使用二维小波收缩法去除弹性成像蠕虫噪声

本文研究使用二维小波收缩去噪法去除弹性成像过程中产生的蠕虫噪声。先使用Sym8小波函数对含有蠕虫噪声的应变估计值矩阵进行3级二维离散小波分解,并使用Birg-éMassart算法获取二维小波变换的域值;然后分别使用硬域值函数和软域值函数对各尺度的水平方向、垂直方向、对角方向的高频系数进行量化;最后将第3层低频系数和各层被量化后的高频系数进行二维小波重构产生去噪后的弹性图像。仿真结果显示,提出的技术有效去除了弹性成像的蠕虫噪声,增强了弹性图像的信噪比(SNRe)和对比度噪声比(CNRe),提高了弹性图像与理想弹性图的相关系数(е);与二维低通滤波去噪法相比,使用二维小波收缩法产生的弹性图像有更高的SNRe和CNRe,能更清晰地显示硬物边界。同时,仿真结果也表明该技术对不同应变量的弹性图像的蠕虫噪声均能有效抑制。本研究表明二维小波收缩去噪法能有效去除弹性图像的蠕虫噪声并提高弹性图像性能。     

数字图像增强中灰度变换方法在乳腺X线片中的应用

图像增强技术作为一种基本的图像处理技术,其目的是对原始图像进行加工,得到视觉效果更好更有用的图像.乳腺X线片是当今早期诊断乳腺癌的有效手段,但由于人体肉眼分辨能力有限以及人为疏忽等原因,其中有很大一部分诊断信息没有被人们所利用,因此对乳腺X线片进行增强处理很重要.本文在讨论包括线性变换、非线性变换和直方图均衡化三种用于图像增强灰度变换方法基础上,利用MATLAB编程实现相关算法,将其用于乳腺X线片的处理.结果表明,以上三种灰度变换方法均提高了图像的对比度,改善了图像的显示效果.上述三种灰度变换方法应用于临床,均将有利于医生进行微钙化点检测和疾病诊断.     

金属对金属人工髋关节的磨损预测

目的发展复杂动态载荷与瞬态运动条件下的球面共型接触硬对硬人工髋关节的磨损预测模型,并用于典型的金属对金属人工髋关节在复杂三维生理运动条件下的磨损预测研究。方法建立有限元模型用于接触力学问题求解,采用固定-跟踪法(fixed-tracked method)完成具有三维欧拉运动的人工髋关节双侧界面动态磨损几何再现及相应的接触与磨损问题模拟的数值交换。结果磨损预测表明,磨损导致金属对金属人工髋关节接触界面几何由球面向非球面过渡,接触区域随磨损周期而增大,接触压力变化趋于平缓、最大接触压力逐渐减小。结论本研究所发展的三维复杂动态、具有双侧界面几何磨损变化的人工髋关节磨损预测模型,能够很好地进行金属对金属髋关节磨损数值预测模拟实验,为认识人工髋关节磨损机理提供了新的方法。     

A machine learning approach for distinguishing age of infants using auditory evoked potentials

Objective

To develop a high performance machine learning (ML) approach for predicting the age and consequently the state of brain development of infants, based on their event related potentials (ERPs) in response to an auditory stimulus.

Methods

The ERP responses of twenty-nine 6-month-olds, nineteen 12-month-olds and 10 adults to an auditory stimulus were derived from electroencephalogram (EEG) recordings. The most relevant wavelet coefficients corresponding to the first- and second-order moment sequences of the ERP signals were then identified using a feature selection scheme that made no a priori assumptions about the features of interest. These features are then fed into a classifier for determination of age group.

Results

We verified that ERP data could yield features that discriminate the age group of individual subjects with high reliability. A low dimensional representation of the selected feature vectors show significant clustering behavior corresponding to the subject age group. The performance of the proposed age group prediction scheme was evaluated using the leave-one-out cross validation method and found to exceed 90% accuracy.

Conclusions

This study indicates that ERP responses to an acoustic stimulus can be used to predict the age and consequently the state of brain development of infants.

Significance

This study is of fundamental scientific significance in demonstrating that a machine classification algorithm with no a priori assumptions can classify ERP responses according to age and with further work, potentially provide useful clues in the understanding of the development of the human brain. A potential clinical use for the proposed methodology is the identification of developmental delay: an abnormal condition may be suspected if the age estimated by the proposed technique is significantly less than the chronological age of the subject.     

A new sulcus-corrected approach for assessing cerebellar volume in spinocerebellar ataxia

Precise volumetry of the cerebellum still remains challenging, due to thin sulci and gyri. We present a new fast and reliable sulcus-corrected approach for quantitative assessment of cerebellar atrophy, evaluated on patients with spinocerebellar ataxia (SCA). Thin-sliced T1-weighted magnetic resonance images (MPRAGE) were acquired in 11 genetically confirmed SCA6 patients and in a group of age-matched control subjects (n = 14). Post-processing involves a morphological image segmentation pipeline as a basis for a sulcus-corrected cerebellar volume measurement. Cerebellar volumes and intra-rater, inter-rater and scan-rescan reproducibility were quantified. Reliability of the measurements was validated using an anatomical preparation of the cerebellum. Repeatability coefficients (RC: intra-rater/inter-rater/scan-rescan) of the method were 1.07%/1.11%/1.35%. Absolute cerebellar volumes showed good agreement with the actual volume of the anatomical preparation. The cerebellar volume of the SCA 6 was 96.3 ± 12.1 ml (mean ± S.D.), which was significantly lower than the results of the corresponding control groups. The cerebellar volume correlated significantly to clinical dysfunction in SCA6. This is the first study to demonstrate the feasibility of a new sulcus-corrected approach to assess cerebellar volume. In contrast to currently used methods, this new approach may be more sensitive even to small atrophic changes affecting sulcal widening.     

Genome‐wide transcriptome analyses reveal p53 inactivation mediated loss of miR‐34a expression in malignant peripheral nerve sheath tumours

Malignant peripheral nerve sheath tumours (MPNSTs) are aggressive soft tissue tumours that occur either sporadically or in patients with neurofibromatosis type 1. The malignant transformation of the benign neurofibroma to MPNST is incompletely understood at the molecular level. We have determined the gene expression signature for benign and malignant PNSTs and found that the major trend in malignant transformation from neurofibroma to MPNST consists of the loss of expression of a large number of genes, rather than widespread increase in gene expression. Relatively few genes are expressed at higher levels in MPNSTs and these include genes involved in cell proliferation and genes implicated in tumour metastasis. In addition, a gene expression signature indicating p53 inactivation is seen in the majority of MPNSTs. Subsequent microRNA profiling of benign and malignant PNSTs indicated a relative down‐regulation of miR‐34a in most MPNSTs compared to neurofibromas. In vitro studies using the cell lines MPNST‐14 (NF1 mutant) and MPNST‐724 (from a non‐NF1 individual) show that exogenous expression of p53 or miR‐34a promotes apoptotic cell death. In addition, exogenous expression of p53 in MPNST cells induces miR‐34a and other miRNAs. Our data show that p53 inactivation and subsequent loss of expression of miR‐34a may significantly contribute to the MPNST development. Collectively, our findings suggest that deregulation of miRNAs has a potential role in the malignant transformation process in peripheral nerve sheath tumours. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Chromophobe renal cell carcinoma with liposarcomatous dedifferentiation - report of a unique case

Sarcomatous transformation of chromophobe renal cell carcinoma (CRCC) is a well recognized phenomenon. Of the published cases with sarcomatous transformation of CRCC, none have shown liposarcomatous differentiation. Out of a cohort of 250 cases of CRCC, 19 (7.6%) showed sarcomatous differentiation. In one case (female, age 46 years), the sarcomatous component of the tumor displayed histological features of a pleomorphic liposar-coma. Light microscopic examination revealed a biphasic pattern with a chromophobe renal cell carcinoma(CRCC) and a high-grade sarcomatous component containing large pleomorphic lipoblasts. In several areas both components were intermingled. The conventional CRCC component showed classic histological features with calcifications, medium-sized polygonal cells arranged in solid-alveolar structures with raisinoid nuclei, pale-eosinophilic flocculent cytoplasm with perinuclear haloes. In addition, a microcystic-adenomatous component had luminal spaces filled with erythrocytes. The CRCC was positive with Hale''s colloidal iron-stain whereas the sarcomatous component was negative. The CRCC component was diffusely positive for cytokeratin 7, parvalbumin and racemase but negative for cy-tokeratin 20, vimentin, CD10, carboanhydrase IX and S100-protein. The pleomorphic liposarcomatous component displayed immunereactivity for CD10, vimentin, racemase and focally for carboanhydrase IX. The proliferative activity (Mib-1/Ki-67) was 5% in the CRCC and 30% in the pleomorphic liposarcomatous component. No immunereactivity for MDM2 or CDK4 was detected.This is the first reported case of a sarcomatoid CRCC where the sarcomatous component displayed features of a pleomorphic liposarcoma. The patient died from widespread metastatic disease 12 months after nephrectomy.     

Clear cell adenocarcinoma of the vagina in a patient with vaginal endometriosis

BACKGROUND: Malignant transformation of endometriosis is an infrequent complication of endometriosis. Extragonadal disease is uncommon. CASE: 55-year-old female presented with postmenopausal bleeding. Physical examination revealed a 2-cm polypoid lesion at the posterior vaginal apex, which was found to be a moderately differentiated invasive adenocarcinoma. Final pathology at the time of definitive surgery demonstrated a clear cell adenocarcinoma of the vagina arising in vaginal endometriosis. CONCLUSION: Vaginal endometriosis may lead to the development of cancer. Malignancy arising in endometriotic foci is rare, but most commonly occurs in the ovary. We report a case of clear cell malignancy arising in vaginal endometriosis, adding to only seven cases previously reported. Risk factors include unopposed estrogen and obesity, but it may occur in the absence of either.     

Detection of gastric dysrhythmia using WT and ANN in diabetic gastroparesis patients

Gastric myoelectrical activity can be measured by a noninvasive technique called electrogastrography where surface electrodes are placed on the epigastric area of the abdomen. The electrogastrogram (EGG) signal is by nature a nonstationary signal in terms of its frequency, amplitude and wave shape. Unlike the other methods discrete wavelet analysis (DWT) was designed for nonstationary signals. For automatic assessment of EGG, we used artificial neural networks (ANNs) that have been widely employed in pattern recognition due to their great potential of high performance, flexibility, robust fault tolerance, cost-effective functionality and capability for real-time applications. So we developed a new method for classification of EGG based on DWT and ANN.