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

Purpose: 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 ${\delta }_f$ , T₁ , and T₂ tissue properties.

Methods: 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 ${\delta }_f$ , T₁ , T₂ , as well as the distribution width of intravoxel frequency dispersion, $\Gamma$ . A dictionary, generated through Bloch simulation, containing possible signal evolutions within the physiological range of ${\delta }_f$ , T₁ , T₂ , and $\Gamma$ , was used to perform parameter estimation. The estimated T₂ and $\Gamma$ were subsequently used to estimate T₂^* . The proposed method was evaluated in phantom experiments and healthy volunteers (N = 5).

Results: 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.

Conclusion: The proposed qRF-MRF method demonstrated the potential for simultaneous quantification of ${\delta }_f$ , T₁ , T₂ , and T₂^* tissue properties.