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.
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.
Prospective cross-sectional study.
Fourteen healthy subjects and a multipurpose phantom.
Carr-Purcell-Meiboom-Gill sequence at a 3T scanner.
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.
Root mean square distance (RMSD) to the reference method and region of interest analysis.
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).
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.
2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.