Proton relaxation studies and particle size analysis of suspensions of magnetic and radioactive metal colloids

分子成像使现代医学能够检查活生物体中分子和细胞的功能。本建议的目的是增加我们关于使用金属胶体在磁共振成像中提供正对比的知识。这些胶体由钆和锰合成，在细胞标记和跟踪方面显示出巨大的潜力。在磁共振成像（MRI）和正电子发射断层扫描（PET）中提供高特异性信号的造影剂和示踪剂（生物标志物）的发展可以与下一代MRI和PET相结合的扫描仪有利地使用，这将很快成为临床的现实。MRI是一种无创成像技术，可在低密度组织中提供高分辨率图像。磁性分子或纳米颗粒通常是精细描绘脉管系统、精确识别疾病伪影和跟踪细胞所必需的。PET也是一种非侵入性成像技术，基于对放射性示踪剂的高灵敏度检测。纳米颗粒形式的磁性金属胶体可以用来提高MRI信号的特异性。通过将这些晶体“纳米材料”与精心挑选的放射性原子掺杂，下一代生物标志物可以用于PET/MRI双重程序。磁性金属胶体的物理化学表征需要使用一种快速准确的技术来测量悬浮在流体中的纳米颗粒的流体动力学半径。然后，通过测量zeta电位，就有可能评估粒子聚集的趋势。最后，对比剂在MRI图像中产生强烈对比效果的潜力，可以用专用弛豫仪在不同温度下精确测量（测量质子弛豫时间）。核磁共振质子弛豫分析仪也可以用来测量用磁性示踪剂标记的细胞悬浮液产生的对比度。这些技术的结合使用对于双PET/MRI的磁性和放射性示踪剂的开发至关重要。

Molecular imaging allows modern medicine to examine the functions of molecules and cells in living organisms. The aim of this proposal is to increase our knowledge regarding the use of metal colloids providing positive contrast in magnetic resonance imaging. Synthesized with gadolinium and manganese, these colloids display huge potential for cell labelling and tracking. The development of contrast agents and tracers (biomarkers) providing high and specific signal in magnetic resonance imaging (MRI) and positron emission tomography (PET) could be advantageously used with a next generation of scanners combining MRI and PET, that will soon become a reality in the clinic. MRI is a non-invasive imaging technique providing high resolution pictures in low density tissues. Magnetic molecules or nanoparticles are often necessary to finely delineate the vasculature, to precisely identify disease artefacts, and to track cells. PET is also a non-invasive imaging technique, based on the detection at very high sensitivity, of radioactive tracers. Magnetic metal colloids in the form of nanoparticles can be used to improve the specificity of the MRI signal. By doping these crystalline "nanomaterials" with carefully selected radioactive atoms, a next generation of biomarkers could become available for dual PET/MRI procedures. The physico-chemical characterization of magnetic metal colloids for MRI requires the use of a fast and accurate technique for measuring the hydrodynamic radius of the nanoparticles suspended in fluids. Then, by measuring the zeta potential, it is possible to evaluate the tendency of the particles to aggregate. Finally, the potential of the contrast agent to generate strong contrast effects in MRI pictures, can be precisely measured at varying temperatures with a dedicated relaxometer (measurement of proton relaxation times). NMR proton relaxation analyzers can also be used to measure the contrast generated by suspensions of cells marked with magnetic tracers. The combined use of these technologies are crucial for the  development of magnetic and radioactive tracers for dual PET/MRI.