超灵敏129Xe磁共振分子影像学新方法---化学交换反转转移

项目名称： 超灵敏129Xe磁共振分子影像学新方法---化学交换反转转移

项目编号： No.21475147

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 罗晴

作者单位： 中国科学院武汉物理与数学研究所

项目金额： 90万元

中文摘要： 磁共振成像MRI在结构成像和功能成像中都取得巨大成功并应用于临床医学，但灵敏度成为传统MRI技术应用于分子影像学的巨大障碍。基于激光抽运超极化技术、新型探针分子发展出的超灵敏129Xe分子影像技术，将磁共振方法对生物分子进行靶向检测的灵敏度增强了约5 个数量级，是目前国际上分子影像学研究中是最前沿的技术领域。HYPERCEST是超灵敏129Xe分子影像技术中最常用也是灵敏度最高的成像方法。本项目针对该方法在实验中因为高占空比带来的诸多问题：如生物体热效应、MRI仪器硬件负载过大等，提出了一种新的化学交换反转转移MRI成像方法。预期该方法不仅能大幅度缓解上述困难，还将在现有技术的基础上进一步将灵敏度提升50%以上。本项研究的成果将提高超灵敏MRI分子影像学技术的可行性和成熟度。在该项目中，我们还将发展与此新的MRI成像方法之相匹配的，兼具超灵敏度和靶向性的生物探针分子。

中文关键词： 超灵敏磁共振；分子影像学；分子探针；超极化技术；化学交换

英文摘要： Magnetic resonance imaging (MRI) is a safe and painless test that uses a magnetic field and radio waves to produce detailed pictures of the body's organs。 However, the intrinsic low sensitivity of MRI in comparison to the other medical imaging techniques, e.g. optical analysis, CT, greatly limits its applications in molecular imaging. Molecular imaging is a novel biomedical discipline, and it could visualize the biological processes at cellular and subcellular levels by in vivo imaging modalities, such as PET, SPECT, MRI, optical imaging and etc. An important potential utilization of MR molecular imaging is to develop highly sensitive methods to diagnose the malignant diseases, like cancers or tumors, at the very early stages. As an unconventional MR method, optically pumped hyperpolarized 129Xe possesses a 4-5 orders of magnitude higher spin polarization comparing to the conventional one. Functionalized cryptophane cages with specific targeting ability is able to trap the dissolved xenon and confer 129Xe NMR signals with molecular specificity . The signal of xenon-based molecular sensors can be further amplified through the CEST. In such method, the spin polarization of the trapped xenon in cage is saturated by selective RF irradiation in a time scale of few seconds to tens of seconds, and eventually the saturation is accumulated in the polarization of free xenon, through the repeating exchange between free xenon and trapped xenon atoms. The long time saturation RF irradiation introduces the problem of high duty cycle,which is a harsh challenge to MRI amplifier. In this project, the inversion pulses separated with blanking of several ms or even longer are used instead of the continuous irradiation, and it demonstrates a higher efficiency to built the contrast with lower duty cycle.

英文关键词： Ultra-high sensitivity NMR;Molecular Imaging;biosensor;hyperpolarization;chemical exchange