亚像素级的图像配准方法

在很多应用领域,要求图像配准的精度达到亚像素级,而多数亚像素级配准方法的运算量较大。文中阐述了一种高效的基于奇异值分解（SVD）的相位相关法。在无噪声干扰的情况下,该方法的精度达到0.02像素。通过对已知平移关系的图像的配准实验,比较了其与灰度相关函数内插法在无噪声和有噪声的情况以及应用于多光谱图像配准时的配准精度。实验表明,2种方法都有较好的抗噪声性能,在受噪声干扰不严重的情况下,基于SVD的相位相关法的配准精度优于灰度相关函数内插法。     

Cutting edge acoustics. Non-invasive surgery using ultrasound

Focused ultrasound surgery is a procedure whereby high-power ultrasound is pinpointed into the body. At high enough intensities, the tissue at the focus can be thermally burned or mechanically destroyed. Tissue in front or behind the focus is not affected since the intensity is much lower. This results in less overall internal trauma; i.e., faster healing. The goal at the Focused Ultrasound Surgery Lab at Brigham and Women's Hospital in Boston, MA is to use this technique to non-invasively treat tumors. This could eliminate the need for surgically removing tissue, thus offering the patient a blood-free alternative. More importantly, it could offer a cure to those patients whose illness cannot be treated by traditional surgery. Time will tell what therapeutic ultrasound's impact will have in treating disease in the long term. Nevertheless, the medical profession's desire for less invasive treatments has grown tremendously. As a result, ultrasound's preliminary success indicates that using therapeutic ultrasound will increasingly benefit patients     

超声修复有记忆性铅蓄电池研究

应用超声空化原理对有记忆性铅蓄电池进行修复,采用对比法实验方法:在充电过程、放电过程以及静置三种状态下对有记忆性铅蓄电池进行超声处理,研究修复有记忆性铅蓄电池的较佳超声处理方式;在该方式下进行不同时间的超声处理,研究较佳超声处理时间。得出超声修复有记忆性铅蓄电池的较佳条件为静置状态下超声处理60 min。     

Automated registration of brain images using edge and surfacefeatures

We present an automated multimodality (CT & MRI) registration algorithm based on hierarchical feature extraction. Two kinds of shape representations-edge and surface-are extracted hierarchically from different image modalities. The registration then is performed using least-squares matching of the user-specified (but automatically extracted) corresponding features. In our implementation, the 3-D version of the Canny edge detector is employed in the extraction of corresponding edge information. An automatic segmentation algorithm is introduced to extract the corresponding surfaces from the edges efficiently. The geometric matching of those extracted shape features then is performed using the iterative closest-point matching method     

基于KAZE的自适应模糊图像配准算法

为了提高图像配准算法对于模糊图像的配准性能,提出一种融合非线性尺度空间和空间余弦相似度的自适应模糊图像配准算法。该算法将非线性尺度空间理论应用于图像的局部特征提取,采用KAZE算法提取图像的特征点,以构成M-SURF特征描述符;利用空间余弦对图像特征点进行匹配,并且根据不同的图像特性进行自适应阈值匹配,以得到便于寻求最优变换关系的合理数量的匹配点对;最后采用RANSAC算法滤除误匹配点对,以提升算法精度。实验结果表明,该算法可以有效地提高模糊图像配准的匹配准确率和精度,准确率和精度比KAZE算法最大可以提高25%和7.909像素,具有更好的配准性能。     

融合肌电信号与A型超声的新型肌肉疲劳检测方法

为了提高肌肉的疲劳检测效果,提出了一种双传感融合的方式来弥补单传感模式下信息容易丢失的不足。 该方式将表 面肌电信号的时频域特征与 A 型超声信号的肌肉厚度特征多维度融合,实现了双传感疲劳检测新模式。 采用支持向量机和神 经网络多模型训练,表面肌电信号与 A 型超声双传感融合在 3 种疲劳状态下的检测准确率可以达到 85%以上。 相较于仅仅使 用表面肌电信号的时频域特征(76. 99%)与 A 型超声的肌肉厚度(74. 87%)进行疲劳检测,准确率提升了 8% ~ 13%。 结果表明 对于疲劳检测,表面肌电信号与超声信号双传感融合模式比单传感模式更加准确有效。     

基于亚像素红外与可见光图像配准方法

为了提高不同分辨率的红外与可见光图像配准的精度,提出了一种基于亚像素纠正的红外与可见光自动配准方法.采用了Shi—— Tomasi角点检测器和Taylor多项式将角点的坐标纠正到亚像素级,在六参数仿射变换模型基础上采用改进的Hausdorff距离进行精确匹配.与传统方法比较,该方法提高精度10％左右.实验表明,该方法配...     

Simultaneous registration and fusion of multiple dissimilar sensors for cooperative driving

The fusion of multiple sensory information plays a key role in cooperative driving for flexible platooning of automated vehicles over a couple of lanes within a short intervehicle distance. In this paper, the problem of online sensor fusion with spatially and temporally misaligned dissimilar sensors is considered. A spatial-temporal registration model for the popular intelligent vehicular sensors including radar, global positioning system, inertial navigation system, and camera is first developed for sensor alignment. An unscented Kalman filter (UKF) is proposed here to fuse and register these sensors that are installed on a platoon of vehicles simultaneously. When the road geometry information is available from a digital map database, a constrained UKF is further developed to improve the fusion accuracy. The effect of spatial-temporal sensor misalignment upon the vehicle-state estimation is also analyzed theoretically. Simulations show that the proposed UKF method not only can align the dissimilar vehicular sensors properly with both spatial and temporal biases, but can also obtain accurate fused tracks of vehicles in a platoon.     

CT和信息缺失CBCT图像变形配准方法研究

研究一种应用于自适应放射治疗中的CT和信息缺失锥形束CT(cone-beam CT,CBCT)图像的图像变形配准方法。通过构建及求解联合迭代重建与配准的能量函数,将CBCT全部投影图像信息以迭代前向投影与反投影的形式融入变形配准模型,同时完成CT与CBCT在投影域和图像域的匹配。分别利用5套临床头颈部肿瘤病人图像模拟CBCT截断和1套胸腹部肿瘤病人图像数据对算法进行了验证,实验结果表明,该方法能有效、精确完成CT和信息缺失CBCT图像之间的变形配准。图像变形配准是自适应放疗中的关键技术,对于减少放疗分次间病人的CBCT受照剂量以及提高放射治疗计划重设计精度具有较好的临床应用价值。     

血管内超声图像的预处理

对血管内超声图像进行噪声滤波和边缘增强是对图像进一步处理分析的基础工作。针对采集到的强背景噪声的血管内超声图像,双边滤波利用像素间的空间距离和灰度值之差来控制滤波效果,即平滑了图像又保持了边缘。Retinex算法把图像分解为反射物体图像和入射光图像,在增强管壁边缘的同时对噪声影响小。实验结果表明,综合利用双边滤波和Retinex增强算法,在滤除噪声增强边缘有较满意的效果,对血管壁边缘检测有明显的改善。     

基于水平集的弱边缘医学超声图像分割算法

图像分割在医学超声图像的定量、定性分析中均扮演着重要的角色,并直接影响到后续的分析、处理工作。但在医学超声图像中,待分割的图像目标经常包括弱边缘,这为利用传统图像分割算法对目标进行分割带来了困难。本文通过对Chan-Vese水平集方法进行研究,利用零水平集曲线的平均边缘能量来对其演化速度进行控制,实现了对图像中目标弱边缘的检测。本文方法在对包含弱边缘的医学超声图像进行分割时,得到了很好的效果。     

An investigation on attenuation UCT with wave paths enhancement for breast ultrasound

Breast cancer is one of the most prevalent health hazards in women all over the world. An annual screening test using a diagnostic ultrasound seems to be an appropriate method to handle this physical threat. In this paper, we propose the use of a two‐dimensional reflection‐mode ultrasonic tomography system for a general breast ultrasound investigation enhanced by an echo wave path using a wave reflecting plate. Our virtual imaging setup system is composed of a 128‐element conventional linear array transducer placed on the top of a water bath and a wave reflector attached around this setup. The shape of the wave reflector was designed as a single plate shape, rectangular shape and curve shape. For projection data, we estimate a line integral insonifying data by using a classical integration slope of attenuation coefficient method in which its derivative is independent of transmittance, reflectance, and noise. By imaging a virtual breast phantom model, the reconstruction results obtained from an iterative algebraic reconstruction technique (ART) algorithm show a promising image. The image is not only indicates a tissue characterization from quantitative attenuation data, but also restores an area covered by hard tissue due to an increased wave path direction from our nonrotational imaging system. These results encourage us to implement our concept with a clinical study in the near future. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

相机阵列中无视场重合图像时间配准方法研究

多路商业相机组阵在进行信息融合与视场拼接之前需要对采集的多路图像进行时间配准。为保证通用性,需要研究一种与系统相对独立的多路图像时间配准方法。提出一种利用多路图像序列内变换关系的算法,首先提取多路图像中与时间相关的共同特征,然后通过改进的奇异值分解方法判定共同特征的相似度完成时间配准。本文算法不需要提前对相机进行标定,对序列内图像配准精度要求较低,且能够在多路图像之间没有视场重合的情况下完成时间配准。经实验验证,配准精度达到了亚帧级。     

不同分布下红外主动目标特征点配准方法研究

视觉测量中经常需要用到特征匹配来计算位姿信息,但尚无针对红外主动目标设计特征匹配可用的算法,为实现对不同分布红外主动目标的匹配,本文提出了一种通用的两阶段特征点匹配方法。第一阶段为粗配准,首先检测图像特征点集的凸包,获取最外围点;通过构建三角形特征集,并使用马氏距离进行相似三角形计算搜索实现快速粗配准。第二阶段为精匹配,首先通过粗匹配特征计算欧拉角避免匹配结果的180°旋转对称;针对粗配准后的可能存在的特征点缺失问题,采用极线约束精匹配策略,充分利用已匹配特征点的几何信息,有效实现对剩余点的精确匹配。理论分析与实验表明,在13个红外发光点组成的旋转对称点集及非旋转对称点集下,该方法在绝对大小0°~40°的旋转范围内能高效匹配,实验测试极限性能能够达到50°,并对实际场景下特征点的遮挡等情况具有较好的鲁棒性,实验结果验证其适应性与稳定性,具有较高的实用价值。     

A large dynamic range voltage controlled attenuator with improved linearity-in-dB for ultrasound applications

A large dynamic range (DR) and high linearity-in-dB voltage controlled attenuator (VCAT) for ultrasound applications was presented. Continuous tunable VCAT implemented with Metal-Oxide-Semiconductor (MOS) transistors used as shunt devices was proposed in this work, and the linearity-in-dB performance was analyzed in detail. Nonlinearity of the shunt transistors operated in different regions resulted in poor linearity-in-dB attenuation of the VCAT, which was undesirable in an ultrasonic receiver system. An effective linearity-in-dB improvement scheme was then proposed. The full scale range of the input control voltage was divided into N intervals with a same equal-length by uniformly distributed voltage values. At these division voltages, the attenuation gains were corrected to be the ideal ones by the tracing and comparing circuits. In this way, the non-linearity-in-dB was limited to the intervals between the two adjacent corrected attenuation gains, and the overall linearity of the VCAT was improved greatly. Measurement results showed that the dynamic range of the proposed attenuator was 36-dB, and the gain errors were in a range from − 1.22 to − 0.55 dB. The noise figures (NF) at the commonly used ultrasonic frequencies was below 6-dB, and the S11 was better than − 10 dB over the input range of the control voltage.     

Cardiac magnetic resonance T1 and extracellular volume mapping with motion correction and co-registration based on fast elastic image registration

Objective

Our aim was to investigate the technical feasibility of a novel motion compensation method for cardiac magntic resonance (MR) T1 and extracellular volume fraction (ECV) mapping.

Materials and methods

Native and post-contrast T1 maps were obtained using modified look-locker inversion recovery (MOLLI) pulse sequences with acquisition scheme defined in seconds. A nonrigid, nonparametric, fast elastic registration method was applied to generate motion-corrected T1 maps and subsequently ECV maps. Qualitative rating was performed based on T1 fitting-error maps and overlay images. Local deformation vector fields were produced for quantitative assessment. Intra- and inter-observer reproducibility were compared with and without motion compensation.

Results

Eighty-two T1 and 39 ECV maps were obtained in 21 patients with diverse myocardial diseases. Approximately 60% demonstrated clear quality improvement after motion correction for T1 mapping, particularly for the poor-rating cases (23% before vs 2% after). Approximately 67% showed further improvement with co-registration in ECV mapping. Although T1 and ECV values were not clinically significantly different before and after motion compensation, there was improved intra- and inter-observer reproducibility after motion compensation.

Conclusions

Automated motion correction and co-registration improved the qualitative assessment and reproducibility of cardiac MR T1 and ECV measurements, allowing for more reliable ECV mapping.

     

Doppler ultrasound observation of pathological heart valves

A simple, noninvasive technique based on Hilbert transform (HT) time-signal displays is described. The authors discuss methods of showing forward- and reverse-flow Doppler echocardiograph signals as a time course of events relating to valve stenosis and regurgitation for providing additional cardiac insonation diagnostic information. The Doppler ultrasound demodulated signals are separated using the HT technique and then shown as segments of waveforms along with the corresponding electrocardiogram. This allows one to relate cardiac activity events, to assess valve leaflet thickness in severe mitral-valve stenosis cases, and to examine the opening and closing of valve leaflets for diagnosis     

Efficient design of ultrasound true-velocity flow mapping

The authors describe the general theory of the classical Doppler technique for flow mapping and show that its main assumptions do not generally hold for ultrasound imaging. They then develop a generalized model for frequency-domain flow mapping in practical ultrasound imaging situations. Using this model, the authors show that it is possible to compute the true velocity from single-aperture configurations. They discuss improving the resolution and velocity estimation accuracies and propose a novel approach based on a generalization of the radar ambiguity function model. They also consider the same problems for time-domain techniques. They propose a generalization of the correlation technique that takes into account the ultrasound field effect, and show that it is theoretically possible to obtain true-velocity flow maps from single-aperture configurations. Finally, the authors discuss the relative advantages and disadvantages of both frequency-domain and time-domain techniques