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

Background Quantitative T 2 measurements are sensitive to intra‐ and extracellular water accumulation and myelin loss. Therefore, quantitative T 2 promises to be a good biomarker of disease. However, T 2 measurements require long acquisition times. Purpose To accelerate T 2 quantification and subsequent generation of synthetic T 2 ‐weighted (T 2 ‐w) image contrast for clinical research and routine. To that end, a recently developed model‐based approach for rapid T 2 and M 0 quantification (MARTINI) based on undersampling k ‐space, was extended by parallel imaging (GRAPPA) to enable high‐resolution T 2 mapping with access to T 2 ‐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 T 2 quantification was assessed. Validations comprised MRI studies on a phantom as well as the brain, knee, prostate, and liver from healthy volunteers. Synthetic T 2 ‐w images were generated from computed T 2 and M 0 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 T 2 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 T 2 values in regions of interest between scan and rescan (<0.4 msec) and across subjects (<4 msec). Data Conclusion GRAPPATINI provides highly reproducible and fast whole‐brain T 2 maps and arbitrary synthetic T 2 ‐w images in clinically compatible acquisition times of less than 2 minutes. These abilities are expected to support more widespread clinical applications of quantitative T 2 mapping. Level of Evidence: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:359–368.