Comparison between GdDTPA and two gadolinium polyoxometalates as potential MRI contrast agents

Two gadolinium polyoxometalates, Gd2P2W18O62 and K-15[(GdO)(3)(PW9O34)(2)], have been evaluated by in vivo as well as in vitro experiments as the candidates of tissue-specific magnetic resonance imaging (MRI) contrast agents. T-1-relaxivities of 28.4 mM(-1)-s(-1) for Gd2P2W18O62 and 11.2 mM(-1)-s(-1) for K-15[(GdO)(3)(PW9O34)(2)] (400 MHz, 25 degreesC) were higher than that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in bovine serum albumin and human serum transferrin were also reported. The favorable liver-specific contrast enhancement and renal excretion capability in in vivo MRI with Sprague-Dawley rats after i.v. administration of K-15[(GdO)(3)(PW9O34)(2)] was demonstrated. In vivo and in vitro assay showed that K-15[(GdO)(3)(PW9O34)(2)] is a promising liver-specific MRI contrast agent. However, Gd2P2W18O62 did not show the favorable quality in vivo as expected from its high relaxivity in vitro, which was attributed to low bioavailability, indicating that it is of limited value as tissue-specific MRI contrast agent.

An evaluation of gadolinium polyoxornetalates as possible MRI contrast agent

Two gadolinium polyoxometalates, K9GdW10O36 and K-11 [Gd(PW11O39)(2)], have been evaluated both in vivo and in vitro as candidates for tissue-specific MRI contrast agents. T-1-relaxivities of 6.89 mM(-1) . s(-1) for K9GdW10O36 and 5.27 mM(-1) . s(-1) for K-11[Gd(PW11O39)(2)] are slightly higher than that of the commercial MRI contrast agent (Gd-DTPA). Both compounds bind with bovine serum albumin and human serum transferrin and favorable liver-specific contrast enhancement in in vivo MRI with Sprague-Dawley rats after i.v. administration has been demonstrated. Imaging studies demonstrate that the two agents have a long residence time, showing MR signal enhancement in the liver for more than 40 min, longer than commercially available contrast agents. In vivo and in vitro assays showed that GdW10 and Gd(PW11)(2) are promising liver-specific MRI contrast agents and GdW10 may be used in the diagnosis of the pathological state. However, with the higher acute toxicity, the two gadolinium polyoxometalates need to be modified and studied further before clinical use.

电中性的GdDTPA双酰胺衍生物作为MRI造影剂

1988年德国卫生局批准(NMG)_2[Gd(DTPA)·H_2O]可作为 MRI 造影剂临床应用(商品名为 Magnevist),NMG 为 N-甲基葡萄糖胺根。从药物动力学角度看,Gd(DTPA)具有弛豫性强、毒性小、细胞外分布、不通过正常的血脑屏障、迅速由肾脏排出、在人体内结构稳定、具有高溶解度等特征。Gd(DTPA)对中枢神经系统病变增强效果良好,但是组织分布无特异性,对腹部器官如肝脏、脾脏的成像效果较差。为了改善其器官选择性,而且使生物体更易接受,减少毒副作用,人们在电中性的 GdDTPA 衍生物方面作了许多努力。

NMR titration and molecular model MOPAC calculation of protonation processes of two MRI ligands

The protonation process of two DTPA bis(amide) derivatives, DTPA-BDMA and DTPA-BDEA, was studied by using H-1 NMR titration and MOPAC calculation. Their protonation process was proposed in the order of the central amine, the terminal amines, the central carboxyl, the terminal carboxyl, the other terminal carboxyl and central amine. During the protonation of the terminal amine, there existed a large fraction of proton transfer from the central amine to the other terminal amine.

稀土化合物的一种新用途(上)——核磁共振成像(MRI)用造影剂

磁共振成像(Magnetic Resonance Imaging简称MRI)是近十几年来发展起来的一种新的医疗诊断手段,与x-射线计算机断层扫描(Computed Tomography简称x-CT)相比,具有明显的优点,如对脑部、腹腔部、椎间盘组织等的病变有较高的灵敏度。同时,由于磁场和射频电波对人体健康的损害远远小于x-CT产生的x-射线,因此,MRI法已成为当前

稀土化合物的一种新用途(下)——核磁共振成像(MRI)用造影剂

对选择MRI造影剂的要求及其应用MRI造影剂的选择除需遵循生物药剂的一般要求,如溶解性、稳定性等外,尚需有以下特殊要求。弛豫性质:所选择的试剂必须能大大增强靶组织被观测核的弛豫速率。能使弛豫速率增强10～20%的试剂,则可在MRI中应

Does multiparametric MRI increase Oncologic outcomes in prostate cancer?

The purpose of this study is to compare the 4-year biochemical disease-free survival (BDFS) of patients with prostate cancer (PCa) staged according to multiparametric MRI (mpMRI) and treated with radical prostatectomy (RP) versus intensity-modulated radiation therapy (IMRT) ≥76 Gy ± hormonal therapy (HT).

POCS-based reconstruction of multiplexed sensitivity encoded MRI (POCSMUSE): A general algorithm for reducing motion-related artifacts.

PURPOSE: A projection onto convex sets reconstruction of multiplexed sensitivity encoded MRI (POCSMUSE) is developed to reduce motion-related artifacts, including respiration artifacts in abdominal imaging and aliasing artifacts in interleaved diffusion-weighted imaging. THEORY: Images with reduced artifacts are reconstructed with an iterative projection onto convex sets (POCS) procedure that uses the coil sensitivity profile as a constraint. This method can be applied to data obtained with different pulse sequences and k-space trajectories. In addition, various constraints can be incorporated to stabilize the reconstruction of ill-conditioned matrices. METHODS: The POCSMUSE technique was applied to abdominal fast spin-echo imaging data, and its effectiveness in respiratory-triggered scans was evaluated. The POCSMUSE method was also applied to reduce aliasing artifacts due to shot-to-shot phase variations in interleaved diffusion-weighted imaging data corresponding to different k-space trajectories and matrix condition numbers. RESULTS: Experimental results show that the POCSMUSE technique can effectively reduce motion-related artifacts in data obtained with different pulse sequences, k-space trajectories and contrasts. CONCLUSION: POCSMUSE is a general post-processing algorithm for reduction of motion-related artifacts. It is compatible with different pulse sequences, and can also be used to further reduce residual artifacts in data produced by existing motion artifact reduction methods.

A Diffusion MRI Tractography Connectome of the Mouse Brain and Comparison with Neuronal Tracer Data.

Interest in structural brain connectivity has grown with the understanding that abnormal neural connections may play a role in neurologic and psychiatric diseases. Small animal connectivity mapping techniques are particularly important for identifying aberrant connectivity in disease models. Diffusion magnetic resonance imaging tractography can provide nondestructive, 3D, brain-wide connectivity maps, but has historically been limited by low spatial resolution, low signal-to-noise ratio, and the difficulty in estimating multiple fiber orientations within a single image voxel. Small animal diffusion tractography can be substantially improved through the combination of ex vivo MRI with exogenous contrast agents, advanced diffusion acquisition and reconstruction techniques, and probabilistic fiber tracking. Here, we present a comprehensive, probabilistic tractography connectome of the mouse brain at microscopic resolution, and a comparison of these data with a neuronal tracer-based connectivity data from the Allen Brain Atlas. This work serves as a reference database for future tractography studies in the mouse brain, and demonstrates the fundamental differences between tractography and neuronal tracer data.

Automated analysis of non-mass-enhancing lesions in breast MRI based on morphological, kinetic, and spatio-temporal moments and joint segmentation-motion compensation technique

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) represents an established method for the detection and diagnosis of breast lesions. While mass-like enhancing lesions can be easily categorized according to the Breast Imaging Reporting and Data System (BI-RADS) MRI lexicon, a majority of diagnostically challenging lesions, the so called non-mass-like enhancing lesions, remain both qualitatively as well as quantitatively difficult to analyze. Thus, the evaluation of kinetic and/or morphological characteristics of non-masses represents a challenging task for an automated analysis and is of crucial importance for advancing current computer-aided diagnosis (CAD) systems. Compared to the well-characterized mass-enhancing lesions, non-masses have no well-defined and blurred tumor borders and a kinetic behavior that is not easily generalizable and thus discriminative for malignant and benign non-masses. To overcome these difficulties and pave the way for novel CAD systems for non-masses, we will evaluate several kinetic and morphological descriptors separately and a novel technique, the Zernike velocity moments, to capture the joint spatio-temporal behavior of these lesions, and additionally consider the impact of non-rigid motion compensation on a correct diagnosis.

MRI diffusion tractography study in individuals with schizotypal features: A pilot study

Diffusion tensor imaging (DTI) studies have identified changes in white matter tracts in schizophrenia patients and those at high risk of transition. Schizotypal samples represent a group on the schizophrenia continuum that share some aetiological risk factors but without the confounds of illness. The aim of the current study was to compare tract microstructural coherence as measured by
fractional anisotropy (FA) between 12 psychometrically defined schizotypes and controls. We investigated bilaterally the uncinate and arcuate fasciculi (UF and AF) via a probabilistic tractography algorithm (PICo), with FA values compared between groups. Partial correlations were also examined between measures of subclinical hallucinatory/delusional experiences and FA values. High schizotypes
were found to have significantly higher FA values in bilateral UF only, but failed to reach significance in each hemisphere. In the whole sample there was a positive correlation between increasing FA values and measures of hallucinatory experience in the right AF. These findings suggest subtle changes in microstructural coherence are present in schizotypes. Correlations between mild hallucinatory experience and increasing FA values could indicate increasing coherence could be associated with symptom formation.

Partial volume correction using bimodal contrast agents in PET-MRI

Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2014