Feasibility of coronary artery wall thickening assessment in asymptomatic coronary artery disease using phase-sensitive dual-inversion recovery MRI at 3 T

Objectives

The purpose of this study was to (a) investigate the image quality of phase-sensitive dual-inversion recovery (PS-DIR) coronary wall imaging in healthy subjects and in subjects with known coronary artery disease (CAD) and to (b) investigate the utilization of PS-DIR at 3 T in the assessment of coronary artery thickening in subjects with asymptomatic but variable degrees of CAD.

Materials and Methods

A total of 37 subjects participated in this institutional review board-approved and HIPAA-compliant study. These included 21 subjects with known CAD as identified on multidetector computed tomography angiography (MDCT). Sixteen healthy subjects without known history of CAD were included. All subjects were scanned using free-breathing PS-DIR magnetic resonance imaging (MRI) for the assessment of coronary wall thickness at 3 T. Lumen–tissue contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and quantitative vessel parameters including lumen area and wall thickness were measured. Statistical analyses were performed.

Results

PS-DIR was successfully completed in 76% of patients and in 88% of the healthy subjects. Phase-sensitive signed-magnitude reconstruction, compared to modulus-magnitude images, significantly improved lumen–tissue CNR in healthy subjects (26.73 ± 11.95 vs. 14.65 ± 9.57, P < .001) and in patients (21.45 ± 7.61 vs. 16.65 ± 5.85, P < .001). There was no difference in image CNR and SNR between groups. In arterial segments free of plaques, coronary wall was thicker in patients in comparison to healthy subjects (1.74 ± 0.27 mm vs. 1.17 ± 0.14 mm, P < .001), without a change in lumen area (4.51 ± 2.42 mm² vs. 5.71 ± 3.11 mm², P = .25).

Conclusions

This is the first study to demonstrate the feasibility of successfully obtaining vessel wall images at 3 T using PS-DIR in asymptomatic patients with known variable degrees of CAD as detected by MDCT. This was achieved with a fixed subject-invariant planning of blood signal nulling. With that limitation alleviated, PS-DIR coronary wall MRI is capable of detecting arterial thickening and positive arterial remodeling at 3 T in asymptomatic CAD.     

Novel S-Gal analogs as H MRI reporters for in vivo detection of β-galactosidase

The quantitative assessment of gene expression and related enzyme activity in vivo could be important for the characterization of gene altering diseases and therapy. The development of imaging techniques, based on specific reporter molecules may enable routine non-invasive assessment of enzyme activity and gene expression in vivo. We recently reported the use of commercially available S-Gal^® as a β-galactosidase reporter for ¹H MRI, and the synthesis of several S-Gal^® analogs with enhanced response to β-galactosidase activity. We have now compared these analogs in vitro and have identified the optimal analog, C3-GD, based on strong T₁ and T₂ response to enzyme presence (ΔR₁ and ΔR₂ ~ 1.8 times S-Gal^®). Moreover, application is demonstrated in vivo in human breast tumor xenografts. MRI studies in MCF7-lacZ tumors implanted subcutaneously in athymic nude mice (n = 6), showed significant reduction in T₁ and T₂ values (each ~ 13%) 2 h after intra-tumoral injection of C3-GD, whereas the MCF7 (wild type) tumors showed slight increase. Thus, C3-GD successfully detects β-galactosidase activity in vivo and shows promise as a lacZ gene ¹H MR reporter molecule.     

Clarification of the recovery mechanism of Escherichia coli after hydrostatic pressure treatment

High hydrostatic pressure (HP) technology has gained more attention as a non-thermal food pasteurization technology. Recently, a limitation of the HP technology was reported by Koseki and Yamamoto [Recovery of Escherichia coli ATCC 25922 in phosphate buffered saline after treatment with high hydrostatic pressure. Int. J. Food Microbiol. 2006;110:108–111], who completely recovered Escherichia coli species after HP treatment. We investigated the recovery mechanism of E. coli after HP treatment. The cells were treated with 200–300 MPa at 0–25°C for 24 h. The HP-treated E. coli was recovered in phosphate-buffered saline (PBS) during 120 h of incubation at 25°C, confirming the results reported by them. However, E. coli did not grow in PBS but grew with inactivated cells in PBS. In addition, the results of our “population size experiments” demonstrated that the recovery of E. coli cells depended on both the degree of pressure and the population size. These results suggest that some portion of cells recovered from the damage and then grew by using inactivated cells.     

容积式压缩机内部热力过程试验台的研制

随着压缩机的发展,压缩机的性能检测方面也逐渐受到重视.容积式压缩机内部热力过程试验台可用于压缩机热力性能的测量分析.试验台通过labview平台开发了测试软件,对容积式压缩机运行过程中测得的转速、温度、压力、流量、功率等热力参数进行计算处理,获得压缩机工作过程指示图(p-V图),为优化压缩机热力过程、节约能耗提供重要依据.     

基于图像扩散去噪的距离特征量提取研究

距离特征量反映了目标运动过程中的距离变化率,该观测量可由目标辐射噪声LOFAR谱图的干涉条纹中提取得到。低信噪比情况下,由于噪声的影响,干涉条纹特征会变模糊,提取的距离特征量值精度会降低。为提高提取精度,提出了一种边缘定向增强型扩散方程去噪方法,对LOFAR谱图进行处理,使条纹特征更加明显。迭代次数对扩散方程去噪效果影响很大,根据相关性原理,提出了一种迭代次数选择方法。为了使条纹特征更加易于区分,提出了一种基于区域分割的图像二值化方法。数值模拟实验和海试数据处理结果表明,LOFAR谱图经过处理后,提取出的距离特征量精度明显提高。     

Proximity point algorithm for low-rank matrix recovery from sparse noise corrupted data

The method of recovering a low-rank matrix with an unknown fraction whose entries are arbitrarily corrupted is known as the robust principal component analysis （RPCA）. This RPCA problem, under some conditions, can be exactly solved via convex optimization by minimizing a combination of the nuclear norm and the 11 norm. In this paper, an algorithm based on the Douglas-Rachford splitting method is proposed for solving the RPCA problem. First, the convex optimization problem is solved by canceling the constraint of the variables, and ~hen the proximity operators of the objective function are computed alternately. The new algorithm can exactly recover the low-rank and sparse components simultaneously, and it is proved to be convergent. Numerical simulations demonstrate the practical utility of the proposed algorithm.     

Some Aspects of Current Interruption Physics in High Voltage Circuit Breakers

Recent results of experimental and theoretical investigations on current interruption processes are presented with a focus on SF₆ high voltage circuit breakers. Various aspects of thermal interruption at the zero crossing of the current are shown, including the scatter and the distribution of arc voltage shortly before CZ and the role of turbulence. The thermal interruption capability of air and CO₂ are compared to that of SF₆. Investigations on the dielectric recovery are shown for SF₆ and CO₂. The breakdown voltage during the dielectric recovery can be described by simple streamer and leader inception models. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一种基于混沌和汉明码的数字图像篡改检测及修复算法

提出了一种基于混沌映射和汉明码的数字图像篡改检测及修复算法.该算法采用了目前在信道编码中广泛使用的编组码汉明码,将差错控制应用于图像认证和修复,并使用混沌映射保证算法的有效性和安全性.分析及实验表明:该算法在保证良好的视觉效果,嵌入较少认证信息的前提下,可以有效地进行数字图像篡改检测,并能够完成一定程度的图像修复.     

利用高翅管换热器提高压力恢复系统效率

为提高压力恢复系统效率,设计并制造了一台高翅管换热器。采用滚扎而成的整体式螺旋高翅片管,代替套片式圆形普通翅片管,翅片管材料为紫铜,管束按等腰三角形叉排布置,管内强制水冷。测试了高翅管换热器的阻力特性,对比分析了加入换热器前后压力恢复系统性能的变化。结果表明:随着背压的提高,该换热器流阻逐渐降低,当背压达到9.366kPa时,换热器流阻为0.133kPa,仅占换热器入口激光尾气压力的1.4%;与不加换热器相比,加入高翅管换热器后的引射器混合室入口压力降低了12.95%,压力恢复系统的效率得到了提高。     

Weighted $\ell_p$-Minimization for Sparse Signal Recovery under Arbitrary Support Prior

Weighted $\ell_p$ ($0相似文献