Volume 30, Issue 4

Compressed sensing (CS) has the potential to reduce magnetic resonance (MR) data acquisition time. In order for CS-based imaging schemes to be effective, the signal of interest should be sparse or compressible in a known representation, and the measurement scheme should have good mathematical properties with respect to this representation. While MR images are often compressible, the second requirement is often only weakly satisfied with respect to commonly used Fourier encoding schemes. This paper investigates the use of random encoding for CS-MRI, in an effort to emulate the “universal” encoding schemes suggested by the theoretical CS literature. This random encoding is achieved experimentally with tailored spatially-selective radio-frequency (RF) pulses. Both simulation and experimental studies were conducted to investigate the imaging properties of this new scheme with respect to Fourier schemes. Results indicate that random encoding has the potential to outperform conventional encoding in certain scenarios. However, our study also indicates that random encoding fails to satisfy theoretical sufficient conditions for stable and accurate CS reconstruction in many scenarios of interest. Therefore, there is still no general theoretical performance guarantee for CS-MRI, with or without random encoding, and CS-based methods should be developed and validated carefully in the context of specific applications.

压缩感知(CS)有潜力减少磁共振(MR)数据采集时间。为了使基于CS的成像方案有效，感兴趣的信号应在已知表示中具有稀疏性或可压缩性，并且测量方案应相对于该表示具有良好的数学性质。虽然MR图像通常是可压缩的，但第二个要求相对于常用的傅里叶编码方案往往只能弱满足。本文研究随机编码在CS-MRI中的应用，以模拟理论CS文献中建议的“通用”编码方案。这种随机编码通过定制的空间选择性射频(RF)脉冲实验实现。通过仿真和实验研究，探讨了这种新方案相对于傅里叶方案的成像特性。结果表明，随机编码在某些场景下可能优于传统编码。然而，我们的研究也表明，在许多感兴趣的场景中，随机编码未能满足稳定和准确CS重建的理论充分条件。因此，对于CS-MRI，无论是否使用随机编码，目前仍没有普遍的理论性能保证，基于CS的方法应在特定应用的背景下仔细开发和验证。

This paper introduces two real-time elastography techniques based on analytic minimization (AM) of regularized cost functions. The first method (1D AM) produces axial strain and integer lateral displacement, while the second method (2D AM) produces both axial and lateral strains. The cost functions incorporate similarity of radio-frequency (RF) data intensity and displacement continuity, making bo...

本文介绍了两种基于正则化代价函数解析最小化（AM）的实时弹性成像技术。第一种方法（一维AM）产生轴向应变和整数横向位移，而第二种方法（二维AM）产生轴向和横向应变。代价函数结合了射频（RF）数据强度的相似性和位移连续性，使得...

Proliferative diabetic retinopathy is a rare condition likely to lead to severe visual impairment. It is characterized by the development of abnormal new retinal vessels. We describe a method for automatically detecting new vessels on the optic disc using retinal photography. Vessel-like candidate segments are first detected using a method based on watershed lines and ridge strength measurement. F...

增殖性糖尿病视网膜病变是一种罕见的疾病，可能导致严重的视力损伤。其特征是异常新生视网膜血管的生成。我们描述了一种使用视网膜摄影自动检测视盘上新血管的方法。首先，基于分水岭线和脊强度测量的方法检测血管样候选段。

When reading mammograms, radiologists combine information from multiple views to detect abnormalities. Most computer-aided detection (CAD) systems, however, use primitive methods for inclusion of multiview context or analyze each view independently. In previous research it was found that in mammography lesion-based detection performance of CAD systems can be improved when correspondences between M...

在阅读乳腺X线图像时，放射科医生会结合多个视图的信息来检测异常。然而，大多数计算机辅助检测（CAD）系统使用原始方法包含多视图上下文或独立分析每个视图。在先前的研究中发现，在乳腺摄影中，当建立...之间的对应关系时，基于病灶的CAD系统检测性能可以得到改善。

We examined the application of an iterative penalized maximum likelihood (PML) reconstruction method for improved detectability of microcalcifications (MCs) in digital breast tomosynthesis (DBT). Localized receiver operating characteristic (LROC) psychophysical studies with human observers and 2-D image slices were conducted to evaluate the performance of this reconstruction method and to compare ...

我们研究了迭代惩罚最大似然（PML）重建方法在数字乳腺断层合成（DBT）中提高微钙化（MCs）可检测性的应用。通过人类观察者和二维图像切片进行了局部接收器操作特征（LROC）心理物理研究，以评估该重建方法的性能并进行比较...

Wireless capsule endoscopy is a revolutionary technology that allows physicians to examine the digestive tract of a human body in the minimum invasive way. Physicians can detect diseases such as blood-based abnormalities, polyps, ulcers, and Crohn's disease. Although this technology is really a marvel of our modern times, currently it suffers from two serious drawbacks: 1) frame rate is low (3 fra...

无线胶囊内窥镜是一种革命性技术，使医生能够以最小侵入性方式检查人体消化道。医生可以检测出血异常、息肉、溃疡和克罗恩病等疾病。尽管这项技术是现代医学的奇迹，但目前存在两个严重缺点：1）帧率低（3帧...

The 4D extended cardiac-torso (XCAT) phantom was developed to provide a realistic and flexible model of the human anatomy and cardiac and respiratory motions for use in medical imaging research. A prior limitation to the phantom was that it did not accurately simulate altered functions of the heart that result from cardiac pathologies such as coronary artery disease (CAD). We overcame this limitat...

开发了4D扩展心脏-躯干（XCAT）体模，为医学成像研究提供真实且灵活的人体解剖结构以及心脏和呼吸运动模型。该体模先前的一个局限在于它未能准确模拟由冠状动脉疾病（CAD）等心脏病理导致的心脏功能改变。我们克服了这一限制……

A new statistical reconstruction method based on origin ensembles (OE) for emission tomography (ET) is examined. Using a probability density function (pdf) derived from first principles, an ensemble expectation of numbers of detected event origins per voxel is determined. These numbers divided by sensitivities of voxels and acquisition time provide OE estimates of the voxel activities. The OE expe...

研究了一种基于起源集成（OE）的发射断层扫描（ET）新统计重建方法。利用从第一性原理推导出的概率密度函数，确定了每个体素检测事件起源数的集合期望。这些数除以体素的灵敏度和采集时间，得到体素活度的OE估计。OE预期...

In this paper, we present a novel approach to segment dense, homogeneous objects in a tomographic reconstruction (or tomogram). A popular method to extract such objects from a tomogram is global thresholding, in which the threshold value is determined from the image histogram. However, accurate threshold selection is not straightforward, since, due to noise or artefacts in the reconstruction, the ...

本文提出了一种在断层重建（或称断层图像）中分割密集匀质物体的新方法。从断层图像中提取此类物体的常用方法是全局阈值分割，其中阈值由图像直方图确定。然而，精确的阈值选择并不直接，因为由于重建中的噪声或伪影...

The recent advances in meaningful constraining models have resulted in increasingly useful quantitative information recovered from cardiac images. Nevertheless, as most frameworks utilize either functional or structural images, the analyses cannot benefit from the complementary information provided by the other image sources. To better characterize subject-specific cardiac physiology and pathology...

有意义约束模型的最新进展使得从心脏图像中恢复出越来越有用的定量信息。然而，由于大多数框架仅使用功能图像或结构图像，分析无法从其他图像源提供的互补信息中受益。为了更好地表征特定对象的心脏生理和病理...

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