Volume 37, Issue 2

Inspired by recent advances in deep learning, we propose a framework for reconstructing dynamic sequences of 2-D cardiac magnetic resonance (MR) images from undersampled data using a deep cascade of convolutional neural networks (CNNs) to accelerate the data acquisition process. In particular, we address the case where data are acquired using aggressive Cartesian undersampling. First, we show that when each 2-D image frame is reconstructed independently, the proposed method outperforms state-of-the-art 2-D compressed sensing approaches, such as dictionary learning-based MR image reconstruction, in terms of reconstruction error and reconstruction speed. Second, when reconstructing the frames of the sequences jointly, we demonstrate that CNNs can learn spatio-temporal correlations efficiently by combining convolution and data sharing approaches. We show that the proposed method consistently outperforms state-of-the-art methods and is capable of preserving anatomical structure more faithfully up to 11-fold undersampling. Moreover, reconstruction is very fast: each complete dynamic sequence can be reconstructed in less than 10 s and, for the 2-D case, each image frame can be reconstructed in 23 ms, enabling real-time applications.

受深度学习最新进展的启发，我们提出了一种框架，利用卷积神经网络（CNN）的深度级联，从未完全采样的数据中重建二维心脏磁共振（MR）图像的动态序列，以加速数据采集过程。具体来说，我们处理使用激进笛卡尔欠采样获取数据的情况。首先，我们展示了当每个二维图像帧独立重建时，所提方法在重建误差和重建速度方面优于最先进的二维压缩感知方法，如基于字典学习的MR图像重建。其次，当联合重建序列的帧时，我们证明了CNN可以通过组合卷积和数据共享方法有效地学习时空相关性。我们展示了所提方法始终优于最先进的方法，并且能够在高达11倍的欠采样下更忠实地保留解剖结构。此外，重建速度非常快：每个完整的动态序列可以在不到10秒内重建，对于二维情况，每个图像帧可以在23毫秒内重建，从而实现实时应用。

Incorporation of prior knowledge about organ shape and location is key to improve performance of image analysis approaches. In particular, priors can be useful in cases where images are corrupted and contain artefacts due to limitations in image acquisition. The highly constrained nature of anatomical objects can be well captured with learning-based techniques. However, in most recent and promisin...

将关于器官形状和位置的先验知识纳入是提高图像分析方法性能的关键。特别是，在图像因采集限制而损坏并包含伪影的情况下，先验知识非常有用。学习技术能够很好地捕捉解剖对象的高度约束特性。然而，在最近和最有希望...

Heavy smokers undergoing screening with low-dose chest CT are affected by cardiovascular disease as much as by lung cancer. Low-dose chest CT scans acquired in screening enable quantification of atherosclerotic calcifications and thus enable identification of subjects at increased cardiovascular risk. This paper presents a method for automatic detection of coronary artery, thoracic aorta, and card...

接受低剂量胸部CT筛查的重度吸烟者患心血管疾病的风险与患肺癌的风险相当。筛查中获取的低剂量胸部CT扫描能够量化动脉粥样硬化钙化，从而识别心血管风险增加的受试者。本文提出了一种自动检测冠状动脉、胸主动脉和...的方法。

Automated detection of vascular structures is of great importance in understanding the mechanism, diagnosis, and treatment of many vascular pathologies. However, automatic vascular detection continues to be an open issue because of difficulties posed by multiple factors, such as poor contrast, inhomogeneous backgrounds, anatomical variations, and the presence of noise during image acquisition. In ...

血管结构的自动检测对于理解许多血管病理的机制、诊断和治疗具有重要意义。然而，由于多种因素造成的困难，如对比度差、背景不均匀、解剖变异以及图像采集过程中噪声的存在，自动血管检测仍然是一个开放性问题。在...

This paper presents an image reconstruction method based on parametric level set (PLS) method using electrical impedance tomography. The conductivity to be reconstructed was assumed to be piecewise constant and the geometry of the anomaly was represented by a shape-based PLS function, which we represent using Gaussian radial basis functions (GRBF). The representation of the PLS function significan...

本文提出了一种基于参数水平集（PLS）方法的电阻抗断层成像图像重建方法。假设待重建的电导率是分段常数，异常几何形状由基于形状的PLS函数表示，该函数使用高斯径向基函数（GRBF）表示。PLS函数的表示显著提高了重建的准确性和效率。

Tumor growth is associated with cell invasion and mass-effect, which are traditionally formulated by mathematical models, namely reaction-diffusion equations and biomechanics. Such models can be personalized based on clinical measurements to build the predictive models for tumor growth. In this paper, we investigate the possibility of using deep convolutional neural networks to directly represent ...

肿瘤生长与细胞侵润和占位效应相关，传统上通过数学模型（即反应-扩散方程和生物力学）进行描述。这些模型可以基于临床测量进行个性化，以构建肿瘤生长预测模型。在本文中，我们研究了使用深度卷积神经网络直接表示...的可能性。

In this article, we evaluate Parallel Level Sets (PLS) and Bowsher’s method as segmentation-free anatomical priors for regularized brain positron emission tomography (PET) reconstruction. We derive the proximity operators for two PLS priors and use the EM-TV algorithm in combination with the first order primal-dual algorithm by Chambolle and Pock to solve the non-smooth optimization problem for PE...

本文评估了并行水平集（PLS）和Bowsher方法作为正则化脑正电子发射断层扫描（PET）重建的无分割解剖先验。我们推导了两个PLS先验的邻近算子，并使用EM-TV算法结合Chambolle和Pock的一阶原始对偶算法来解决非光滑优化问题。

Respiratory motion during positron emission tomography (PET)/computed tomography (CT) imaging can cause significant image blurring and underestimation of tracer concentration for both static and dynamic studies. In this paper, with the aim to eliminate both intra-cycle and inter-cycle motions, and apply to dynamic imaging, we developed a non-rigid event-by-event (NR-EBE) respiratory motion-compens...

在正电子发射断层扫描（PET）/计算机断层扫描（CT）成像过程中，呼吸运动会导致静态和动态研究中的图像模糊和示踪剂浓度低估。本文旨在消除周期内和周期间的运动，并将其应用于动态成像，开发了一种非刚性逐事件（NR-EBE）呼吸运动补偿...

Imaging corneal biomechanical changes or abnormalities is important for better clinical diagnosis and treatment of corneal diseases. We propose a novel ultrasound-based method, called ocular pulse elastography (OPE), to image corneal deformation during the naturally occurring ocular pulse. Experiments on animal and human donor eyes, as well as synthetic radiofrequency (RF) data, were used to evalu...

对角膜生物力学变化或异常进行成像对于更好地诊断和治疗角膜疾病至关重要。我们提出了一种基于超声的新型方法，称为眼脉冲弹性成像（OPE），用于在自然发生的眼脉冲期间对角膜变形进行成像。在动物和人眼供体以及合成射频（RF）数据上进行的实验用于评估...

The classification of blood vessels into arterioles and venules is a fundamental step in the automatic investigation of retinal biomarkers for systemic diseases. In this paper, we present a novel technique for vessel classification on ultra-wide-field-of-view images of the retinal fundus acquired with a scanning laser ophthalmoscope. To the best of our knowledge, this is the first time that a full...

将血管分类为小动脉和小静脉是自动研究全身疾病视网膜生物标志物的基本步骤。在本文中，我们提出了一种新颖的血管分类技术，用于在扫描激光眼底镜获取的超宽视野视网膜眼底图像上。据我们所知，这是首次完全...

Optimal control approaches have proved useful in designing RF pulses for large tip-angle applications. A typical challenge for optimal control design is the inclusion of constraints resulting from physiological or technical limitations that assure the realizability of the optimized pulses. In this paper, we show how to treat such inequality constraints, in particular, amplitude constraints on the ...

最优控制方法在设计大翻转角应用的射频脉冲中已被证明是有用的。最优控制设计的一个典型挑战是如何包含由生理或技术限制导致的约束条件，以确保优化脉冲的可实现性。本文展示了如何处理此类不等式约束，特别是对射频脉冲的幅度限制等。

Iterative algorithms have become increasingly popular in computed tomography (CT) image reconstruction, since they better deal with the adverse image artifacts arising from low radiation dose image acquisition. But iterative methods remain computationally expensive. The main cost emerges in the projection and back projection operations, where accurate CT system modeling can greatly improve the qua...

迭代算法在计算机断层扫描(CT)图像重建中变得越来越流行，因为它们能更好地处理低辐射剂量图像采集带来的不良图像伪影。但迭代方法计算成本仍然很高。主要成本出现在投影和反投影操作中，其中精确的CT系统建模可以大大提高...

In high-dimensional magnetic resonance imaging applications, time-consuming, sequential acquisition of data samples in the spatial frequency domain (k-space) can often be accelerated by accounting for dependencies in linear reconstruction, at the cost of noise amplification that depends on the sampling pattern. Common examples are support-constrained, parallel, and dynamic MRI, and k-space samplin...

在高维磁共振成像应用中，通过在空间频率域（k空间）中考虑线性重建的依赖性，通常可以加速数据样本的顺序采集，但代价是依赖于采样模式的噪声放大。常见的例子包括支撑约束、并行和动态MRI以及k空间采...

Plane-wave-based ultrafast imaging has become the prevalent technique for non-conventional ultrasound imaging. The image quality, especially in terms of the suppression of artifacts, is generally compromised by reducing the number of transmissions for a higher frame rate. We hereby propose a new ultrafast imaging framework that reduces not only the side lobe artifacts but also the axial lobe artif...

平面波超快成像已成为非常规超声成像的主流技术。图像质量，特别是伪影抑制方面，通常因提高帧率而减少发射次数而受损。本文提出一种新的超快成像框架，不仅降低旁瓣伪影，还降低轴向瓣伪影...

There is intense interest in fMRI research on whole-brain functional connectivity, and however, two fundamental issues are still unresolved: the impact of spatiotemporal data resolution (spatial parcellation and temporal sampling) and the impact of the network construction method on the reliability of functional brain networks. In particular, the impact of spatiotemporal data resolution on the res...

在fMRI研究中，全脑功能连接引起了强烈关注，然而，有两个基本问题仍未解决：时空数据分辨率（空间分区和时间采样）以及网络构建方法对功能脑网络可靠性的影响。

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to pred...

介绍磁共振介导的射频消融（MR-RFA），其中MRI扫描仪独特地同时承担诊断和治疗角色。在MR-RFA中，扫描仪诱导的射频加热通过拉莫尔频率射频拾取装置和针系统被引导至消融部位，并通过脉冲序列进行控制。通过电和磁场的模拟对MR-RFA进行了评估...

Principal component analysis (PCA) is an exploratory tool widely used in data analysis to uncover the dominant patterns of variability within a population. Despite its ability to represent a data set in a low-dimensional space, PCA's interpretability remains limited. Indeed, the components produced by PCA are often noisy or exhibit no visually meaningful patterns. Furthermore, the fact that the co...

主成分分析（PCA）是一种广泛用于数据分析的探索性工具，旨在揭示人群中变异的 dominant 模式。尽管PCA能将数据集降至低维空间，但其可解释性仍然有限。实际上，PCA产生的成分往往含有噪声或缺乏视觉上有意义的模式。此外，系数…

Macular holes are blinding conditions, where a hole develops in the central part of retina, resulting in reduced central vision. The prognosis and treatment options are related to a number of variables, including the macular hole size and shape. High-resolution spectral domain optical coherence tomography allows precise imaging of the macular hole geometry in three dimensions, but the measurement ...

黄斑孔是一种致盲性疾病，在视网膜中央部分形成孔洞，导致中心视力下降。预后和治疗方案与多种因素相关，包括黄斑孔的大小和形状。高分辨率谱域光学相干断层扫描能够精确三维成像黄斑孔的几何结构，但测量...

Diffusion MRI data are generally acquired using hyperpolarized gases during patient breath-hold, which yields a compromise between achievable image resolution, lung coverage, and number of b-values. In this paper, we propose a novel method that accelerates the acquisition of diffusion MRI data by undersampling in both the spatial and b-value dimensions and incorporating knowledge about signal deca...

扩散磁共振成像数据通常在患者屏气期间使用超极化气体获取，这需要在可实现的图像分辨率、肺部覆盖范围和b值数量之间进行折衷。在本文中，我们提出了一种新方法，通过在空间和b值维度上进行欠采样，并结合关于信号衰减的知识，来加速扩散磁共振成像数据的采集。

A new reconstruction method, coined MIRAGE, is presented for accurate, fast, and robust parameter mapping of multiple-echo gradient-echo (MEGE) imaging, the basis sequence of novel quantitative magnetic resonance imaging techniques such as water content and susceptibility mapping. Assuming that the temporal signal can be modeled as a sum of damped complex exponentials, MIRAGE performs model-based ...

提出了一种新的重建方法，称为MIRAGE，用于对多回波梯度回波（MEGE）成像进行准确、快速和稳健的参数映射，MEGE是新型定量磁共振成像技术（如水分含量和磁化率映射）的基础序列。假设时间信号可以建模为阻尼复指数之和，MIRAGE执行基于模型的...

Patients who have implanted medical devices with long conductive leads are often restricted from receiving MRI scans due to the danger of RF-induced heating near the lead tips. Phantom studies have shown that this heating varies significantly on a case-by-case basis, indicating that many patients with implanted devices can receive clinically useful MRI scans without harm. However, the difficulty o...

植入带有长导电导线的医疗设备的患者通常被限制接受MRI扫描，因为存在射频诱导的导线尖端附近加热的危险。模型研究表明，这种加热因个案而异，表明许多植入设备的患者可以安全地接受临床上有用的MRI扫描。然而，困难在于...

For magnetic resonance imaging of tissues with very short transverse relaxation times, radio-frequency excitation must be immediately followed by data acquisition with fast spatial encoding. In zero-echo-time (ZTE) imaging, excitation is performed while the readout gradient is already on, causing data loss due to an initial dead time. One major dead time contribution is the settling time of the fi...

对于横向弛豫时间极短的组织进行磁共振成像时，射频激发后必须立即进行快速空间编码的数据采集。在零回波时间（ZTE）成像中，激发是在读出梯度已经开启的情况下进行的，导致由于初始死时间而造成数据丢失。一个主要的死时间贡献是滤波器的稳定时间...

Contrast-enhanced ultrasound (CEUS) is a non-invasive imaging technique extensively used for blood perfusion imaging of various organs. This modality is based on the acoustic detection of gas-filled microbubble contrast agents used as intravascular flow tracers. Recent efforts aim at quantifying parameters related to the enhancement in the vascular compartment using time-intensity curve (TIC), and...

对比增强超声（CEUS）是一种非侵入性成像技术，广泛用于各种器官的血流灌注成像。该模态基于对用作血管内血流示踪剂的充气微泡造影剂的声学检测。最近的工作旨在利用时间-强度曲线（TIC）量化与血管腔增强相关的参数，并...

Image guidance has become the standard of care for patient positioning in radiotherapy, where image registration is often a critical step to help manage patient motion. However, in practice, verification of registration quality is often adversely affected by difficulty in manual inspection of 3-D images and time constraint, thus affecting the therapeutic outcome. Therefore, we proposed to employ b...

图像引导已成为放射治疗中患者定位的标准方法，其中图像配准通常是帮助管理患者运动的关键步骤。然而，在实践中，配准质量的验证常常受到三维图像手动检查困难和时间限制的不利影响，从而影响治疗效果。因此，我们提出使用...

Developing custom-built MR coils is a cumbersome task, in which an a priori prediction of the coils' SNR performance, their sensitivity pattern, and their depth of penetration helps to greatly speed up the design process by reducing the required hardware manufacturing iterations. The simulation-based design flow presented in this paper takes the entire MR imaging process into account. That is, it ...

开发定制MR线圈是一项繁琐的任务，其中对线圈的信噪比性能、灵敏度模式以及穿透深度的先验预测有助于通过减少所需的硬件制造迭代次数来大大加快设计过程。本文提出的基于仿真的设计流程考虑了整个MR成像过程。也就是说，它……