在用核磁共振成像的方法来检测疾病的时候,水中质子的纵向弛豫时间T_1的值,是一个很重要而且很灵敏的物理量。这个量是由一系列很复杂的物理现象来决定的。因此,在通过T_1值变化的测量来检测疾病的时候,准确度的提高是不容易的,要受到多种因素的干扰。例如,脉冲序列的时间间隔的选择,该时间间隔比波谱的情况下更短;射频场的不均匀性;分子和组织的杂质;活体中的运动和血流等。然而,由于T_1值对比度的图像在临床上能提供 The value of T 1, the longitudinal relaxation time of protons in water, is a very important and sensitive physical quantity when detecting diseases by using magnetic resonance imaging. This quantity is determined by a series of very complex physical phenomena. Therefore, when the disease is detected by the measurement of the change in the value of T 1, the improvement of the accuracy is not easy and is disturbed by many factors. For example, the choice of the time interval of the pulse sequence, which is shorter than in the case of spectroscopy; the inhomogeneity of the radio-frequency field; the impurities of molecules and tissues; the movement and blood flow in the living body and the like. However, images due to T_1 contrast can be clinically available