Using T as a direct detection dimension in two-dimensional time-domain NMR experiments using CWFP regime.

The transverse relaxation time (T), measured with Carr-Purcell-Meiboom-Gill (CPMG) sequence, has been widely used to obtain the direct dimension data in two-dimension time domain NMR (2D TD-NMR). In this paper we are demonstrating that Continuous Wave Free Precession sequence, with low flip angle (CWFP-T), can be an alternative to CPMG as direct detection dimension. CWFP-T is a fast single shot sequence, like CPMG, and yields an exponential signal governed predominantly by the longitudinal (T) relaxation time. To obtain the correlations between T and T (T-T maps) we are proposing the use of CPMG-CWFP-T pulse sequence. In this sequence CPMG encodes T information (indirect dimension) that modulates the CWFP-T (direct dimension) signal amplitudes. CPMG-CWFP-T experiments were compared with classical 2D sequences such as Saturation-Recovery-CPMG (SR-CPMG) and Inversion-Recovery-CPMG (IR-CPMG) sequence and yields similar results in phantom sample. The experimental time for the 2D sequences, using single scan, shows that SR-CPMG ≤ CPMG-CWFP-T < IR-CPMG. Experimental and simulated results demonstrated that 2D-CPMG-CWFP-T maps have higher resolution in T dimension than the techniques that uses CPMG as direct dimension. CPMG-CWFP-T sequence was also applied to study beef samples, and 2D maps showed higher resolution in the two fat signals than the classical IR-CPMG method.