An improved method to accelerate the acquisition efficiency of the T1-T2 spectrum based on the IR-BSSFP-CPMG pulse sequence

The correlation map of the longitudinal relaxation time (T1) and the transverse relaxation time (T2) offers valuable information of different proton contributions and is served as a significant data for identifying, quantifying and characterizing complex relaxation components in unconventional reservoirs. However, the acquisition speed and spectral resolution for existing pulse sequences cannot be guaranteed simultaneously. We designed an improved pulse sequence which integrates the inversion recovery-balanced steady-state free precession (IR-BSSFP) sequence and the Carr-Purcell-Meiboom-Gill (CPMG) sequence, allowing for the measurement of two-dimensional T1-T2 spectrums. The IR-BSSFP sequence adopts a low refocusing angle and reduced flip angle pulse transmission power, eliminating the need for complete polarization. Moreover, the parameters of the improved pulse sequence such as the value and the number of the flip angle, the repetition time are discussed by numerical simulations. The result showed that the new pulse sequence achieves high-precision measurement performance, and the T1-T2 spectrum can be achieved within a few seconds. •The IR-BSSFP-CPMG is developed for the measurement of the T1-T2 correlation map.•Both the signal quality and acquisition efficiency can be guaranteed by the new pulse sequence.•Proper selection of the pulse sequence parameters is necessary for the precise measurement.