Quesson B, Thiaudière E, Delalande C, Dousset V, Chateil J F, Canioni P
Résonance Magnétique des Systèmes Biologiques, UMR 5536 CNRS, Université Victor Segalen Bordeaux, France.
Magn Reson Med. 1997 Dec;38(6):974-80. doi: 10.1002/mrm.1910380617.
Proton magnetization transfer contrast (MTC) imaging, using continuous wave off-resonance irradiation, was performed on the rat brain in vivo at 4.7 Tesla. The observed MTC was studied in three different brain regions: the corpus callosum, the basal ganglia, and the temporal lobe. By systematically varying the offset frequency and the amplitude of the RF irradiation, the observed signal intensities for each region of interest were modeled using a system including free water and a pool of protons with restricted motions (R. M. Henkelman, X. Huang, Q. Xiang, G. J. Stanisz, SD Swanson, M. J. Bronskill, Magn. Res. Med. 29, 759 (1993)). Most of the relaxation parameters of both proton pools remained fairly constant for the three regions of interest, with a T2 value of about 9 micros for the immobilized protons, whereas the rate of exchange increased significantly from the temporal lobe to the corpus callosum. The optimal acquisition parameters for the improved MTC under steady-state saturation were found to be 2-10 kHz offset frequency and 500-800 Hz RF irradiation amplitude. Conversely, an irradiation amplitude of 3 kHz at an offset frequency of 12 kHz is required to minimize the direct effect of off-resonance irradiation. Such an approach could be extended to human brain imaging with the aim of characterizing tissue-specific disease.
利用连续波失谐照射的质子磁化传递对比（MTC）成像，在4.7特斯拉场强下对大鼠脑进行了活体研究。在三个不同脑区研究了观察到的MTC：胼胝体、基底神经节和颞叶。通过系统地改变射频照射的偏移频率和幅度，使用包括自由水和具有受限运动的质子池的系统对每个感兴趣区域观察到的信号强度进行建模（R.M.亨克尔曼、X.黄、Q.向、G.J.斯塔尼斯、SD斯旺森、M.J.布罗斯基尔，《磁共振医学》29卷，759页（1993年））。对于三个感兴趣区域，两个质子池的大多数弛豫参数保持相当恒定，固定化质子的T2值约为9微秒，而交换率从颞叶到胼胝体显著增加。发现在稳态饱和下改进的MTC的最佳采集参数为偏移频率2 - 10千赫兹和射频照射幅度500 - 800赫兹。相反，为了最小化失谐照射的直接影响，在12千赫兹的偏移频率下需要3千赫兹的照射幅度。这种方法可以扩展到人类脑成像，目的是表征组织特异性疾病。
