Magnetic resonance fingerprinting with quadratic RF phase for measurement of T2* simultaneously with δf , T1 , and T2

The proposed qRF-MRF method demonstrated the potential for simultaneous quantification of δfδf<math><msub><mi>δ</mi><mi>f</mi></msub></math> , T1 , T2 , and T2* tissue properties.

The proposed quadratic RF phase-based MRF method (qRF-MRF) combined a varied RF excitation phase with the existing balanced SSFP (bSSFP)-based MRF method to generate signals that were uniquely sensitive to δfδf<math><msub><mi>δ</mi><mi>f</mi></msub></math> , T1 , T2 , as well as the distribution width of intravoxel frequency dispersion, ΓΓ<math><mi>Γ</mi></math> . A dictionary, generated through Bloch simulation, containing possible signal evolutions within the physiological range of δfδf<math><msub><mi>δ</mi><mi>f</mi></msub></math> , T1 , T2 , and ΓΓ<math><mi>Γ</mi></math> , was used to perform parameter estimation. The estimated T2 and ΓΓ<math><mi>Γ</mi></math> were subsequently used to estimate T2* . The proposed method was evaluated in phantom experiments and healthy volunteers (N = 5).

This study explores the possibility of using a gradient moment balanced sequence with a quadratically varied RF excitation phase in the magnetic resonance fingerprinting (MRF) framework to quantify T2* in addition to δfδf<math><msub><mi>δ</mi><mi>f</mi></msub></math> , T1 , and T2 tissue properties.

The T1 and T2 values from the phantom by qRF-MRF demonstrated good agreement with values obtained by traditional gold standard methods (r2 = 0.995 and 0.997, respectively; concordance correlation coefficient = 0.978 and 0.995, respectively). The T2* values from the phantom demonstrated good agreement with values obtained through the multi-echo gradient-echo method (r2 = 0.972, concordance correlation coefficient = 0.983). In vivo qRF-MRF-measured T1 , T2 , and T2* values were compared with measurements by existing methods and literature values.