ORACLE: An analytical approach for T1, T2, proton density, and off-resonance mapping with phase-cycled balanced steady-state free precession

Purpose: To develop and validate a novel analytical approach simplifying T-1, T-2, proton density (PD), and off-resonance Delta f quantifications fromphase- cycled balanced steady-state free precession (bSSFP) data. Additionally, to introduce a method to correct aliasing effects in undersampled bSSFP profiles. Theory and Methods: Off-resonant-encoded analytical parameter quantification using complex linearized equations (ORACLE) provides analytical solutions for bSSFP profiles. which instantaneously quantify T-1, T-2, proton density (PD), and Delta f. An aliasing correction formalism was derived to allow undersampling of bSSFP profiles. ORACLE was used to quantify T-1, T-2, PD, T-1/T-2, and Delta f based on fully sampled (N = 20) bSSFP profiles from numerical simulations and 3T MRI experiments in phantom and 10 healthy subjects' brains. Obtained values were compared with reference scans in the same scan session. Aliasing correction was validated in subsampled (N = 4) bSSFP profiles in numerical simulations and human brains. Results: ORACLE quantifications agreed well with input values from simulations and phantom reference values (R-2 = 0.99). In human brains, T1 and T2 quantifications when compared with reference methods showed coefficients of variation below 2.9% and 3.9%, biases of 182 and 16.6 ms, and mean white-matter values of 642 and 51 ms using ORACLE. The Delta f quantification differed less than 3Hz between both methods. PD and T-1 maps had comparable histograms. The.. maps effectively identified cerebrospinal fluid. Aliasing correction removed aliasing-related quantification errors in undersampled bSSFP profiles, significantly reducing scan time. Conclusion: ORACLE enables simplified and rapid quantification of T1, T2, PD, and Delta f from phase-cycled bSSFP profiles, reducing acquisition time and eliminating biomarker maps' coregistration issues.