基于改进SUSAN算法的医学图像边缘检测

背景:医学图像的边缘检测是医学图像处理中的一项重要的技术,也是医学图像进一步处理的基础。目的:运用改进的SUSAN算法对医学图像进行边缘检测,取得更丰富的医学图像边缘信息,以便于医学图像的进一步处理。方法:运用Sobel算子对SUSAN算法进行了改进,采用C++语言编程,并在VC++6.0开发平台上实现了改进算法。结果与结论:实验结果表明,该算法能实现阈值的自适应选取,对医学图像中的低对比度的图像边缘有较好的检测效果。     

骨科X线图像的边缘检测

目的 利用计算机图像处理技术进行骨科x线图像的边缘检测。方法 对X线图像进行数字化和滤波后，使用常规的边缘检测算子对图像进行处理，结合不同算子的原理进行结果分析，然后在对比实验中使用基于数学形态学的边缘检测方法。结果 各种边缘检测算子获得不同的结果，经对比讨论后，可见使用数学形态学方法的结果较好。结论 基于数学形态学的方法适用于骨科X线图像的处理。     

基于目标区域小波CT图像压缩算法

目的:在以往对二维X射线影像进行基于SPIHT的区域压缩编码算法研究的基础上,探讨基于目标区域小波SPIHT算法对三维CT图像的压缩方法。方法:利用目标区域的SPIHT小波算法压缩CT图像。通过灰度门限法分割目标和背景,检测并膨胀边缘以确定目标区域。对体数据分块,并进行快速小波变换。利用SPIHT算法对小波系数重要性进行判断、排序和分类形成多层位流结构。排序过程首先对小波系数建立空间树结构,然后沿空间方向树对系数进行重要性测试,分类过程对重要系数从高位到低位分成不同分辨率的位平面依次输出。结果:基于优化分割的SPIHT算法对CT目标区域压缩好于JPEG2000及JPEG算法,对CT图像目标区域以1bpp的高码率进行小波SPIHT压缩,背景以0.15bpp低码率JPEG压缩压缩,全图平均压缩码率为0.5bpp,目标区域的PSNR为43.2dB,目标区域PSNR比JPEG2000区域压缩算法提高0.8dB。结论:对于CT图像,基于目标区域的SPIHT小波压缩算法优于JPEG2000、JPEG和传统的SPIHT算法,并能在高压缩比情况下保证医学图像的质量。     

基于小波变换的医学图像融合技术

医学图像融合作为信息融合技术的一个重要领域，在90年代受到学术界的广泛重视。现代医学影像成像系统的应用，为临床诊断提供了不同模态的图像，它们可提供的医学信息各有其特点，如CT骨窗图像骨骼成像非常清晰，分辨率极高，可为病灶的定位起到良好的参照，MRI图像分辨率不及CT，但软组织成像清晰，可用于病灶范围的确定，PET图像提供了人体的功能信息，但图像模糊，分辨率低。如果我们能够把这些信息综合显示，就能够为临床诊断提供更加充分的信息。     

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.     

基于小波变换的医学超声图像去噪及增强方法

目的探求一种基于小波变换的医学超声图像去噪及增强方法。方法提出了一种基于小波分析理论的医学超声图像噪声的综合抑制方法,首先对医学超声图像进行对数变换,将乘性噪声变成加性噪声;然后进行多尺度小波变换,将图像分解成一系列不同尺度上的小波系数,对变换后不同尺度的高频子图像进行非线性小波软阈值处理,阈值处理后的高频子图像进行增强;最后,经小波逆变换和指数变换恢复去噪后图像。结果原图像中斑纹噪声被有效去除,图像边缘细节得以保留。结论该方法可有效保留细节信号,极大限度地去除斑纹噪声。     

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。     

血管内皮生长因子与放射性视网膜病变新生血管的形成

目的:放射性视网膜病变作为头、颈部肿瘤放射治疗的一种眼部并发症,国内外的报道不多,其发病机制尚未完全明确,因此归纳总结放射性视网膜病变的发病机制以为临床治疗提供依据。资料来源:应用计算机检索Pubmed数据库1990-01/2006-06期间有关放射性视网膜病变的文章,检索词“VEGF,Radiation Retinopathy,New Blood Vessels”,限定文章语言种类为English。同时计算机检索中国期刊全文数据库1990-01/2006-06期间的相关文章,检索词“血管内皮生长因子,放射性视网膜病变,新生血管生成”,限定文章语言种类为中文。资料选择:对资料进行初审,取符合研究要求的有关文章找全文。资料提炼:共收集到60篇有关血管内皮生长因子及放射性视网膜病变的文章,其中45篇为血管内皮生长因子在各系统器官中的作用,涉及糖尿病视网膜病变,放射性视网膜病变等方面;其中15篇为放射性视网膜病变文章,涉及病例个案报道,临床观察等方面。资料综合:①放射性视网膜病变眼底视网膜新生血管形成是其特点性病变。血管内皮生长因子近年来被确定为对新生血管性疾病发展过程有重要影响的细胞因子。②血管内皮生长因子可诱导视网膜下新生血管的形成。缺氧启动了血管新生的过程。③发病机制考虑为放射线诱导的DNA损伤使内皮细胞在有丝分裂过程中死亡,当正常分裂的细胞数量难以补偿丢失的细胞时,血管内皮连续性破坏,功能障碍。结论:目前放射性视网膜病变的发病机制仍有争议,但眼底新生血管出现是其重要的临床表现。血管内皮生长因子的表达高低与新生血管形成有关。     

视网膜血管直径与2型糖尿病视网膜病变的关系

目的探讨视网膜微血管直径与2型糖尿病（DM2）并发症糖尿病视网膜病变（DR）的关系。方法选取2009年1月11月住院确诊DM2患者200例,根据眼底彩色照相结果将患者分为DR组和NDR组,测量视网膜血管直径、测定生化指标及血压,用非条件Logistic回归分析糖尿病视网膜病变发生的危险因素。结果 V1扩张10μm时,DM2患者并发DR危险性增加（OR1.75,95%CI1.14～3.04,P〈0.05）;空腹血糖水平增加1mmol/L,DM2患者并发DR的危险性增加（OR1.87,95%CI1.43～2.81,P〈0.05）;糖化血红蛋白增加1个单位,DM2患者并发DR的危险性增加（OR1.08,95%CI1.02～1.13,P〈0.05）;DM病程增加1年,DM2患者并发DR的危险性增加（OR1.41,95%CI1.18～1.70,P〈0.05）。结论在DM2患者中,视网膜静脉直径大小、空腹血糖水平、糖化血红蛋白水平、糖尿病病程是DR发生的危险因素。     

重组人血管内皮抑素对视网膜新生血管的抑制作用

目的探讨重组人血管内皮抑素（恩度）对高氧诱导的小鼠视网膜病变模型中新生血管的抑制作用。方法将60只C57BL／6J小鼠随机分为正常对照组、高氧对照组、生理盐水对照组与恩度干预组,每组15只。除正常对照组外。其余各组均建立视网膜病变模型。正常对照组与高氧对照组小鼠不做处理,生理盐水对照组于第12天给予腹腔注射0．1mL生理盐水,恩度干预组于第12天给予腹腔注射恩度0．1mL（17．5μg）,连续注射5d,鼠龄17d时,视网膜组织切片行HE染色计数突破内界膜的新生血管内皮细胞核数目;采用免疫组织化学染色法检测视网膜中血管内皮生长因子表达情况。结果高氧对照组和生理盐水对照组突破内界膜的新生血管内皮细胞核数目及血管内皮生长冈子表达阳性率明显高于正常对照组及恩度干预组（P〈0．01）,恩度干预组高于正常对照组（P〈0．05）。结论恩度可抑制小鼠模型中视网膜新生血管形成,有可能成为防治血管增生性视网膜病变的一种方法。     

基于Mallat金字塔算法的小波的局部图像重建

本文利用Mallat金字塔算法对Shepp-Logan图进行局部重建,利用小波所具有的多尺度特性和良好的局部特性,能够仅用局部投影数据重建出感兴趣的局部区域,由此不仅降低了X射线的辐射剂量,而且缩短了成像时间.     

Automated edge detection versus manual edge measurement in analysis of brachial artery reactivity: a comparison study

High resolution ultrasound, combined with computer imaging technology, is commonly used to measure changes in brachial artery diameter for the determination of endothelial-dependent vasodilation (EDD) and endothelial independent-vasodilation (EID). Currently, two methods of computerized edge-detection systems are in use to measure changes in artery diameter. One system involves the sonographer manually tracking the artery walls while the second system involves a computer automated edge-detection system that automatically tracks the artery wall. The purpose of this study was to compare the two types of computerized edge-detection systems for measuring vascular function and structure. One hundred fifty (female = 70, male = 80) participants agreed to participate. Baseline brachial diameter, carotid intima-medial thickness (cIMT), EDD and EID were measured by the two computerized edge-detection systems utilizing the same ultrasound B-mode image. Mean values (+/-standard error) for baseline diameter, cIMT, EDD and EID were 3.53 (+/-0.10) mm, 0.43 (+/-0.01) mm, 5.72 (+/-0.20)% and 22.17 (+/-0.60)%, respectively for the manual edge-detection software system. Mean values for baseline diameter, cIMT, EDD and EID were 3.59 (+/-0.10) mm, 0.44 (+/-0.01) mm, 7.33 (+/-0.30)% and 25.77 (+/-0.60)%, respectively for the automated edge-detection software system. Bland-Altman plots displayed large variations between the two edge-detection methods for assessing cIMT and changes in artery diameter following brachial EDD and EID. The results of the study demonstrate that manual and automated computerized edge-detection systems track dynamic changes in brachial artery diameter and cIMT measures differently. Therefore, caution should be used when comparing research utilizing different computerized edge-detection systems for measuring vascular function and structure. (E-mail: will0188@umn.edu).     

Improved measurement of LINE-1 sequence methylation for cancer detection

BackgroundMethylation of long interspersed nuclear element-1 (LINE-1) sequences varies among normal cells and it is often decreased in cancer genomes and white blood cells (WBC) of cancer patients. Current measurement techniques of genome-wide level are inadequate because LINE-1 methylation is distinctive at each locus. Here, we improved the detection of cancer by combining information of LINE-1 methylation pattern and level.MethodsCombined bisulfite restriction analysis (COBRA) of LINE-1, COBRA LINE-1, was used to test cancer cell lines, two oral rinse cohorts, and WBC from normal and cancer patients. COBRA LINE-1 separated LINE-1 sequences into 4 products depending on the methylation statuses of 2 CpG dinucleotides, as follows: 2 unmethylated CpGs (^uC^uC), partial methylation (^mC^uC), 1 methylated CpG (^mC), and 1 unmethylated CpG (^uC).ResultsThe association between ^mC^uC and ^uC^uC was directly correlated in normal cells (r = 0.4895, p = 0.0009) but inversely correlated in cancer (r = ? 0.8979, p = 0.0002). Oral rinse AUC values of ^uC^uC were 0.763 and 0.926 and methylation levels were 0.707 and 0.621, respectively. ^uC^uC, but not overall methylation level, differentiated cancer WBC from normal (p = 0.0082 and p = 0.4830, respectively).ConclusionLINE-1 partial methylation represents hypomethylation in normal cells but hypermethylation in cancer cells. This information improves LINE-1 methylation detection in cancer.     

Label free measurement of retinal blood cell flux,velocity, hematocrit and capillary width in the living mouse eye

Measuring blood cell dynamics within the capillaries of the living eye provides crucial information regarding the health of the microvascular network. To date, the study of single blood cell movement in this network has been obscured by optical aberrations, hindered by weak optical contrast, and often required injection of exogenous fluorescent dyes to perform measurements. Here we present a new strategy to non-invasively image single blood cells in the living mouse eye without contrast agents. Eye aberrations were corrected with an adaptive optics camera coupled with a fast, 15 kHz scanned beam orthogonal to a capillary of interest. Blood cells were imaged as they flowed past a near infrared imaging beam to which the eye is relatively insensitive. Optical contrast of cells was optimized using differential scatter of blood cells in the split-detector imaging configuration. Combined, these strategies provide label-free, non-invasive imaging of blood cells in the retina as they travel in single file in capillaries, enabling determination of cell flux, morphology, class, velocity, and rheology at the single cell level.OCIS codes: (170.4460) Ophthalmic optics and devices, (330.4300) Vision system - noninvasive assessment, (110.1080) Active or adaptive optics, (330.7324) Visual optics, comparative animal models     

Sonographic measurement of lateral ventricular width in early ventricular dilation

Cerebral real-time ultrasound examinations from 35 high-risk premature newborn infants and 25 normal-term infants were reviewed for early signs of ventricular dilation. Measurements of the midbody lateral wall of the lateral ventricle to falx distance and ratio of this distance to the hemispheric width were obtained. Midbody lateral ventricular widths were also measured. Results indicate that displacement of the medial wall of the body of the lateral ventricle toward the midline is an earlier sign of ventricular dilation than is displacement of the lateral wall away from the midline.     

Automated measurement of mandibular cortical width on dental panoramic radiographs

Purpose   Mandibular cortical width (MCW) measured on dental panoramic radiographs (DPRs) was significantly correlated with bone mineral density. We developed a computer-aided diagnosis scheme that automatically measures MCW to assist dentists in describing a possible osteoporotic risk and suggesting further examinations. Methods   In our approach, potential mandible edges are detected by modified Canny edge detector. On the basis of the edge information, a contour model is selected from the reference data and is fitted to the test case by using the active contour model. The reference mental foramina positions of the model are employed as the MCW measurement locations. The MCW is measured on the basis of the grayscale profiles obtained along the lines perpendicular to the fitted mandible contour. One hundred DPRs, including 26 DPRs from osteoporotic cases, were used to evaluate our proposed scheme. Results   Experimental results showed that the average MCWs for osteoporotic and control cases were 2.2 and 3.9 mm, respectively. When a threshold of 2.7 mm was applied, the sensitivity and specificity for identifying osteoporotic patients were 88.5 and 97.3 %, respectively. Conclusion   An automated MCW measurement technique is feasible using DPRs, and this method has a potential to identify asymptomatic osteoporotic patients.     

胎儿外耳正常超声测值

目的 探讨胎儿外耳正常超声测值.方法 随机选取孕龄17～41周的孕妇632名、1052只胎耳进行超声显像,测量其长、宽径,计算不同孕周胎耳长、宽及长×宽的均数、标准差、95%双侧可信区间.结果 17～38周的超声测值既满足t分布条件又满足U分布条件,39～41周只满足t分布条件.结论 本研究初步建立了胎儿外耳正常超声测值,为诊断胎儿耳异常提供了参考标准.     

Improved segmentation of low-contrast lesions using sigmoid edge model

Purpose

The intensity profile of an image in the vicinity of a tissue’s boundary is modeled by a step/ramp function. However, this assumption does not hold in cases of low-contrast images, heterogeneous tissue textures, and where partial volume effect exists. We propose a hybrid algorithm for segmentation of CT/MR tumors in low-contrast, noisy images having heterogeneous/homogeneous or hyper-/hypo-intense abnormalities. We also model a smoothed noisy intensity profile by a sigmoid function and employ it to find the true location of boundary more accurately.

Methods

A novel combination of the SVM, watershed, and scattered data approximation algorithms is employed to initially segment a tumor. Small and large abnormalities are treated distinctly. Next, the proposed sigmoid edge model is fitted to the normal profile of the border. The estimated parameters of the model are then utilized to find true boundary of a tissue.

Results

We extensively evaluated our method using synthetic images (contaminated with varying levels of noise) and clinical CT/MR data. Clinical images included 57 CT/MR volumes consisting of small/large tumors, very low-/high-contrast images, liver/brain tumors, and hyper-/hypo-intense abnormalities. We achieved a Dice measure of \(0.83\,(\pm 0.07)\) and average symmetric surface distance of \(2.56\,(\pm 6.31)\) mm. Regarding IBSR dataset, we fulfilled Jaccard index of \(0.85\,(\pm 0.07)\). The average run-time of our code was \(154\,(\pm 71)\) s.

Conclusion

Individual treatment of small and large tumors and boundary correction using the proposed sigmoid edge model can be used to develop a robust tumor segmentation algorithm which deals with any types of tumors.

     

Non-invasive detection of acute renal allograft rejection by measurement of vascular endothelial growth factor in urine

Urinary vascular endothelial growth factor (VEGF) was determined by enzyme-linked immunosorbent assay in 199 renal allograft recipients and 80 healthy controls. Urinary VEGF level did not change significantly during the first 8 weeks after transplantation in 119 patients with stable renal function and there were no abnormal histological findings (No-AR). In 67 patients with acute rejection, urinary VEGF was significantly higher (28.57 +/- 6.21 pg/micromol creatinine) than in the No-AR patients (3.05 +/- 0.45 pg/micromol creatinine) and healthy controls (2.87 +/- 0.35 pg/micromol creatinine). At a cut-off point of 3.26 pg/micromol creatinine, sensitivity and specificity for diagnosis of acute rejection were 86.6 and 71.4%, respectively. The 13 patients with subclinical rejection excreted urinary VEGF (16.14 +/- 4.09 pg/micromol creatinine) at a significantly higher level than No-AR patients (3.05 +/- 0.45 pg/micromol creatinine). At a cut-off point of 4.69 pg/micromol creatinine, sensitivity and specificity for diagnosis of subclinical rejection were 84.6 and 79.8%, respectively. In conclusion, monitoring VEGF in urine might offer a new non-invasive way to detect acute and subclinical rejection in renal transplant recipients.