Pulse sequences for T1- and T1T2-contrast enhancement in NMR imaging

Probing pulse sequences of the type 90°- τ₀-180°-τ₁-...180°-τ_n with optimized intervals τ_i provide a higher T₁-contrast in the NMR imaging compared to that obtained using the saturation-recovery or stimulated echo pulse sequences. Signals obtained with the proposed pulse sequences, unlike that for the inversion-recovery sequence, do not change sign and provide more reliable information. The new pulse sequences serve as filters that select only signals with short relaxation times T₁. The filter bandwidth increases with the number of RF pulses in the sequence. It is suggested that the new sequences can be used in combination with the CPMG pulse sequence to provide the T₁T₂-contrast. The domain of interest, in which the T₁T₂-contrast is enhanced, is determined by measuring two time intervals in the combined pulse sequence. In the first interval, the signal reaches a preset level in the course of the spin-lattice relaxation, and during the second interval, a preset level is attained for the spin-spin relaxation.