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. 2018 Aug;48(2):359-368.
doi: 10.1002/jmri.25972. Epub 2018 Feb 15.

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

Tom Hilbert  1   2   3 , Tilman J Sumpf  4 , Elisabeth Weiland  5 , Jens Frahm  4 , Jean-Philippe Thiran  2   3 , Reto Meuli  2 , Tobias Kober  1   2   3 , Gunnar Krueger  2   3   6
Affiliations

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

Tom Hilbert et al. J Magn Reson Imaging. 2018 Aug.

Abstract

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 (<4 msec).

Data conclusion: GRAPPATINI provides highly reproducible and fast whole-brain T2 maps and arbitrary synthetic T2 -w images in clinically compatible acquisition times of less than 2 minutes. These abilities are expected to support more widespread clinical applications of quantitative T2 mapping.

Level of evidence: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:359-368.

Keywords: T2 mapping; model-based reconstruction; parametric mapping; quantitative MRI.

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