving multiple anticonvulsants and also have significant medical problems in addition to severe epilepsy. The risk is considerably lower for patients over the age of 2 years on valproate monotherapy. In contrast to the risk profile with other AEDs, adults receiving valproate as monotherapy have the lowest risk of hepatotoxicity. Fatal hepatic dysfunction coincident with valproate may be the result of aberrant drug metabolism. Concomitant use of AEDs that induce microsomal P450 enzymes (e.g., phenytoin and phenobarbital) may enhance the production of a toxic metabolite, and hence the greater risk of hepatotoxicity with polypharmacy.     

Vascular Malformations and Epilepsy: Clinical Considerations and Basic Mechanisms

Summary: Vascular malformations (VMs) are associated with epilepsy. The natural history of the various VMs, clinical presentation, and tendency to provoke epilepsy determine treatment strategies. Investigations have probed the mechanisms of epileptogenesis associated with these lesions. Electrophysiologic changes are associated with epileptogenic cortex adjacent to VMs. Putative pathophysiologic mechanisms of epileptogenesis include neuronal cell loss, glial proliferation and abnormal glial physiology, altered neurotransmitter levels, free radical formation, and aberrant second messenger physiology.     

Diagnostic Difficulties and Treatment Implications

Summary: Differentiation between types of epileptic seizures has been aided in recent years by the introduction of intensive neurodiagnostic techniques and the development of increasingly detailed classification systems. Paradoxically, these developments have not simplified the task of matching the appropriate antiepileptic drug to a particular seizure type. It is reasonable to assume that anticonvulsant drugs will have different effects on different types of seizures, but faulty, circular reasoning can enter the picture if one also assumes that responses of seizures to different drugs signify different seizure types. There are several examples of differential diagnoses that can fall prey to this problem, including the diagnosis between partial seizures with secondary generalization and generalized tonic-clonic seizures, and the diagnosis between complex partial seizures and absence seizures with automatisms, among others. Considerations of etiology in future classification systems can further complicate the problem: should one then choose an anticonvulsant drug on the basis of individual seizure type or on the basis of the type of epilepsy? Ramifications of this issue extend even to the drug approval process. Official sanction is not given for use of a drug for a seizure type not included in the original efficacy studies, even if later scientific evidence shows that seizure type to be related to a type that is included. New trials must be undertaken. These problems arise from how we choose to classify seizures.     

Cognitive Dysfunction Associated with Antiepileptic Drug Therapy

Summary: Epilepsy is frequently associated with cognitive dysfunction. However, the reasons for this correlation are unclear. Possible influential factors include patient age; duration, frequency, etiology, and type of seizures; hereditary factors; psychosocial issues; and antiepileptic drug (AED) therapy. Whereas many of these factors are beyond the physician's control, AED therapy is one element that can be addressed in treatment decisions by recognizing the potential cognitive effects of particular AEDs. For example, phenobarbital impairs memory and concentration; phenytoin affects attention, problem solving ability, and performance of visuomotor tasks. In contrast, carbamazepine may affect concentration, while valproate would appear to have minimal effects on cognition. Moreover, cognitive effects of AEDs are amplified with coadministration of multiple anticonvulsants (polytherapy). A review of studies on the cognitive effects of monotherapy with AEDs, as opposed to those of polytherapy, provides evidence that drug-related cognitive dysfunction can be reversed if patients are switched to a simpler therapeutic regimen. Future research should be directed toward developing reliable measures for assessing and monitoring cognition, and understanding the particular cognitive side effects of each AED. Physicians also need to revise their opinions about which side effects are "tolerable" for epileptic patients.     

Epilepsy and anomalies of neuronal migration: MRI and clinical aspects

Neuronal migration disorders are the result of disturbed brain development. In such disorders, neurons are abnormally located. In diagnosing these conditions, magnetic resonance imaging is superior to any other imaging technique. This enables us to improve our knowledge of the clinical correlates of neuronal migration. With reference to migrational disorder, a retrospective study of all 303 patients with epileptic seizures referred for magnetic resonance imaging during a 3-year period was performed, 13 patients (aged 12-41, mean age 27) were identified. They represent 4.3% of the entire study group. Of the patients with known epilepsy, 6.7% and of the mentally retarded, 13.7% had migrational disorders. Four patients had schizencephaly as the dominant finding, one was classified as hemimegalencephaly, 2 had isolated heterotopias, and 6 had localized pachy- and/or poly-microgyria. The clinical pictures are complex. Ectopias of grey matter are recognised foci of epilepsy, but from an epileptological and a clinical viewpoint little attention has been given to these disorders. The present study shows that malmigration is not rare in epilepsy patients, especially not in the mentally retarded.     

Carbamazepine Efficacy and Utilization in Children

Summary: Carbamazepine is effective for preventing partial and generalized tonic-clonic seizures in children. Although absence epilepsies are more common in children than adults, an estimated 80% of children with epilepsy have seizure types or epilepsies that are potentially responsive to carbamazepine. The differential diagnosis of ictal staring is an especially important issue in children because absence and atypical absence seizures are more prevalent in children than adults. Age-related pharmacokinetic differences and drug interactions are major considerations in children. On average, children have higher clearance rates of carbamazepine, shorter half-lives, and higher ratios of carbamazepine-10, 11-epoxide to carbamazepine than adults. In addition, children with severe epilepsy are more likely to require multiple-drug therapy, which can lead to complex drug interactions. When carbamazepine is administered along with valproate, drug protein binding interactions can cause intermittent side effects.     

Carbamazepine Efficacy in Adults With Partial and Generalized Tonic-Clonic Seizures

Summary: Carbamazepine and phenytoin are drugs of choice in initial monotherapy for adult partial and secondarily generalized tonic-clonic seizures. These designations reflect the results of the Veterans Administration Epilepsy Cooperative Study Group of 1985. An earlier comparative study of carbamazepine and phenytoin by Ramsay and associates found both drugs equally effective in controlling new-onset seizures. Among the advantages of carbamazepine is that it causes relatively few cognitive and dysmorphic side effects. Its disadvantages are its unavailability in parenteral formulation and its metabolic autoinduction. The latter must be compensated for by planned dosage increases to maintain therapeutic plasma steady-state levels during the first 2 or 3 months of treatment. Carbamazepine is judged a drug of choice in the treatment of these secondarily generalized tonic-clonic seizures, and the drug of choice in children, adolescents, and women susceptible to the dysmorphic side effects associated with other anticonvulsant agents.     

Etiologic and Preventive Aspects of Epilepsy in the Child–Bridging the Gap Between Laboratory and Clinic

Summary: Four broad categories of basic phenomena are pertinent to developing ways to prevent epilepsy. These include mechanisms of epileptogenesis, ictal initiation and temporary entrainment by the seizure discharge of normally functioning brain, seizure propagation, and control mechanisms that function both to restrain the cascade of epileptic events culminating in a seizure and to arrest the epileptic event and restore the interictal state. In newborns and children, hypoxia-ischemia is a major factor leading to epileptogenesis, and several schemes are proposed to classify, quantify, and prevent hypoxic-ischemic encephalopathy. Control mechanisms must be better understood in order to develop prophylactic recommendations for epilepsy, and an experimental model of "kindling antagonism" may increase our understanding of these. Programs of prevention of seizures in children will evolve only if basic researchers and clinicians work productively together to develop an adequate understanding of factors important in epileptogenesis and antiepileptogenic control mechanisms.     

Predisposing and Causative Factors in Childhood Epilepsy

Summary: We review information from large studies of defined populations, examining the role of known factors and especially of prenatal and perinatal factors in contributing to nonfebrile seizure disorders of early childhood. We depend especially, but not exclusively, on the recently completed analyses from the Collaborative Perinatal Project of the National Institute of Neurological and Communicative Disorders and Stroke, the NCPP. About 4% of children in the NCPP who had at least one non-febrile nonsymptomatic seizure by the age of 7 years had a previous seizure during acute neurologic illness, such as meningitis or during the acute illness after trauma. Many such seizures should potentially be preventable. Of children with seizures, 10% had had a neonatal seizure and 13% had had a febrile seizure. Among the hundreds of prenatal and perinatal factors explored as predictors of childhood seizure disorders, the principal predictors identified were congenital malformations of the fetus, cerebral and noncerebral; family history of certain neurologic disorders; and neonatal seizures. In agreement with the British National Child Development Study, labor and delivery factors in the NCPP appeared to contribute very little to childhood seizure disorders. Maldevelopment, rather than damage at birth to an initially intact nervous system, appeared to be the more common mechanism. Most seizure disorders of early childhood remained unexplained by the large set of prenatal and perinatal characteristics examined.     

Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES.