Roell S A, Dreher W, Leibfritz D
Universität Bremen, Fachbereich 2 (Chemie), Bremen, Germany.
Magn Reson Med. 1999 Aug;42(2):222-7. doi: 10.1002/(sici)1522-2594(199908)42:2<222::aid-mrm2>3.0.co;2-d.
Selective saturation of bound nuclei attenuates the MR visible CH(2) and the CH(3) signal of total creatine (tCr) in rat brain in vivo. The low contrast to noise ratio achieved during the limited experiment time makes it difficult to quantify the effect. It is shown that by combining data from continuous-wave and pulsed saturation experiments, quantitation is possible using the standard magnetization transfer model. The model parameters obtained are the transverse relaxation time of the bound spin fraction B, T2R = 31 +/- 8 micros, the exchange rate r(x) = 0.36 +/- 0.04 s(-1), and the concentration ratio of bound nuclei taking part in the exchange to free tCr magnetization, f = M0B/M0A = 0.04 +/- 0.01. The phenomenon can be explained by either an intermolecular exchange of free and bound creatine molecules or by through-space interaction with bound nuclei showing not necessarily the same chemical shift. Magn Reson Med 42:222-227, 1999.
结合连续波和脉冲饱和实验的数据表明，通过标准的磁化传递模型可以实现定量分析。体内大鼠脑内结合核的选择性饱和减弱了总肌酸（tCr）的磁共振可见CH(2)和CH(3)信号。在有限的实验时间内实现的低对比度噪声比使得难以量化该效应。获得的模型参数为结合自旋分数B的横向弛豫时间，T2R = 31 +/- 8微秒，交换率r(x) = 0.36 +/- 0.04 s(-1)，以及参与交换的结合核与游离tCr磁化的浓度比，f = M0B/M0A = 0.04 +/- 0.01。这种现象可以通过游离和结合肌酸分子的分子间交换，或者通过与不一定具有相同化学位移的结合核的空间相互作用来解释。《磁共振医学》42:222 - 227，1999年。
