An MR imaging method for simultaneous measurement of gaseous diffusion constant and longitudinal relaxation time
An MR imaging method for simultaneous measurement of gaseous diffusion constant and longitudinal relaxation time
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DOI：
10.1016/s0730-725x(98)00106-4
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发表时间：
1999-02-01
影响因子：
2.5
通讯作者：
Leigh, JS
中科院分区：
文献类型：
--
作者：
Dimitrov, IE;Charagundla, SR;Leigh, JS
本文介绍一种同时精确测定气体扩散常数和纵向弛豫时间的磁共振成像方法。该方法是基于扩散运动的直接观察。最初，在He-3/O-2体模（9 atm/2 atm）上进行氦-3（He-3）自旋的切片选择性饱和，饱和后引入时间延迟间隔，允许自旋扩散进出标记的切片。在延迟间隔之后，采集体模的一维（1-D）投影图像。收集了一系列21张图像，每个后续图像都是以增加的延迟间隔采集的。因此观察到由于扩散而导致的切片边界的逐渐扩展。将投影轮廓拟合到针对扩散运动校正的Bloch方程的解，拟合过程产生D-3 He = 0.1562 +/- 0.0013 cm（2）/s的值，与用标准脉冲场梯度技术的修改版本获得的测量结果非常一致。该方法还使我们能够准确地测量3 He自旋的纵向弛豫，通过拟合投影轮廓下的总面积的变化的指数。记录了T-1 = 1.67 s（2 T场）的值，与反转恢复测量非常一致。(C)1999 Elsevier Science Inc.
A magnetic resonance imaging method for simultaneous and accurate determination of gaseous diffusion constant and longitudinal relaxation time is presented. The method is based on direct observation of diffusive motion. Initially, a slice-selective saturation of helium-3 (He-3) spins was performed on a He-3/O-2 phantom (9 atm/2 atm), A time-delay interval was introduced after saturation, allowing spins to diffuse in and out of the labeled slice. Following the delay interval a one-dimensional (1-D) projection image of the phantom was acquired. A series of 21 images was collected, each subsequent image having been acquired with an increased delay interval. Gradual spreading of the slice boundaries due to diffusion was thus observed. The projection profiles were fit to a solution of the Bloch equation corrected for diffusive motion, The fitting procedure yielded a value of D-3He = 0.1562 +/- 0.0013 cm(2)/s, in good agreement with a measurement obtained with a modified version of the standard pulsed-field gradient technique. The method also enabled us to accurately measure the longitudinal relaxation of 3He spins by fitting the change of the total area under the projection profiles to an exponential. A value of T-1 = 1.67 s (2 T field) was recorded, in excellent agreement with an inversion recovery measurement. (C) 1999 Elsevier Science Inc.