Volume 34, Issue 4

Most of ultrasound medical imaging systems currently on the market implement standard Delay and Sum (DAS) beamforming to form B-mode images. However, image resolution and contrast achievable with DAS are limited by the aperture size and by the operating frequency. For this reason, different beamformers have been presented in the literature that are mainly based on adaptive algorithms, which allow achieving higher performance at the cost of an increased computational complexity. In this paper, we propose the use of an alternative nonlinear beamforming algorithm for medical ultrasound imaging, which is called Delay Multiply and Sum (DMAS) and that was originally conceived for a RADAR microwave system for breast cancer detection. We modify the DMAS beamformer and test its performance on both simulated and experimentally collected linear-scan data, by comparing the Point Spread Functions, beampatterns, synthetic phantom and in vivo carotid artery images obtained with standard DAS and with the proposed algorithm. Results show that the DMAS beamformer outperforms DAS in both simulated and experimental trials and that the main improvement brought about by this new method is a significantly higher contrast resolution (i.e., narrower main lobe and lower side lobes), which turns out into an increased dynamic range and better quality of B-mode images.

目前市场上大多数超声医学成像系统采用标准的延迟与和（DAS）波束形成来生成B模式图像。然而，DAS的图像分辨率和对比度受限于孔径大小和工作频率。因此，文献中提出了不同的波束形成器，主要基于自适应算法，这些算法以增加计算复杂度为代价实现了更高的性能。在本文中，我们提出将一种替代的非线性波束形成算法用于医学超声成像，该算法称为延迟相乘与和（DMAS），最初是为用于乳腺癌检测的雷达成像微波系统而设计的。我们修改了DMAS波束形成器，并通过比较使用标准DAS和所提算法获得的点扩散函数、波束图、合成体模和体内颈动脉图像，在模拟和实验采集的线性扫描数据上测试其性能。结果表明，DMAS波束形成器在模拟和实验试验中均优于DAS，并且这种新方法带来的主要改进是显著更高的对比度分辨率（即更窄的主瓣和更低的旁瓣），从而提高了动态范围和B模式图像的质量。

Automated tracking of living cells in microscopy image sequences is an important and challenging problem. With this application in mind, we propose a global track linking algorithm, which links cell outlines generated by a segmentation algorithm into tracks. The algorithm adds tracks to the image sequence one at a time, in a way which uses information from the complete image sequence in every link...

在显微镜图像序列中自动追踪活细胞是一个重要且具有挑战性的问题。基于此应用，我们提出了一种全局轨迹连接算法，该算法将由分割算法生成的细胞轮廓连接成轨迹。该算法每次向图像序列添加一条轨迹，每次连接时都利用整个图像序列的信息。

Electrical impedance tomography (EIT) is used to image the electrical property distribution of a tissue under test. An EIT system comprises complex hardware and software modules, which are typically designed for a specific application. Upgrading these modules is a time-consuming process, and requires rigorous testing to ensure proper functioning of new modules with the existing ones. To this end, ...

电阻抗成像（EIT）用于对被测组织的电特性分布进行成像。EIT系统包含复杂的硬件和软件模块，通常是针对特定应用而设计的。升级这些模块是一个耗时的过程，并且需要严格的测试以确保新模块与现有模块的正常运行。为此，……

This paper introduces a new algorithm for recognizing surgical tasks in real-time in a video stream. The goal is to communicate information to the surgeon in due time during a video-monitored surgery. The proposed algorithm is applied to cataract surgery, which is the most common eye surgery. To compensate for eye motion and zoom level variations, cataract surgery videos are first normalized. Then...

本文介绍了一种在视频流中实时识别手术任务的新算法。目标是在视频监控手术过程中及时向外科医生传达信息。该算法应用于白内障手术，这是最常见的眼科手术。为了补偿眼球运动和缩放水平的变化，首先对白内障手术视频进行归一化。然后...

We present a novel descriptor for the characterization of pulmonary nodules in computed tomography (CT) images. The descriptor encodes information on nodule morphology and has scale-invariant and rotation-invariant properties. Information on nodule morphology is captured by sampling intensity profiles along circular patterns on spherical surfaces centered on the nodule, in a multi-scale fashion. E...

我们提出了一种新颖的描述符，用于表征计算机断层扫描（CT）图像中的肺结节。该描述符编码了结节形态信息，并具有尺度不变性和旋转不变性。通过以多尺度方式沿以结节为中心的球面上的圆形图案采样强度分布，捕获结节形态信息。

We develop a new approach to functional brain connectivity analysis, which deals with four fundamental aspects of connectivity not previously jointly treated. These are: temporal correlation, spurious spatial correlation, sparsity, and network construction using trajectory (as opposed to marginal) Mutual Information. We call the new method Sparse Conditional Trajectory Mutual Information (SCoTMI)....

我们开发了一种新的功能脑连接分析方法，该方法同时处理了连接性分析的四个基本方面：时间相关性、空间伪相关性、稀疏性以及基于轨迹（而非边际）互信息的网络构建。我们将这种新方法称为稀疏条件轨迹互信息（SCoTMI）。

Echocardiography is a potential alternative to X-ray fluoroscopy in cardiac catheterization given its richness in soft tissue information and its lack of ionizing radiation. However, its small field of view and acoustic artifacts make direct automatic segmentation of the catheters very challenging. In this study, a fast catheter segmentation framework for echocardiographic imaging guided by the se...

超声心动图因其丰富的软组织信息和无电离辐射，在心导管介入术中有望成为X射线透视的替代方案。然而，其视野小且存在声学伪影，使得导管的直接自动分割非常具有挑战性。在本研究中，我们提出了一种基于对应X射线透视分割引导的超声心动图快速导管分割框架。

Dynamic magnetic resonance (MR)-imaging can provide functional and positional information in real-time, which can be conveniently used online to control a cancer therapy, e.g., using high intensity focused ultrasound or radio therapy. However, a precise real-time correction for motion is fundamental in abdominal organs to ensure an optimal treatment dose associated with a limited toxicity in nearb...

动态磁共振成像可以实时提供功能性和位置信息，可方便地在线用于控制癌症治疗，例如使用高强度聚焦超声或放射治疗。然而，腹部器官中精确的实时运动校正对于确保最佳治疗剂量并减少附近毒性至关重要...

Ultra-high field magnetic resonance imaging (MRI) scanners ( ≥ 7T) require radio-frequency (RF) coils to operate in the range of the electromagnetic spectrum where the effective wavelength in the tissue approaches the patient dimensions. Multi-channel transmit arrays, driven in parallel, have been developed to increase the transmit field (B1+) uniformity in this wavelength regime. However, the clo...

超高场磁共振成像（MRI）扫描仪（≥7T）需要射频（RF）线圈在电磁频谱范围内工作，其中组织中的有效波长接近患者尺寸。并行驱动的多通道发射阵列已被开发出来，以在此波长范围内提高发射场（B1+）均匀性。然而，接近...

Multi-channel radio-frequency (RF) transmit coil arrays have been developed to mitigate many of the RF challenges associated with ultra-high field ( ≥ 7T) magnetic resonance imaging (MRI). These arrays can be used for parallel RF transmission to produce spatially tailored RF excitation over the field of view. However, the realization of such arrays remains a challenge due to significant reactive i...

多通道射频发射线圈阵列已被开发用于缓解与超高场（≥7T）磁共振成像相关的许多射频挑战。这些阵列可用于并行射频传输，以在视场上产生空间定制的射频激发。然而，由于显著的无功...

Virtually all biomedical applications of positron emission tomography (PET) use images to represent the distribution of a radiotracer. However, PET is increasingly used in cell tracking applications, for which the “imaging” paradigm may not be optimal. Here, we investigate an alternative approach, which consists in reconstructing the time-varying position of individual radiolabeled cells directly ...

几乎所有正电子发射断层扫描（PET）的生物医学应用都使用图像来代表放射性示踪剂的分布。然而，PET越来越多地用于细胞追踪应用，对于这些应用，“成像”范式可能并非最优。在这里，我们研究了一种替代方法，该方法直接重建单个放射性标记细胞的时变位置...

Low-dose-rate brachytherapy is a radiation treatment method for localized prostate cancer. The standard of care for this treatment procedure is to acquire transrectal ultrasound images of the prostate in order to devise a plan to deliver sufficient radiation dose to the cancerous tissue. Brachytherapy planning involves delineation of contours in these images, which closely follow the prostate boun...

低剂量率近距离治疗是针对局限性前列腺癌的一种放射治疗方法。该治疗的标准流程是获取前列腺的经直肠超声图像，以制定向癌组织输送足够辐射剂量的计划。近距离治疗计划涉及在这些图像中勾画轮廓，这些轮廓紧密遵循前列腺边界...

Iterative image reconstruction for positron emission tomography can improve image quality by using spatial regularization. The most commonly used quadratic penalty often oversmoothes sharp edges and fine features in reconstructed images, while nonquadratic penalties can preserve edges and achieve higher contrast recovery. Existing optimization algorithms such as the expectation maximization (EM) a...

正电子发射断层扫描的迭代图像重建可以通过空间正则化提高图像质量。最常用的二次罚函数常常会使重建图像中的尖锐边缘和精细特征过度平滑，而非二次罚函数可以保留边缘并实现更高的对比度恢复。现有的优化算法，如期望最大化（EM）……

In standard B-mode ultrasound (BMUS), segmentation of the lumen of atherosclerotic carotid arteries and studying the lumen geometry over time are difficult owing to irregular lumen shapes, noise, artifacts, and echolucent plaques. Contrast enhanced ultrasound (CEUS) improves lumen visualization, but lumen segmentation remains challenging owing to varying intensities, CEUS-specific artifacts and la...

在标准B型超声（BMUS）中，由于不规则管腔形状、噪声、伪影及无回声斑块，动脉粥样硬化颈动脉管腔的分割及其随时间变化的几何形状研究较为困难。对比增强超声（CEUS）改善了管腔可视化，但由于强度变化、CEUS特定伪影及低对比度等因素，管腔分割仍具挑战性...

We propose a new method to measure directional modulation transfer function (MTF) using sphere phantoms in a cone beam computed tomography (CBCT) system. To measure spatially varying 3-D MTFs, we model FDK reconstruction in local regions and calculate the plane integrals of an ideal sphere phantom and reconstructed sphere phantoms. Then, we modify the Richardson-Lucy (RL) deconvolution method to r...

我们提出了一种利用球体模体在锥束计算机断层扫描（CBCT）系统中测量方向调制传递函数（MTF）的新方法。为了测量空间变化的3D MTF，我们对局部区域的FDK重建进行建模，并计算理想球体模体和重建球体模体的平面积分。然后，我们修改了Richardson-Lucy（RL）反卷积方法以...

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Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

敬请有意投稿的作者提交新的、未发表的稿件，以收录于本次征文通知中描述的即将举行的活动。

Provides a listing of the editorial board, current staff, committee members and society officers.

提供编辑委员会、现任工作人员、委员会成员和学会官员的名单。

Presents the table of contents for this issue of the publication.

展示了本期出版物的目录。

Presents information for authors publishing in this journal.

向在本期刊发表文章的作者提供相关信息。