Accelerated T₂ mapping combining parallel MRI and model-based reconstruction: GRAPPATINI.

Background Quantitative T2 measurements are sensitive to intra- and extracellular water accumulation and myelin loss. Therefore, quantitative T2 promises to be a good biomarker of disease. However, T2 measurements require long acquisition times. Purpose To accelerate T2 quantification and subsequent generation of synthetic T2-weighted (T2-w) image contrast for clinical research and routine. To that end, a recently developed model-based approach for rapid T2 and M0 quantification (MARTINI) based on undersampling k-space, was extended by parallel imaging (GRAPPA) to enable high-resolution T2 mapping with access to T2-w images in less than 2 minutes acquisition time for the entire brain. Study Type Prospective cross-sectional study. Subjects/Phantom Fourteen healthy subjects and a multipurpose phantom. Field Strength/Sequence Carr–Purcell–Meiboom-Gill sequence at a 3T scanner. Assessment The accuracy and reproducibility of the accelerated T2 quantification was assessed. Validations comprised MRI studies on a phantom as well as the brain, knee, prostate, and liver from healthy volunteers. Synthetic T2-w images were generated from computed T2 and M0 maps and compared to conventional fast spin-echo (SE) images. Statistical Tests Root mean square distance (RMSD) to the reference method and region of interest analysis. Results The combination of MARTINI and GRAPPA (GRAPPATINI) lead to a 10-fold accelerated T2 mapping protocol with 1:44 minutes acquisition time and full brain coverage. The RMSD of GRAPPATINI increases less (4.3%) than a 10-fold MARTINI reconstruction (37.6%) in comparison to the reference. Reproducibility tests showed low standard deviation (SD) of T2 values in regions of interest between scan and rescan (<0.4 msec) and across subjects (