Abstract
Spin-lattice proton relaxation times (TI) 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 TI of the sample was measured with the two-data point method. In the case of bi-exponential relaxation the value of a single TI is strongly dependent on the TI and TR selected. With short TI the TI value obtained by using the two point method is approximately equal to the weighted average of the two relaxation time components (TIs and TII), while at long inversion times TI the single TI is more dependent on the long component TII. The more the true short and long relaxation time components TIs and TII of the bi-exponential relaxation differ from each other, the greater is the potential error, provided that the weights ws and wI 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 TI 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.