Center for Neuroscience and Regenerative Medicine, Henry M. Jackson Foundation, Bethesda, MD, USA.
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
Sci Rep. 2021 Jan 8;11(1):106. doi: 10.1038/s41598-020-80181-9.
Magnetic resonance imaging (MRI) is a widely used non-invasive methodology for both preclinical and clinical studies. However, MRI lacks molecular specificity. Molecular contrast agents for MRI would be highly beneficial for detecting specific pathological lesions and quantitatively evaluating therapeutic efficacy in vivo. In this study, an optimized Magnetization Prepared-RApid Gradient Echo (MP-RAGE) with 2 inversion times called MP2RAGE combined with advanced image co-registration is presented as an effective non-invasive methodology to quantitatively detect T1 MR contrast agents. The optimized MP2RAGE produced high quality in vivo mouse brain T1 (or R1 = 1/T1) map with high spatial resolution, 160 × 160 × 160 µm voxel at 9.4 T. Test-retest signal to noise was > 20 for most voxels. Extremely small iron oxide nanoparticles (ESIONPs) having 3 nm core size and 11 nm hydrodynamic radius after polyethylene glycol (PEG) coating were intracranially injected into mouse brain and detected as a proof-of-concept. Two independent MP2RAGE MR scans were performed pre- and post-injection of ESIONPs followed by advanced image co-registration. The comparison of two T1 (or R1) maps after image co-registration provided precise and quantitative assessment of the effects of the injected ESIONPs at each voxel. The proposed MR protocol has potential for future use in the detection of T1 molecular contrast agents.
磁共振成像（MRI）是一种广泛应用于临床前和临床研究的非侵入性方法。然而，MRI 缺乏分子特异性。用于 MRI 的分子对比剂对于检测特定的病理病变和体内定量评估治疗效果将非常有益。在这项研究中，提出了一种优化的磁化准备快速梯度回波（MP-RAGE），它有两种反转时间，称为 MP2RAGE，并结合了先进的图像配准，作为一种有效的非侵入性方法来定量检测 T1 MR 对比剂。优化的 MP2RAGE 在 9.4 T 下产生了高质量的体内小鼠脑 T1（或 R1=1/T1）图，具有高空间分辨率，160×160×160 µm 体素。大多数体素的测试-重复信号噪声比>20。经过聚乙二醇（PEG）涂层后，具有 3nm 核尺寸和 11nm 水动力半径的超小氧化铁纳米颗粒（ESIONPs）被颅内注射到小鼠脑中，并作为概念验证进行了检测。在注射 ESIONPs 之前和之后进行了两次独立的 MP2RAGE MR 扫描，然后进行了先进的图像配准。图像配准后对两个 T1（或 R1）图进行比较，为每个体素注射的 ESIONPs 的效果提供了精确和定量的评估。所提出的磁共振方案有可能用于未来检测 T1 分子对比剂。
