CRMSB, UMR 5536, University Bordeaux Segalen, CNRS, France.
Contrast Media Mol Imaging. 2012 Jan-Feb;7(1):45-50. doi: 10.1002/cmmi.464.
Overhauser-enhanced MRI (OMRI) offers the potentiality of detecting low-concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D-OMRI of a free radical injected in tumor-bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C-shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain-implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm³ , providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time-course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI-visible free radicals.
超极化增强磁共振成像（OMRI）具有检测特定生物过程产生的低浓度物质的潜力。然而，OMRI 的分子成像应用需要在空间定位方面有显著的改进。本文表明，在恒场中可以在高解剖分辨率下对荷瘤小鼠中注射的自由基进行 3D-OMRI。在 0.194 T 的质子磁共振成像中，将一个工作频率为 5.43GHz 的 30mm 空腔插入 C 形磁铁中。将带有或不带有脑内植入 C6 大鼠神经胶质瘤的裸鼠置于空腔中，并注射 TOPCA（1-氧代-2,2,5,5-四甲基-2,5-二氢-1H-吡咯-3-羧酸）。在没有动物过热的情况下，在几分钟内可以在脑部区域进行 3D-OMRI。体素大小为 0.5×0.5×1mm³，可以很好地区分脑区。在注射 TOPCA 几分钟后，信号增强幅度从肿瘤中的 2 到血管中的 10 不等。通过在局部薄层中以 15s 的时间间隔进行 2D-OMRI，可以测量信号增强的时间过程。该方法为能够产生 OMRI 可见自由基的生物活性的分子成像开辟了道路。
