Accelerated Simultaneous T 2 and T 2 * Mapping of Multiple Sclerosis Lesions Using Compressed Sensing Reconstruction of Radial RARE-EPI MRI.

(1) Background: Radial RARE-EPI MRI facilitates simultaneous T 2 and T 2 * mapping (2in1-RARE-EPI). With modest undersampling (R = 2), the speed gain of 2in1-RARE-EPI relative to Multi-Spin-Echo and Multi-Gradient-Recalled-Echo references is limited. Further reduction in scan time is crucial for clinical studies investigating T 2 and T 2 * as imaging biomarkers. We demonstrate the feasibility of further acceleration, utilizing compressed sensing (CS) reconstruction of highly undersampled 2in1-RARE-EPI. (2) Methods: Two-fold radially-undersampled 2in1-RARE-EPI data from phantoms, healthy volunteers ( n = 3), and multiple sclerosis patients ( n = 4) were used as references, and undersampled (R extra = 1-12, effective undersampling R eff = 2-24). For each echo time, images were reconstructed using CS-reconstruction. For T 2 (RARE module) and T 2 * mapping (EPI module), a linear least-square fit was applied to the images. T 2 and T 2 * from CS-reconstruction of undersampled data were benchmarked against values from CS-reconstruction of the reference data. (3) Results: We demonstrate accelerated simultaneous T 2 and T 2 * mapping using undersampled 2in1-RARE-EPI with CS-reconstruction is feasible. For R extra = 6 (TA = 01:39 min), the overall MAPE was ≤8% (T 2 *) and ≤4% (T 2 ); for R extra = 12 (TA = 01:06 min), the overall MAPE was <13% (T 2 *) and <5% (T 2 ). (4) Conclusion: Substantial reductions in scan time are achievable for simultaneous T 2 and T 2 * mapping of the brain using highly undersampled 2in1-RARE-EPI with CS-reconstruction.