Magnetic resonance image denoising using nonlocal maximum likelihood paradigm in DCT‐framework

The data acquired by magnetic resonance (MR) imaging system are inherently degraded by noise that has its origin in the thermal Brownian motion of electrons. Denoising can enhance the quality (by improving the SNR) of the acquired MR image, which is important for both visual analysis and other post processing operations. Recent works on maximum likelihood (ML) based denoising shows that ML methods are very effective in denoising MR images and has an edge over the other state‐of‐the‐art methods for MRI denoising. Among the ML based approaches, the Nonlocal maximum likelihood (NLML) method is commonly used. In the conventional NLML method, the samples for the ML estimation of the unknown true pixel are chosen in a nonlocal fashion based on the intensity similarity of the pixel neighborhoods. Euclidean distance is generally used to measure this similarity. It has been recently shown that computing similarity measure is more robust in discrete cosine transform (DCT) subspace, compared with Euclidean image subspace. Motivated by this observation, we integrated DCT into NLML to produce an improved MRI filtration process. Other than improving the SNR, the time complexity of the conventional NLML can also be significantly reduced through the proposed approach. On synthetic MR brain image, an average improvement of 5% in PSNR and 86%reduction in execution time is achieved with a search window size of 91 × 91 after incorporating the improvements in the existing NLML method. On an experimental kiwi fruit image an improvement of 10% in PSNR is achieved. We did experiments on both simulated and real data sets to validate and to demonstrate the effectiveness of the proposed method. © 2015 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 25, 256–264, 2015     

Dendrimer as nanocarrier for drug delivery

Dendrimers are novel three dimensional, hyperbranched globular nanopolymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery and cavities in the interior distinguish them amongst the available polymers. Applications of dendrimers in a large variety of fields have been explored. Drug delivery scientists are especially enthusiastic about possible utility of dendrimers as drug delivery tool. Terminal functionalities provide a platform for conjugation of the drug and targeting moieties. In addition, these peripheral functional groups can be employed to tailor-make the properties of dendrimers, enhancing their versatility. The present review highlights the contribution of dendrimers in the field of nanotechnology with intent to aid the researchers in exploring dendrimers in the field of drug delivery.     

111In-octreotide生长抑素受体显像与CT/MRI显像比较

比较了＾１１１Ｉｎ－ｏｃｔｒｅｏｔｉｄｅ生长抑素受体显像（ＳＲＩ）与ＣＴ／ＭＲＩ检测生长抑素受体阳性肿瘤的敏感性。２２例患者接受了ＳＲＩ平面和ＳＰＥＣＴ断层显像,并同期接受ＣＴ／ＭＲＩ检查;将ＳＲＩ结果与ＣＴ／ＭＲＩ、临床和组织病理结果比较,结果表明＾１１１Ｉｎ－ｏｃｔｅｏｔｉｄｅ生长抑素受体显像检测生长抑素受体阳性肿瘤的敏感性和准确性明显高于ＣＴ／ＭＲＩ,尤其是对于肝外肿瘤。提示功能显像和解剖显     

多模态影像学检查在诊断早期强直性脊柱炎骶髂关节疾病中的效果

目的:探究在早期强直性脊柱炎骶髂关节疾病诊断中不同放射影像学检查方法的应用效果.方法:抽取2018年5月-2020年1月本院收治的早期强直性脊柱炎骶髂关节疾病患者65例作为研究对象,所有患者均开展X线、CT、MRI影像学检查,对比三种不同影像学检查方法的检出率、影像学特征.结果:X线、CT、MRI检出率分别为38.46...     

A Novel Yolk–Shell Fe3O4@ Mesoporous Carbon Nanoparticle as an Effective Tumor-Targeting Nanocarrier for Improvement of Chemotherapy and Photothermal Therapy

Owing to their good stability and high photothermal conversion efficiency, the development of carbon-based nanoparticles has been intensively investigated, while the limitation of unsatisfactory cellular internalization impedes their further clinical application. Herein, we report a novel strategy for fabrication of Fe₃O₄ yolk–shell mesoporous carbon nanocarriers (Fe₃O₄@hmC) with monodispersity and uniform size, which presented significantly higher cell membrane adsorption and cellular uptake properties in comparison with common solid silica-supported mesoporous carbon nanoparticles with core–shell structure. Moreover, the MRI performance of this novel Fe-based nanoparticle could facilitate precise tumor diagnosis. More importantly, after DOX loading (Fe₃O₄@hmC-DOX), owing to synergistic effect of chemo–phototherapy, this therapeutic agent exhibited predominant tumor cell ablation capability under 808 nm NIR laser irradiation, both in vitro and in vivo. Our work has laid a solid foundation for therapeutics with hollowed carbon shell for solid tumor diagnosis and therapy in clinical trials.     

MRI图像的基于窄带的递进多分区C-V分割方法

提出了递进的基于窄带的多分区C-V方法,并对多幅医学脑部MRI图像进行了分割实验。由于该递进方法分为多个阶段,每阶段只需一个水平集函数,并且在每一阶段应用窄带区域,即只处理窄带区域中的点,从而使计算量大大减少。实验结果证明本算法是有效的,在提高计算速度的同时,可大大改进复杂几何结构的分割效果。     

一种基于蚁群算法的Snake模型与MRI分割

Snake模型以其收敛快速、精确度可达到亚像素等优点,被广泛地应用于医学图像分割,但该模型依赖于初始曲线的选取,易于收敛到局部最优且难以达到凹陷区域。为此提出一种基于蚁群算法的Snake模型,首先利用区域内灰度统计特征自动进行Snake初始化,然后在Snake演化过程中加入一向心力,使其能进入凹陷区域,最后用蚁群算法对演化结果进行优化,使其收敛到全局最优,获得最终的分割结果。实验结果表明,改进的模型在MRI分割中可以得到较好的分割结果。     

大鼠C6脑胶质细胞移植瘤肿瘤模型动态生长核磁共振表现

目的: 建立大鼠C6脑胶质瘤模型。在不同时段以磁共振平扫、增强扫描、DWI和MRS多种技术对大鼠脑组织进行扫描成像分析, 动态观察接种后大鼠脑组织内胶质瘤的生长情况, 测量肿瘤体积变化, 细胞的凋亡情况以及肿瘤细胞密集区域, 无创性检测活体组织器官能量代谢、生化改变和特定化合物定量分析。建立大鼠C6脑胶质瘤模型MRI肿瘤动态生长数据库。方法: 建立大鼠C6脑胶质瘤模型。大鼠接种C6脑胶质瘤细胞的不同时段(接种前、接种后第7天、第14天、第21天)在活体无创状态下, 在不同时段分别运用MRI常规、增强扫描, DWI和MRS多种技术对大鼠脑组织进行扫描成像分析, 建立大鼠C6脑胶质瘤模型MRI肿瘤动态生长数据库, 最后将大鼠处死取脑组织进行肉眼、病理和电镜验证。结果: 肿瘤体积生长第14天与第7天均值比是5.010 0±0.450 0倍, 第21天与7天均值比是17.990 0±0.910 0倍, 解剖肉眼、病理、电镜均可见肿瘤及肿瘤细胞。正常脑组织DWI弥散成像ADC值测定, 平均值(B＝1 000)420.183 3±75.598 0)明显低于各时间肿瘤组, 接种肿瘤后7、14、21天ADC均值为738.598 0±219.568 0、660.645 0±105.322 0、551.366 7±103.578 0均高于正常脑组织, ADC均值T检验正常脑组织与7天及14天肿瘤组比, P值＜0.05, 有显著差异。 肿瘤生长的第14、21天ADC值不断的降低。大鼠C6脑胶质瘤移植瘤模型接种不同时间MRS测定cho/NAA均值, 正常脑在第1、7、14、21天在0.5左右, 而接种后的大鼠C6脑胶质瘤7、14、21天测定cho/NAA均值为5.532 0±4.066 4、6.560 0±3.440 0、8.938 0±4.079 4, 随着肿瘤的长大比值均值在不断加大。结论: 磁共振平扫、增强扫描、DWI和MRS多种技术对大鼠脑组织进行扫描成像分析, 能在无创情况下动态观察接种后大鼠脑组织内胶质瘤的生长情况, 测量肿瘤体积变化, 细胞的凋亡情况以及肿瘤细胞密集区域, 无创性检测活体组织器官能量代谢、生化改变和特定化合物定量分析。     

Well‐Defined Protein‐Based Supramolecular Nanoparticles with Excellent MRI Abilities for Multifunctional Delivery Systems

Protein‐based nanoparticles are widely used for effective biomedical applications. The objective of this work is to design series of magnetic resonance imaging (MRI)‐visible cationic supramolecular nanoparticles (PGEA@BSA‐Ad/Gd³⁺) based on bovine serum albumin (BSA) and β‐cyclodextrin‐cored star ethanolamine‐functionalized poly(glycidyl methacrylate) (CD‐PGEA) in the presence of Gd³⁺ ions for multifunctional delivery systems. CD‐PGEA is prepared via atom transfer radical polymerization and ring‐opening reaction. It is found that in the absence of Gd³⁺ ions, CD‐PGEA does not well interact with adamantine‐modified BSA (BSA‐Ad). The well‐defined PGEA@BSA‐Ad/Gd³⁺ supramolecular nanoparticles could be produced through the synergistic actions of the host–guest and electrostatic self‐assemblies by mixing aqueous solutions of CD‐PGEA, BSA‐Ad, and Gd³⁺. In comparison with CD‐PGEA assembly units, such kinds of uniform PGEA@BSA‐Ad/Gd³⁺ supramolecular nanoparticles exhibit better pDNA condensation ability, lower cytotoxicity, higher gene transfection, and easier cellular uptake. In addition, PGEA@BSA‐Ad/Gd³⁺ also produces outstanding MRI abilities, much better than Magnevist (Gd‐diethylenetriaminepentacetate acid). The present design of protein–polymer supramolecular nanoparticles with MRI contrast agents would provide a new way for multifunctional gene/drug delivery systems.     

心脏MRI图像快速分割方法

在分析心脏MR图像特点的基础上,提出了先对心脏MRI图像进行K均值聚类,把K均值聚类后的图像作为特征图像,在特征上用Song和Chan提出的快速分割方法进行粗分割,再用粗分割的曲线作为水平集的初始曲线,在心脏MRI图像上用Chan和Vese方法进行细分割的心脏MR图像分割方法.并对Song和Chan快速算法中扫描图像的区域进行了改进,提高了分割速度.分割实验证明,用该方法能够快速、准确地分割心脏MRI图像.