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着的有机体中分子和细胞的功能。这项建议的目的是增加我们对使用金属胶体在磁共振成像中提供阳性对比度的知识。用Gd和锰合成的这些胶体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(生物标记物)的开发将有利于结合MRI和PET的下一代扫描仪的使用，这将很快在临床上成为现实。磁共振成像是一种在低密度组织中提供高分辨率图像的非侵入性成像技术。磁性分子或纳米颗粒通常是精细描绘血管系统、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用于提高MRI信号的特异性。通过在这些结晶的“纳米材料”中掺入精心挑选的放射性原子，下一代生物标记物可以用于双重PET/MRI程序。用于磁共振成像的磁性金属胶体的物理化学表征要求使用一种快速而准确的技术来测量悬浮在液体中的纳米颗粒的流体动力学半径。然后，通过测量Zeta电位，可以评估粒子聚集的趋势。最后，可以使用专用的弛豫计(质子弛豫时间的测量)在不同温度下精确测量造影剂在MRI图像中产生强对比效果的潜力。核磁共振质子弛豫分析仪也可以用来测量标记有磁性示踪剂的细胞悬浮液产生的对比度。这些技术的结合使用对于进一步开发用于双重PET/MRI的磁性和放射性示踪剂至关重要。

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.