Komu M, Alanen A, Määttänen H, Kormano M
Department of Diagnostic Radiology, University Central Hospital, Turku, Finland.
Acta Radiol. 1989 Jan-Feb;30(1):97-100.
Spin-lattice proton relaxation times (T1) in several biologic and phantom samples have been measured and analysed by using standard inversion recovery (IR) and spin echo (SE) sequences at 0.02 T. The average T1 of the sample was measured with the two-data point method. In the case of bi-exponential relaxation the value of a single T1 is strongly dependent on the TI and TR selected. With short TI the T1 value obtained by using the two point method is approximately equal to the weighted average of the two relaxation time components (T1s and T1l), while at long inversion times TI the single T1 is more dependent on the long component T1l. The more the true short and long relaxation time components T1s and T1l of the bi-exponential relaxation differ from each other, the greater is the potential error, provided that the weights ws and wl do not differ very much. When two-data point analyzing method is used, the possible multi-exponential behaviour of the relaxation in tissues will be missed. For more reliable T1 values a series of images with as many values of TI as possible should be taken. Knowledge of true multi-exponential relaxation parameters helps in optimizing the sequence parameters and the image contrast between the various tissues.
利用标准反转恢复（IR）和自旋回波（SE）序列，在0.02T磁场下对多种生物样本和模型样本的自旋晶格质子弛豫时间（T1）进行了测量和分析。采用两点法测量样本的平均T1。在双指数弛豫情况下，单个T1值强烈依赖于所选的TI和TR。当TI较短时，用两点法获得的T1值近似等于两个弛豫时间分量（T1s和T1l）的加权平均值，而在较长的反转时间TI时，单个T1更依赖于长分量T1l。在双指数弛豫中，真正的短弛豫时间分量T1s和长弛豫时间分量T1l彼此差异越大，潜在误差就越大，前提是权重ws和wl差异不是很大。当使用两点分析法时，组织中弛豫可能的多指数行为将会被遗漏。为了获得更可靠的T1值，应采集一系列具有尽可能多TI值的图像。了解真正的多指数弛豫参数有助于优化序列参数以及不同组织之间的图像对比度。
