在辐射阻尼存在下有效横向弛豫时间T＊2的快速测定

THE MEASURREMENT OF THE EFFECTIVE TRANSVERSE RELAXATION TIME IN THE PRESENCE OF RADIATION DAMPING

利用CPMG自旋回波技术 ,通过一连串 1 80°脉冲抑制辐射阻尼效应 ,让磁化矢量经过横向弛豫T2 过程大幅度衰减后再检测回波信号的线宽 ,该方法可直接获得有效横向弛豫时间T 2 ,并可在CPMG测试T2 值的同时进行 .另外 ,当饱和恢复法用于估计T 2 值时 ,信号检测必须使用小角度脉冲 .所有结果已进行了实验验证 .

A new procedure for measuring the effective transverse relaxation time T\+*\-2 in the presence of radiation damping is proposed here. After the amplitude of the echo obtained by CPMG pulse sequence is largely decayed by the intrinsic T\-2 relaxation process, its linewidth is no longer broadened by the radiation damping effect and thus a good measure of the true value of T\+*\-2 is possible. Accordingly, for the damped case, the T\+*\-2 and T\-2 can in fact be simultaneously determined in a CPMG spin echo experiment. In addition, when the saturation recovery experiment was utilized to measure T\+*\-2 , the small flip angle pulse must be applied to detect the signals. \;