Computer-aided lesion diagnosis in automated 3-D breast ultrasound using coronal spiculation

A computer-aided diagnosis (CAD) system for the classification of lesions as malignant or benign in automated 3-D breast ultrasound (ABUS) images, is presented. Lesions are automatically segmented when a seed point is provided, using dynamic programming in combination with a spiral scanning technique. A novel aspect of ABUS imaging is the presence of spiculation patterns in coronal planes perpendicular to the transducer. Spiculation patterns are characteristic for malignant lesions. Therefore, we compute spiculation features and combine them with features related to echotexture, echogenicity, shape, posterior acoustic behavior and margins. Classification experiments were performed using a support vector machine classifier and evaluation was done with leave-one-patient-out cross-validation. Receiver operator characteristic (ROC) analysis was used to determine performance of the system on a dataset of 201 lesions. We found that spiculation was among the most discriminative features. Using all features, the area under the ROC curve (A(z)) was 0.93, which was significantly higher than the performance without spiculation features (A(z)=0.90, p=0.02). On a subset of 88 cases, classification performance of CAD (A(z)=0.90) was comparable to the average performance of 10 readers (A(z)=0.87).     

Observer efficiency in discrimination tasks simulating malignant and benign breast lesions imaged with ultrasound

We investigate and extend the ideal observer methodology developed by Smith and Wagner to detection and discrimination tasks related to breast sonography. We provide a numerical approach for evaluating the ideal observer acting on radio frequency (RF) frame data, which involves inversion of large nonstationary covariance matrices, and we describe a power-series approach to computing this inverse. Considering a truncated power series suggests that the RF data be Wiener-filtered before forming the final envelope image. We have compared human performance for Wiener-filtered and conventional B-mode envelope images using psychophysical studies for 5 tasks related to breast cancer classification. We find significant improvements in visual detection and discrimination efficiency in four of these five tasks. We also use the Smith-Wagner approach to distinguish between human and processing inefficiencies, and find that generally the principle limitation comes from the information lost in computing the final envelope image.     

Segmentation of skin lesions in 2-D and 3-D ultrasound images using a spatially coherent generalized Rayleigh mixture model

This paper addresses the problem of jointly estimating the statistical distribution and segmenting lesions in multiple-tissue high-frequency skin ultrasound images. The distribution of multiple-tissue images is modeled as a spatially coherent finite mixture of heavy-tailed Rayleigh distributions. Spatial coherence inherent to biological tissues is modeled by enforcing local dependence between the mixture components. An original Bayesian algorithm combined with a Markov chain Monte Carlo method is then proposed to jointly estimate the mixture parameters and a label-vector associating each voxel to a tissue. More precisely, a hybrid Metropolis-within-Gibbs sampler is used to draw samples that are asymptotically distributed according to the posterior distribution of the Bayesian model. The Bayesian estimators of the model parameters are then computed from the generated samples. Simulation results are conducted on synthetic data to illustrate the performance of the proposed estimation strategy. The method is then successfully applied to the segmentation of in vivo skin tumors in high-frequency 2-D and 3-D ultrasound images.     

Perspective on biomedical quantitative ultrasound imaging

This paper discusses the recent advances in the highly multidisciplinary field of quantitative ultrasound (QUS) imaging. QUS relies heavily on signal processing techniques to extract information about underlying tissue microstructure. As such, modern signal processing strategies will prove to be critical in further improving and refining QUS techniques.     

基于DWT-IRLS算法的超声断层成像方法研究

超声成像因非侵入式、成本低且实时性好而被广泛应用。超声系统需要大量的采集通道数据和较高的采样率来提高图像重建质量,导致成像耗时,系统复杂。压缩感知(compressed sensing, CS)算法能够在欠采样的条件下用较少的测量值重构出原始信号。因此,针对系统面临的采样率高,数据量大的问题,本文将CS理论中的DWT-IRLS算法应用在超声成像中,通过离散小波变换基(discrete wavelet transformation, DWT)对超声数据进行稀疏转换,对高低频系数进行采样测量,并使用迭代重加权最小二乘法(iterative reweighted least squares, IRLS)进行测量系数重构,最后对变换域系数进行DWT逆转换得到重建图像。通过实验分析,以50%原始数据重建图像效果逐渐趋于稳定,在均方误差和峰值信噪比方面进行对比分析,DWT-IRLS算法相比较于DWT-OMP、DWT-CoSamp和DCT-IRLS等重构算法,成像质量更高,细节特征更为明显。     

Next-gen ultrasound

Almost invariably, a new baby's photo album begins with a grainy black-and-white picture taken months before birth- a prenatal ultrasound image, which is often detailed enough to inspire comments about the child's resemblance to various members of the family. But jokes about balding uncles notwithstanding, such scans serve a serious purpose and can prove immensely important, as when they allow doctors to diagnose and sometimes even repair a congenital malformation while the baby is still in the womb.     

车轮轮辋应力超声波测量法的研究

通过利用标准测量设备和超声横波直探头两种测试方法,验证了超声双折射法在轮辋应力测量中的可行性。为车轮轮辋应力检测提供了一种新的高效无损的检测手段,对于列车安全运行状态的判断具有重要意义。     

基于混合阶偏微分方程的超声图像降噪

针对偏微分方程在医学超声图像处理中的斑点噪声滤除问题,在全变分去噪模型和四阶LLT降噪模型的基础上,提出一种针对医学超声图像的混合阶变分降噪方法。该方法引入二阶全变分和四阶偏微分的混合阶偏微分方程作为正则项,并利用斑点噪声分布构建保真项。用标准测试数据和真实数据对所提混合阶变分降噪模型进行验证,试验结果表明,该模型在有效滤除超声图像斑点噪声的同时,能较好地保护图像的边缘和纹理细节信息。处理后的图像在峰值信噪比PSNR、均方误差MSE、运行效率方面均优于全变分和LLT模型。     

基于超声波测距的倒车雷达系统设计

介绍了以单片机为核心的倒车雷达系统,它利用超声波实现无接触测距.系统主要包括超声波发射接触以及温度测量电路,突出点是利用数字传感器DS18B20对温度进行测量,并利用声速与温度之间的校正公式对声速进行校正,提高了渡越时间的测量精度,进而提高了测量距离的准确度.适合测量的距离在5m以下,可以满足倒车安全的要求.     

离焦量对激光超声测厚的影响

为了研究离焦量对激光超声信号幅值的影响,采用相同能量的脉冲激光辐照不同厚度的铝质试块进行了工件测厚的实验。光路会聚采用焦距100mm的平凸球面聚焦透镜,将该透镜固定于5维光学调整架上,调节水平轴旋钮以改变离焦量;利用中心频率5MHz的压电探头接收激光超声波信号,并记录所有试块在每个离焦量下的超声信号数据;依据信号之间的时间间隔,求出每个铝质试块的厚度。结果表明,测厚结果与工件实际厚度之间的相对误差均在3%范围内;在等量激光脉冲激励下,当工件表面处于离焦量-10mm时,获得信号的幅值最大。     

基于光纤激光传感器的双频超声测量

提出一种基于分布布拉格反射式(DBR)光纤激光传感器用于液体环境中的双频超声测量系统。选用3MHz和7MHz的双频超声信号,通过改变调频指数,获得了四种不同情况下DBR光纤激光器的频谱输出,与理论分析相一致。结果证明,DBR光纤激光传感器可以用来检测双频超声信号。     

Programmable ultrasound imaging using multimedia technologies: anext-generation ultrasound machine

High computational and throughput requirements in modern ultrasound machines have restricted their internal design to algorithm-specific hardware with limited programmability. The authors have architected a programmable ultrasound processing system, Programmable Ultrasound Image Processor (PUIP), to facilitate engineering and clinical ultrasound innovations. Multiple high-performance multimedia processors were used to provide a computing power of 4 billion operations per second. Flexibility was achieved by making the system programmable and multimodal, e.g., B-mode, color flow, cine and Doppler data can be processed. They have successfully designed and implemented the PUIP to fit within an ultrasound machine. It provides a platform for rapid testing of new concepts in ultrasound processing and enables software upgrades for future technologies. Current and future clinical applications include extended fields of view, quantitative measurements, three-dimensional ultrasound reconstruction and visualization, adaptive persistence, speckle reduction, edge enhancement, image segmentation, and motion analysis. The PUIP is a significant step in the evolution of ultrasound machines toward more flexible and generalized systems bridging the gap between many innovative ideas and their clinical use in ultrasound machines     

基于特征值分解的时间反转超声成像技术

由于声波衍射的关系,超声成像系统的检测效果会受到检测深度、传播介质等因素的影响,难以取得理想的高分辨率成像结果。文中基于时间反转声学理论,将基于时间反转矩阵特征值分解的成像算法引入超声成像技术中。在该算法中,每一个非零的特征值均对应一个散射体,通过对时间反转矩阵进行特征值分解得到包含检散射体相位信息的特征向量,将得到的时间反转信号反向发射从而实现对不同散射体的成像。仿真实验结果表明,该算法对于一定深度的缺陷具有更好的检测效果,且缺陷的横向分辨率明显优于一般超声成像算法,这一结果有益于提升超声系统区分多个近距离目标的能力。     

维纳斯激光在皮肤色素性疾病和血管性疾病中的应用

目的：探皮肤色素性疾病和血管性疾病的治疗方法和方案。方法：皮肤色素性疾病142例（太田痣58例,雀斑84例）和血管性疾病58例（面部毛细血管扩张和蜘蛛痣40例,鲜红斑痣18例）在局部麻醉软膏（5％EMLA,瑞典产）麻醉下用波长为1064毫米,755毫米和可变脉宽波长为532毫米的激光分别对其进行治疗。结果：色素性疾病治疗中疗效最好为雀斑,其欠为太田痣需四次左右;血管性疾病治疗中疗效最好为毛细血管扩张和蜘蛛痣,其次为鲜红斑痣,需五次以上。结论：维纳斯多波长激光解决了以往任何激光都无法解决的难题,疗效好,值得推广。     

基于超声图像的自适应谱聚类方法研究

为精确提取超声肿瘤图像的肿瘤区域,基于分裂合并思想,结合自协调谱聚类方法,提出一种基于超声图像的自适应谱聚类方法。该方法在分裂阶段用SLIC算法将图像分割成超像素,根据肿瘤区域和背景区域的纹理特征差异选取合适的纹理特征,在合并阶段用自协调谱聚类算法自动确定谱聚类数目,聚出肿瘤区域,并用先验知识提取分割结果中的肿瘤区域。将该算法提取的肿瘤区域和人工分割的肿瘤区域比较,准确度达到93. 41%,结果比较准确。     

Nonparametric estimation of ultrasound pulses

An algorithm for nonparametric estimation of 1D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori knowledge about the structure of RF line echo data and can employ a number of adjacent RF lines from an image. The prime application of the algorithm is to yield a pulse suitable for deconvolution algorithms. This will enable these algorithms to properly take into account the frequency dependence of the attenuation and its variation within a patient and among patients. It is also possible to use the estimated pulse for attenuation estimation, and the consistency of the assumptions underlying the proposed technique is demonstrated by its ability to recover low variance attenuation estimates in the normal liver from in vivo pulse-echo data. Estimates are given for 8 different patients     

基于色度比特性的显示器色度特性化

为了对显示器进行色度特性化,探讨了显示器颜色控制值RGB与其CIE系统X、Y、Z颜色三刺激值之间的对应关系.根据显示器通道色光的光谱比例不变性,确定了每个通道的色度比常数,由此将红、绿、蓝通道的数字量R、G、B分别与其色光的Xr、Yg、Zb(称为主颜色刺激值)相关联,再将复色光的颜色刺激CIE XYZ与各通道的主刺激Xr、Yg、Zb建立联系.在一个LCD和一个CRT显示器上的应用结果表明,对729个检验颜色分别得到了4.74和1.48的CIELAB色差,表明该方法具有较高的显示器色度颜色转换精度.     

基于衍射横波的裂纹激光超声检测方法

为了评估表面开口裂纹, 采用激光超声衍射横波的方法测量其参量。激光激励的横波传播至裂纹尖端产生衍射信号, 随后被处于裂纹另一侧的传感器所接收。依据不同接收点衍射横波的渡越时间, 推导出裂纹参量的计算公式; 模拟分析了横波在工件中的传播过程, 搭建了裂纹的激光超声测量实验系统, 并采集了衍射横波数据。结果表明, 在有效的检测范围内, 测量值与实际值之间的误差在5%之内。该结果可促进激光超声在表面裂纹检测中的应用。     

聚焦超声治疗慢性宫颈炎临床观察

目的：探讨聚焦超声治疗慢性宫颈炎的有效性及安全性。方法：采用海极星超声妇科治疗仪对384例宫颈糜烂患者进行聚焦超声治疗的临床观察,根据超声治疗后的临床症状、体征的改善情况,进行统计学分析与疗效评价。结果聚焦超声治疗后,白带多,性交后出血等症状基本缓解,轻、中和重度宫颈糜烂有效率分别达到100%、95.68%和96.98%。聚焦超声治疗后,宫颈局部组织有短暂的渗出性炎症反应,阴道排液的时间约3~21天,1月后可基本恢复正常;无组织结痂脱落出血的过程,无宫颈瘢痕形成。结论：治疗剂量的聚焦超声波能安全有效地治疗慢性宫颈炎。