the condition of the spin as shown in fig5 a 2 moreover this spin condition of fig5 a 2 is changed into another spin condition of fig5 a 3 due to dephasing by the effects of field inhomogeneity within 1 2 t e u03c4 when the spin condition is brought into such a condition as shown in fig5 a 3 the non selective excitation 180 u00b0 pulse is applied to reverse the polarity of the spin as represented in fig5 b subsequently when the next compensating slicing gradient field g s2 is applied see fig3 b the spin condition of fig5 b is changed into another spin condition of fig5 c namely the spins are rephased thereafter the spin is refocused to induce the echo signals during the data acquisition period see fig3 b and 5d generally speaking as a result of the spin behaviour the net vector value of the spin caused by the spin precession is reduced in accordance with the 34 t 2 34 relaxation time accordingly as previously explained since the total echo time 34 t e 34 of the present invention is considerably shorter than that of the convention spin echo method reduction of the net spin vector value is not so large as compared with that of the conventional spin echo method this advantage of the present invention will now be visually explained with reference to fig6 a and 6b as illustrated in fig6 a with regard to a spin having a constant relaxation time 34 t 2 34 for instance when u03c4 1 2 msec i e echo time t e 2 u03c4 1 4 msec a strength of an echo signal acquired by the first specific spin echo method of the present invention is attenuated from one point 34 a 34.