Quantitative Proton Density Mapping With Data‐Driven Reception Profile Correction Derived From Macromolecular Proton Fraction

Purpose Proton density ( PD ) and macromolecular proton fraction ( MPF ) are fundamental MR parameters characterizing water and macromolecular content in tissues. Both parameters can be mapped using a time‐efficient MRI protocol, though PD maps require additional corrections for the reception profile ( RP ) non‐uniformity and global scaling. Existing PD mapping methods suffer from uncertainties related to PD normalization to reference tissue. This study aimed to develop a data‐driven RP correction method for PD mapping based on MPF as an internal scale. Theory and Methods One‐parameter model linking PD and MPF was derived under the assumption of proportionality between total macromolecular volume and proton concentration. This model, with a uniform parameter value across brain tissues, generates a surrogate PD map, which is used to estimate RP from an uncorrected PD map. The proposed algorithm was tested against a common PD mapping method utilizing bias‐field correction and normalization to cerebrospinal fluid. Brain MRI data were acquired at 3 T from seven healthy individuals. The protocol included 3D multi‐echo T 1 ‐, PD‐, and magnetization‐transfer‐weighted gradient‐echo sequences. Parametric maps were reconstructed using the single‐point MPF mapping algorithm with data‐driven B 1 correction. Results MPF ‐based and bias‐field corrections yielded similar PD measurements in white and gray matter with no significant bias and remarkably small variability (coefficients of variation < 0.6%). Conclusions MPF ‐based RP correction enables computationally simple and robust quantitative PD mapping at no additional cost if MPF maps are available. The main advantage of the proposed method is the automatic elimination of global scaling that obviates the need for PD normalization.